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Report ITU-R F.2475-0 (09/2019)

Sharing and compatibility studies of High Altitude Platform Station systems

in the fixed service in the 38-39.5 GHz frequency range

F Series

Fixed service

ii Rep. ITU-R F.2475-0

Foreword

The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the

radio-frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without

limit of frequency range on the basis of which Recommendations are adopted.

The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional

Radiocommunication Conferences and Radiocommunication Assemblies supported by Study Groups.

Policy on Intellectual Property Right (IPR)

ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Resolution

ITU-R 1. Forms to be used for the submission of patent statements and licensing declarations by patent holders are

available from http://www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent

Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found.

Series of ITU-R Reports

(Also available online at http://www.itu.int/publ/R-REP/en)

Series Title

BO Satellite delivery

BR Recording for production, archival and play-out; film for television

BS Broadcasting service (sound)

BT Broadcasting service (television)

F Fixed service

M Mobile, radiodetermination, amateur and related satellite services

P Radiowave propagation

RA Radio astronomy

RS Remote sensing systems

S Fixed-satellite service

SA Space applications and meteorology

SF Frequency sharing and coordination between fixed-satellite and fixed service systems

SM Spectrum management

Note: This ITU-R Report was approved in English by the Study Group under the procedure detailed in

Resolution ITU-R 1.

Electronic Publication

Geneva, 2019

ITU 2019

All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU.

http://www.itu.int/ITU-R/go/patents/en

http://www.itu.int/publ/R-REP/en

Rep. ITU-R F.2475-0 1

REPORT ITU-R F.2475-0

Sharing and compatibility studies of High Altitude Platform Station systems

in the fixed service in the 38-39.5 GHz frequency range

(2019)

TABLE OF CONTENT

Page

1 Introduction .................................................................................................................... 2

2 Allocation information in the 38-39.5 GHz frequency range ......................................... 2

3 Technical characteristics ................................................................................................. 3

3.1 Technical and operational characteristics of HAPS systems operating in the

38-39.5 GHz frequency range ............................................................................. 3

3.2 Technical and operational characteristics of fixed service operating in the


3.3 Technical and operational characteristics of Mobile service operating in the


3.4 Technical and operational characteristics of Fixed Satellite service operating

in the 38-39.5 GHz frequency range ................................................................... 8

3.5 Technical and operational characteristics of Space Research service (space-

to-Earth) operating in the 37-38 GHz frequency range ...................................... 9

3.6 Propagation models for sharing and compatibility studies in the 38-39.5 GHz

frequency range .................................................................................................. 9

4 Sharing and compatibility studies................................................................................... 9

5 Abbreviations and acronyms .......................................................................................... 9

Annex 1 (FS) – Sharing and compatibility of fixed service and HAPS systems operating in

the 38-39.5 GHz frequency range ................................................................................... 10

1 Technical analysis ........................................................................................................... 10

1.1 Study A ............................................................................................................... 10

2 Summary and analysis of the results of studies .............................................................. 29

Annex 2 – Sharing and compatibility of Mobile service and HAPS systems operating in the

38-39.5 GHz frequency range ........................................................................................ 31

1.1 Study A ............................................................................................................... 34

1.2 Study B ............................................................................................................... 47

1.3 Study C ............................................................................................................... 52

2 Rep. ITU-R F.2475-0

Page

Annex 3 – Sharing and compatibility study of Fixed Satellite service and HAPS systems

operating in the 38-39.5 GHz frequency range .............................................................. 94

1 Technical Study .............................................................................................................. 94

1.1 Study A (Interference from the transmitting HAPS GW and HAPS CPE into

receiving FSS earth station ................................................................................. 94

1.2 Study B ............................................................................................................... 99

1.3 Study C: Sharing studies in the ground-to-HAPS direction ............................... 108

1.4 Study D: sharing studies in the HAPS-to-ground direction ................................ 114


2.1 Impact from transmitting HAPS ground station into receiving FSS Earth

station .................................................................................................................. 156

2.3 Impact from transmitting FSS space station Satellite into receiving HAPS....... 158

2.4 Impact from transmitting FSS space station into receiving HAPS ground

station .................................................................................................................. 158

Annex 4 – Compatibility study of Space Research service in the adjacent band 37-38 GHz

and HAPS systems operating in 38-39.5 GHz frequency range..................................... 159

1 Technical analysis ........................................................................................................... 159

1.1 Study A ............................................................................................................... 159


1 Introduction

This Report includes the sharing and compatibility studies of High Altitude Platform Station

(HAPS) systems in the 38-39.5 GHz frequency range with the Fixed Service (FS), the Mobile

Service (MS) and the Fixed Satellite Service (FSS) to which the bands are allocated on a primary

basis, and also with the Space Research Service (SRS) in the adjacent band.

This Report provides the sharing and compatibility studies referenced under further resolves 1 of

Resolution 160 (WRC-15), to ensure the protection of the existing services allocated to the

frequency range and taking into account relevant footnotes of Article 5 of the RR.

2 Allocation information in the 38-39.5 GHz frequency range

The Radio Regulations Table of allocations is provided for reference below.

Rep. ITU-R F.2475-0 3

TABLE 1

Radio Regulation table of allocations

Allocation to services

Region 1 Region 2 Region 3

38-39.5 FIXED

FIXED-SATELLITE (space-to-Earth)

MOBILE

Earth exploration-satellite (space-to-Earth)

5.547

3 Technical characteristics

3.1 Technical and operational characteristics of HAPS systems operating in the

38-39.5 GHz frequency range

Technical and operational characteristics of HAPS systems are provided in Report ITU-R F.2439-0.

3.2 Technical and operational characteristics of fixed service operating in the


The technical characteristics of the FS stations are taken from Recommendation ITU-R F.758-6,

Recommendation ITU-R F.2086-0 and Recommendation ITU-R F.1245-2.

TABLE 2

FS-Point-to-Point parameters used in simulation

Parameter Value Distribution Source

Modulation QPSK 4096-QAM Discrete Rec. ITU-R F.758-6

Tx output power density range

(dB(W/MHz))

–68.4…

–23.4

–37.5…

–16.5

Uniform Rec. ITU-R F.758-6

Feeder/multiplexer loss range (dB) 0.0 0.0 Fixed Rec. ITU-R F.758-6

Antenna diagram - Fixed Rec. ITU-R F.1245-2

Antenna gain range (dBi) 34…45 34…46 Uniform Rec. ITU-R F.758-6

Antenna efficiency 60 Fixed Rec. ITU-R F.1245-2

e.i.r.p. density range (dB(W/MHz)) –29.2…21.5 –15.7…17 Uniform Rec. ITU-R F.758-6

Receiver noise figure typical (dB) 8 7 Discrete Rec. ITU-R F.758-6

Elevation Mean value: –0.004

Standard deviation: 3.6

Normal Rec. ITU-R F.2086-0

Azimuth 0…360 Uniform Rec. ITU-R F.758-6

Antenna height (m) Mean value: 33.5

Standard deviation: 26.5

Normal Rec. ITU-R F.2086-0

Short-term protection criteria +10 dB 0.01% of the time in any month Rec. ITU-R F.1495-2

Long-term protection criteria –10 dB 20% of the time Rec. ITU-R S.1432-1

4 Rep. ITU-R F.2475-0

3.3 Technical and operational characteristics of Mobile service operating in the


3.3.1 Deployment-related parameters for bands between 37 GHz and 43.5 GHz

TABLE 3

Deployment-related parameters for bands between 37 GHz and 43.5 GHz

Suburban

Outdoor Urban

hotspot Indoor

Outdoor

suburban

open space

hotspot

Outdoor

Suburban

hotspot

Base station characteristics/Cell structure

Network topology and

characteristics

0 or

1 BS/km2

10 BS/km2 30 BSs/km2 (1) Indoor office:

Floor dimensions:

120 m × 50 m × 3 m

No. of cells: 4

ISD = 30 m

Frequency reuse 1 1 1 1

Antenna height

(radiation centre)

15 m

(above ground

level)

6 m

(above ground

level)

6 m

(above ground

level)

3 m (above a floor level)

Sectorization Single sector Single sector Single sector Single sector

Downtilt 15 degrees 10 degrees 10 degrees 90 degrees/ceiling-mounted

Antenna deployment At the edge

of the roof

Below roof

top

Below roof

top

N/A

Network loading factor (2)

(Average base station

activity)

20%, 50% 20%, 50% 20%, 50%

BS TDD activity factor 80% 80% 80%

1 Antenna

Characteristics

1.1 Antenna pattern Refer to Rec. ITU-R M.2101

1.2 Element gain

(dBi)

5 5 5

1.3 Horizontal/vertica

l 3 dB beamwidth

of single element

(degree)

65º for both H/V 65º for both

H/V

90º for both H/V


l front-to-back

ratio (dB)

30 for both H/V 30 for both H/V 25 for both H/V

1.5 Antenna

polarization

Linear ±45° Linear ±45° Linear ±45°

1.6 Antenna array

configuration

(row × column) (3)

8 × 16 elements 8 × 16 elements 8 × 16 elements

Rep. ITU-R F.2475-0 5

TABLE 3 (continued)

Suburban

Outdoor Urban

hotspot Indoor

Outdoor

suburban

open space

hotspot

Outdoor

Suburban

hotspot

1.7 Horizontal/Vertic

al radiating

element spacing

0.5 of wavelength

for both H/V

0.5 of

wavelength

for both H/V

0.5 of wavelength for both H/V

1.8 Array Ohmic loss

(dB)

3 3 3

1.9 Conducted power

(before Ohmic

loss) per antenna

element

(dBm/200 MHz)

8 8 2

1.12 Base station

maximum

coverage angle in

the horizontal

plane (degrees)

120 120 120

User terminal characteristics

Indoor user terminal usage 5% 5% 95%

User Equipment density

for terminals that are

transmitting

simultaneously

30 UEs/km2 100 UEs/km2 Depending on building type

(Office/Residence/School/Hall)

3 UEs per BS

Body loss resulting from

proximity effects (3)

4 dB 4 dB 4 dB

UE TDD activity factor 20% 20% 20%

1 Antenna

characteristics

1.1 Antenna pattern Refer to Recommendation ITU-R M.2101

1.2 Element gain 5 5 5


l 3 dB beamwidth

of single element

(degree)

90ºfor both H/V 90ºfor both H/V 90ºfor both H/V


l front-to-back

ratio (dB)

25 for both H/V 25 for both H/V 25 for both H/V

1.5 Antenna

polarization

Linear ±45° Linear ±45° Linear ±45°

1.6 Antenna array

configuration

(row × column) (4)

4 × 4 elements 4 × 4 elements 4 × 4 elements

1.7 Horizontal/Vertic

al radiating

element spacing

0.5 of wavelength

for both H/V

0.5 of

wavelength

for both H/V

0.5 of wavelength for both H/V

1.8 Array Ohmic loss

(dB)

3 3 3

6 Rep. ITU-R F.2475-0

TABLE 3 (end)

Suburban

Outdoor Urban

hotspot Indoor

Outdoor

suburban

open space

hotspot

Outdoor

Suburban

hotspot

1.9 Conducted power

per antenna

element (dBm)

10 10 10

2 Transmit power

control

2.1 Power control

model

Refer to Rec. ITU-R M.2101

2.2 Maximum user

terminal output

power PCMAX (5)

22 dBm 22 dBm 22 dBm

2.3 Transmit power

(dBm) target value

per 180 kHz,

P0_PUSCH

–95 –95 –95

2.4 Path loss

compensation

factor,

1 1 1

(1) 20% would normally represent a typical/average value for the loading of base stations across a network and

therefore can be used for wide area analysis (province, national or larger satellite footprint, for example). In order

to provide adequate quality of service, IMT networks are dimensioned to avoid undue congestion, such that, over

all the cells in a network, most of the cells are not heavily loaded simultaneously and only a small percentage of

cells being heavily loaded at any specific point in time. For studies involving only a smaller area (e.g. within a

local area), a maximum value of not more than 50% for BS/network loading may be used. For worst-case studies

involving a single IMT base station/cell, a loading of 100% may be used.

(2) The BS (sector) density must be translated into the Inter-Site Distance (ISD) according to the network topology for

use as input in Recommendation ITU-R M.2101. Dense urban environments are likely to be served by single

sector small cells.

(3) Although preliminary studies suggest that the impact of proximity effects/body loss will in most cases be in excess

of 4 dB, a value of 4 dB has been selected as a typical value.

(4) The antenna pattern for base station or user equipment depends on the antenna array configuration and the antenna

element pattern and gain. For example, the antenna array composed of 8 × 8 identical antenna elements with 5 dBi

gain each produces a maximum 23 dBi main beam antenna gain for base stations and an antenna array composed

of 4 × 4 identical antenna elements with 5 dBi gain each produces a maximum 17 dBi main beam antenna gain for

user terminal. Antenna gain in directions other than the main beam is reduced according to the antenna model

described in Recommendation ITU-R M.2101. The use of antenna array configurations other than those indicated

in the table above should not lead to an increase of interference to other services to which the bands are currently

allocated and should not increase the e.i.r.p., by adjusting the other relevant parameters.

(5) Maximum user terminal output power depends on the antenna array configuration and conducted power (before

Ohmic loss) per antenna element. For example, the antenna array composed of 4 × 4 identical antenna elements

with conducted power per antenna element 10 dBm produces 22 dBm maximum user terminal output power. The

reduction of maximum user terminal output power resulting from power control model is applied to each element

within antenna array; i.e. conducted power (before Ohmic loss) per antenna element is reduced to same extent as

PPUSCH reduced compared to PCMAX.

3.3.2 Deployment consideration in a relatively large area

It is based on a log-normal/Rayleigh distribution for the distance between UE and BS hotspot using

a Rayleigh distribution parameter for the distance (BS, UE) of σ = 32.

Rep. ITU-R F.2475-0 7

An illustration of the UE distribution is shown in Fig. 1 below:

FIGURE 1

UE deployment used in the simulations

3.3.3 Noise figure and protection criteria

Irrespective of the number of cells and independent of the number of interferers.

TABLE 4

IMT-2020 noise figure in the 37-52.6 GHz range

Base station 12 dB

User terminal 12 dB

TABLE 5

Protection criterion for IMT-2020

Protection criterion (I/N) –6 dB

3.3.4 Polarisation losses

– For single-entry studies: 1.5 dB.

– For aggregate interference studies: 3 dB.

3.3.5 Body losses

A fixed value of 4 dB is considered. This value is only applicable to sharing studies involving UE.

8 Rep. ITU-R F.2475-0

3.4 Technical and operational characteristics of Fixed Satellite service operating in the


TABLE 6

FSS receive parameters

FSS downlink parameters (Interfered with)

Frequency range (GHz) 38-39.5 38-39.5

Carrier Carrier #06 Carrier #26

Noise bandwidth (MHz) 100-600 50-500

Earth Station

Antenna diameter (m) 6.8 1

Peak receive antenna gain (dBi) 68 50

Antenna receive gain pattern (ITU-R Recommendation) Rec. ITU-R S.465-6 Rec. ITU-R S.465-6

System receive noise temperature (K) 250 150

Minimum earth station elevation angle (degree) 10 10

Interference Protection Criteria

Interference to noise ratio I/N (dB) –10.5 dB not to be

exceeded more than 20%

–6 dB not to be exceeded

more than 1%

8 dB not to be exceeded

more than 0.02%

–10.5 dB not to be

exceeded more than 20%

–6 dB not to be exceeded

more than 1%

8 dB not to be exceeded

more than 0.02%

Other

Additional notes NGSO system with an

circular, orbit having an

altitude of 1 400 km

TABLE 7

FSS transmit parameters

FSS downlink parameters (interferer)

Frequency range ( GHz) 38-39.5 38-39.5 38-39.5

SPACE STATION CARRIER Carrier #05 Carrier #20 Carrier #25, 26

Peak transmit antenna gain (dBi) 43.7 39 45

Peak satellite e.i.r.p. spectral density

(dB(W/Hz))

–5 –34.6 –31.1

Transmit antenna gain pattern and

(3-dB) beamwidth

Section 1.1 of Annex 1

of ITU-R S.672-4

beamwidth:

1.15 LS = –25

Rec. ITU-R S.1528

(LS = –25)

BW = 1.9

Rec. ITU-R S.1528

LS = –25

BW= 0.95

Other

Additional notes NGSO system with a

circular orbit having

an altitude of

8 062 km.

NGSO system with a

circular, orbit having

an altitude of

1 400 km.

Rep. ITU-R F.2475-0 9

3.5 Technical and operational characteristics of Space Research service (space-to-Earth)

operating in the 37-38 GHz frequency range

The telecommunication requirements and parameters for manned and unmanned SRS systems are

given in Recommendation ITU-R SA.1014. This Recommendation also includes a list of SRS earth

stations that need to be protected. Reference gain pattern for large earth station antennas is given in

Recommendation ITU-R SA. 1811 for the 37-38 GHz band. The maximum gain of the SRS earth

station antenna is 86 dB.

The protection criterion is specified in Recommendation ITU-R SA.1396 as I0/N0 = –6 dB. Using

SRS system noise temperature of 60 K, the protection criterion is specified as –217 dB(W/Hz) not

to be exceeded 0.001% for manned SRS missions and 0.1% for unmanned SRS missions. This

protection criteria is intended to protect unique operations during critical mission events in the

space research service from unexpected interference. Levels in excess of the protection criteria may

be acceptable on a case-by-case basis.

3.6 Propagation models for sharing and compatibility studies in the 38-39.5 GHz

frequency range

The sharing and compatibility studies, in accordance with Resolution 160 (WRC-15), are to be

conducted based on the propagation models as provided by the relevant groups.

4 Sharing and compatibility studies

Annex 1 Sharing and compatibility study of Fixed Service and HAPS systems operating in the


Annex 2 Sharing and compatibility study of Mobile Service and HAPS systems operating in the


Annex 3 Sharing and compatibility study of Fixed Satellite Service and HAPS systems operating

in the 38-39.5 GHz frequency range

Annex 4 Compatibility study of Space Research Service in the adjacent band 37-38 GHz

frequency range and HAPS systems operating in 38-39.5 GHz frequency range

5 Abbreviations and acronyms

BS MS base station

CDF Cumulative distribution function

CPE Customer premises equipment

EESS Earth exploration-satellite service

e.i.r.p. Equivalent isotopically radiated power

ES Earth station

FS Fixed service

FSS Fixed Satellite Service

GSO Geostationary satellite orbit

GW Gateway

HAPS ground station Ground station transmitting to or receiving from HAPS

10 Rep. ITU-R F.2475-0

HAPS High Altitude Platform Station

IHD Inter-HAPS distance

ISS Inter-satellite service

MS Mobile Service

MCL Minimum coupling loss

CNGSO Non-geostationary satellite orbit

pfd Power flux-density

QAM Quadrature amplitude modulation

QPSK Quadrature phase shift keying

RF Radio frequency

SRS Space Research Service

Tx Transmitter

UE MS User Equipment

Annex 1

Sharing and compatibility of fixed service and HAPS systems operating


1 Technical analysis

TABLE 8

Summary of scenarios considered in study A, B

Study A Study B

HAPS ground station to FS X

HAPS to FS X

FS to HAPS ground station X

FS to HAPS X

1.1 Study A

1.1.1 Impact from the transmitting HAPS into FS receiving stations

This study aims to define the maximum pfd level from HAPS versus elevation angle in order to

protect FS stations receivers.

1.1.1.1 HAPS to ground transmitters into FS receivers (single entry analysis)

The following steps have been performed to derive such pfd mask versus elevation angle taking into

account the impact of a single HAPS station emission:

Rep. ITU-R F.2475-0 11

Step 0: Initiate the simulation considering the following parameters:

– 0° is taken for the elevation angle at the FS station towards the HAPS;

– 0° is taken for the azimuth angle at the FS station towards the HAPS.

Step 1: Compute the FS antenna gain towards the HAPS based on the following input parameters.

– FS station antenna pointing azimuth: random variable with a uniform distribution between

–180° to 180°;

– FS station antenna pointing elevation: random variable with a normal distribution (median

–0.004° and standard deviation 3.6° based on Recommendation ITU-R F.2086-0), see

Table 2;

– FS maximum antenna gain: random variable with a uniform distribution between 34 dBi

and 46 dBi.

Step 2: Compute and store the maximum possible HAPS pfd level at the FS station using the

following equation:

𝑝𝑓𝑑𝑚𝑎𝑥(θ) = 𝐼𝑚𝑎𝑥 + 10 log10 (4π

λ2) − 𝐺𝑟(φ) + 𝐴𝑡𝑡𝑔𝑎𝑠(θ)

where:

: elevation angle in degrees (angle of arrival above the horizontal plane)

Imax: maximum interference level (–147 dB(W/MHz) long term protection criteria)

Gr(φ): FS antenna gain towards the HAPS based on Recommendation ITU-R F.1245

which include a polarisation loss of 1.7 dB in the main beam of FS (3 dB

beamwidth) (see step 1) (dBi)

φ: angle between the vector FS to HAPS and FS antenna main beam pointing

vector (degree)

Attgas(θ) : gaseous attenuation (Recommendation ITU-R SF.1395) (dB).

FIGURE 2

Atmospheric gaseous attenuation

12 Rep. ITU-R F.2475-0

Step 3: Redo step 1 and 2 sufficiently to obtain a stable pfd cumulative distribution function (CDF)

curve and store it.

Step 4: Redo step 1 to 3 with an increased FS elevation angle towards the HAPS of 0.1°.

Step 5: Redo step 1 to 4 until the elevation angle towards the HAPS is 90°.

Figure 3 provides the results for the clear sky/long term.

FIGURE 3

Maximum pfd level CDF to meet the FS protection criteria

Step 6: Determine the pfd mask versus elevation to protect FS station receiver.

The following pfd mask at the Earth surface should be sufficient to protect FS station receivers

under clear sky condition from a single HAPS emission:

–137 dB(W/(m2 ‧ MHz)) θ ≤ 13°

–137 + 3.125 (θ dB(W/(m2 ‧ MHz)) 13° < θ ≤ 25°

–99.5 + 0.5 (θ dB(W/(m2 ‧ MHz)) 25° < θ≤ 50°

–87 dB(W/(m2 ‧ MHz)) 50° < θ ≤ 90°

where θ is elevation angle in degrees (angle of arrival above the horizontal plane).

Rep. ITU-R F.2475-0 13

FIGURE 4

Proposed pfd mask versus elevation angle

The following two approaches address the use of ATPC to compensate for rain fade.

Approach 1: In order to compensate for additional propagation impairments in the boresight of any

beam of the HAPS due to rain, the HAPS can be operated so that the pfd mask can be increased in

any corresponding beam (i.e. suffering the rain fade) by a value only equivalent to the level of rain

fading and limited to a maximum of 20 dB. This level is the difference between long-term

protection criteria of I/N = –10 dB that can be exceeded for no more than 20% of the time (i.e. clear

sky) and assumed short-term protection criteria of I/N = +10 dB that is never exceeded.

Approach 2: Automatic transmit power control may be used to increase the e.i.r.p. density to

compensate for rain attenuation to the extent that the pfd at the FS station does not exceed the value

resulting from use by HAPS station of an e.i.r.p. meeting the above limits in the clear sky

conditions.

Since the above pfd mask has been developed taking into account attenuation due to atmospheric

gases, compliance verification of a HAPS system with this mask should be conducted using the free

space propagation model.

Furthermore, for the purpose of when field measurements are required for a deployed HAPS

system, administrations may therefore use the pfd levels provided below could be considered. These

additional pfds levels, in dB(W/(m2.MHz)), do not take into account any attenuation due to

atmospheric gases and are only provided for measurement purposes. This material is provided for

information in this section.

137 – 14.44 / (1 + 0.7365 θ + 0.01542 θ2) for θ ≤ 13°

–137 + 3.125 (θ – 13) – 14.44 / (1 + 0.7365 θ + 0.01542 θ2) for 13° < θ ≤ 25°

–99.5 + 0.5 (θ – 25) – 14.44 / (1 + 0.7365 θ + 0.01542 θ2) for 25° < θ ≤ 50°

–87 – 14.44 / (1 + 0.7365 θ + 0.01542 θ2) for 50° < θ ≤ 90°


14 Rep. ITU-R F.2475-0

1.1.1.2 Aggregate impact from transmitting HAPS into FS receiving station

The following steps have been performed to define if the aggregate impact of several HAPS in

visibility from the FS station is close to the one from a single HAPS station emission.

Step 1: Locate N HAPS distributed on a grid over the spherical cap visible from the FS station

(see Fig. 5). The distance between HAPS (Inter HAPS Distance is IHD in km). The grid position

versus FS location is randomly selected.

FIGURE 5

HAPS on a spherical cap

where:

h: HAPS altitude (20 km)

Radius_sph: Earth radius plus 20 km

Radius_cap: distance between the HAPS and the FS when the HAPS is seen from the FS

station with an elevation angle of 0°.

Step 2: Compute, for each HAPS from step 1, the angle between the horizontal plane at the FS

station location and the vector from the FS station location towards the HAPS ( angle of arrival

above the horizontal plane).

Step 3: Based on step 2 and the pfd mask from § 1.3.2, compute for each HAPS the maximum pfd

level produced at the FS station location.

Step 4: Compute the FS antenna gain towards the HAPS based on the following input parameters:

– the elevation angle towards the HAPS from step 2;

– azimuth 0° is taken for the FS azimuth towards the HAPS;


–180° to 180°;


–0.004° and standard deviation 3.6°);


and 46 dBi.

Step 5: compute and store the level of aggregate interference-to-noise ratio in dB produced by all

HAPS at the FS receiver input using the following equation:

Rep. ITU-R F.2475-0 15

𝐼𝑀𝑁⁄ = 10 ∗ 𝑙𝑜𝑔10 (∑ 10

pfd𝑛(θ𝑛)+10 log10(λ2

4π)+𝐺𝑟𝑛(φ𝑛)−𝐴𝑡𝑡𝑛𝑔𝑎𝑠(θ𝑛)

10

𝑁

𝑛=1

) − 𝑁

where:

n: index of the HAPS

IM: aggregate interference level produced by N HAPS for a certain HAPS

configuration M (dB(W/MHz))

Grn(φn): FS antenna gain towards the HAPS with the index n (dBi)

φn: angle between the vector FS to HAPSn and FS antenna main beam pointing

vector (degree)

pfdn (θn): pfd produced using a free space model at the FS station location by the HAPS

with index n (dB(W/(m2 ‧ MHz))) and is dependant to the elevation angle θn

Attngas(θn): gaseous attenuation for the link with index n (Recommendation

ITU-R SF.1395) which is dependent to the elevation angle θn (dB)

N: FS receiver noise level (–147 dB(W/MHz)).

Step 6: Redo step 1 to 5 sufficiently to obtain a stable I cumulative distribution function curve

(CDF) and store it.

In the following, results are given with an IHD of 100 km. This value means that from any point of

the Earth, a maximum of 81 HAPS is possibly visible with an elevation angle higher than 0°. This is

considered as a worst-case scenario as such a HAPS density would represent around 67 HAPS

operating at the maximum pfd over a territory having the same surface than France, which is a

huge, unrealistic number.

Results for step 6 are provided in Fig. 6.

FIGURE 6

Aggregate I/N in dB

16 Rep. ITU-R F.2475-0

1.1.1.3 Compliance with proposed pfd mask

In the following, the above proposed HAPS pfd mask to protect FS receivers is compared with

System 4a1 maximum pfd level versus elevation. As shown in Fig. 7, System 4a pfd meets the

proposed pfd mask. It is therefore possible to design a HAPS system that meets the proposed pfd

mask and thus protect FS receivers.

FIGURE 7

HAPS System 4a compliance with the proposed pfd mask

1 See Report ITU-R F.2439-0.

Rep. ITU-R F.2475-0 17

The pfd is computed using the following equation:

𝑝𝑓𝑑(θ) = 𝐸𝐼𝑅𝑃(θ) − 10log10(4π𝑑2)

where:

d: distance between the HAPS and the FS station (m)

elevation angle in degrees (angle of arrival above the horizontal plane)

EIRP: nominal HAPS e.i.r.p. spectral density in at a specific elevation angle

(dB(W/MHz)).

1.1.2 Impact from the transmitting FS station into HAPS receiving ground station and

comparison with the impact from transmitting FS station into FS receiving station

HAPS systems is an application that can operate as applications under the FS. The characteristics of

HAPS ground stations are similar to conventional fixed stations. However, HAPS ground stations

normally point at higher elevations than conventional fixed stations. The study below compares:

• the impact of a transmitting conventional fixed service station into a HAPS ground station

with;

• the impact of a transmitting conventional fixed service station into another conventional

fixed service station.

The study is based on a statistical single-entry analysis. The purpose of the study is to provide an

indication to administrations on whether sharing the band between HAPS ground stations and

conventional fixed service stations is more challenging than sharing the band between conventional

fixed service stations.

1.1.2.1 Impact from transmitting FS station into HAPS receiving ground station

The following steps have been performed to derive the minimum separation distance CDF between

a single FS station (interferer) and HAPS ground station (victim).

In this study, System 4a characteristics are taken into account and consequently HAPS ground

stations are System 4a CPE receiving stations.


– 0° is taken for the elevation angle at the FS station towards the HAPS CPE;

– 0° is taken for the azimuth angle at the FS station towards the HAPS CPE;

– 0° is taken for the elevation angle towards the FS;

– 180° is taken for the azimuth towards the FS;

Step 1: Compute the FS antenna gain towards the HAPS CPE and the FS maximum e.i.r.p. density

based on the following input parameters:


–180° to 180°;



Table 2;


and 46 dBi

– FS antenna pattern: ITU-R F.1245-2;

– FS maximum e.i.r.p. density: random variable with a uniform distribution between

−15.7 dB(W/MHz) and 17 dB(W/MHz).

18 Rep. ITU-R F.2475-0

Step 2: Compute the HAPS CPE antenna gain towards the FS based on the following input

parameters:

– HAPS station antenna pointing azimuth: random variable with a uniform distribution

between –180° to 180°;

– HAPS CPE maximum antenna gain (from System 4a characteristics): 49.8 dBi for the CPE;

– HAPS station antenna pointing elevation: random variable with a distribution between 21

and 90 degrees that is shown in Fig. 8.

FIGURE 8

Statistics of HAPS CPE antenna pointing elevation

Step 3: Compute the required propagation loss to meet the HAPS protection criteria:

𝐴𝑡𝑡𝑃.452−16 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐹𝑆 − 𝐺𝑚𝑎𝑥𝐹𝑆+ 𝐺𝐹𝑆→𝐻𝐴𝑃𝑆𝐺𝑆

+ 𝐺𝑟𝐻𝐴𝑃𝑆 − 𝐼𝑚𝑎𝑥

where:

EIRPmaxFS : FS station maximum e.i.r.p. density (in the main beam) (dB(W/MHz))

GmaxFS : maximum FS station antenna gain (dBi)

𝐺𝐹𝑆→𝐻𝐴𝑃𝑆𝐺𝑆: FS station antenna gain towards the HAPS ground station (dBi)

GrHAPS : HAPS ground station antenna gain towards the FS station (dBi)

(GrHAPSmax = 49.8 dBi for System 4a)

Imax : HAPS ground station maximum allowable interference level (dB(W/MHz)).

For HAPS system 4a: –156 dB(W/MHz) (I/N of –10 dB) not be exceeded by

more than 20% of the time and –136 dB(W/MHz) (I/N of +10 dB) not be

exceeded by more than 0.01% of the time

AttP.452-16 : propagation loss (dB) needed to meet the HAPS protection criteria based on

Recommendation ITU-R P.452-16 (P.452-16) propagation model with p = 20%

when Imax/N = –10 dB and p = 0.01% when Imax/N = 10 dB. The land path type

is used, the typical temperature is taken at 20°, the pressure at 1013 mbar and

no clutter.

Step 4: Store the calculated separation distance and repeat steps 1 through 3 sufficiently to obtain a

stable CDF.

Rep. ITU-R F.2475-0 19

1.1.2.2 Impact from transmitting FS station into FS receiving station


a single FS station (interferer) and HAPS ground (victim).


– 0° is taken for the elevation angle at the FS transmitting station towards the FS impacted

station;

– 0° is taken for the azimuth angle at the FS transmitting station towards the FS impacted

station;

– 0° is taken for the elevation angle towards the transmitting FS;

– 180° is taken for the azimuth towards the transmitting FS.

Step 1: Compute the FS transmitter station antenna gain towards the FS impacted station and the FS

transmitter maximum e.i.r.p. density based on the following input parameters:


–180° to 180°;


–0.004° and standard deviation 3.6° based on Recommendation ITU-R F.2086-0),

see Table 2;


and 46 dBi;

– FS antenna pattern: ITU-R F.1245-2;


−15.7 dB(W/MHz) and 17 dB(W/MHz).

Step 2: Compute the FS impacted station antenna gain towards the FS transmitting station based on

the following input parameters:

– 0° is taken for the elevation angle towards the FS transmitting station;

– 180° is taken for the azimuth towards the FS transmitting station;

– FS impacted station antenna pointing azimuth: random variable with a uniform distribution



-0.004° and standard deviation 3.6° based on Recommendation ITU-R F.2086-0),

see Table 2;


and 46 dBi.

Step 3: Compute the propagation loss needed to meet the FS protection criteria

𝐴𝑡𝑡𝑃−452−16 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐹𝑆 − 𝐺𝑚𝑎𝑥𝐹𝑆+ 𝐺𝐹𝑆→𝐹𝑆 + 𝐺𝑟𝐹𝑆 − 𝐼𝑚𝑎𝑥

where:

EIRPmaxFS: FS transmitting station maximum e.i.r.p. density (in the main beam)

(dB(W/MHz))

GmaxFS: maximum FS transmitting station antenna gain (dBi)

GFS→FS: FS transmitting station antenna gain towards the FS impacted station (dBi)

GrFS: FS impacted station antenna gain towards the FS transmitting station (dBi)

20 Rep. ITU-R F.2475-0

AttP.452-16: propagation loss (dB) needed to meet the HAPS protection criteria in dB based

on P.452-16 propagation model with p = 20% when Imax/N = –10 dB and

p = 0.01% when Imax/N = 10 dB. The land path type is used, the typical

temperature is taken at 20°, the pressure at 1013 mbar and no clutter

Imax: FS maximum allowable interference level (dB(W/MHz)): –147 dB(W/MHz)

(I/N of –10 dB) that should not be exceeded by more than 20% of the time and

–127 dB(W/MHz) (I/N of +10 dB) that should not be exceeded by more than

0.01% of the time.


stable CDF.

1.1.2.3 Results

Figure 9 provides results for respectively the long term and short term protection criteria.

FIGURE 9

Required separation distances distributions for long term and short term protection criteria

considering FS to HAPS ground stations and FS to FS scenario

From the above results it can be concluded that the short term protection criteria compliance is the

most dimensioning one, and that separation distances between FS systems are higher than

separation distances between FS and HAPS. Figure 9 shows also that coordination areas for the

protection of HAPS receiving ground stations will also be significantly smaller that coordination

areas for FS receiving stations.

1.1.3 Summary and analysis of the results of study A

–137 dB(W/(m2 ‧ MHz)) θ ≤ 13°

–137 + 3.125 (θ – 13) dB(W/(m2 ‧ MHz)) 13° < θ ≤ 25°

–99.5 + 0.5 (θ – 25) dB(W/(m2 ‧ MHz)) 25° < θ ≤ 50°

–87 dB(W/(m2 ‧ MHz)) 50° < θ ≤ 90°


Note that the pfd level shown above is derived from a maximum interference level of

−147 dB(W/MHz) (i.e. I/N = −10 dB not to be exceeded more than 20% of the time) for the FS

long-term protection criteria. The FS parameters and deployment density are taken from

Recommendations ITU-R F.758 and ITU-R F.2086, respectively. The FS antenna pattern is based

on ITU-R F.1245 and gaseous atmospheric attenuation is considered (Recommendation

ITU-R SF.1395).

Rep. ITU-R F.2475-0 21









compensate for rain attenuation to the extent that the power flux density at the FS station does not

exceed the value resulting from use by HAPS station of an e.i.r.p. meeting the above limits in the

clear sky conditions.

To verify the compliance with the propose pfd mask the following equation should be used:

pfd(θ) = EIRP(θ) – 10log10(4d²)

where:

d : distance between the HAPS and the ground (elevation angle dependent)

: elevation angle in degrees (angle of arrival above the horizontal plane)

EIRP : nominal HAPS e.i.r.p. spectral density in dB(W/MHz) at a specific elevation

angle2.

The impact of the gaseous attenuation in not included in the verification formula since it is already

taken into account in the pfd mask.

In addition, this study shows that the antennas used for both HAPS ground terminals and FS

stations are directional, therefore, the required separation distance between the two systems can be

reduced by appropriate site-configuration. Protection between HAPS ground stations and

conventional FS stations can be managed on a case-by-case basis by coordination amongst

administrations or usual link/planning method and procedures used at national level for

conventional FS stations. Therefore, there may be no need of additional regulatory provisions in the

Radio Regulations for this case.

1.2 Study B

1.2.1 Impact from transmitting HAPS ground station into FS receiving station and

comparison with the impact from transmitting FS station into FS receiving station

HAPS systems is an application that can operate as applications under the FS. The characteristics of

HAPS ground stations are similar to conventional fixed stations. However, HAPS ground stations

normally point at higher elevations than conventional fixed stations. The study below compares:

• the impact of a transmitting HAPS ground station into a conventional fixed service station

with;

• the impact of a transmitting conventional fixed service station into another conventional

fixed service station.


indication to administrations on whether sharing the band between HAPS ground stations and

conventional fixed service stations is more challenging than sharing the band between conventional

fixed service stations.

2 This corresponds to the maximum EIRP at which the system operates under clear sky conditions.

22 Rep. ITU-R F.2475-0

1.2.1.1 Impact from transmitting HAPS ground station into FS receiving station


a single HAPS system 2, system 4a or 4b ground stations (interferer) and FS receiving station

(victim).

Step 1: Compute the HAPS transmitting station antenna gain towards the FS impacted station based

on the following input parameters:

– 0° is taken for the elevation angle towards the FS impacted station;

– 0° is taken for the azimuth angle towards the FS impacted station;

– HAPS ground station antenna pointing azimuth: random variable with a uniform

distribution between –180° to 180°;

– HAPS ground station antenna pointing elevation: random variable with a uniform

distribution between:

– 33.3° and 90° for the HAPS system 2 Gateways.

– 21° and 90° for HAPS system 2 CPE and for System 4a/4b/6 CPE and gateways.

The elevation statistics are shown in Fig. 10.

FIGURE 10

Elevation statistics

– HAPS ground station maximum antenna gain:

– for HAPS system 2: 55 dBi for the GW and 49 dBi for the CPE;

– for HAPS System 6: 56.5 dBi for the GW and 51.4 dBi for the CPE;

– for GW of HAPS Systems 4a and 4b: 57.4 dBi;

– for CPE of HAPS System 4a: 49.8 dBi;

– for CPE of HAPS System 4b: 47.2 dBi and 39.3 dBi.

– HAPS antenna patterns:

– for System 2 and System 6: ITU-R F.1245-2;

– for Systems 4a and 4b: ITU-R S.580-6.

Step 2: Compute the FS impacted station antenna gain towards the HAPS system 2 transmitting

station based on the following input parameters:

– 0° is taken for the elevation angle towards the HAPS station;

– 180° is taken for the azimuth towards the HAPS station;

Rep. ITU-R F.2475-0 23

– FS station antenna pointing azimuth: random variable with a uniform distribution between -

180° to 180°;


-0.004° and standard deviation 3.6°);

– FS maximum antenna gain: random variable with a uniform distribution between 34 and

46 dBi;

– FS antenna pattern: ITU-R F.1245.

Step 3: Compute the propagation loss needed to meet the FS protection criteria:

𝐼𝑚𝑎𝑥 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐻𝐴𝑃𝑆 − 𝐺𝑚𝑎𝑥𝐻𝐴𝑃𝑆+ 𝐺𝐻𝐴𝑃𝑆→𝐹𝑆 − 𝐴𝑡𝑡𝑃−452−16 + 𝐺𝑟𝐹𝑆

𝐴𝑡𝑡𝑃−452−16 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐻𝐴𝑃𝑆 − 𝐺𝑚𝑎𝑥𝐻𝐴𝑃𝑆+ 𝐺𝐻𝐴𝑃𝑆→𝐹𝑆 + 𝐺𝑟𝐹𝑆 − 𝐼𝑚𝑎𝑥

where:

EIRPmaxHAPS : HAPS ground station maximum e.i.r.p. density (in the main beam)

(dB(W/MHz)) as given Table 9.

TABLE 9

HAPS ground station maximum e.i.r.p. density

ddB(W/MHz) GW CPE

Clear sky Raining condition Clear sky Raining condition

System 2 –1.8 33.2 9.2 33.5

System 4a 11 26

15 30

System 4b 19.5 / 14.5 35.5 / 26.5

System 6 –2 33 5 30.3

GmaxHAPS : maximum HAPS ground station antenna gain (dBi)

GHAPS→FS : transmitting HAPS ground station antenna gain towards the FS impacted

station (dBi)

GrFS : FS impacted station antenna gain towards the FS transmitted station (dBi)

AttP-452-16 : propagation loss (dB) needed to meet the FS protection criteria based on

P.452-16 propagation model with p = 20% when Imax/N = –10 dB and



Imax : FS maximum allowable interference level (dB(W/MHz)): –147 dB(W/MHz)

(I/N of –10 dB) not to be exceeded by more than 20% of the time and

−127 dB(W/MHz) (I/N of 10 dB) not to be exceeded by more than 0.01% of

the time.

Step 4: Compute the separation distance needed to meet the FS protection criteria based on the

P.452 propagation model.


stable CDF.

1.2.1.2 Impact from transmitting FS station into FS receiving station


a single FS station (interferer) and FS ground (victim).

24 Rep. ITU-R F.2475-0

Step 1: Compute the FS transmitting station antenna gain towards the FS impacted station based on


– 0° is taken for the elevation angle towards the FS impacted station;

– 0° is taken for the azimuth towards the FS impacted station;


−180° to 180°;


−0.004° and standard deviation 3.6°);


46 dBi;

– FS antenna pattern: ITU-R F.1245-2.

Step 2: Compute the FS impacted station antenna gain towards the FS transmitting station based on





180° to 180°;

– FS station antenna pointing elevation: random variable with a normal distribution (median -

0.004° and standard deviation 3.6°);


46 dBi;



𝐼𝑚𝑎𝑥 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐹𝑆 − 𝐺𝑚𝑎𝑥𝐹𝑆+ 𝐺𝐹𝑆→𝐹𝑆 − 𝐴𝑡𝑡𝑃−452−16 + 𝐺𝑟𝐹𝑆

𝐴𝑡𝑡𝑃−452−16 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐹𝑆 − 𝐺𝑚𝑎𝑥𝐹𝑆+ 𝐺𝐹𝑆→𝐹𝑆 + 𝐺𝑟𝐹𝑆 − 𝐼𝑚𝑎𝑥

where:

EIRPmaxFS : FS station maximum e.i.r.p. density (in the main beam) (dB(W/MHz)): random

variable with a uniform distribution between –15.7 and 17 dB(W/MHz)

GmaxFS : maximum FS station antenna gain

GFS→FS : FS transmitting station antenna gain towards the FS impacted station (dBi)

GrFS : FS impacted station antenna gain towards the FS transmitting station (dBi)

AttP-452-16 : propagation loss needed to meet the FS protection criteria (dB) based on




Imax : maximum allowable interference level: –147 dB(W/MHz) (I/N of –10 dB) not

to be exceeded by more than 20% of the time and –127 dB(W/MHz) (I/N of

10 dB) not to be exceeded by more than 0.01% of the time.

Step 4: Compute the separation distance needed to meet the FS protection criteria based on the

P.452-16 propagation model.


stable CDF.

Rep. ITU-R F.2475-0 25

1.2.1.3 Results


FIGURE 11

Results for the long and short term protection criteria

SYSTEM 6, p=20%

From the above results it can be concluded that HAPS ground stations can be considered as any FS

station as the result of the impact of HAPS ground station emissions into FS station receivers is less

than the impact of an FS emitting station into another FS receiving station.

26 Rep. ITU-R F.2475-0

1.2.1.4 Interference mitigation techniques

In some cases, mitigation techniques could be considered to ease coordination and sharing

feasibility, such as:

− careful positioning of HAPS ground terminals and with respect to incumbent systems;

− when required and feasible, site shielding could be applied to the HAPS GW to reduce side

lobe radiation, while maintaining system performance.

1.2.2 Impact from transmitting FS stations into receiving HAPS

The aim of the study is to assess the aggregate impact of FS station emission into HAPS system 2

receivers. The following steps are performed for this assessment:

Step 1: The HAPS is arbitrarily located at longitude 0° and latitude 0° and 20 km altitude;

Step 2: N FS emitting station are located randomly in the HAPS visibility area (up to the HAPS

horizon);

Step 3: The HAPS ground station (CPE or gateways) is randomly located in the HAPS coverage

area with a uniform distribution in surface. The direction between the HAPS and the HAPS ground

determine the HAPS main beam direction. Figure 12 provides an example of the steps 1 to 3 result

with N=10 000.

FIGURE 12

First 3 steps

Step 4: The HAPS antenna gains towards each of the N FS station are computed based on the

following input parameters:

• HAPS maximum antenna gain of 29 dBi for the CPE beam and 39.3 dBi for the GW beam;

• HAPS station antenna type: beam forming for the CPE beam and dish for the GW beam.

Figure 13 provides examples (gateway beam right and CPE beam left).

Rep. ITU-R F.2475-0 27

FIGURE 13

Step 4 example

Step 5: The FS stations antenna gains towards the HAPS are computed based on the following input

parameters:

• FS station maximum antenna gain: random variable with a uniform distribution between 34

and 46 dBi.

• FS station antenna pointing elevation: random variable with a normal distribution (median -

0.004° and standard deviation 3.6°).

Figure 14 provides an example.

FIGURE 14

Step 5 examples

Step 6: The total free space loss plus the atmospheric loss (from Recommendation ITU-R SF.1395

middle latitude) are computed;

28 Rep. ITU-R F.2475-0

FIGURE 15

Step 6 computation

Step 7: The interference level produced by each FS transmitting station is computed using the

following equation:

𝐼𝑛 = 𝐸𝐼𝑅𝑃𝑛 − 𝐴𝑡𝑡𝑛 + 𝐺𝑟𝑛

where:

EIRPn: e.i.r.p. density of FS station with index n towards the HAPS in: random

variable with a uniform distribution between –15.7 and 17 dB(W/MHz)

Attn: the free space loss plus the atmospheric loss (from Recommendation

ITU-R SF.1395) in dB.

FIGURE 16

Step 7 computation

Step 8: The aggregate interference is computed based on the following equation and stored:

𝐼𝑎𝑔𝑔 = 10 ∗ 𝑙𝑜𝑔10 (∑ 10𝐼𝑛10

𝑁

𝑛=1

)

Step 9: Redo Step 1 to 8 sufficiently to obtain a stable cumulative distribution function of the

aggregate interference.

Rep. ITU-R F.2475-0 29

Figure 17 provides the results for N equal to 10 000 FS stations in the HAPS visibility area which is

assumed to be realistic (gateway beams right and CPE beam left).

FIGURE 17

Aggregate interference cumulative distribution functions

The HAPS gateway beam station short term protection criteria is never exceeded. The long term is

exceeded for less than 1 over 900 deployments scenarios in the case of HAPS gateway beam and

less than 1 over 2000 deployments scenarios in case of HAPS CPE beam.

It should be noted that HAPS should operate in areas where the density of FS station should be

much less than the one used in the study.

2 Summary and analysis of the results of studies

Impact from transmitting HAPS into FS receiving stations

One study has shown that the following pfd mask in dB(W/(m2 · MHz)), to be applied under clear

sky conditions at the surface of the Earth, ensures the protection of the Fixed Service by meeting its

long term protection criteria:

–137 dB(W/(m2 · MHz)) θ ≤ 13°

–137 + 3.125 (θ dB(W/(m2 · MHz)) 13° < θ≤ 25°

–99.5 + 0.5 (θ dB(W/(m2 · MHz)) 25° < θ ≤ 50°

–87 dB(W/(m2 · MHz)) 50° < θ ≤ 90°

where θ is the elevation angle in degrees (angle of arrival above the horizontal plane).

Note that the pfd level shown above is derived from on a maximum interference level of

−147 dB(W/MHz) (i.e. I/N = –10 dB not to be exceeded more than 20% of the time) for the FS

long-term protection criteria. The FS parameters and deployment density are taken from

Recommendations ITU-R F.758 and ITU-R F.2086, respectively. Note that gaseous atmospheric

attenuation was taken into account (Recommendation ITU-R SF.1395).






30 Rep. ITU-R F.2475-0




compensate for rain attenuation to the extent that the power flux density at the FS station does not



To verify that the pfd produced by HAPS does not exceed the proposed pfd mask, the following

equation was used:

𝑝𝑓𝑑(θ) = 𝐸𝐼𝑅𝑃(θ) + 10𝑙𝑜𝑔10(4π𝑑²(θ))

where:

d : distance between the HAPS and the FS station (m) – function of the elevation

angle

EIRP : nominal HAPS e.i.r.p. spectral density in at a specific elevation angle

(dB(W/MHz)). The impact of the gas attenuation in not included in the

verification formula since it is already taken into account in the pfd mask.

Impact from transmitting HAPS ground stations into FS stations receiving stations

The studies show that the antennas used for both HAPS ground terminals and FS stations are

directional, therefore, the required separation distance between the two systems can be reduced by

appropriate site-configuration. Protection between HAPS ground stations and conventional FS

stations can be managed on a case-by-case basis by coordination amongst administrations or usual

link/planning method and procedures used at national level for conventional FS stations.

Impact from transmitting FS stations towards HAPS receiving ground stations

One study show that the antennas used for both HAPS ground terminals and FS stations are

directional, therefore, the required separation distance between the two systems can be reduced by

appropriate site-configuration. Protection between HAPS ground stations and conventional FS

stations can be managed on a case-by-case basis by coordination amongst administrations or usual

link/planning method and procedures used at national level for conventional FS stations.

Impact from transmitting FS stations into receiving HAPS

One study shows that the HAPS gateway beam station short term protection criteria (I/N = +10 dB)

is never exceeded. The long term (I/N = –10 dB) is exceeded for less than 1 over 900 deployments

scenarios in the case of HAPS gateway beam and less than 1 over 2000 deployments scenarios in

case of HAPS CPE beam.

Rep. ITU-R F.2475-0 31

Annex 2

Sharing and compatibility of Mobile service and HAPS systems operating



TABLE 10

Summary of scenarios considered in study A, B, C, D and E

MS

Study A Study B Study C Study D Study E

HAPS ground station to BS X X X X

HAPS ground station to UT X X X X

HAPS to BS X X X X

HAPS to UT X X X X

BS to HAPS ground station X X X

UT to HAPS ground station X X X

BS to HAPS X X

UT to HAPS X X

TABLE 11

Attenuation/assumption considered in studies

Study A

Ground to HAPS HAPS to Ground Comments

Polarisation loss 3 dB 3 dB Source: Relevant group

Body loss (UT) 4 dB 4 dB Source: Relevant group

Ohmic loss (UE, BS) No (0 dB) No (0 dB)

Gaseous attenuation Rec. ITU-R P.452 Rec. ITU-R SF.1395

Propagation model Rec. ITU-R P.452 Rec. ITU-R P.525

(FSL)

20% of time and 0.01% of time for

Rec. ITU-R P.452

Clutter loss Rec. ITU-R P.2108 Values depends on the random

samples following the distribution in

the document.

Apportionment None None

Aggregate HAPS

consideration

No (single-entry,

statistical)

Yes (81 HAPS,

including all beams,

with an IHD of

100 km)

Aggregate of multiple co-frequency

beams in the verification of the

compliance was considered.

IMT deployment considered N/A N/A UE/BS considered under free space

without additional impact from

environment

HAPS system System 2 and 6 System 4a

Distribution of the UE and

BS Pointing

Rayleigh distribution

32 Rep. ITU-R F.2475-0

TABLE 11 (continued)

Study B


Polarisation loss 3

Body loss (UE) 4

Ohmic loss (UE, BS) No (0dB)

Gaseous attenuation Rec. ITU-R P.452

Propagation model Rec. ITU-R P.452

Clutter loss Rec. ITU-R F.2108

(1% location)

Apportionment No

Aggregate HAPS

consideration

No (single-entry,

statistical)

IMT deployment considered outdoor suburban

hotspot

HAPS system System 6

Main beam consideration Statistical analysis

randomising

pointing

For MCL analysis, both systems

pointing towards each other in

azimuth

For Monte Carlo analysis, the

azimuth is randomized between

0-360 degrees.

Study C

Polarisation loss No No

Body loss (UE) No No

Ohmic loss (UE, BS) No (0 dB) No (0 dB)

Gaseous attenuation Rec. ITU-R P.452 No

Propagation model Rec. ITU-R P.452 Rec. ITU-R P.525

(FSL)

Clutter loss No No

Apportionment No No

Aggregate HAPS

consideration

No Yes

IMT deployment considered outdoor suburban

hotspot

outdoor suburban

hotspot

HAPS system System 5 System 5

Main beam consideration For MCL analysis, both systems

pointing towards each other in

azimuth

For Monte Carlo analysis, the

azimuth is randomized between

0-360 degrees.

Rep. ITU-R F.2475-0 33

TABLE 11 (end)

Study D


Polarisation loss 3 dB Not included in proposed pfd mask

but in the compliance

Body loss (UE) 4 dB Not included in proposed pfd mask

but in the compliance

Ohmic loss (UE, BS) No (0 dB)


Propagation model Rec. ITU-R P.525

(FSL)

Clutter loss No

Apportionment 3 dB Not included in proposed pfd mask

Aggregate HAPS

consideration

No The number of co-frequency beams

aggregated is based on the

characteristics of each HAPS systems

IMT deployment considered

HAPS system


BS Pointing

Uniform distribution

(pfd mask

calculation)

Study E

Polarisation loss 3 dB Not considered in the pfd mask but

only in the compliance analysis -

Source: Relevant group

Body loss (UE) 4 dB Not considered in the pfd mask but

only in the compliance analysis -


Ohmic loss (UE, BS) 3 dB Taken into account in the pfd mask

and not in the compliance analysis -



Propagation model Rec. ITU-R P.452 1% of time assumed

Clutter loss Rec. ITU-R P.2108 Values depends on the random

samples following the distribution in

the document. Percentage of location

between 0 and 100 %.

Apportionment None

Aggregate HAPS

consideration

No (single HAPS

transmitter)

IMT deployment considered Full IMT-2020

ubiquitous

deployment within

the HAPS coverage

HAPS system System 6


BS Pointing

(From relevant

group

Rayleigh distribution

34 Rep. ITU-R F.2475-0

1.1 Study A

1.1.1 Sharing in the ground-to-HAPS direction

HAPS systems can operate as applications under the FS. The characteristics of HAPS ground

stations are similar to conventional fixed stations. However, HAPS ground stations normally point

at higher elevations than conventional fixed stations. The study below compares:

• the impact of a transmitting conventional fixed service station into a station of the Mobile

Service with;

• the impact of a transmitting HAPS ground station into the same station of the Mobile

Service.


indication to administrations on whether sharing the band between a single HAPS ground station

and a single mobile service station is more challenging than sharing the band between a single

conventional fixed service station and a single mobile service station. However, Mobile Service

deployment is expected to be based on a cluster of multiple base stations.

1.1.1.1 Methodology – HAPS ground station into MS receiving station

TABLE 12

Recap of IMT-2020 characteristics

Parameter IMT-2020 (Base station) IMT-2020 (UE)

Receiver characteristics

Noise figure (dB) 12 12

Protection criteria (I/N) (dB) –6 –6

Max interference in dBW (ddB(W/MHz)) –138 –138

Maximum composite antenna gain (dBi) 26 17

Mechanical downtilt (degree) 10 See distribution below

Body loss (dB) N/A 4

Clutter model ITU-R P.2108 with a randomized % of location between 1 and 100

Antenna pattern ITU-R M.2101

Deployment scenario Outdoor suburban hotspot


a single HAPS station (interferer) and MS ground (victim).

Step 1: Compute the HAPS transmitting ground station antenna gain towards the MS impacted


– 0° is taken for the elevation angle towards the MS impacted station;

– 0° is taken for the azimuth towards the MS impacted station;



– HAPS station antenna pointing elevation: see table below for the assumed elevation

distribution for HAPS gateways (GW) and CPEs for each system.

Rep. ITU-R F.2475-0 35

TABLE 13

Assumed elevation

HAPS system 2 HAPS system 6

GW

Random variable with uniform

distribution between 33.3 and

90 degrees:


distribution between 21 and

90 degrees:

CPE



90 degrees:



90 degrees:

– HAPS ground station maximum antenna gain (from HAPS system 2): see table below for

the assumed maximum gains for HAPS gateways (GW) and CPEs for each system.

TABLE 14

HAPS ground station maximum gain

HAPS system 2 HAPS system 6

GW (dBi) 55 56.5

CPE (dBi) 49 51.4

– HAPS antenna pattern: ITU-R F.1245-2

Step 2: Compute the MS impacted station antenna gain towards the HAPS transmitting ground


– 0° is taken for the elevation angle towards the HAPS ground station;

– 180° is taken for the azimuth towards the HAPS ground station;

– MS station antenna mechanical tilt in azimuth: random variable with a uniform distribution


– MS station antenna mechanical tilt in elevation: 10° for BS and random variable with a

uniform distribution between –90° and 90° for UE;

36 Rep. ITU-R F.2475-0

– MS station beam pointing azimuth compare to the panel azimuth (azimuth electrical tilt):

for the BS and UE a random variable with a normal distribution N(0°, 30°) with cutting off

at ±60° angular sector;

FIGURE 18

Step 2 computation

– MS station beam pointing elevation (combination of mechanical downtilt and electrical

elevation tilt) is based on UE distance from the BS that is a random variable with a

Rayleigh distribution (σ = 32).

FIGURE 19

Elevation computation

– MS maximum antenna gain: 17 dBi for the UE and 26 dBi for the BS;

– MS antenna pattern: ITU-R M.2101;

Step 3: Compute the propagation loss needed to meet the MS protection criteria

𝐼𝑚𝑎𝑥 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐻𝐴𝑃𝑆 − 𝐺𝑚𝑎𝑥𝐻𝐴𝑃𝑆+ 𝐺𝐻𝐴𝑃𝑆→𝑀𝑆 − 𝐴𝑡𝑡𝑃−452−16(𝑑) − 𝐴𝑡𝑡𝐶𝑙𝑢𝑡𝑡𝑒𝑟(𝑑) + 𝐺𝑟𝑀𝑆

𝐴𝑡𝑡𝑃−452−16(𝑑) + 𝐴𝑡𝑡𝐶𝑙𝑢𝑡𝑡𝑒𝑟(𝑑) = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐻𝐴𝑃𝑆 − 𝐺𝑚𝑎𝑥𝐻𝐴𝑃𝑆+ 𝐺𝐻𝐴𝑃𝑆→𝑀𝑆 + 𝐺𝑟𝑀𝑆 − 𝐼𝑚𝑎𝑥

Rep. ITU-R F.2475-0 37

where:

EIRPmaxHAPS : HAPS station maximum e.i.r.p. density (in the main beam):

• For system 2: –1.8 dB(W/MHz) (GW clear sky), 33.2 dB(W/MHz)

(GW raining condition), 9.2 dB(W/MHz) (CPE clear sky) and

33.5 dB(W/MHz) (CPE raining condition)

• For system 6: –2 dB(W/MHz) (GW clear sky) and 33 dB(W/MHz)

(GW raining condition), 9.25 dB(W/MHz) (CPE clear sky) 30.3 dB(W/MHz)

(CPE raining condition)

GmaxHAPS : maximum HAPS ground station antenna gain

GHAPS→MS : HAPS transmitting ground station antenna gain towards the MS impacted

station in dBi

GrMS : MS impacted station antenna gain towards the HAPS transmitting station in

dBi

AttP-452-16 : propagation loss needed to meet the MS protection criteria in dB based on

P.452-16 propagation model and is distance dependant as well as percentage of

time dependant

AttClutter : clutter loss from ITU-R P.2108 which is distance dependant

Imax : maximum allowable interference level: –138 dB(W/MHz )(I/N of –6 dB and a

BS/UE receiver noise figure of 12 dB).

Step 4: Compute AttP-452-16 + AttClutter needed to meet the MS protection criteria based on the

P.452-16 propagation model. The required separation distance cannot be computed as there is no

percentage of time link to the MS protection criteria. In order to assess the impact of p on the

required separation distance, p = 20% and p = 0.01% are used.

Step 5: Store the calculated AttP-452-16 and repeat steps 1 through 4 sufficiently to obtain a stable

CDF.

1.1.1.2 Methodology - FS into MS receiving station


a single FS (interferer) stations and an IMT-2020 equipment (victim).

Step 1: Compute the IMT-2020 antenna gain towards the FS: This is done following the same

methodology as the one described in Step 1 of the previous section.

Step 2: Compute the FS antenna gain towards the IMT-2020 station based on the following input

parameters:


-180° to 180°;


-0.004° and standard deviation 3.6° based on Recommendation ITU-R F.2086-0), see

Table 2;


and 46 dBi;


Step 3: Compute the minimum separation distance needed to meet the IMT-2020 protection criteria:


−15.7 dB(W/MHz) and 17 dB(W/MHz);

– Propagation model used: P.452 with a percentage of time of p = 20% and p = 0.01%;

38 Rep. ITU-R F.2475-0

– Statistical clutter loss model: ITU-R P.2108 with a percentage of location randomly

distributed between 1 and 100%.


stable CDF

1.1.1.3 Results

For HAPS system 2, the plots in Fig. 20 present the separation distance CDF for the impact of

HAPS GW and HAPS CPE into MS BS or MS UE. This Figure provides results for respectively for

p = 0.01% and p = 20%.

FIGURE 20

Results for p = 0.01% and p = 20%

System 2

System 6

From the above results it can be concluded that HAPS ground stations can share with MS stations

(BS and UE) as the maximum required separation distance is less than 160 m for p = 20% (clear sky

condition) and 4 km for p = 0.01% (raining condition).

From the above Figure, it can be concluded that the impact of HAPS ground station emissions on

IMT-2020 deployment is less than the impact of typical FS deployment operating in the band.


In some cases, mitigation techniques could be considered to ease coordination and sharing

feasibility, such as:

Rep. ITU-R F.2475-0 39

– careful positioning of HAPS ground terminals and with respect to incumbent systems;

– when required and feasible, site shielding could be applied to the HAPS GW to reduce side

lobe radiation, while maintaining system performance.

1.1.2 Sharing in the HAPS-to-ground direction


protect MS stations receivers.

1.1.2.1 Impact from transmitting HAPS into MS receiving station


protect MS stations receivers.

1.1.2.2 Impact from a single transmitting HAPS into MS receiving station


account the impact of a single HAPS emission:


– 0° is taken for the elevation angle at the MS station towards the HAPS;

– 0° is taken for the azimuth angle at the MS station towards the HAPS;

Step 1: Compute and store the maximum possible HAPS pfd level at the MS station using the

following equation:

𝑝𝑓𝑑𝑚𝑎𝑥(θ) = 𝐼𝑚𝑎𝑥 + 10 × log10 (4π

λ2) − 𝐺𝑀𝑆(θ𝑚, θ𝑒 , θ𝛿) + 𝐿𝑝𝑜𝑙 + 𝐿𝑏𝑜𝑑𝑦+𝐴𝑡𝑡𝑔𝑎𝑧(θ)

where:

θ elevation angle in degrees (angle of arrival above the horizontal plane)

Imax: maximum interference level (–138 dB(W/MHz))

m: mechanical tilt of mobile service (10°)

e: electronic tilt of mobile service (degree)

: elevation angle toward the HAPS (degree)

GMS(m, e, ): MS station (BS,UE) antenna gain toward the HAPS taking into account all

possible e (dBi)

Lpol: polarization loss (3 dB)

Lbody: body loss in dB (0 dB for BS and 4 dB for UE)

Attgas(θ): atmospheric attenuation for the link (Recommendation ITU-R SF.1395) which

is dependent to the elevation angle θ (dB).

Step 2: Redo step 1 sufficiently to obtain a stable pfd CDF curve and store it.

Step 3: Redo steps 1 to 2 with an increased MS elevation angle towards the HAPS of 0.1°.

Step 4: Redo steps 1 to 3 until the elevation angle towards the HAPS is 90°.

Figure 21 provides the results of the maximum pfd level to meet the MS protection criteria as well

as a proposed pfd mask in dB(W/(m2 · MHz)) that should not be exceeded to protect MS service.

40 Rep. ITU-R F.2475-0

FIGURE 21

Maximum pfd level to meet the MS protection criteria and proposed pfd mask

The resulting pfd mask equation:

–102 dB(W/(m² · MHz)) θ ≤ 5°

–102 + 0.25 (θ dB(W/(m² · MHz)) 5° < θ ≤ 25°

–97 dB(W/(m² · MHz)) 25° < θ ≤ 90°



Approach 1: To compensate for additional propagation impairments in the main beam of the HAPS

due to rain, the pfd mask can be increased in the corresponding beam by a value equivalent to the

level of rain fading.


compensate for rain attenuation to the extent that the power flux density at the MS station does not



Since the above pfd mask has been developed taking into account attenuation due to atmospheric

gases, compliance verification of a HAPS system with this mask should be conducted using the free

space propagation model.

Furthermore, for the purpose of when field measurements are required for a deployed HAPS

system, administrations may therefore use the pfd levels provided below could be considered. These

additional pfd levels, in dB(W/(m2 · MHz)), do not take into account any attenuation due to

atmospheric gases and are only provided for measurement purposes. This material is provided for

information in this section.

–102 – 14.44 / (1 + 0.7365 θ + 0.01542 θ2) for θ ≤ 5°

–102 + 0.25 (θ – 5) – 14.44 / (1 + 0.7365 θ + 0.01542 θ2) for 5° < θ ≤ 25°

–97 – 14.44 / (1 + 0.7365 θ + 0.01542 θ2) for 25° < θ ≤ 90°


Rep. ITU-R F.2475-0 41

1.1.2.3 Aggregate impact from transmitting HAPS into MS receiving stations

The following steps have been performed to define if the aggregate impact of several HAPS in

visibility from the MS station is close to the one from a single HAPS emission.

Step 1: locate N HAPS distributed on a grid over the spherical cap visible from the MS station

(see Fig. 22 below). The grid position versus MS location is randomly selected.

FIGURE 22

HAPS on a spherical cap

where

h : HAPS altitude (20 km)

Radius_sph : Earth radius plus 20 km

Radius_cap : distance between the HAPS and the MS when the HAPS is seen from the MS

station with an elevation angle of 0°.

Step 2: compute, for each HAPS from step 1, the angle between the horizontal plane at the MS

station location and the vector from the MS station location toward the HAPS (θ: angle of arrival

above the horizontal plane).

Step 3: based on step 2 and the pfd mask, compute for each HAPS the maximum pfd level produced

at the MS station location.

Step 4: compute the MS antenna gain towards the HAPS based on the following input parameters:

– the elevation angle towards the HAPS from Step 2;

– azimuth 0° is taken for the azimuth towards the HAPS;

– MS station antenna pointing azimuth: random variable with a uniform distribution between

–180° to 180°;

– MS BS mechanical downtilt 10°;

– MS station antenna pointing elevation: based on the deployment of MS with respect to a

BS;

– MS maximum antenna gain: base station: 8 × 16, mobile station: 4 × 4.

Step 5: compute and store the level of aggregate interference in dB(W/MHz) produced by all HAPS

at the MS receiver input using the following equation:

42 Rep. ITU-R F.2475-0

𝐼𝑀𝑁⁄ = 10 ∗ 𝑙𝑜𝑔10 (∑ 10

pfd𝑛+10×log10(λ2

4π)+𝐺𝑟𝑛(ϕ𝑛)−𝐴𝑡𝑡𝑛𝑔𝑎𝑧(θ𝑛)

10

𝑁

𝑛=1

) − 𝑁

where:

n: index of the HAPS

ϕn: angle between the vector MS to HAPSn and MS antenna main beam pointing

vector (degree)

θn: elevation angle of the HAPSn as seen from MS station (degree)

IM: aggregate interference level produced by N HAPS for a certain HAPS

configuration M (dB(W/MHz))

Grn: MS antenna gain towards the HAPS with the index n

pfdn: pfd based on free space produced at the MS station location by the HAPS with

index n (dB(W/(m2 ‧ MHz))

Attngas: atmospheric attenuation for the link with index n (Recommendation

ITU-R SF.1395) which is dependent to the elevation angle θn (degree)

N: MS receiver noise level (–138 dB(W/MHz)).

Step 6: redo steps 1 to 5 sufficiently to obtain a stable I cumulative distribution function curve and

store it.

In the following, results are given with an IHD of 100 km. This value means that from any point of

the Earth, a maximum of 81 HAPS is possibly visible with an elevation angle higher than 0°. This is

considered as a worst-case scenario as such a HAPS density would represent around 67 HAPS

operating at the maximum pfd over a territory having the same surface than France, which is a

huge, unrealistic number.

FIGURE 23

Aggregate I/N at MS BS and UE in dB

Rep. ITU-R F.2475-0 43

1.1.2.4 Compliance with proposed pfd mask

In Fig. 24, the above proposed HAPS pfd mask to protect MS receivers is compared with System 4a

nominal pfd level versus elevation (clear sky conditions). As shown in the Figure below, System 4a

pfd meets the proposed pfd mask. It is therefore possible to design a HAPS system that meets the

proposed pfd mask and thus protect MS receivers.

FIGURE 24

HAPS systems 4a compliance with the proposed pfd mask

1.1.3 Impact from transmitting MS station into receiving HAPS ground stations



at higher elevations than conventional fixed stations. The study below compares:

• the impact of a transmitting Mobile Service station into a conventional FS station with;

• the impact of a transmitting Mobile Service station into a HAPS ground station.




conventional fixed service station and a single mobile service station. However Mobile Service

deployment is expected to be based on a cluster of multiple base stations.

1.1.3.1 Impact from transmitting MS station into receiving HAPS ground stations


a single MS station (interferer) and HAPS ground station (victim).


– 0° is taken for the elevation angle at the MS BS station towards the HAPS;

– 0° is taken for the azimuth mechanical angle at the MS BS station towards the HAPS;

– 0° is taken for the elevation angle towards the MS;

– 180° is taken for the azimuth towards the MS.

Step 1: Compute the MS antenna gain towards the HAPS ground station and the MS maximum

e.i.r.p. density based on the following input parameters:

– MS BS station antenna pointing azimuth: random variable with a uniform distribution


44 Rep. ITU-R F.2475-0

– MS BS station antenna pointing mechanical elevation: –10°;

– Consider MS UE stations deployed according to the relevant group;

– Calculate electronical azimuth and elevation of the MS BS towards each MS UE;

– Calculate electronical azimuth and elevation of the MS UE towards each MS BS;

– Calculate the gain of each MS UE/BS towards the HAPS;

– BS conducted power: 8 dBm/200 MHz;

– MS conducted power: 10 dBm.

Step 2: Compute the HAPS ground station antenna gain towards the MS based on the following

input parameters:



– HAPS ground station maximum antenna gain (from System 4a characteristics): 49.8 dBi;

– HAPS ground station antenna pointing elevation: random variable with a distribution

between 21 and 90 degrees that is shown in Fig. 25.

FIGURE 25

Statistics of HAPS CPE antenna pointing elevation


𝐴𝑡𝑡𝑃.452−16 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝑀𝑆 − 𝐺𝑚𝑎𝑥𝑀𝑆+ 𝐺𝑀𝑆→𝐻𝐴𝑃𝑆𝐺𝑆


where:

EIRPmaxMS : MS station maximum e.i.r.p. density (in the main beam) (dB(W/MHz))

GmaxMS : maximum MS station antenna gain (dBi)

𝐺𝑀𝑆→𝐻𝐴𝑃𝑆𝐺𝑆: MS station antenna gain towards the HAPS ground station (dBi)

GrHAPS: HAPS ground station antenna gain towards the MS station (dBi)

(GrHAPSmax = 49.8 dBi for HAPS system 4a)

Imax : HAPS ground station maximum allowable interference level (dB(W/MHz)).

For HAPS system 4a:

–156 dB(W/MHz) (I/N of –10 dB) that should not be exceeded by more than

20% of the time and

–136 dB(W/MHz )(I/N of +10 dB) that should not be exceeded by more than

0.01% of the time

Rep. ITU-R F.2475-0 45

AttP.452-16 : propagation loss (dB) needed to meet the HAPS protection criteria based on

P.452-16 propagation model with p=20% when Imax/N = –10 dB and p = 0.01%

when Imax/N = 10 dB. The land path type is used, the typical temperature is

taken at 20°, the pressure at 1013 mbar and no clutter.


stable CDF.

1.1.3.2 Impact from transmitting MS stations into receiving FS stations


a single MS station (interferer) and FS station (victim).


– 0° is taken for the elevation angle at the MS BS station towards the FS;

– 0° is taken for the azimuth mechanical angle at the MS BS station towards the FS;

– 0° is taken for the elevation angle towards the MS;

– 180° is taken for the azimuth towards the MS.

Step 1: Compute the MS antenna gain towards the FS and the MS maximum e.i.r.p. density based

on the following input parameters:

– MS BS station antenna pointing azimuth: random variable with a uniform distribution


– MS BS station antenna pointing mechanical elevation: –10°;

– Consider MS UE stations deployed according to the relevant group;

– Calculate electronical azimuth and elevation of the MS BS towards each MS UE;

– Calculate electronical azimuth and elevation of the MS UE towards each MS BS;

– Calculate the gain of each MS UE/BS towards the FS;

– BS conducted power: 8 dBm/200 MHz;

– MS conducted power: 10 dBm.

Step 2: Compute the FS impacted station antenna gain towards the MS transmitting station based on


– 0° is taken for the elevation angle towards the MS transmitting station;

– 180° is taken for the azimuth towards the MS transmitting station;

– FS impacted station antenna pointing azimuth: random variable with a uniform distribution



-0.004° and standard deviation 3.6° based on Recommendation ITU-R F.2086-0), see

Table 2;


and 46 dBi.


𝐴𝑡𝑡𝑃.452−16 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝑀𝑆 − 𝐺𝑚𝑎𝑥𝑀𝑆+ 𝐺𝑀𝑆→𝐻𝐴𝑃𝑆𝐺𝑆


where:

EIRPmaxMS : MS station maximum e.i.r.p. density (in the main beam) (dB(W/MHz))

GmaxMS : maximum MS station antenna gain (dBi)

46 Rep. ITU-R F.2475-0

𝐺𝑀𝑆→𝐹𝑆 : MS station antenna gain towards the FS station (dBi)

GrFS : FS station antenna gain towards the MS station (dBi)

Imax : FS maximum allowable interference level (dB(W/MHz)):

–146 dB(W/MHz) (I/N of –10 dB) that should not be exceeded by more than

20% of the time and

–126 dB(W/MHz) (I/N of +10 dB) that should not be exceeded by more than

0.01% of the time

AttP.452-16 : propagation loss (dB) needed to meet the MS protection criteria based on



temperature is taken at 20°, the pressure at 1 013 mbar and no clutter.


stable CDF.

1.1.3.3 Results


FIGURE 26

Required separation distances distribution for long term and short term protection criteria

considering MS to HAPS ground stations and MS to FS scenario

From the above results it can be concluded that the short term protection criteria compliance is the

most dimensioning one, and that separation distances between MS and FS systems are higher than

separation distances between MS and HAPS systems. Figure 26 shows also that coordination areas

for the protection of HAPS receiving ground stations will also be significantly smaller that

coordination areas for HAPS receiving stations.

1.1.4 Summary and analysis of study A

HAPS technology can coexist with incumbent MS in the 38 GHz band in case the pfd level

produced at the Earth surface is below the proposed pfd mask. This is the case for HAPS System 4a

emissions for all elevation angles.

Proposed pfd mask in dB(W/(m2 · MHz)) at the Earth surface to protect MS station receivers in the

38-39.5 GHz band, under clear sky conditions:

–102 θ ≤ 5°

–102 + 0.25 (θ – 5) 5° < θ ≤ 25°

–97 25° < θ ≤ 90°

Rep. ITU-R F.2475-0 47


Note that for the pfd level above, polarisation and gaseous atmospheric (ITU-R SF.1395) losses are

considered. In addition, body loss is considered for the user equipment pfd level calculation.







exceed the value resulting from use by HAPS station of an e.i.r.p. density meeting the above limits

in the clear sky conditions.

To verify the compliance with the proposed pfd mask the following equation should be used:

𝑝𝑓𝑑(θ) = 𝐸𝐼𝑅𝑃(θ) − 10log(4π𝑑²)

where:

d : distance between the HAPS and the ground (elevation angle dependent)

EIRP : HAPS nominal e.i.r.p. spectral density in dB(W/MHz) at a specific elevation

angle under clear sky conditions.

The impact of the gaseous attenuation in not included in the verification formula since it is already

taken into account in the pfd mask.

In addition, studies show that HAPS ground stations can be considered as any FS station as the

result of the impact of MS station emissions into HAPS ground station receivers is less or

equivalent than the impact of an MS emitting station into FS receiving station. Therefore, there may

be no need of additional regulatory provisions in the Radio Regulations for this case.

1.2 Study B

1.2.1 Summary

This study investigates the coexistence between HAPS System 6 and MS in a suburban

environment. This study will first present a statistical study. Then various mitigation techniques will

be provided.

In this frequency range, the flowing directions are considered for HAPS.

– HAPS gateway to (UL);

– HAPS CPE to (UL).

1.2.2 Introduction

This band is a candidate band for IMT-2020 under Resolution 238 (WRC-15). This Report includes

the sharing and compatibly study between HAPS system and IMT-2020.

The HAPS parameters (gateway and CPE links) used in this study is from System 6 Report ITU-R

F.2439-0. For HAPS protection criteria, I/N = –6 dB (may exceed 20% of the time) is assumed for

this study.

The IMT-2020 parameters used in this study are based on the parameters provided by the relevant

group. The outdoor suburban hotspot for IMT-2020 (base station and user terminal) was considered,

as HAPS System 6 will not be deployed in urban area. The protection criteria considered for

IMT-2020 is I/N = –6 dB. The following table provides a summary of these characteristics:

48 Rep. ITU-R F.2475-0

TABLE 15

Recap of IMT-2020 characteristics

Parameter IMT-2020 (Base station) IMT-2020 (UE)


Noise figure (dB) 12 12

Protection criteria (I/N) (dB) –6 –6

Max interference in dBW (ddB(W/MHz)) –138 –138

Maximum composite antenna gain (dBi) 23 17

Mechanical downtilt 10 See distribution below

Body loss (dB) N/A 4

Clutter model ITU-R P.2108 with 1% of location

Antenna pattern ITU-R M.2101

Deployment scenario Outdoor suburban hotspot

1.2.3 Methodology and results – HAPS CPE/Gateway to IMT-2020



at higher elevations than conventional fixed stations.

The study below compares the impact of a transmitting conventional fixed service station into a

station of the MS with the impact of a transmitting HAPS ground station into the same station of the

MS.




conventional fixed service station and a single mobile service station. However, MS deployment is

expected to be based on a cluster of multiple base stations.

1.2.3.1 Methodology – HAPS ground station into MS receiving station


a single HAPS ground (interferer) stations and an IMT-2020 equipment (victim).

Step 1: Compute the IMT-2020 antenna gain towards the HAPS GW/CPE based on the following

input parameters:

– 0° is taken for the elevation angle towards the HAPS;

– 0° is taken for the azimuth towards the HAPS;

– IMT-2020 station antenna pointing azimuth: random variable with a uniform distribution


– IMT-2020 station tilt:

• For the IMT-2020 base station: the mechanical downtilt is fixed to 10 degrees.

Figure 27 presents the electrical tilt distribution used for the study.

Rep. ITU-R F.2475-0 49

FIGURE 27

IMT-2020 BS electrical tilt distribution

• For the IMT-2020 user equipment: Figure 28 present the mechanical and electrical tilt

distributions used for the study:

FIGURE 28

IMT-2020 UE mechanical tilt (left figure), and electrical tilt (right figure)

– IMT-2020 station phiscan (equivalent to an electrical tilt in azimuth): random variable with

a distribution presented in Fig. 29:

50 Rep. ITU-R F.2475-0

FIGURE 29

IMT-2020 station phiscan

– IMT-2020 antenna pattern: ITU-R M.2101.

Step 2: Compute the HAPS GW/CPE antenna gain towards the IMT-2020 station based on the


– 0° is taken for the elevation angle towards the IMT-2020 station;

– 180° is taken for the azimuth towards the IMT-2020 station;



– HAPS station antenna pointing elevation: random variable with a uniform distribution

between 20 and 90 degrees;

– HAPS station maximum antenna gain (from System 6 characteristics): 56.5 dBi for the GW

and 51.4 dBi for the CPE (1.2 m antenna).

Step 3: Compute the minimum separation distance needed to meet the FS protection criteria

– HAPS System 6 station nominal e.i.r.p. density: –2 dB(W/MHz) for the GW and

5 dB(W/MHz) for the CPE;

– Propagation model used: ITU-R P.452 with a percentage of time of p = 0.01%;

– Statistical clutter loss model: ITU-R P.2108 with a percentage of location of 1%.

Step 4: Store the calculated separation distance and repeat Steps 1 through 3 for 500 000 iterations

1.2.3.2 Methodology – FS into IMT-2020 receiving station


a single FS (interferer) stations and an IMT-2020 equipment (victim).

Step 1: Compute the IMT-2020 antenna gain towards the FS: This is done following the same

methodology as the one described in Step 1 of the previous section.

Step 2: Compute the FS antenna gain towards the IMT-2020 station based on the following input

parameters:


–180° to 180°;

Rep. ITU-R F.2475-0 51



Table 2;


and 46 dBi;


Step 3: Compute the minimum separation distance needed to meet the IMT-2020 protection criteria


−15.7 dB(W/MHz) and 17 dB(W/MHz);

– Propagation model used: ITU-R P.452 with a percentage of time of p = 20% and

p = 0.01%;

– Statistical clutter loss model: ITU-R P.2108 with a percentage of location of 1%.

Step 4: Store the calculated separation distance and repeat steps 1 through 3 for 500 000 iterations

1.2.3.3 Results

The following plots present the separation distance CDF for a HAPS GW and a HAPS CPE into

IMT-2020 BS.

FIGURE 30

HAPS GW/CPE to IMT-2020 BS, minimum separation distance CDF

The following plots present the separation distance CDF for a HAPS GW and a HAPS CPE into

IMT-2020 UE.

52 Rep. ITU-R F.2475-0

FIGURE 31

HAPS GW/CPE to IMT-2020 UE, minimum separation distance CDF


Additional mitigation techniques can be considered to improve coordination and sharing feasibility,

such as:

– The positioning of HAPS ground terminals and to increase angular separation.

– Site shielding applied to the HAPS GW (up to 30 dB) to reduce side lobe radiation, while

maintaining system performance.

1.2.3.5 Summary of HAPS ground terminal to IMT-2020

A statistical method presenting a minimum separation CDF for the following scenarios:

– HAPS ground terminal (CPE and gateway) to IMT-2020 UE.

– HAPS ground terminal (CPE and gateway) to IMT-2020 BS.

1.2.4 Summary and analysis of the results of study B

HAPS ground into IMT-2020 stations

The statistical analysis shows that the separation distance between a HAPS ground terminal and

IMT-2020 UE is 0 km for less than 1 out of 10 cases to 2 km for 1 out 100 000 cases and the

separation distance between a HAPS ground terminal and an IMT-2020 BS is 0 km for less than

1 out of 10 cases to 5 km for 1 out 100 000 cases for HAPS system 6 in a suburban deployment area

with p = 0.01 for path loss and 1% for clutter loss.

1.3 Study C

1.3.1 Introduction

The IMT-2020 parameters used in this study are based on liaison statement provided by the relevant

group - Technical and operational parameters and deployment characteristics for IMT-2020 for use

in sharing studies under WRC-19 agenda items. The study considers that HAPS will not be

deployed in urban area, so the parameters of outdoor suburban hotspot scenario for IMT-2020 are

used. The protection criteria considered for IMT-2020 system is I/N = –6 dB is I/N = –6 dB for

0.01% of the time.

Rep. ITU-R F.2475-0 53

The HAPS parameters used in this study are from System 5 from Report ITU-R F.2439-0. For

HAPS system, a threshold of I/N = –10 dB is used in this study.

This sharing study adopts Minimum Coupling Loss (MCL) method to analyse the potential

coexistence conditions between HAPS and IMT-2020 systems. The following Figures shows the

two working systems. In Fig. 32 there are four coexistence scenarios, which are, HAPS

CPE/Gateway to IMT-2020 (Scenario 1), HAPS to IMT-2020 (Scenario 2), IMT-2020 to HAPS

CPE/Gateway (Scenario 3), and IMT-2020 to HAPS (Scenario 4).

FIGURE 32

Typical scenario for sharing study: HAPS and IMT-2020 Systems

1.3.2 Methodology – HAPS CPE/Gateway to IMT-2020

The MCL analysis will conclude a separation distance between HAPS and IMT-2020 systems in the

worst case scenario. If the distance between the two systems is greater than the separation distance,

then the two systems will not interfere with each other. However, if the separation distance is less

than the minimum separation distance, HAPS or IMT-2020 may interfere with each other in rare

cases corresponding to the worst situation when the HAPS CPE/Gateway and IMT-2020 receiver

pointing to each other in azimuth and with the worst case elevation angles since the interference

exceeds the required level of the protection criterion.

54 Rep. ITU-R F.2475-0

Single HAPS interference

FIGURE 33

Scenario 1: HAPS CPE/Gateway to IMT-2020

The interference I at MS receiver is determined by the following equation:

I = Ptx + Gtx(α) + Grx(α) – PL – Lrx – Ltx–Lbody–Lclutter

where:

I: Interfering signal power density (dB(W/MHz))

Ptx: HAPS CPE/Gateway maximum transmit power spectral density (dB(W/MHz))

Gtx(α): Antenna gain of HAPS GW/CPE transmitter towards MS receiver (dBi)

Grx(α): Antenna gain of MS receiver towards HAPS GW/CPE transmitter (dBi)

PL: Propagation loss (dB)

Ltx: Feeder loss of HAPS GW/CPE (dB) (assumed 0 dB)

Lrx: Feeder loss of MS (dB)

Lbody: body loss in dB (for IMT-2020 cases, 0 dB for BS and 4 dB for UE)

Lclutter: Clutter loss (dB) (based on ITU-R P.2108)

Lgas: Gas attenuation in dB (based on ITU-R P.2041).

The ratio of the interference power to the receiver thermal noise, I/N, is obtained by the following

equation:

I/N (dB) = I – 10 log(kTB)

where:

k: Boltzmann’s constant = 1.38 × 10–23 (J/K)

T: System noise temperature of MS receiver (K) (Noise figure (12 dB) included

in T)

B: Noise bandwidth = 1 MHz.

In the calculation of the separation distance, path loss is calculated based on Recommendation

ITU-R P.452-16 with time percentage p = 20% and clutter loss is based on Recommendation

Rep. ITU-R F.2475-0 55

ITU-R P.2108. Then according to the protection criteria and the given parameters of HAPS and

IMT-2020 system, the propagation loss for every gateway/CPE elevation angle can be calculated.

So, the separation distance can be calculated for every HAPS CPE/Gateway elevation angle.

In MCL analysis, the worst situation is considered where the separation distance is calculated

between HAPS CPE/Gateway and IMT-2020 receiver pointing to each other in azimuth directly.

1.3.3 Methodology – HAPS Platform to IMT-2020

FIGURE 34

Scenario 2: HAPS Platform to IMT-2020

1.3.3.1 Single HAPS interference

Figure 35 shows the approximation of the curved earth surface.

56 Rep. ITU-R F.2475-0

FIGURE 35

Distance calculation of the curved earth surface

where:

δ : elevation angle from the MS receiver to the HAPS

H : altitude of the HAPS

D : distance from the HAPS to the MS receiver

R : radius of the earth.

First, from the triangle (with the three sides value D, R and H+R) in Fig. 35 above, the total interior

angle sum is 180°, so there will be the follow equation:

Φ + δ + θ + 90° = 180°

With the transposition of the terms of the equation:

θ = 90 − Φ − δ

Then:

𝑆 = 𝑅 · θ (θ is in radians)

Hence:

𝑆 = 𝑅 · (90 − Φ − δ)π

180

Finally, the distance D can be approximated to:

𝐷 = √𝑆2 + 𝐻2

Rep. ITU-R F.2475-0 57

When the distance D between the HAPS and the MS receiver is calculated, the off-axis angles Φ𝑇𝑥

and Φ𝑅𝑥 in Fig. 36 can be determined. Both Φ𝑇𝑥 and Φ𝑅𝑥 are the input parameters of the

calculation of antenna gains.

It is assumed that if the MS receiver is inside the HAPS coverage, the HAPS is pointing directly at

the MS receiver. However, if the MS receiver is outside the HAPS coverage area, the off-axis angle

Φ𝑇𝑥 and Φ𝑅𝑥 between the HAPS’ beam closest to the edge of coverage and the direction to the MS

receiver needs to be calculated.

Figure 36 shows the related parameters in the calculation of the off-axis angles Φ𝑇𝑥 and Φ𝑅𝑥 of the

transmitter and the receiver.

FIGURE 36

HAPS to MS receiver

This Figure also takes into account the effect of the curved earth assumption explained above, the

off-axis angles Φ𝑇𝑥 and Φ𝑅𝑥 can be calculated as follows,

Φ𝑇𝑥 = {0

Φ − γ

where:

Φ𝑇𝑥 : off-axis angle of the HAPS

Φ : angle of HAPS from pointing at the MS receiver to the centre of the coverage

area

γ : angle of HAPS from pointing at the edge of coverage to the centre of the

coverage area.

In the cases where a user terminal (UT) receiver is considered, it was assumed that the UT is

theoretically pointing to the HAPS so the receiver’s off-axis is set to 0. The maximum gain will be

considered for the UT.

Φ𝑅𝑥 = 0 𝑓𝑜𝑟 𝑈𝑇

For the cases where base station receiver is considered, the downtilt angle is taken for the elevation

at which the base station is pointing.

Φ𝑅𝑥 = |δ − 𝐵𝑆𝑑𝑜𝑤𝑛𝑡𝑖𝑙𝑡|

58 Rep. ITU-R F.2475-0

where:

𝐵𝑆𝑑𝑜𝑤𝑛𝑡𝑖𝑙𝑡: is the base station’s downtilt, –10° is used.

Knowing the two off-axis angles, the relative gains can be calculated according to the associated

antenna pattern for the service.

The interfering signal power density, I, at MS receiver is determined by the following equation:

I (dB(W/MHz)) = Ptx – Lf,tx + Gtx(Φ𝑇𝑥) – Ls + Grx(Φ𝑅𝑥) – Lf,rx – Lbody

where:

Ptx: HAPS maximum transmit power density (dB(W/MHz))

Lf,tx: feeder loss of HAPS in the transmit side (dB) (assumed 0 dB)

Gtx(Φ𝑇𝑥): antenna gain of HAPS transmitter towards MS receiver (dBi)

Ls: free space path loss between MS receiver and HAPS (dB) shown in the

following:

Ls = 92.45 + 20 log(fGHz) + 20 log10 (dkm)

dkm: distance between MS receiver and (km)

fGHz: frequency (GHz)

Grx(Φ𝑅𝑥): receive antenna gain of MS receiver towards HAPS (dBi)

Lf,rx: feeder loss of MS receiver in the receive side (dB)

Lbody: body loss in dB (For IMT-2020 cases, 0 dB for BS and 4 dB for UE)

Lgas: gas attenuation in dB (Based on ITU-R P.2041).


equation:


where:

k: Boltzmann’s constant = 1.38 × 10-23 (J/K)

T: System noise temperature of MS receiver (K) Noise figure (12 dB) included

in T)


For studies between IMT-2020 user terminal and HAPS, the user terminal can be oriented in any

given way. For MCL analysis (deterministic), the user terminal is considered to receive with

maximum gain towards the HAPS when the HAPS is seen with an elevation angle below 60°

(see above note and elevation angle distribution).

This methodology is based on a minimum coupling loss (MCL) approach, which calculates the I/N

between HAPS nadir and IMT-2020 receiver where the HAPS is pointing directly towards the

IMT-2020 terminal in azimuth.

In this scenario (HAPS Platform to IMT-2020), there is another expression for the sharing study. It

is the pfd mask expression, the final calculation results are described as the pfd limits which is

dependent to the elevation angle of the system receiver).

1.3.3.2 pfd expression

The pfd level 𝑝𝑓𝑑(δ), at MS receiver is determined by the following equation:

𝑝𝑓𝑑(δ) = 𝐼 + 10 × log (4𝜋

𝜆2) − 𝐺𝑟𝑥(θ𝑚, θ𝑒 , δ) + 𝐿𝑏𝑜𝑑𝑦+𝐿𝑔𝑎𝑠(δ, ℎ) + 𝐿𝑓, 𝑟𝑥

Rep. ITU-R F.2475-0 59

where:

I: maximum interference level

Grx(Φ𝑅𝑥): antenna gain of HAPS transmitter towards MS receiver (dBi)

m: mechanical tilt of IMT-2020 BS (10°)

e : electronic tilt of IMT-2020 BS (degrees)

δ : elevation angle toward the HAPS (degrees)

Lbody: body loss in dB (0 dB for BS and 4 dB for UE)

Lgas(h): atmospheric attenuation for the link which is dependent to the elevation angle

and altitude h (km) (dB)

Lf,rx: feeder loss of MS receiver in the receive side (dB).


equation:

I= I/N (dB) + 10 log (kTB)

where:


T: System noise temperature of MS receiver (K) Noise figure (12 dB) included

in T)


1.3.4 Methodology – IMT-2020 to HAPS CPE/Gateway

Same as methodology in § 1.1.1 above for the HAPS CPE/GW into IMT-2020, the difference is that

the IMT-2020 base stations and terminals become the interferer. Scenario 3 (IMT-2020 to HAPS

CPE/Gateway) is shown in Fig. 37, IMT-2020 base station and user terminal may interfere with

HAPS CPE and Gateway.

FIGURE 37

Scenario 3: IMT-2020 to HAPS CPE/Gateway

60 Rep. ITU-R F.2475-0

1.3.5 Methodology – IMT-2020 to HAPS Platform

Same as methodology in § 1.3.2 above for the HAPS Platform into IMT-2020, the difference is that

the IMT-2020 base stations and terminals become the interferer. Scenario 4 (IMT-2020 to HAPS

Platform) is shown in Fig. 38, IMT-2020 base station and user terminal may interfere with HAPS

Platform in the air.

FIGURE 38

Scenario 4: IMT-2020 to HAPS Platform

1.3.6 Results of studies

1.3.6.1 HAPS CPE/Gateway to IMT-2020

1.3.6.1.1 HAPS gateway to IMT-2020

Figure 39 shows the worst case separation distance (based on MCL) between HAPS System 5

gateway transmitter and IMT-2020 base station receiver. The results presented below are based on

maximum transmit power that will be transmitted during a small percentage of time (during worst

case raining conditions).

Rep. ITU-R F.2475-0 61

FIGURE 39

Worst case separation distance from IMT-2020 BS vs. HAPS GW elevation angle

Figure 39 shows the worst case separation distance (base on MCL) between HAPS gateway

transmitter and IMT-2020 base station receiver. The worst case separation distance is between

0.25 km and 0.42 km.

Figure 40 shows the worst case separation distance (base on MCL) between HAPS gateway

transmitter and user terminal receiver. The results presented below are based on maximum transmit

power that will be transmitted during a small percentage of time (during worst case raining

conditions).

FIGURE 40

Worst case separation distance from IMT-2020 user terminal vs. HAPS GW elevation angle

Figure 40 presents the worst case separation distance (base on MCL) between HAPS gateway

transmitter and IMT-2020 user terminal receiver. The worst case separation distance (i.e. elevation

angle of 20 degrees for the HAPS gateway) is from 0.2 km to 0.27 km. The MCL results presented

above are based on the maximum transmit power that will be transmitted during a small percentage

of time (during worst case raining conditions).

62 Rep. ITU-R F.2475-0

1.3.6.1.2 HAPS CPE to IMT-2020

Figure 41 shows the worst case separation distance (base on MCL) between HAPS CPE transmitter

and base station receiver. The results presented below are based on the maximum transmit power

that will be transmitted during a small percentage of time (during worst case raining conditions).

FIGURE 41

Worst case separation distance from IMT-2020 base station vs. HAPS CPE elevation angle

Figure 41 above presents the worst case separation distance (base on MCL) between HAPS CPE

transmitter and IMT-2020 base station receiver. The worst case separation distance is from 0.2 km

to 0.42 km with different elevation angles.

Figure 42 shows the worst case separation distance (base on MCL) between HAPS CPE transmitter

and user terminal receiver.

FIGURE 42

Worst case separation distance from IMT-2020 user terminal vs. HAPS CPE elevation angle

This Figure presents the worst case separation distance (base on MCL) between HAPS CPE

transmitter and IMT-2020 user terminal receiver. The minimum required separation distance is

from 0.2 km to 0.27 km with different elevation angles. The MCL results presented above are based

on the maximum transmit power that will be transmitted during a small percentage of time (during

worst case raining conditions).

Rep. ITU-R F.2475-0 63

The results above assume that the HAPS CPE is pointing directly towards IMT-2020 receiver in

azimuth. These are based on MCL analysis.

1.3.6.1.3 Summary of HAPS CPE/Gateway to IMT-2020

Results of the MCL analysis

For the gateway uplinks to the HAPS, the studies indicate that worst case separation distance

between the HAPS gateway and the IMT-2020 base station is 0.42 km.

For the gateway uplinks to the HAPS, the studies indicate that worst case separation distance

between the HAPS gateway and the IMT-2020 user terminal is 0.27 km.

For the CPE uplinks to the HAPS, the studies indicate that worst case separation distance between

the HAPS CPE and the IMT-2020 base station is 0.42 km.

For the CPE uplinks to the HAPS, the studies indicate that worst case separation distance between

the HAPS CPE and the IMT-2020 user terminal is 0.27 km.

Conclusion

For the worst case (HAPS CPE/Gateway and IMT-2020 are pointing to each other in azimuth

directly), a minimum separation distance of 0.42 km is required to guarantee IMT-2020 system is

not be interfered by HAPS CPE/Gateway. For the other of cases, the separation distance will be

lower.

1.3.6.2 HAPS to IMT-2020

1.3.6.2.1 HAPS (gateway link) to IMT-2020

Figure 43 shows the calculated I/N for the base station to HAPS nadir (gateway downlink). The

results presented below are based on the maximum transmit power that will be transmitted during a

small percentage of time (during worst case raining conditions).

FIGURE 43

I/N vs. distance of BS to HAPS nadir (GW downlink)

For the base station case in this Figure, the calculated I/N is below IMT-2020 threshold for

I/N = −6 dB when the distance to HAPS nadir is 60 km.

64 Rep. ITU-R F.2475-0

Figure 44 shows the calculated I/N for the user terminal to HAPS nadir. The results presented below

are based on the maximum transmit power that will be transmitted during a small percentage of

time (during worst case raining conditions).

FIGURE 44

I/N vs. distance of UT to HAPS nadir (GW downlink)

For the user terminal case in this figure, the calculated I/N is below the IMT-2020 protection criteria

(–6 dB) for a separation distance above 58 km and these are based on MCL analysis,

1.3.6.2.2 HAPS (CPE link) to IMT-2020

Figure 45 shows the calculated I/N for the IMT-2020 base station to HAPS nadir (CPE downlink).

The results presented in the Figure are based on the maximum transmit power that will be

transmitted during a small percentage of time (during worst case raining conditions).

FIGURE 45

I/N vs. distance of BS to HAPS nadir (CPE downlink)

Rep. ITU-R F.2475-0 65

For the base station case in this Figure, the calculated I/N is below IMT-2020 threshold for

I/N = −6 dB when the distance to HAPS nadir is 53 km.

Figure 46 shows the calculated I/N for the user terminal to HAPS nadir (CPE downlink). The results

presented below are based on maximum transmit power that will be transmitted during a small

percentage of time (during worst case raining conditions).

FIGURE 46

I/N vs. distance of UT to HAPS nadir (CPE downlink)

As shown in Fig. 46, the calculated I/N is below the IMT-2020 protection criteria (–6 dB) for a

separation distance of 45 km.

According to the pfd expression and the system parameters of IMT-2020, the maximum possible

pfd level at the MS station is shown as below:

Pfd mask equation:

–103 dB(W/(m2 ‧ MHz)) ≤ 5°

–103 + 0.33 ( – 5) dB(W/(m2 ‧ MHz)) 5° < ≤ 20°

–98 dB(W/(m2 ‧ MHz)) 20° < ≤ 90°

The results above assume that the HAPS is pointing directly towards IMT-2020 receiver in azimuth,

and these are based on MCL analysis.

1.3.6.2.3 HAPS to IMT-2020


For HAPS gateway link to IMT-2020 base station, the studies indicate worst case separation

distance of 60 km to HAPS nadir is required in some rare cases.

For HAPS gateway link to IMT-2020 user terminal, the studies indicate that worst case separation


For HAPS CPE link to IMT-2020 base station, the studies indicate that worst case separation


For HAPS CPE link to IMT-2020 user terminal, the studies indicate that worst case separation


66 Rep. ITU-R F.2475-0

Conclusion

From the results above, for the HAPS to IMT-2020:

For the worst case (HAPS and IMT-2020 are pointing to each other in azimuth directly), a

minimum separation distance of 60 km (IMT-2020 to HAPS nadir) is required to guarantee

IMT-2020 system will not be interfered by HAPS.

For the pfd analysis, the maximum pfd level for HAPS at the IMT-2020 receiver side is described

as below:

Pfd mask equation:

–103 dB(W/(m2 ‧ MHz)) ≤ 5°

–103 + 0.33 ( – 5) dB(W/(m2 ‧ MHz)) 5° < ≤ 20°

–98 dB(W/(m2 ‧ MHz)) 20° < ≤ 90°

1.3.6.3 IMT-2020 to HAPS CPE/Gateway

1.3.6.3.1 IMT-2020 to HAPS gateway

Figure 47 shows the worst case separation distance between base station transmitter and HAPS

gateway receiver for I/N = –10 dB for 20% of the time, respectively.

FIGURE 47

Worst case separation distance from IMT-2020 base station vs. HAPS GW elevation angle

Figure 47 presents the worst case separation distance between IMT-2020 base station transmitter

and HAPS gateway receiver. The worst case separation distance is between 0.6 km to 0.9 km for

I/N of –10 dB.

Figure 48 shows the worst case separation distance between user terminal transmitter and HAPS

gateway receiver for I/N = –10 dB or 20% of the time, respectively.

Rep. ITU-R F.2475-0 67

FIGURE 48

Worst case separation distance from IMT-2020 user terminal vs. HAPS GW elevation angle

Figure 48 presents the worst case required separation distance between IMT-2020 user terminal

transmitter and HAPS gateway receiver. The worst case separation distance is from 0.4 km to

0.55 km for I/N = –10 dB, respectively.

1.3.6.3.2 IMT-2020 to HAPS CPE

Figure 49 shows the worst case separation distance between base station transmitter and HAPS CPE

receiver for both I/N = –10 dB, respectively.

FIGURE 49

Worst case separation distance from IMT-2020 base station vs. HAPS CPE elevation angle

Figure 49 presents the worst case separation distance between IMT-2020 base station transmitter

and HAPS CPE receiver. The worst case separation distance is from 0.6 km to 0.93 km for

I/N = –10 dB, respectively.

The results above assume that the base station is pointing directly towards HAPS CPE receiver in

azimuth, and these are based on MCL analysis.

68 Rep. ITU-R F.2475-0

Figure 50 presents the worst case separation distance between IMT-2020 user terminal transmitter

and HAPS CPE receiver. The largest worst case separation distance is from 0.3 km to 0.37 km, for

I/N = –10 dB for 20% of the time, respectively.

FIGURE 50

Worst case separation distance from IMT-2020 user terminal vs. HAPS CPE elevation angle

1.3.6.3.3 Summary of study B IMT-2020 to HAPS CPE/Gateway+


For the IMT-2020 base station to HAPS gateway, the studies indicate that a worst case separation

distance of 0.9 km is required in some rare cases.

For the IMT-2020 user terminal to HAPS gateway, the studies indicate that a worst case separation


For the IMT-2020 base station to HAPS CPE, the studies indicate that a worst case separation


For the IMT-2020 user terminal to HAPS CPE, the studies indicate that a worst case separation


Conclusion

From the results above, for theIMT-2020 to HAPS CPE/Gateway:

For the worst case (IMT-2020 and HAPS CPE/Gateway are pointing to each other in azimuth

directly), a minimum separation distance of 0.93 km is required to guarantee HAPS CPE/Gateway

is not be interfered by IMT-2020 system. For the other cases, the separation distance will be lower.

1.3.6.4 IMT-2020 to HAPS

1.3.6.4.1 IMT-2020 to HAPS (gateway link)

Figure 51 shows the calculated I/N versus worst case separation distance between base station and

HAPS nadir and compared to the I/N threshold of –10 dB.

Rep. ITU-R F.2475-0 69

FIGURE 51

I/N vs. worst case distance of BS to HAPS nadir (gateway uplink)

For the base station case in this Figure, the calculated I/N is in any case below HAPS threshold for

I/N = –10 dB when the distance to HAPS nadir is higher than 62 km.

As shown in Fig. 52, for the user terminal case, the calculated I/N is any case below the HAPS

threshold I/N = –10 dB of IMT-2020 UT to HAPS nadir.

FIGURE 52

I/N vs. distance of UT to HAPS nadir (gateway uplink)

1.3.6.4.2 IMT-2020 to HAPS (CPE link)

Figure 53 shows the calculated I/N versus worst case separation distance between base station to

and HAPS nadir and compared to I/N threshold of –10 dB, respectively.

70 Rep. ITU-R F.2475-0

FIGURE 53

I/N vs. worst case distance of BS to HAPS nadir (CPE uplink)

As shown in Fig. 53, for the base station case, the calculated I/N is in any case below the HAPS

threshold I/N = –10 dB at any distance of the IMT-2020 BS to the HAPS nadir.

Figure 54 shows the calculated I/N versus worst case separation distance between user terminal and

HAPS nadir and compared to I/N threshold of I/N = –10 dB.

FIGURE 54

I/N vs. worst case distance of UT to HAPS nadir (CPE uplink)

As shown in Fig. 54, for the user terminal case, the calculated I/N is in any case below the HAPS

threshold I/N = –10 dB at any distance of the IMT-2020 UT to the HAPS nadir.

1.3.6.4.3 Summary of IMT-2020 to HAPS


For the IMT-2020 base station to HAPS gateway link, the studies indicate that a worst case

separation distance of 62 km between the BS and the HAPS nadir is required in some rare cases.

For the IMT-2020 user terminal to HAPS gateway link, I/N is always below the HAPS threshold

I/N = –10 dB at any distance of the IMT-2020 UT to the HAPS nadir.

Rep. ITU-R F.2475-0 71

For the IMT-2020 base station to HAPS CPE link, I/N is always below the HAPS threshold

I/N = –10 dB at any distance of the IMT-2020 BS to the HAPS nadir.

For the IMT-2020 user terminal to HAPS CPE link, I/N is always below the HAPS threshold

I/N = –10 dB at any distance of the IMT-2020 UT to the HAPS nadir.

Conclusion

From the results above, for theIMT-2020 to HAPS:

For the worst case (HAPS and IMT-2020 are pointing to each other in azimuth directly), a

minimum separation distance of 62 km (IMT-2020 to HAPS nadir) is required to guarantee HAPS

will not be interfered by IMT-2020 base station. For the other cases, the separation distances will be

lower. With regard to the impact of UE into HAPS no separation distance is required.

1.3.7 Summary and analysis of the results of study C

Based on the results of sharing and compatibility study of HAPS and mobile service (IMT-2020),

the compatibility between HAPS and IMT-2020 should be taken into account, and the minimum

separation distance should be obeyed to avoid the interference and guarantee the quality of service.

1.4 Study D

This study performs the sharing study between the potential interference from HAPS towards the

IMT-2020 receivers.

1.4.1 Summary

This study performs a single-entry interference case, i.e. potential of interference of single HAPS

towards a single IMT-2020 Base Station (BS) or mobile User Equipment (UE).

The pdf mask, as a feasible approach, is proposed for addressing the protection of the IMT-2020

from HAPS downlink. Based on that, the required additional isolation and potential protection

mechanism (e.g. e.i.r.p. reduction, protection distance) were evaluated.

1.4.2 pfd mask

With the technical parameters and antenna pattern model of the IMT-2020 provided by the relevant

group, the following steps have been performed to derive the pfd mask versus elevation angle for

HAPS.

Step 1: Compute the BS antenna gain versus elevation angle with the parameters set as follows:

φ𝑚−𝑠𝑐𝑎𝑛 = 0º is taken for the mechanical azimuth angle of BS antenna;

φ𝑒−𝑠𝑐𝑎𝑛 = 0º is taken for the electrical scan of azimuth angle of BS antenna;

θ𝑚 = −10º is taken for the mechanical downtilt angle of BS antenna;

θ𝑒 is scanning from –50ºto 10º for electrical tilting of BS antenna.

The electrical tilting range of the IMT-2020 receiver is not being defined by the relevant group, the

final down tilting range is assumed considering both mechanical and electrical tilting, of the IMT

BS is from 0ºto 60º.

72 Rep. ITU-R F.2475-0

FIGURE 55

Explanation of each parameter for calculating pfd

Step 2: with the antenna gains calculated in step 1, use the formula below to calculate the pfd level

for BS.

pfd limit(θ𝑒𝑙) = floor (I

N𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑑+ 10 log10 𝐾𝑇𝐵𝐹 + 10 log10 (

4π

λ2) − 𝐺𝑀𝑆(θ𝑚 , θ𝑒 , θ𝑒𝑙)) − 𝑅𝐴𝑝𝑝𝑜𝑟𝑡𝑖𝑜𝑛𝑚𝑒𝑛𝑡

where:

θ𝑒𝑙: elevation angle of IMT-2020 based on horizon

GMS : antenna gain calculated of IMT-2020 in given θ𝑒, θ𝑚, and θ𝑒𝑙

𝑅𝐴𝑝𝑝𝑜𝑟𝑡𝑖𝑜𝑛𝑚𝑒𝑛𝑡 : apportionment for interference criteria with other services, 3 dB.

FIGURE 56

BS pfd limit

Step 3: Redo steps 1 and 2 for UE with the parameters having followed different ranges:

θ𝑚 is scanning from –180ºto 180º of UE antenna;

θ𝑒 is scanning from −θ𝑚 to 90° − θ𝑚 for electrical tilting of UE antenna.

Rep. ITU-R F.2475-0 73

FIGURE 57

UE pfd limit

Step 4: With the calculated pfd level of BS and UE, derive the pfd level and mask to protect

IMT-2020 system.

FIGURE 58

IMT-2020 pfd mask

The pfd mask to protect IMT-2020:

−109 + 0.72 × θ dB(W/(m2 ‧ MHz)) θ ≤ 10°

−101.8 dB(W/(m2 ‧ MHz)) 10° < θ ≤ 90°

In the case that IMT-2020 system is coexisting with FS in the same geographical area, the

apportionment for interference criteria, 3 dB, need to be considered when evaluate the pfd mask for

HAPS system to protect IMT-2020 system.

1.4.3 Deterministic study

This study performs a single-entry deterministic interference case, i.e. potential of interference of a

single HAPS towards a single IMT-2020 Base Station (BS) or mobile User Equipment (UE). Since

the IMT-2020 receivers’ technical characteristics has already been considered in pfd calculation

procedure, this study will simulate the interference pfd received at the IMT-2020 receiver surface

74 Rep. ITU-R F.2475-0

without considering the receiver gain, and then compare this power density with the pfd mask

proposed in previous section.

1.4.3.1 Interference scenarios from single HAPS

This study assumes that the BS and UE are inside the HAPS’s service coverage area and their

positions and pointing directions are fixed and under conservative assumptions. The characteristics

of the IMT-2020 BS and UE follow the guidance of the relevant group, while the characteristics of

HAPS system follows Report ITU-R F.2439-0. The examples of these scenarios for the BS and the

UE are represented in Fig. 59.

FIGURE 59

Interference scenario examples: (a) IMT-2020 base station, (b) IMT-2020 user equipment

(a) (b)

Multiple HAPS beams that fall within the IMT-2020 receiver’s bandwidth are considered, refer to

the co-frequency beam configuration of each HAPS system. Also, in order to consider a

conservative scenario, it is assumed that the beams affecting the IMT-2020 receiver either affect it

directly or surround it in a way that the resulting interference is the highest. In order to ensure that

co-frequency beams are not adjacent with each other, similar frequency reuse scheme as used for

cellular networks was assumed and applied to determine the beams’ coverage with respect to each

other.

Figure 60 illustrates an example of resulting beams’ coverage with one HAPS GW beam and four

sets of HAPS CPE beams (total 16 beams), with all beams falling within the IMT-2020 receiver’s

bandwidth, with the IMT-2020 receiver located in the center (i.e. inside the HAPS-to-gateway

beam). A more detailed step-by-step simulation procedure is described in the next section.

Rep. ITU-R F.2475-0 75

FIGURE 60

Relative positions and beam pointing directions between a HAPS and an IMT-2020 receiver

(example of HAPS system 6)

Furthermore, when the system claimed it supports Adaptive Transmit Power Control (ATPC)

described in Report ITU-R F.2439-0, including System 6, 1 and 2, this study applies ATPC to the

interference scenarios.

The following three interference scenarios between HAPS and MS have been considered:

– The MS station location is close to the HAPS ground station location. In that case, the links

HAPS to HAPS ground station and HAPS to MS suffer from the same attenuation due to

rain. It can be considered that ATPC is equal to AttrainHAPS->MS and Gmax equal G(θ). This

case is equivalent to the case of clear sky condition as the above equation becomes:

𝐸𝐼𝑅𝑃𝑛𝑜𝑚𝑖𝑛𝑎𝑙 − 10 ∗ log10(4 ∗ 𝑝𝑖 ∗ 𝑑2) < 𝑝𝑓𝑑𝑚𝑎𝑠𝑘 𝑐𝑙𝑒𝑎𝑟 𝑠𝑘𝑦

– The MS station location is far enough to the HAPS ground station location and there is no

cloud in the link toward the MS receiver. It can be considered that AttrainHAPS->MS is equal to

0 and 𝐺𝑚𝑎𝑥 − 𝐺(θ) ≥ 𝐴𝑇𝑃𝐶. This case is equivalent or better to the case of clear sky

condition.

– For MS stations located in area in between the two above areas the situation is more

difficult to assess. The correlation between the weather in the link HAPS to HAPS ground

station and the weather in the link HAPS to MS station as well as the difference in terms of

antenna gain need to be considered and no ITU-R Recommendation provides such

correlation.

Hence, in the deterministic study, it is considered the HAPS to victim downlink under clear sky

condition, which applies nominal e.i.r.p. instead of maximum e.i.r.p.. While for the other HAPS

downlinks, raining condition is considered, which applies maximum e.i.r.p.. Figure 61 describes

this principle in our interference scenarios.

FIGURE 61

ATPC in deterministic interference scenarios

76 Rep. ITU-R F.2475-0

1.4.3.2 Methodology to calculate interference pfd and simulation procedure

Methodology to calculate the level interference to an IMT-2020 receiver:

The interference pfd from a HAPS to an IMT-2020 receiver is calculated by the following equation:

𝑝𝑓𝑑𝑏(θ) = 𝑃𝐻(𝑏) + 𝐺𝑡𝑥𝐻 ((b)) − 𝐹𝑆𝐿 − 𝐴𝐿 − 𝐿𝑃𝑜𝑙 − 𝐿𝑏𝑜𝑑𝑦 (1)

where:

𝑃𝐻(𝑏): transmit power density of beam b generated by the HAPS (dB(W/MHz)).

Transmit power of the HAPS downlink under clear sky condition is nominal

e.i.r.p density. If applicable, transmit power of the HAPS downlink under

raining condition is maximum e.i.r.p. density if applicable

(𝑏): discrimination angle (degrees) at the HAPS between the pointing direction of a

HAPS spot beam b and the IMT-2020 receiver

𝐺𝑡𝑥𝐻 ((𝑏)): transmitter antenna pattern gain (dBi) of the HAPS for off-axis angle (𝑏)

𝐹𝑆𝐿: free space loss (dB) between the IMT-2020 receiver and the HAPS

𝐴𝐿: atmospheric loss (dB) between the IMT-2020 receiver and the HAPS, based on

Recommendation ITU-R P.619

𝐿𝑝𝑜𝑙: polarization discrimination in dB (3 dB)

𝐿𝑏𝑜𝑑𝑦: body loss in dB (4 dB), only applied when θ ≥ 10°.

The aggregate interference pfd at the IMT-2020 receiver is calculated from the addition of

interference from all beams of the HAPS:

𝑝𝑓𝑑(θ) = 10 log(∑ 10𝑝𝑓𝑑𝑏(𝜃)/10𝑏𝑛𝑏=1 ) (dB(W/(m2 ‧ MHz))) (2)

where:

bn : number of co-frequency beams.

Then the additional isolation for HAPS to coexistence with IMT-2020 is calculated.

𝐴𝑑𝑑𝑖𝑡𝑖𝑜𝑛𝑎𝑙 𝐼𝑠𝑜𝑙𝑎𝑡𝑖𝑜𝑛 = Max(𝑝𝑓𝑑(θ) − 𝑝𝑓𝑑𝑚𝑎𝑠𝑘(θ)) (dB) (3)

FIGURE 62

Example of multiple co-frequency beams falling into an IMT-2020 receiver per MHz

Simulation procedure:

The following describes the general simulation procedure implemented for the sharing study

between HAPS and IMT-2020 system in study D.

Beam1

Beam2

Beam3

BeamN

…

f/MHz

MS

Rep. ITU-R F.2475-0 77

Step 1: Load the system characteristics to generate the antenna element patterns for the CPE and

GW in HAPS.

Step 2: Calculate the coordinates of the victim UE/BS, HAPS, CPE and GW in the coordinate

system to evaluate the maximum possible interference levels the victim UE/BS may receive from

the HAPS.

(2a) Place the victim UE/BS starting from the nadir of the HAPS, where θ𝑒𝑙 = 90°.

(2b) With the coordinates of the victim UE/BS, generate GW and/or CPE coordinates accordingly

to ensure the HAPS-GW/HAPS-CPE downlink is also pointing directly to the victim UE/BS.

(2c) Generate a series of coordinates for all other co-frequency GWs and CPEs around the centre

GW/CPE in hexagonal cell structures while respecting minimum separations for co-frequency

reuse, to simulate and evaluate the positions of these GWs and CPEs that lead to the maximum

interference level from the HAPS towards the victim UE/BS. Then deploy the CPEs and GWs at the

coordinates with the maximum interference level.

FIGURE 63

Relative positioning in simulation procedure (example of UE case)

Step 3: Point all co-frequency beams of the HAPS that fall within the IMT-2020 receiver to the

GWs and CPEs coordinates generated in Step 2.

Step 4: Determine the discrimination angles (𝑏) for each HAPS-GW/CPE DL, and calculate the

total antenna gains 𝐺𝑡𝑥𝐻 ((𝑏)) and the interference pfd by each beam with the element patterns

generated in Step 1 and equation (1).

Step 5: Calculate the aggregated interference pfd from all HAPS’s downlink co-frequency beams

transmitted at the victim UE/BS receiver and compare it with the pfd mask and pfd mask with

apportionment as we proposed in § 1.4.2.

1.4.3.3 Study results between HAPS systems and IMT-2020 system

1.4.4 Monte-Carlo study

1.4.4.1 Monte-Carlo methodology

In Monte-Carlo study, unlike the deterministic study scenario described in Fig. 63 above, the study

considered all HAPS downlinks are under clear sky condition. Which means, the transmit power of

HAPS, 𝑃𝐻(𝑏) in equation (1), will use nominal e.i.r.p. density for all HAPS downlinks instead of

maximum e.i.r.p. density.

The following steps are conducted to perform the statistical Monte-Carlo analysis:

θ𝑒𝑙 = 90°

θ𝑒𝑙 = 70°

45º

HAPS service

coverage 10º 0° … …

78 Rep. ITU-R F.2475-0

Step 1: Drop the HAPS transmitter at the origin with the altitude follows the HAPS technical

characteristics from latest chairman report;

Step 2: Set the position-wise elevation angle θ𝑒𝑙 of victim UE/BS from 1° to 90°;

Step 3: With the θ𝑒𝑙 set in Step 2, run 50000 snap shots. In each snap shot,

(3a) Generate the coordinates of UE randomly with θ𝑒𝑙;

(3b) Generate coordinates of HAPS GWs and CPEs randomly in the HAPS service coverage;

(3c) The HAPS transmission off axis and gains towards the victim UE/BS are calculated, which

depends on the HAPS GWs and CPEs’ locations, the UE/BS location and the pattern used;

(3d) Calculate the aggregated interference pfd of all beams using equations (1) and (2).

Step 4: Redo Step 2 and 3 until θ𝑒𝑙 reaches 90°.

Step 5: The output of the Monte-Carlo gives the CDF distribution of calculated interference pfd

versus the pfd mask proposed and the pfd mask with apportionment.

1.4.4.2 Study results between HAPS systems and IMT-2020 systems

1.4.5 Summary and analysis of the results of study D

According to the request protection criteria of IMT-2020, the HAPS system downlink emission

should not be higher than the following unified pfd mask (in dB(W/(m2 ‧ MHz))) at the receivers of

IMT-2020 stations.

−109 + 0.72 × θ dB(W/(m2 ‧ MHz)) θ ≤ 10°

−101.8 dB(W/(m2 ‧ MHz)) 10° < θ ≤ 90°

Note that for the pfd level above, polarisation, body loss, and gaseous atmospheric losses are not

considered.

In the case that IMT-2020 system is coexisted with HAPS and FS in the same geographical area,

3 dB apportionment should be applied to the pfd mask for HAPS system to protect IMT-2020

system.

In addition, there are other methodologies presented which also can be used to determine the e.i.r.p.

reduction and/or protection distance to be applied (see §§ 1.4.3 and 1.4.4).

1.5 Study E

1.5.1 Methodology

To contribute actively with ITU-R studies, the Spectrum, Orbit and Broadcasting Division of the

Brazilian National Telecommunication Agency (ANATEL) has been developing, in cooperation

with partners in the industry and academia, an open-source simulation tool, named SHARC, to

support sharing and compatibility studies between IMT and other radio communication systems,

according to the framework proposed by Recommendation ITU-R M.2101.

SHARC is a static system-level simulator using the Monte-Carlo method. It has the main features

required for a common system-level simulator, such as antenna beamforming, IMT uplink power

control, resource blocks allocation, among others. The simulator is written in Python and the source

code is available at GitHub (https://github.com/SIMULATOR-WG/SHARC).

At each simulation snapshot, the hotspot base stations (BS) and user equipments (UE) are randomly

generated and located within a simulation scenario. The coupling loss is calculated between the UEs

and their respective serving BSs. The simulation then performs resource scheduling and power

https://github.com/SIMULATOR-WG/SHARC

Rep. ITU-R F.2475-0 79

control, enabling the interference calculation among the systems. Finally, system performance

indicators are collected, and this procedure is repeated for a fixed number of snapshots.

With SHARC, it is possible to study the coexistence between IMT 2020 and other services, such as

Fixed Satellite Service (FSS), High-altitude system (HAPS), Fixed Service (FS), among others.

This Annex presents a sharing study where HAPS system generates interference into IMT stations.

The following subsections present the simulation scenario and the main key performance indicator

presented in this study.

1.5.2 Simulation scenarios

1.5.2.1 GW to HAPS (uplink) and IMT system

In this scenario, the gateway transmits to the HAPS and generates interference into the IMT

stations. It is considered the case of ubiquitous deployment where, at each snapshot, the gateway is

randomly located inside the HAPS coverage area and its antenna is pointing to the. It is also

assumed that the IMT network is geographically deployed in the same suburban HAPS coverage

area. Figure 64 illustrates this simulation scenario.

FIGURE 64

Simulation scenario for GW → HAPS (uplink) and IMT system

1.5.2.2 CPE to HAPS (uplink) and IMT system

In this case, the active CPE’s are located inside the beam coverage radius. They transmit to the

HAPS and generates interference into the IMT stations. It is considered the case of ubiquitous

deployment where, at each snapshot, the CPE’s are randomly located inside the beam radius and

their antennas are perfectly pointed to the. It is also assumed that the IMT network is geographically

deployed in the same suburban HAPS coverage area.

Figure 65 illustrates the HAPS deployment that is considered in this simulation scenario.

80 Rep. ITU-R F.2475-0

FIGURE 65

HAPS deployment in simulation scenario CPE to HAPS (uplink) and IMT system

1.5.3 Power flux density

In accordance with the information provided by the relevant group, the maximum power flux

density (pfd) level that is required at the IMT receiver antenna in order to meet the protection

criteria (pfd mask) is given by the following equation:

𝑃𝐹𝐷𝑚𝑎𝑠𝑘 =𝐼

𝑁|

𝑝𝑟𝑜𝑡+ 10 ∙ log10 (

4π

𝜆2) + 10 ∙ log10(𝐾𝑇𝐵) − 𝐺𝐼𝑀𝑇(θ, ϕ) + 𝑁𝐹 (𝑑𝐵(𝑊/𝑚2) 𝑖𝑛 1 𝑀𝐻𝑧) (1)

where:

𝐼

𝑁|

𝑝𝑟𝑜𝑡: protection criteria of IMT station, dB

λ: wavelength, m

𝐾: Boltzmann’s constant, Joule/K

𝑇: receiver temperature, Kelvin

𝐵: receiver bandwidth, MHz

𝐺𝐼𝑀𝑇(θ, ϕ): Antenna gain of the IMT station towards HAPS station, dBi

𝑁𝐹: noise figure of IMT station, dB.

On a given deployment, the pfd level generated by a HAPS station (compliance mask) is calculated

as follows:

pfd = EIRP(ψ) + 10 ∙ log10 (1

4πd2) − Att − Ploss − Bloss (dB(W/m2) in 1 MHz) (2)

where:

𝐸𝐼𝑅𝑃(ψ): e.i.r.p. density level of HAPS station at direction 𝜓 towards IMT station,

dB(W/MHz)

𝑑: distance between HAPS and IMT station, m

𝐴𝑡𝑡: additional attenuation that corresponds to diffraction and tropospheric

scattering (Rec. ITU-R P.452) with additional clutter losses (Rec. ITU-R

P.2108)

𝑃𝑙𝑜𝑠𝑠: 3dB polarization loss, dB

𝐵𝑙𝑜𝑠𝑠: body loss, applicable only for IMT user equipments, dB.

Rep. ITU-R F.2475-0 81

Protection of the IMT station is ensured if pfd compliance mask (equation (2)) is smaller than pfd

mask (equation (1)).

1.5.4 Technical characteristics

This section provides the specific parameters used in the sharing study.

1.5.4.1 Technical and operational characteristics of HAPS systems operating in the


This section presents the HAPS parameters that were used in the studies.

TABLE 16

GW to HAPS (uplink) parameters Value

Frequency band 38-39.5 GHz

Occupied bandwidth 1 428.6 MHz

Deployment environment Suburban

Platform service radius 50 km

Platform altitude 20 km

Num. of beams 1

Num. co-frequency beams 1

GW antenna height 10 m

GW antenna pattern Rec. ITU-R F.1245

GW antenna gain 56.5 dBi

GW e.i.r.p. 64.5 dBW

GW e.i.r.p. spectral density 33 dB(W/MHz)

TABLE 17

CPE to HAPS (uplink) parameters Value


Occupied bandwidth 117 MHz

Num. of beams 4

Num. co-frequency beams 4

Coverage radius/beam 3.4 deg

CPE antenna height 10 m

CPE antenna pattern Rec. ITU-R F.1245

CPE antenna diameter 1.2 m

CPE antenna gain 51.4 dBi

CPE e.i.r.p. 51.0 dBW

CPE e.i.r.p. spectral density 30.3 dB(W/MHz)

The antenna pattern used in the HAPS gateway and CPE’s is described in Recommendation

ITU-R F.1245 and it is illustrated in Fig. 66.

82 Rep. ITU-R F.2475-0

FIGURE 66

Recommendation ITU-R F.1245 antenna radiation pattern

1.5.4.2 Technical and operational characteristics of IMT-2020 systems operating in the


These studies focus on an outdoor suburban hotspot scenario, with parameters as specified by the

relevant group.

The considered deployment scenario is a heterogeneous network with randomly distributed hotspots

within a macro-cell network. The study models an IMT-2020 system as a cluster with 57 sectors,

deployed over a very large area, with 2 outdoor hotspot base stations (BS) located randomly within

each sector. Because macro-cells typically operate in lower frequencies, they are not considered in

the simulations. The IMT network topology is illustrated in Fig. 67.

FIGURE 67

IMT network topology

Rep. ITU-R F.2475-0 83

The IMT user equipments (UE) are distributed within the hotspot coverage area, with a Rayleigh

distribution with scale parameter σ𝑑 = 32 m for the distance between UE and BS hotspot, and a

normal distribution for the azimuth between them, truncated at the ±60° range, with mean μ𝑎 = 0° and standard deviation σ𝑎 = 30°.

Hotspot base stations and their respective served UEs are simulated over the whole study area,

resulting in different elevation angles for each link; for each one, the IMT antenna gain towards the

HAPS is calculated. Therefore, all possible deployment scenarios with respect to elevation angles

are being considered. The directions of BS antenna beams towards UEs, and vice-versa, are

calculated with full compliance with the input documents from relevant groups.

The following subsections present the main IMT system- and deployment-related parameters that

were used in the studies.

1.5.4.2.1 System-related parameters

TABLE 18

IMT-2020 system-related parameters Value


Transmitter characteristics

Duplex method TDD

Channel bandwidth 200 MHz

Signal bandwidth > 90% of channel bandwidth

Antenna pattern Rec. ITU-R M.2101, with normalization factor

Antenna array BS: 8 × 16 elements

UE: 4 × 4 elements

Element gain 5 dBi

Ohmic loss 3 dB (BS and UE)

Conducted power per antenna element BS: 8 dBm/200 MHz

UE: 10 dBm/200 MHz (subject to power control)

Maximum UE output power 22 dBm


Noise figure 12 dB (BS and UE)

Body loss BS: 0 dB

UE: 4 dB

Protection criteria –6 dB

Regarding the antenna pattern, Recommendation ITU-R M.2101 presents a beamforming array

model that is assumed to be used by the majority of IMT-2020 systems at this frequency. This

model consists of several identical radiating elements in the yz-plane, having the same individual

radiation pattern and with a certain separation distance. The beam direction is calculated by a

weighting function. All the description and equations of this model can be found in

Recommendation ITU-R M.2101.

Following the guidance of the relevant group, this study presents simulation results considering the

original AAS antenna model and the normalized model, obtained by the application of the

correction factor.

Figure 68 shows horizontal and vertical antenna patterns for IMT base stations (8 × 16 elements)

and user equipments (4 × 4 elements). Original and normalized patterns are showed.

84 Rep. ITU-R F.2475-0

FIGURE 68

IMT base station and user equipment antenna patterns

1.5.4.2.2 Deployment-related parameters

TABLE 19

IMT-2020 Base station characteristics /

Cell structure Value

Outdoor Suburban hotspot

Network topology and characteristics 10 BSs/km2

Frequency reuse 1

Antenna height 6 m (above ground level)

Sectorization Single sector

Antenna deployment Below roof top

Network loading factor (Average base station activity) 50%

UEs/cell 3

Rep. ITU-R F.2475-0 85

TABLE 20

IMT-2020 User equipment characteristics Value

Outdoor Suburban hotspot

Indoor user terminal usage 0%

Antenna height 1.5 m (above ground level)

User equipment density for terminals that are

transmitting simultaneously 3 * BS density

Power control model Refer to Rec. ITU-R M.2101

Maximum user terminal output power PCMAX 22 dBm

Transmit power target value per 180 kHz, P0_PUSCH –95 dBm

Path loss compensation factor, α 1

1.5.4.3 Propagation models for sharing and compatibility studies in the 38-39.5 GHz

frequency range

Different propagation models were used for each transmission link, as follows:

– For the propagation within the IMT system, i.e. links between hotspots and user

equipments, the 3GPP Urban Micro (UMi) channel model was applied.

– For the links between HAPS gateway/CPE and IMT stations, path loss is given by the

model described in Recommendation ITU-R P.452 with additional clutter loss according to

Recommendation ITU-R P.2108.

Regarding the implementation of the clutter loss model described in Recommendation

ITU-R P.2108, for every link it is calculated the p-parameter, with uniform distribution between 0

and 1, in order to calculate the clutter loss. For each location in the study area, given the input

parameters, the clutter loss value is calculated according to the probability density functions

provided in Recommendation ITU-R P.2108.

Regarding the implementation of the path loss model described in Recommendation ITU-R P.452,

it was considered p = 1%, which means that the transmission loss will not exceed the calculated

value in 1% of time.

1.5.5 Derivation of pfd masks of IMT stations

This subsection describes the procedure for deriving the pfd masks as a function of the elevation

angle with respect to HAPS ground stations. The geometry of the scenario is characterized by some

parameters, including θ𝑡𝑖𝑙𝑡, which is the angle between the IMT antenna beam and the line of

horizon, θ𝑒𝑙𝑒𝑣, which is the elevation angle of the IMT antenna beam and the HAPS ground station,

and 𝑑, which is the distance between base station and user equipment.

All IMT parameters that are used in the pfd mask derivation procedure are described in Section 5

and they are the same as the ones used in the Monte Carlo simulations included below in this

Document. As explained in the referred Section, distance between a BS and its served UE’s follows

a Rayleigh distribution with scale parameter σ𝑑 = 32 𝑚. The mask derivation procedure considers

that 𝑑 is in the range between 5 and 100 metres, which encompasses 98% of the UE’s (from 0.01 to

0.99 of the CDF). Considering the antenna heights ℎ𝐵𝑆 = 6 𝑚, ℎ𝑈𝐸 = 1.5 𝑚 and ℎ𝐺𝑊 = ℎ𝐶𝑃𝐸 =10 𝑚, it can be shown that θ𝑡𝑖𝑙𝑡 is in range between 2.57 and 42 degrees. The mechanical downtilt

of the BS antenna is 10 degrees.

The pfd masks are evaluated only for the IMT stations which are inside the HAPS coverage area. It

implies that:

86 Rep. ITU-R F.2475-0

• the elevation angle θ𝑒𝑙𝑒𝑣.𝐵𝑆 of the IMT base stations with respect to the HAPS ground

station is in the range between 0 and 40 degrees, and

• the elevation angle θ𝑒𝑙𝑒𝑣.𝑈𝐸 of the IMT user equipments with respect to the HAPS ground

station is in the range between 0 and 60 degrees.

The procedure for deriving the pfd masks consists of calculating the IMT antenna gain in direction

θ𝑒𝑙𝑒𝑣 for a given θ𝑡𝑖𝑙𝑡 and, then, calculate the pfd value according to equation 1. The IMT antenna

model proposed by WP 5D assumes that the antenna gain is equal to its directivity and the ohmic

loss is considered separately. Considering that the protection criteria evaluates the level of

interfering signal with respect to system noise level, it is necessary to consider the characteristics of

the receive chain, which includes ohmic loss. Then, an additional 3-dB loss is included in the

calculation of the IMT station ‘net’ antenna gain in the direction of the HAPS, in order to calculate

the received interfering power.

The procedure for deriving the UE pfd masks is similar, taking into account the premise that

vertical orientation of the device varies uniformly in the range between –180 and 180 degrees.

Figure 69 shows the pfd masks calculated for IMT base station and user equipment.

FIGURE 69

Ppfd masks to protect IMT base stations and user equipments

Table 21 summarizes the pfd masks that are proposed as a function of elevation angles in order to

protect the IMT stations.

TABLE 21

Proposed pfd masks for IMT base stations and user equipments

IMT station Proposed pfd masks, dB(W/m2) in 1 MHz

BS 𝑝𝑓𝑑(θ𝑒𝑙𝑒𝑣) = {1.14 ∙ θ𝑒𝑙𝑒𝑣 − 109.2, 0° < θ𝑒𝑙𝑒𝑣 < 12°−95.5, 12° ≤ θ𝑒𝑙𝑒𝑣 < 40°

UE 𝑝𝑓𝑑(θ𝑒𝑙𝑒𝑣) = −98.7, 0° < θ𝑒𝑙𝑒𝑣 < 60°

It is noteworthy to mention that, in real deployments, it is necessary to evaluate the overall

performance of protection measures (e.g. pfd masks, separation distances, etc.) that are jointly

applied in order to mitigate harmful interference between services. For sharing analysis between

Rep. ITU-R F.2475-0 87

IMT stations and far away HAPS ground station it is mostly expected that a pfd mask values at

elevation angles approximately 0 degree would be used.

1.5.6 Monte Carlo simulation results

This section presents the Monte Carlo simulations for cases of HAPS ground stations generating

interference into IMT-2020 stations. Each simulation snapshot corresponds to a certain network

deployment that is configured according to the guidelines defined by the ITU relevant groups. The

pfd values are calculated for all active IMT stations using the Monte Carlo-based approach,

described in § 2. The simulation results show the cases of normalized and non-normalized IMT

antenna patterns.

1.5.6.1 Sharing and compatibility of IMT-2020 and HAPS gateways operating in the


The interference from a HAPS gateway, assuming the maximum e.i.r.p. spectral density, into IMT

stations in the 38-39.5 GHz frequency range is analysed in this subsection. Since there is only one

GW generating interference to IMT stations, this is considered a statistical single-entry simulation

case. The output of the simulation tool contains the interference generated by a single-beam

gateway into IMT base stations (and their respective served user equipments) being ubiquitously

deployed on the study area. Simulation results are collected after 15 000 snapshots and they show

the cases of normalized and non-normalized IMT antenna patterns.

Figure 70 shows the IMT antenna gains towards HAPS gateway.

FIGURE 70

Antenna gains of IMT stations towards HAPS gateway

As expected, the normalized antenna patterns provide higher gains than the non-normalized ones. It

can be seen that BS antenna gains achieve higher values with greater probability than UE antenna

gains. This is observed in the Figure when x-axis > ~14 dBi. This result comes from the fact that the

HAPS gateway is randomly placed in the simulation scenario and that there is a non-negligible

probability that it can be placed in the middle of a BS ↔ UE link. This is the situation when IMT

antenna gains towards gateway are higher.

The pfd masks are presented in Fig. 71. The compliance masks are indicated by the leftmost (and

thicker) curves and they are calculated on each simulation snapshot, based on equation (2). The pfd

88 Rep. ITU-R F.2475-0

masks that would meet the protection criteria of BS and UE, calculated according to equation (1),

are also shown. It is assumed that the HAPS gateway transmits at the maximum e.i.r.p. spectral

density of 33 dB(W/MHz). These curves show that there is a very low probability (less than 0.01%)

of the BS compliance masks being greater than –144.0 dB(W/m2) in 1 MHz. Protection of BS’s

with normalized antenna patterns is guaranteed with a minimum margin of 36.3 dB because the pfd

mask of the BS’s is –107.7 dB(W/m2) in 1 MHz. All results are summarized in Table 22 below.

Negative margins indicate that compliance masks are smaller than the pfd mask and, hence, IMT

protection criteria is met.

In this case, the pfd compliance masks are not always less than the pfd masks. This could be

analysed from two perspectives:

1 Figure 71 indicates a probability of the compliance mask being greater than a certain value.

For example, the probability of the BS compliance mask being greater than

−144.0 dB(W/m2) in 1 MHz is 0.01%. The Figure also shows that the pfd mask required to

protect all BS’s is equal to –107.7 dB(W/m2) in 1 MHz. Hence, in 99.99% of the cases, the

protection margin will be at least 36.3 dB. For the other 0.01% of the cases, there are two

possibilities: 1) the protection margin will be less than 36.3 dB or 2) the BS protection

criteria will be exceeded;

2 IMT stations that require more stringent pfd masks are the ones whose antenna beams are

pointing to the interferer HAPS ground station. Figure 71 indicates that 0.001% of the BS

stations require pfd masks less than –107.7 dB(W/m2) in 1 MHz. On the other hand, the

probability of the BS compliance mask being greater than –107.7 dB(W/m2) in 1 MHz is

less than 0.006%. Both conditions must apply for the BS protection criteria being exceeded.

Hence, in this example, the IMT BS protection criteria is exceeded in 6 out of 10 billion

cases.

FIGURE 71

Ppfd masks of IMT stations (IMT-2020 and HAPS gateways)

Rep. ITU-R F.2475-0 89

TABLE 22

Summary of results (IMT-2020 and HAPS gateways)

IMT

station

Ppfd compliance mask

(99.99% of IMT stations)

Normalized

antenna

pattern

Ppfd mask Margin

BS –144.0 dB(W/m2) in 1 MHz Yes –107.7 dB(W/m2) in 1 MHz –36.3 dB

No –107.2 dB(W/m2) in 1 MHz –36.8 dB

UE –147.7 dB(W/m2) in 1 MHz Yes –99.1 dB(W/m2) in 1 MHz –48.6 dB

No –98.7 dB(W/m2) in 1 MHz –50.0 dB

1.5.6.2 Sharing and compatibility of IMT-2020 and HAPS CPE’s operating in the


The aggregate interference from HAPS CPE’s, assuming the maximum e.i.r.p. spectral density into

IMT stations in the 38-39.5 GHz frequency range is analysed in this subsection. The output of the

simulation tool contains the interference generated by CPE’s into IMT base stations (and their

respective served user equipments) being ubiquitously deployed on the study area. Since there are

many CPE’s simultaneously generating interference to IMT stations, this is considered a statistical

multiple-entry simulation case. It is calculated the aggregate interference generated by several

single-beam CPE’s. Simulation results are collected after 15 000 snapshots and they show the cases

of normalized and non-normalized IMT antenna patterns.

Figure 72 shows the IMT antenna gains towards HAPS CPE’s. As expected, the normalized antenna

patterns provide higher gains than the non-normalized ones. This result is very similar to the case

where HAPS gateway is the interferer station because gateway and CPE’s have the same antenna

heights and are deployed in the study area under the same assumptions.

FIGURE 72

Antenna gains of IMT stations towards HAPS CPE’s

90 Rep. ITU-R F.2475-0

The pfd masks are presented in Fig. 73. The compliance masks are indicated by the leftmost (and

thicker) curves and they are calculated on each simulation snapshot, based on equation (2), taking

into account the aggregate pfd levels generated by the CPE’s. The pfd masks that would meet the

protection criteria of BS and UE, calculated according to equation (1), are also shown. It is assumed

that the HAPS CPE’s transmit at the maximum e.i.r.p. spectral density of 30.3 dB(W/MHz). These

curves show that there is a very low probability (less than 0.01%) of the BS compliance masks

being greater than –139.7 dB(W/m2) in 1 MHz. Protection of BS’s with normalized antenna patterns

is guaranteed with a minimum margin of 31.8 dB because the pfd masks of the BS’s is

−107.9 dB(W/m2) in 1 MHz. All results are summarized in Table below. Negative margins indicate

that compliance masks are smaller than the pfd mask and, hence, IMT protection criteria is met.

Similarly, to the case of GW, the pfd compliance masks are not always less than the pfd masks.

This could be analysed from two perspectives:

1 Figure 73 indicates a probability of the compliance mask being greater than a certain value.

For example, the probability of the BS compliance mask being greater than

−139.7 dB(W/m2) in 1 MHz is 0.01%. The Figure also shows that the pfd mask which is

required to protect all BS’s is equal to –107.9 dB(W/m2) in 1 MHz. Hence, in 99.99% of the

cases, the protection margin will be at least 31.8 dB. For the other 0.01% of the cases, there

are two possibilities: 1) the protection margin will be less than 31.8 dB or 2) the BS

protection criteria will be exceeded;

2 IMT stations that require more stringent pfd masks are the ones whose antenna beams are

pointing to the interferer HAPS ground station. Figure 73 indicates that 0.001% of the BS

stations require pfd masks less than –107.8 dB(W/m2) in 1 MHz. On the other hand, the

probability of the BS compliance mask being greater than –107.8 dB(W/m2) in 1 MHz is

less than 0.002%. Both conditions must apply for the BS protection criteria being exceeded.

Hence, in this example, the IMT BS protection criteria is exceeded in 2 out of 10 billion

cases.

FIGURE 73

Ppfd masks of IMT stations (IMT-2020 and HAPS CPE’s)

Rep. ITU-R F.2475-0 91

TABLE 23

Summary of results (IMT-2020 and HAPS CPE’s)

IMT

station

Ppfd compliance mask

(99.99% of IMT stations)

Normalized

antenna

pattern

Ppfd mask Margin

BS –139.7 dB(W/m2) in 1 MHz Yes –107.9 dB(W/m2) in 1 MHz –31.8 dB

No –107.3 dB(W/m2) in 1 MHz –32.4 dB

UE –142.9 dB(W/m2) in 1 MHz Yes –99.2 dB(W/m2) in 1 MHz –43.7 dB

No –98.7 dB(W/m2) in 1 MHz –44.2 dB

1.5.7 Summary and analysis of the results of study E

In this Annex, a sharing study between an IMT and HAPS ground stations operating in the

38-39.5 GHz frequency range is performed. Simulation results indicate that sharing is feasible

under the assumptions and parameters that are described in this study. A summary of the most

stringent margins is provided below for each simulation case.

The GW to HAPS (uplink) case indicates that the pfd mask (–144.0 dB(W/(m2 · MHz))) can be met

for 99.99% of IMT base stations with a margin of at least 36.3 dB. This case represents a scenario

that considers ubiquitous deployment of IMT networks and 1 HAPS gateway on the same

geographical area.

The case of CPE to HAPS (uplink) indicates that the pfd mask (–139.7 dB(W/(m2 · MHz))) can be

met for 99.99% of IMT base stations with a margin of at least 31.8 dB. As well as in the previous

case, this one also represents a scenario that considers ubiquitous deployment of IMT networks and

HAPS CPE’s on the same geographical area.


Impact from transmitting HAPS into MS receivers

One study shows that the following pfd mask in dB(W/(m2 · MHz)), to be applied under clear sky

conditions at the surface of the Earth, ensures the protection of the Mobile Service receivers from

aggregate HAPS emission:

–102 θ ≤ 5°

–102 + 0.25 (θ 5 5° < θ ≤ 25°

–97 25° < θ ≤ 90°

where θ is elevation angle in degrees (angle of arrival above the horizontal plane). Note that for the

pfd level above, polarisation and gaseous atmospheric (Recommendation ITU-R SF.1395) losses

are considered. In addition, body loss is considered for the user equipment pfd level calculation.

The following two approaches address the use of ATPC to compensate for rain fade:








92 Rep. ITU-R F.2475-0

To verify that the pfd produced by HAPS does not exceed the proposed pfd mask, the following

equation was used:

pfd(θ) = EIRP(θ) − 10log(4πd²)

where:

EIRP: nominal HAPS e.i.r.p. density level in dB(W/MHz) (dependent to the elevation

angle)

d: distance between the HAPS and the ground (elevation angle dependent).

The impact of the gas attenuation, body loss (for user equipment), and polarization loss are not

included in the verification formula since it is already taken into account in the pfd mask.

Another study shows that the following pfd mask in dB(W/(m2 ‧ MHz)), to be applied at the surface

of the Earth, should be feasible to protect the IMT-2020 from HAPS systems. And in case that

IMT-2020 system is coexisted with HAPS and FS in the same geographical area, 3 dB

apportionments should be considered additionally to the pfd mask below to ensure this protection.

−109 + 0.72 × θ dB(W/(m2 ‧ MHz)) θ ≤ 10°

−101.8 dB(W/(m2 ‧ MHz)) 10° < θ ≤ 90°

θ is the elevation angle in degrees (angles of arrival above the horizontal plane). Note that the

attenuations are not considered in the pfd mask above, but in the compliance analysis stage. To

verify the compliance of the aggregated interference, from multiple beams of single HAPS, with the

proposed pfd mask, the following equations is used:

𝑝𝑓𝑑𝑏(θ) = 𝑃𝐻(𝑏) + 𝐺𝑡𝑥𝐻 ((𝑏)) − 𝐹𝑆𝐿 − 𝐶𝐿 − 𝐴𝐿

𝑝𝑓𝑑(θ) = 10 log (∑ 10𝑝𝑓𝑑𝑏(θ)/10

𝑏𝑛

𝑏=1

)

where:

𝑃𝐻(𝑏): transmit power density of beam b generated by the HAPS (dB(W/MHz)).

Transmit power of the HAPS downlink under clear sky condition is nominal

e.i.r.p. density if applicable, transmit power of the HAPS downlink under

raining condition is maximum e.i.r.p. density if applicable

(𝑏): discrimination angle (degrees) at the HAPS between the pointing direction of a

HAPS spot beam b and the MS receiver

𝐺𝑡𝑥𝐻 ((𝑏)): transmitter antenna pattern gain (dBi) of the HAPS for off-axis angle (𝑏)

𝐹𝑆𝐿: free space loss (dB) between the MS receiver and the HAPS

𝐴𝐿: atmospheric loss (dB) between the MS receiver and the HAPS, based on Rec.

ITU-R P.619

𝐿𝑝𝑜𝑙: polarization discrimination in dB (3 dB)

𝐿𝑏𝑜𝑑𝑦: body loss in dB (4 dB), only applied when θ ≥ 10°

bn = Number of co-frequency beams.

In addition, in this study, there are other methodologies presented which also can be used to

determine the e.i.r.p. reduction and/or protection distance to be applied.

Another study proposes that a maximum worst-case separation distance, in the case of HAPS

system 5 and an I/N = –6 never exceeded for the IMT-2020 protection criteria, of 60 km (to HAPS

nadir) might be required to protect the communications of these two systems in some rare cases

Rep. ITU-R F.2475-0 93

(when both systems are pointing towards each other in azimuth). For the other cases, the separation

distance will be lower. The results are based on the maximum transmit power that will be

transmitted during a very small percentage of time (during worst case raining conditions).

Impact of HAPS transmitting ground stations into MS stations

One study concluded that HAPS ground stations (CPE/GW) can share with MS stations (BS and

UE) as the maximum required separation distance for a probability of 1 case over 100 000 is less

than 160 m for p = 20% (clear sky conditions) and 4 km for p = 0.01% (raining conditions). For the

majority of cases, the separation distance is much lower.

Another study concluded that between HAPS ground station and IMT-2020, a separation distance

of 0.42 km is required to guarantee the coexistence of two systems when the HAPS CPE/Gateway

and IMT-2020 receiver are pointing to each other in azimuth and with the worst case elevation

angles (MCL analysis). For other cases, the separation distance will be lower. The results are based

on the maximum transmit power that will be transmitted during a very small percentage of time

(during worst case raining conditions).

Another study showed that the GW to HAPS (uplink) case indicates that the pfd mask

(–144.0 dB(W/(m2 · MHz))) can be met for 99.99% of IMT base stations with a margin of at least

36.3 dB. This case represents a scenario that considers ubiquitous deployment of IMT networks and

1 HAPS gateway on the same geographical area. The case of CPE to HAPS (uplink) indicates that

the pfd mask (–139.7 dB(W/(m2 · MHz))) can be met for 99.99% of IMT base stations with a

margin of at least 31.8 dB. As well as in the previous case, this one also represents a scenario that

considers ubiquitous deployment of IMT networks and HAPS CPE’s on the same geographical

area. Impact of transmitting MS stations into receiving HAPS ground stations

One study performed two different percentage of time, i.e. 20% and 0.01%, using P.452

propagation model. The study showed that for both cases, the impact of MS user equipment

emissions into HAPS ground station receivers is in order of 4-14 km for a probability of 1 case over

1 million compared to 28-75 km between the MS and conventional FS station for the same

probability. The impact of MS base station emissions into HAPS ground station receivers is in order

of 2-17 km for a probability of 1 case over 1 million compared to 30-60 km between the MS and

conventional FS station for the same probability. In addition, the required separation distance can be

further reduced by appropriate site-configuration, due to HAPS antenna directivity. Therefore,

protection between HAPS ground stations and MS stations can be managed on a case-by-case basis

by coordination amongst administrations at national level.

Another study shows that the worst case separation distance of 0.93 km might be required in rare

cases to guarantee the coexistence of these two systems when the HAPS CPE/Gateway and

IMT-2020 transmitter are pointing to each other in azimuth and with the worst case elevation angles

(MCL analysis). For the majority of cases, the separation distance is much lower.

Impact of transmitting MS stations into receiving HAPS

One study shows that the worst case separation distance of 62 km might be required in rare cases to

guarantee the coexistence of the two systems when ITM-2020 is co frequency with HAPS gateway

links and when the HAPS Gateway and IMT-2020 transmitter are pointing to each other in azimuth

and with the worst case elevation angles (MCL analysis). For the other cases, the required

separation distances will be lower. With regard to the impact of BS into HAPS CPE link receiver

and UE into HAPS no separation distance is required.

94 Rep. ITU-R F.2475-0

Annex 3

Sharing and compatibility study of Fixed Satellite service and HAPS systems

operating in the 38-39.5 GHz frequency range

Summary of scenarios considered in Study A

TABLE 24

Summary of scenarios considered in the studies

Study Type Study A Study B Study C Study D Study E Study F

HAPS ground station to receiving FSS

earth station

HAPS to receiving FSS earth station

FSS Satellite to receiving HAPS

FSS Satellite to receiving HAPS

ground station

1 Technical Study

1.1 Study A (Interference from the transmitting HAPS GW and HAPS CPE into

receiving FSS earth station

The I/N FSS protection criteria used in this study (I/N = –12.2 dB) is equivalent to the I/N

protection criteria (I/N = –10.5 dB) provided by the relevant group. The N used in this study is

different to those used in the other studies.

1.1.1 HAPS CPE/GW to fixed satellite service

1.1.1.1 Interference analysis

This study aims at studying the protection of GSO FSS Earth Stations links (space-to-Earth) in the

band 38-39.5 GHz, and deriving a separation distance between the transmitting HAPS earth station

and the receiving GSO FSS earth station (ES). Two HAPS earth station sizes are considered in this

study, and labelled as HAPS user terminal (HAPS CPE), and HAPS Gateway (HAPS GW).

1.1.1.2 Technical Parameters of GSO FSS in the frequency band 38-39.5 GHz

The following set of FSS parameters was considered in this compatibility study. Table 25 lists the

earth station parameters, as provided by the relevant group.

Rep. ITU-R F.2475-0 95

TABLE 25

FSS GSO system parameters

FSS downlink parameters (interfered with)

Frequency range (GHz) 38-39.5 38-39.5

CARRIER Carrier #06 Carrier #26

Noise bandwidth (MHz) 100-600 50-500

EARTH STATION

Antenna diameter (m) 6.8 1

Peak receive antenna gain (dBi) 68 50

Antenna receive gain pattern Rec. ITU-R S.465-6 Rec. ITU-R 465-6

System receive noise temperature (K) 250 150

Minimum earth station elevation angle (degree) 10 10

Interference protection criteria

I/N (dB) Criteria as provided above in section xxx

Criteria as provided above in section xxx

Other

Additional Notes NGSO system with a circular, orbit having an

altitude of 1 400 km.

1.1.1.3 Technical Parameters of proposed HAPS systems in the frequency band

38-39.5 GHz

For the purposes of this sharing study, a HAPS system is assumed with the operational parameters

is listed in Table 26. These parameters are captured from the contents of the working document,

which listed the technical and operational parameters of envisaged HAPS systems in the studied

frequency bands.

TABLE 26

HAPS System Parameters

CPE--> HAPS (UL)

System 2

Frequency GHz 38-39.5

Signal Bandwidth MHz 60

No. of beams 16

No of co-frequency beams 4

Coverage radius/beam degree –3 dB beamwidth

Polarisation RHCP/LHCP

CPE Antenna Diameter m 1

CPE Antenna Pattern ITU-R F.1245

CPE Antenna Gain dBi 49

CPE e.i.r.p. dBW 59 (56 per polarisation)

CPE e.i.r.p. Spectral Density dB(W/MHz) 41.2 (38.2 per polarisation)

96 Rep. ITU-R F.2475-0

GW --> HAPS (UL)

System 6

Frequency GHz 38-39.5

Signal Bandwidth MHz 1428.6

No. of beams 1

No of co-frequency beams 1

Coverage radius/beam degree 1.3

Polarization RHCP/LHCP

GW Antenna Diameter m 2

GW Antenna Pattern ITU-R F.1245

GW Antenna Gain dBi 56.5

GW Tx Power W 9

GW e.i.r.p. dBW 64.5

GW e.i.r.p. Spectral Density dB(W/MHz) 33.0

1.1.1.4 FSS GSO Protection Criteria

Recommendation ITU-R S.1432-1 provides guidance on the long-term (“time invariant”) allowable

aggregate interference levels into FSS systems.

The relevant group considered under WRC-19 agenda item 1.14 the nature of the interference that

HAPS systems may cause to the FSS and indicated that it considered such interference to be

“time-variant” in nature. In this regard, the relevant group suggested that there would be

fluctuations in the interference reflecting the movement of the HAPS for station keeping, and due to

the dynamic nature of HAPS links within a given coverage area, as well as the stochastic nature of

user demands. It is worth noting that as obliged by RR No. 1.66A, HAPS deployments must operate

at a nominally fixed location in the stratosphere. Therefore, this interference fluctuation due to the

HAPS movement would be of a long-term nature for the FSS earth stations.

Furthermore, while it is accurate that interference from HAPS to FSS varies with time, the

fluctuation is diurnal in nature reflecting daily variation in the amount of customer usage. This

interference variation occurs over an extended period of time that is significantly more than the 1%

used to define short-term events. Therefore, for GSO FSS earth stations, HAPS clear sky

transmissions (towards earth) would be of a long-term nature.

Due to the long-term nature of HAPS interference into FSS GSO (space-to-Earth) links, this study

uses I/N of –12.2 dB3 as a protection criterion.

1.1.1.5 Apportionment of interference

Recommendation ITU-R S.1432 proposes that FSS links should set aside 6% T/T for all other

primary services operating in the band. As the band is shared on a co-primary basis with the other

services (including MS and FS in this band), then the protection criteria needs to be apportioned

evenly among FS and MS. Therefore, the ΔT/T value for interference from FS is 3%

(I/N = −15.2 dB).

3 It should be noted that the relevant group in ITU-R indicated the use of interference to noise ratio of

−10.5 dB.

Rep. ITU-R F.2475-0 97

1.1.1.6 Technical Analysis

The purpose of this analysis is to assess the interference from HAPS Earth Station uplink

transmissions into the receiving FSS Earth Station, and to employ a sharing methodology between

both systems, ensuring the protection of the primary FSS allocations in the band 38-39.5 GHz

(Space-to-Earth).

In order to achieve the long-term protection criteria of (I/N = −15.2 dB), a separation distance is

calculated between HAPS earth stations (HAPS CPEs and HAPS GWs) and FSS GSO earth

stations (ES).

In Fig. 74, the Earth Station is assumed to be pointing north (0° of azimuth), while HAPS earth

stations (HAPS CPEs and HAPS GWs) are pointing south towards the FSS GSO Earth Station

(180° of azimuth).

The elevation angle of the Earth Station is set to one of three representative values. The HAPS is

assumed to be at maximum distance and lowest altitude from the HAPS CPEs and HAPS GWs in

order to yield the lowest elevation angle. The HAPS CPEs and HAPS GWs sidelobes transmitting

horizontally towards the horizontal sidelobe of the GSO earth station is assumed to be the main

interference contribution from the HAPS earth stations towards the FSS earth stations.

FIGURE 74

HAPS and FSS earth stations interference scenario

Taking into account free space loss and atmospheric gaseous attenuation4, the separation distance

between HAPS GW/CPE and FSS earth stations, where the (I/N = –15.2 dB) level is achieved, is

calculated as demonstrated in Fig. 75.

4 As per Recommendation ITU-R P.676-11.

98 Rep. ITU-R F.2475-0

FIGURE 75

HAPS and FSS Earth stations Exclusion Zone and Separation Distance (Aerial View)

The calculation process is applied for both HAPS CPEs and HAPS GWs, taking into account the

system parameters listed in § 1.1.1.1.2.

This process is then repeated, with the HAPS earth station moved so as to be on the 1 degree

azimuth bearing from the Earth Station but still pointed towards the Earth Station. The separation

distance was again found. This process was repeated for each azimuth bearing around the Earth

Station. Table 27 summarizes the calculated required separation distance around the FSS Earth

Station where “Max” refers to the scenario of mainlobe-to-mainlobe interference, and “Min” refers

to mainlobe-to-sidelobe interference.

TABLE 27

HAPS to FSS Earth Stations Separation Distances

FSS

Earth

station

elevation

HAPS

Earth

station

elevation

Separation distance between HAPS

CPE and FSS Earth station (km)

Separation distance between HAPS

GW and FSS Earth station (km)

GSO NGSO GSO NGSO

Max Min Max Min Max Min Max Min

10°

22°

13.35 3.93 15.66 4.88 3.82 0.86 4.74 1.1

25° 7.6 3.93 9.19 4.88 1.86 0.86 2.35 1.1

40° 4.75 3.93 5.87 4.88 1.06 0.86 1.36 1.1


In this study, the interference from a transmitting HAPS earth station towards a receiving FSS earth

station was studied. The locations of HAPS earth stations and FSS earth stations were varied

resulting in different I/N values around the receiving Earth Station. The analysis used the (I/N) as a

criterion to set a separation distance between HAPS earth stations and FSS earth stations, where

both systems are sharing the frequency bands studied under Agenda Item 1.14. For the long-term

protection of FSS earth stations, a minimum required I/N was assumed to be –15.2 dB. The analysis

Rep. ITU-R F.2475-0 99

was performed with the HAPS earth stations located at the edge of coverage, to achieve the lowest

possible elevation angle. The FSS earth station elevation was varied from a minimum of 10 degrees.

The results of the analysis indicate that, in order to ensure the long-term protection of receiving FSS

GSO earth stations at 10 degrees elevation, transmitting HAPS earth stations must be separated

from the affected Earth Station by typically 13.35 km (for HAPS CPEs) and 3.82 km (for HAPS

GWs) at the main-lobe.

This study also analysed the interference into FSS NGSO systems, and the results indicated that in

order to achieve the long-term protection criteria of an FSS NGSO earth station at a worst-case

elevation of 10°, HAPS transmitting earth stations must be separated by a distance of approximately

15.66 km (for HAPS CPEs) and 4.74 km (for HAPS GWs) at the main-lobe.

Smaller separation distances can be achieved while both earth stations are pointed at higher

elevations, and while the main lobes of both systems are not aligned. This study also investigated

the mainlobe-to-sidelobe interference scenarios, and indicated the minimum separation distances,

required to achieve the I/N protection criteria.

Due to the indicated wide separation distances between HAPS and FSS terminals, sharing between

HAPS and FSS systems would not be feasible, particularly for cases with overlapping HAPS and

FSS coverage areas, and areas with multiple deployments of FSS and HAPS earth stations.

In cases where the potential interference is from downlink HAPS transmissions towards FSS Earth

station, i.e. the FSS Earth station main-lobe is pointed directly at the HAPS airborne antenna, the

interference will be very high and sharing would be highly unfeasible in the shared HAPS and FSS

service areas. Therefore, this study only investigates the impact of transmitting HAPS earth stations

towards FSS earth station in the uplink direction.

This study considers the interference from an individual HAPS earth station towards an individual

FSS Earth Station. However, an FSS Earth Station would receive aggregate interference from all

co-frequency HAPS GWs and HAPS CPEs operating within and in the vicinity of the HAPS

coverage area. This aggregation of interference may well exceed the assumed interference level,

although the individual contribution of each HAPS earth station might still comply with the

protection criteria. Therefore, this may drastically increase the required separation distances

between HAPS earth stations and FSS earth stations. Further study is required to assess the impact

of aggregate interference from multiple HAPS earth stations towards FSS earth stations.

1.2 Study B

1.2.1 Summary

This study investigates the coexistence between HAPS and FSS. This study will first present a

statistical study. Then the impact of the various mitigation techniques will be assessed.

In this frequency range, the following directions are considered for HAPS.

– HAPS gateway to (UL);

– HAPS CPE to (UL).

1.2.2 Introduction

The HAPS parameters (gateway and CPE links) used in this study is for System 6 from Report

ITU-R F.2439-0. The protection criteria for HAPS used in this study is the same as the protection

criteria for FS which are I/N = –10 dB (may exceed 20% of the time) and 10 dB (may exceed 0.01%

of the time).

The FSS (E-s) transmitter and receiver parameters assumed for this study, are carriers 6 (GEO) and

26 (NGSO), respectively. The FSS parameters used for this study are taken from the relevant group.

100 Rep. ITU-R F.2475-0

The FSS protection criteria used for this study are taken from Document 5C/546 which are I/N = +8

(0.02 %), –6 (1%), and –10.5 dB (20%).

1.2.3 Methodology and results – HAPS CPE/gateway to FSS ES

1.2.3.1 FSS ES pfd limits

The pfd level of HAPS ground station at the FSS earth station antenna is calculated with the

following equation:

𝑝𝑓𝑑 = 𝐼/𝑁 + 10log10(𝑘𝑇𝐵) + 10log10 (4π

λ2) − 𝐺𝑚𝑎𝑥𝑅𝑥

where:

I/N: Interference over Noise assumed values for –6 dB (may exceed 1% time),

–10.5 dB (may exceed 20% time), and +8 dB (may exceed 0.02% time)

𝐺𝑚𝑎𝑥𝑅𝑥: antenna gain of the FSS earth station in direction of the HAPS ground station

(dBi). For the worst case, the off-axis angle is equal to the minimum elevation

(10°).

Table 28 presents the pfd limits for both GSO and NGSO earth stations for the different FSS I/N

values assumed in the analysis.

TABLE 28

pfd limits in dB(W/(m2 ‧ MHz)) at the FSS earth station receivers

FSS I/N values Time

percentage

pfd limt at GSO earth station

(dB(W/(m2 ‧ MHz)))

pfd limit at NGSO earth station

(dB(W/(m2 ‧ MHz)))

I/N = –6 dB 1% –104.4 –106.6

I/N = –10.5 dB 20% –108.9 –111.1

I/N = +8 dB 0.02% –90.4 –92.6

Taking the worst-case assumption for each I/N criterion of +8 dB, –6 dB and –10.5 dB for time

percentages 0.02%, 1%, 20% respectively, a pfd level of –92.6 dB(W/(m2 ‧ MHz)),

−106.6 dB(W/(m2 ‧ MHz)), –111.1 dB(W/(m2 ‧ MHz)) should not be exceeded to protect the FSS

earth station receivers.

To verify the compliance with the above pfd limit, the following equation should be used:

𝑝𝑓𝑑(𝐸𝑙) = 𝐸𝐼𝑅𝑃𝑑𝐵𝑊

𝑀𝐻𝑧

(𝐸𝑙) + P. 452(𝑑, %𝑡𝑖𝑚𝑒) − 10 log10(λ2

4π)

where:

P.452: propagation model based on with p = 20%, 1%, and 0.02% of time

𝐸𝐼𝑅𝑃𝑑𝐵𝑊

𝑀𝐻𝑧

(𝐸𝑙): HAPS e.i.r.p. density level (based on clear sky condition) in dB(W/MHz)

(dependent on the maximum antenna gain towards the horizon, el). For 20%

the nominal e.i.r.p. density was assumed and for 1% and 0.02% of time the

maximum e.i.r.p. density was assumed

𝑑: distance between the HAPS grounds station and the FSS earth station

% 𝑜𝑓 𝑡𝑖𝑚𝑒: 20, 1, and 0.02 % of time is used.

The worst-case configuration of the HAPS CPE/GW consists of these stations operating at the

minimum elevation angle (20° for system 6) at the border of coverage of the HAPS and the FSS

Rep. ITU-R F.2475-0 101

earth station operating at its minimum elevation angle (10°) and pointing in the same azimuthal

plane. Figure 76 illustrates this Minimum Coupling Loss scenario:

FIGURE 76

MCL interference scenario studied

The generated pfd levels as a function of the separation distance from this worst-case are shown in

Fig. 77.

FIGURE 77

Calculated pfd at an FSS receiver (for I/N = 0 dB, –6 dB, and –10.5 dB) as a function

of distance caused by a HAPS station

102 Rep. ITU-R F.2475-0

Figure 77 shows that a separation distance of:

• 0.75 km for time percentage of 0.02%;

• 3.9 km for time percentage of 1%;

• 0.32 km for time percentage of 20%

will be sufficient between any HAPS station and FSS earth station, considering the worst-case

analysis (i.e. minimum coupling loss and with the different FSS I/N criteria i.e. +8 dB, –6 dB and

−10.5 dB for time percentages 0.02%, 1%, 20% respectively).

1.2.3.2 Statistical method


a single HAPS ground (interferer) stations and FSS ES (victim) as well as for a typical FS terminal

and a FSS earth station.

Step 1: Compute the FSS antenna gain towards the HAPS GW/CPE based on the following input

parameters:



– FSS station antenna pointing azimuth: random variable with a uniform distribution between

–180° to 180°;

– FSS station antenna pointing elevation: the following distribution were assumed for carrier

6 and 26 (based on the satellite orbital altitude and minimum elevation constraints of

10 degrees).

FIGURE 78

FSS Earth station elevation distribution

– FSS maximum antenna gain: 68 dBi for the FSS GSO (carrier #06) station and 50 dBi for

the FSS NGSO station (carrier #26).

– FSS antenna pattern: Recommendation ITU-R S.465.

Step 2: Compute the HAPS GW/CPE antenna gain towards the FSS earth station based on the


– 0° is taken for the elevation angle towards the FSS earth station;

– 180° is taken for the azimuth towards the FSS earth station;

Rep. ITU-R F.2475-0 103


between -180° to 180°;

– HAPS station antenna pointing elevation: randomized elevation with the lower bound being

set to the minimum elevation (20 degrees) which takes into account the higher probability

of finding HAPS ground terminals located close to the edge of coverage area. See

distribution assumed below.

FIGURE 79

HAPS ground station elevation distribution



Step 3: Compute the FS Point-to-Point antenna gain towards the FSS earth station based on the


– 0° is taken for the elevation angle towards the FSS earth station;

– 180° is taken for the azimuth towards the FSS earth station;


180° to 180°;

– FS station antenna pointing elevation: random variable with a normal distribution (median -

0.004 and standard deviation 3.6);

– FS maximum antenna gain (from Recommendation ITU-R F.758): random uniform

distribution with gain between 34 dBi and 45 dBi.

Step 4: Compute the minimum separation distance needed to meet the FSS I/N values criteria for

both HAPS ground stations and FS terminals:

– Analysis done with the following range of FSS I/N values: +8 dB, –6 dB and –10.5 dB for

time percentages 0.02%, 1%, and 20%, respectively;

– HAPS station nominal e.i.r.p. density: –2 dB(W/MHz) for the GW and 5 dB(W/MHz) for

the CPE;

– FS station e.i.r.p. density: 21.5 dB(W/MHz) taken from Recommendation ITU-R F.758;

– Shielding (only applicable to the GW): no results considering shielding are presented as the

separation distances are very short without considering shielding;

104 Rep. ITU-R F.2475-0

– Propagation model used: Recommendation ITU-R P.452 with the relevant time

percentages.


The plots in Fig. 80 present the separation distance CDF for HAPS GW/CPE into FSS GSO/NGSO

earth stations and FS Point-to-Point into FSS GSO/NGSO earth stations.

FIGURE 80

HAPS GW/CPE and FS (Point-to-Point) to FSS GSO/NGSO earth station, minimum separation distance CDF

Figure 80 shows that the separation between a HAPS ground terminal and an FSS GSO earth station

is between 0.4 m to 1.8 km, depending on the I/N criteria. In the case of an FSS NGSO earth

station, the separation distance with a HAPS ground terminal is between 0.4 m to 2.3 km. Another

key observation is that the separation distance between an FS terminal and an FSS GSO/NGSO

earth station is much greater compared to the separation between a HAPS ground terminal and an

FSS GSO/NGSO earth station. This analysis is presented only to show the possible co-existence

between HAPS and FSS, and does not consider whether the separation distances would lead to

constraints on FSS Earth stations.

It is important to note that the above results consider a worst case in which the HAPS ground

stations are emitting 100% of the time. In reality, HAPS ground stations will operate with a duty

cycle decreasing the actual time for which any potential interference could be perceived by the

incumbent service.



such as:

Rep. ITU-R F.2475-0 105

– The positioning of HAPS ground terminals and to increase angular separation.



These mitigation techniques were not considered in the results presented above and their impact, if

any, should be further studied.

The worst-case separation distance can be reduced to 0.25 km (using 10 dB shieling factor),

0.055 km (using 20 dB shielding factor), and 0.033 km (using 30 dB shielding factor) for FSS GSO,

considering the worst-case scenario (i.e. I/N = –6 dB (1%)). In the case of FSS NGSO, the

separation distance can be reduced to 0.5 km (using 10 dB shielding factor), 0.09 km (using 20 dB

shielding factor), and 0.037 km (using 30 dB shielding factor).




incumbent service.

1.2.3.4 Summary of HAPS ground terminals to FSS ES

Two types of analysis are presented:

1 pfd limit based on the FSS I/N values assumed. This resulted in the following limits

presented in Table 29.

TABLE 29

FSS I/N values Time percentage pfd limit at GSO earth station

(dB(W/(m2 ‧ MHz)))

pfd limit at NGSO earth station

(dB(W/(m2 ‧ MHz)))

I/N = –6 dB 1% –104.4 –106.6

I/N = –10.5 dB 20% –108.9 –111.1

I/N = +8 dB 0.02% –90.4 –92.6

2 a statistical method presenting a minimum separation CDF to compare the following

scenarios:

– HAPS ground terminal (CPE and gateway) to FSS earth station.

– FS to FSS earth station.

This second analysis shows that the separation distance between an FS terminal and an FSS earth

station is much greater compared to the separation between a HAPS ground terminal and an FSS

earth station. Separation distances for the protection of FSS GSO earth station and FSS NGSO earth

station from HAPS ground terminal are in the range 0.4 m to 1.8 km and 0.4 m to 2.3 km

respectively.

1.2.4 Methodology and results – FSS satellite to HAPS Platform

1.2.4.1 I/N calculation – FSS satellite to HAPS Platform

The following methodology is used to calculate the I/N from satellite to HAPS.

It is assumed that the HAPS is pointing towards the edge of the HAPS coverage (i.e. elevation

of 70°) and the satellite is pointing towards the HAPS with an elevation angle varying between the

minimum elevation of 10° and 90° (corresponding to the sub-satellite point).

106 Rep. ITU-R F.2475-0

FIGURE 81

Worst case scenario geometry

The I/N level at the HAPS receiver is calculated using the equation below:

𝐼𝑁⁄ = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥 − 𝐹𝑆𝐿 − 10log(𝐾𝑇𝐵) + 𝐺𝑟𝑥

𝐻𝐴𝑃𝑆()

where:

𝐸𝐼𝑅𝑃𝑚𝑎𝑥 : maximum e.i.r.p. density of satellite antenna (dB(W/MHz))

𝐹𝑆𝐿: free space loss (dB) between HAPS and satellite

𝑋 : elevation angle of the satellite (10° to 90°)

θ: discrimination angle (degrees) at the HAPS between the pointing direction of

the HAPS and satellite, θ = 𝑋 + 20;

𝐺𝑟𝑥𝐻𝐴𝑃𝑆(): receiver antenna gain (dBi) of the HAPS for off axis angle .

Figure 82 shows the variation of HAPS I/N for a range of satellite elevation angles (i.e. 10° to 90°).

Rep. ITU-R F.2475-0 107

FIGURE 82

HAPS I/N vs. elevation

Table 30 shows the I/N from FSS GSO satellite transmitter to HAPS gateway receiver that would

receive the highest interference level.

TABLE 30

Maximum I/N from FSS Satellite to HAPS GW and CPE

I/N (dB)

FSS GSO Satellite

Transmitter:

Carrier 5

FSS NGSO Satellite

Transmitter:

Carrier 25/26

HAPS Platform (Gateway) Receiver:

System 6

–25.39

(at 10° satellite elevation angle)

–44.4


HAPS Platform (CPE) Receiver:

System 6

–39.71


–27.19


The above analysis shows that the I/N level is below the assumed HAPS protection criteria of

I/N = –10 dB (long term) and +10 (short term) dB.

1.2.4.2 Summary of FSS satellite to HAPS

The above analysis shows that the I/N level is below the assumed HAPS protection criteria of

I/N = –10 dB (long term) and +10 (short term) dB for worst case analysis.


HAPS ground into FSS earth stations

The statistical analysis shows that the required minimum separation distance between HAPS ground

terminal and FSS GSO/NGSO earth station are in the range 0.4 m to 1.8 km and 0.4 m to 2.3 km,

respectively, depending on the I/N criteria assumed for the FSS. In addition, the studies show that

the required separation distance between HAPS ground terminal and FSS ES is much less compared

to FS and FSS ES terminal. This analysis is presented only to show the possible co-existence

between HAPS and FSS, and does not consider whether the separation distances would lead to

constraints on FSS Earth stations.

108 Rep. ITU-R F.2475-0




incumbent service.

1.3 Study C: Sharing studies in the ground-to-HAPS direction

Figure 83 presents an overview on the interference scenarios of studies of the HAPS with the GSO

and NGSO FSS systems.

FIGURE 83

Sharing scenarios in the 38-39.5 GHz frequency range

1.3.1 Impact from transmitting HAPS ground station into FSS receiving earth station and

comparison with the impact from transmitting FS station into FSS receiving earth

station

1.3.1.1 Impact from transmitting HAPS ground station into FSS receiving earth station


a single HAPS Systems 2, 4a and 4b station (interferer) and FSS Earth station (victim).

Step 1: Compute the HAPS System 2, 4a and 4b transmitting ground station antenna gain towards

the FSS impacted station based on the following input parameters:

– 0° is taken for the elevation angle towards the FSS impacted station;

– 0° is taken for the azimuth angle towards the FSS impacted station;





• 33.3° and 90° for the HAPS system 2 Gateways;

Rep. ITU-R F.2475-0 109

• 21° and 90° for the HAPS system 2 CPE and for Systems 4a and 4b CPE and

Gateways.


FIGURE 84

Elevation statistics


• for HAPS System 2: 55 dBi for the GW and 49 dBi for the CPE;

• for GW of HAPS Systems 4a and 4b: 57.4 dBi;

• for CPE of HAPS System 4a: 49.8 dBi;

• for CPE of HAPS System 4b: 47.2 dBi and 39.3 dBi.


• For System 2: ITU-R F.1245-2;

• For Systems 4a and 4b: ITU-R S.580-6.

Step 2: Compute the FSS impacted Earth station antenna gain towards the HAPS transmitting

ground station based on the following input parameters:



– FSS Earth station antenna pointing azimuth: random variable with a uniform distribution


– FSS station antenna pointing elevation: 10°;

– FSS maximum antenna gain: random variable with a uniform distribution between 50

(carrier 26) and 68 dBi (carrier 6);

– FSS antenna pattern: ITU-R S.465-6.


𝐼𝑚𝑎𝑥 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐻𝐴𝑃𝑆 − 𝐺𝑚𝑎𝑥𝐻𝐴𝑃𝑆+ 𝐺𝐻𝐴𝑃𝑆→𝐹𝑆𝑆 − 𝐴𝑡𝑡𝑃−452−16 + 𝐺𝑟𝐹𝑆𝑆

𝐴𝑡𝑡𝑃−452−16 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐻𝐴𝑃𝑆 − 𝐺𝑚𝑎𝑥𝐻𝐴𝑃𝑆+ 𝐺𝐻𝐴𝑃𝑆→𝐹𝑆𝑆 + 𝐺𝑟𝐹𝑆𝑆 − 𝐼𝑚𝑎𝑥

where:

EIRPmaxHAPS HAPS station maximum e.i.r.p. density (in the main beam) (dB(W/MHz)) as

given in Table 31.

110 Rep. ITU-R F.2475-0

TABLE 31

HAPS station maximum e.i.r.p. density (dB(W/MHz)

GW CPE


System 2 –1.8 33.2 9.2 33.5

System 4a 11 26

15 30

System 4b 19 / 14.5 35.5 / 26.5

GmaxHAPS maximum HAPS station antenna gain (dBi)

GHAPS→FSS HAPS transmitting ground station antenna gain towards the FSS impacted

station (dBi)

GrFS FSS impacted Earth station antenna gain towards the HAPS transmitted station

(dBi)

AttP-452-16 propagation loss (dB) needed to meet the FSS protection criteria based on

P.452-16 propagation model with p=20% when Imax/N = –10.5 dB p = 1%

when Imax/N = –6 dB and finally p = 0.02% when Imax/N = 8. The land path type

is used, the typical temperature is taken at 20°, the pressure at 1013 mbar and

no clutter

Imax: maximum allowable interference level:

–155.1 dB(W/MHz) (carrier #06) and –157.3 dB(W/MHz) (carrier #26)

(i.e. I/N of –10.5 dB) not to be exceeded by more than 20% of the time


(i.e. I/N of –6 dB) not to be exceeded by more than 1% of the time


(i.e. I/N of 8 dB) not to be exceeded by more than 0.02% of the time.

Step 4: Compute the separation distance needed to meet the FSS protection criteria based on the



stable CDF.

1.3.1.2 Impact from transmitting FS station into FSS receiving Earth station


a single FS station (interferer) and FSS Earth station (victim).

Step 1: Compute the FS transmitting station antenna gain towards the FSS impacted Earth station


– 0° is taken for the elevation angle towards the FSS impacted Earth station;

– 0° is taken for the azimuth towards the FSS impacted Earth station;


−180° to 180°;


−0.004 and standard deviation 3.6);


46 dBi;


Rep. ITU-R F.2475-0 111

Step 2: Compute the FSS impacted Earth station antenna gain towards the FS transmitting station




– FSS station antenna pointing azimuth: random variable with a uniform distribution between

−180° to 180°;

– FSS Earth station antenna pointing elevation: 10°;

– FSS Earth maximum antenna gain: random variable with a uniform distribution between 50

(carrier 26) and 68 dBi (carrier 26);

– FSS antenna pattern: ITU-R S.465-6.


𝐼𝑚𝑎𝑥 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐹𝑆 − 𝐺𝑚𝑎𝑥𝐹𝑆+ 𝐺𝐹𝑆→𝐹𝑆𝑆 − 𝐴𝑡𝑡𝑃−452−16 + 𝐺𝑟𝐹𝑆𝑆

𝐴𝑡𝑡𝑃−452−16 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐹𝑆 − 𝐺𝑚𝑎𝑥𝐹𝑆+ 𝐺𝐹𝑆→𝐹𝑆𝑆 + 𝐺𝑟𝐹𝑆𝑆 − 𝐼𝑚𝑎𝑥

where:

EIRPmaxFS: FS station maximum e.i.r.p. density (in the main beam): random variable with

a uniform distribution between −15.7 and 17 dB(W/MHz)

GmaxFS : maximum FS station antenna gain (dBi)

GFS→FSS : FS transmitted station antenna gain towards the FSS impacted Earth station

(dBi)

GrFSS : FSS impacted Earth station antenna gain towards the FS transmitting station

(dBi)

AttP-452-16 : propagation loss (dB) needed to meet the FSS protection criteria based on

P.452-16 propagation model with p=20%

(Imax/N = –10.5 dB), p = 1% (Imax/N = –6 dB) and finally p = 0.02%

(Imax/N = 8 dB). The land path type is used, the typical temperature is taken at

20°, the pressure at 1013 mbar and no clutter;

Imax : maximum allowable interference level:

–155.1 dB(W/MHz) (I/N of –10.5 dB) not to be exceeded by more than 20% of

the time

–150.6 dB(W/MHz) (I/N of –6 dB) not to be exceeded by more than 1% of the

time

–136.6 dB(W/MHz) (I/N of 8 dB) not to be exceeded by more than 0.02% of

the time.

Step 4: Compute the separation distance needed to meet the FSS protection criteria based on the


Step 5: Store the calculated separation distance and repeat Steps 1 through 4 sufficiently to obtain a

stable CDF.

1.3.1.3 Results


112 Rep. ITU-R F.2475-0

FIGURE 85

Results for the long and short term protection criteria

From the above results it can be concluded that HAPS systems 2, 4a and 4b ground stations can be

considered as any FS station as the result of the impact of HAPS ground station emissions into FSS

Earth station receivers is less than the impact of an FS emitting station into FSS receiving Earth

station.

1.3.2 Impact from FSS space station into HAPS receivers

The power flux-density at the Earth’s surface produced by emissions from a space station, including

emissions from a reflecting satellite, for all conditions and for all methods of modulation, shall not

exceed the limit given in Table 21-4 from Article 21 of the Radio Regulations. The limit relates to

the pfd which would be obtained under assumed free-space propagation conditions and applies to

emissions by a space station of the service indicated where the frequency bands are shared with

equal rights with the fixed or mobile service, unless otherwise stated.

Table 32 is a relevant extract of RR Table 21-4.

TABLE 32

RR Article 21 extract (space station pfd limit in the 39 GHz band)

Frequency

band Service

Limit in dB(W/m²) for angles of arrival () above the

horizontal plane Reference

bandwidth 0 – 5° 5° – 20° 20° – 25° 25° – 90°

37.5-40 GHz Fixed Satellite

Service (non-

geostationary orbit)

–120 –120 + 0.75( – 5) –105 1 MHz

37.5-40 GHz Fixed Satellite

Service (geostationary

orbit)

–127 –127 + (4/3)

( – 5)

–107 + 0.4

( –20)

–105 1 MHz

Rep. ITU-R F.2475-0 113

The maximum HAPS antenna gain above 5 degrees is shown in Fig. 86 and is 2.5 dBi for system 2

CPE to HAPS link and -7 dBi for system 2 GW to HAPS links

FIGURE 86

Maximum HAPS station antenna gain above 5°

(CPE beam left and GW beam right)

The maximum interference level is given by the following equation:

𝐼𝑚𝑎𝑥

𝑁= 𝑝𝑓𝑑𝐹𝑆𝑆𝑚𝑎𝑥 + 10 ∗ log10 (

𝜆2

4𝜋) + 𝐺𝑟 − 𝑁

where:

PfdFSSmax: FSS space station pfd level from the above table in dB(W/(m² · MHz))

Gr: maximum HAPS antenna gain towards FSS satellite (2.5 dBi in the case of

CPE beam and –7 dBi in the case of gateway bean

N: receiver thermal noise (–142.28 dB(W/MHz) for the CPE beam and

–142.58 dB(W/MHz) for the GW beam).

Figure 87provides the level of interfernce over noise for system 2 HAPS receivers. Those are below

the long term HAPS protection criteria.

FIGURE 87

Comparison between long-term HAPS protection criteria and received interference from FSS systems

114 Rep. ITU-R F.2475-0

It can be concluded that HAPS receivers will not be impacted and can accept interference from FSS

downlink that are compliant with Table 21-4 of the RR Article 21.

1.4 Study D: sharing studies in the HAPS-to-ground direction

1.4.1 Summary

This study aims to study the sharing between HAPS downlink emissions and FSS receiving earth

stations. Both GSO and NGSO FSS links are considered in these studies, and FSS technical

parameters considered are the ones provided in Table 7 as reminded below:

− Carrier #06 relating to a GSO FSS system.

− Carrier #26 relating to a NGSO system.

1.4.2 FSS protection criteria

The values for GSO FSS protection criteria are provided by the relevant group. These values are

summarized in Table 33.

TABLE 33

FSS protection criteria used in the following sharing studies

Long-term

interference Short-term interference

I/N (dB) –10.5 dB –6 dB +8 dB

Not to be exceeded for

more than

20% of the time 1% of the time 0.02% of the time

1.4.3 Impact from transmitting HAPS into receiving FSS earth station

1.4.3.1 Impact from transmitting HAPS into GSO FSS earth station receiver

1.4.3.1.1 Impact from transmitting HAPS into receiving GSO FSS earth station

This study aims to study the sharing between HAPS downlink emissions and GSO FSS receiving

earth stations

This study aims to define the maximum pfd levels from HAPS versus elevation angle in order to

protect GSO FSS receiving earth stations.

Step 1: Consider a GSO FSS earth station based on the following input parameters:

– latitude of the GSO FSS earth station: 0°

– pointing elevation of the GSO FSS earth station: 10°

Step 2: Divide the sky into cells of approximately equal solid angles as described in the section 1 of

Annex 2 of Recommendation ITU-R S.1586-1 (see Fig. 88), and locate randomly a HAPS within

each cell considered.

Rep. ITU-R F.2475-0 115

FIGURE 88

Division of the sky into 2334 cells of approximately equal solid angle

Step 3: For each cell, compute the GSO FSS earth station antenna gain towards the HAPS location.

Step 4: For each cell, compute and store the HAPS pfd level required at the GSO FSS earth station

to meet the FSS protection criterion using the following equation:

𝑝𝑓𝑑𝑖(θ) = 𝐼𝑁⁄ + 𝑁 + 10 × log10 (

4𝜋

𝜆2) − 𝐺𝑟(φ) + 𝐴𝑡𝑡𝑔𝑎𝑧(θ)

where:

i: index of the cell (1 to 2334)

θ: elevation angle at the GSO FSS earth station towards the HAPS (angle of

arrival above the horizontal plane) (degrees)

pfdi(): required pfd at the GSO FSS earth station location by the HAPS located in cell

i (dB(W/(m².MHz)))

I/N: FSS protection criteria (see section 1.4.2 above)

N: GSO FSS earth station receiver noise level (dB(W/MHz))

φ: angle between the vector GSO FSS earth station to HAPS and the GSO FSS

earth station antenna main beam pointing vector (degrees)

Gr(φ): GSO FSS earth station antenna gain towards the HAPS (see Step 3), (dBi)

Attgaz(θ): gaseous attenuation (Rec. ITU-R SF.1395) for the slant-path of θ°(dB).

Step 5: Redo steps 2 to 4 for 5000 iterations

Step 6: For each cell, determine the maximum required pfd level of HAPS to ensure the GSO FSS

protection criteria of –10.5 dB in all iterations considered using the following equation:

𝑝𝑓𝑑𝑖 𝑚𝑎𝑥(θ) = 𝑚𝑖𝑛𝑗(𝑝𝑓𝑑𝑖(θ))

where:

i: index of the cell

j: index of iteration.

Note that in this case the GSO FSS protection criteria of –10.5 dB is met for 100% of the time.

116 Rep. ITU-R F.2475-0

Step 7: Redo steps 2 to 6 considering other latitudes for the location of GSO FSS earth station

(20° and 40°), and pointing elevations of the GSO FSS earth station:

40° and 80° for GSO FSS earth station located at 0° latitude;

40° and 66.5° for GSO FSS earth station located at 20° latitude;

43.7° for GSO FSS earth station located at 40° latitude.

Figure 89 provide the results for the different latitudes/GSO FSS antenna point elevations.

FIGURE 89

Required maximum pfd levels to meet the FSS long-term protection criteria of –10.5 dB

0° LATITUDE, 10° ELEVATION

0°

LATITUDE, 40° ELEVATION

0°

LATITUDE, 80° ELEVATION 20° LATITUDE, 10° ELEVATION

Rep. ITU-R F.2475-0 117

20° LATITUDE, 40° ELEVATION 20° LATITUDE, 66.5° ELEVATION


The above Figure shows that the pfd level required to protect the GSO FSS station highly depends

on the relative locations of the HAPS with respect to the GSO FSS station and on the pointing

direction of the GSO FSS earth station towards the GSO arc.

In the largest part of the sky, the GSO FSS earth station can tolerate high pfd levels. This

corresponds to locations in the sky where HAPS are seen in the back-lobes or even side-lobes of the

FSS stations. This corresponds to a large portion of the sky as, by nature, GSO FSS earth stations

can point only in specific directions, corresponding to directions where the GSO arc is visible at a

given latitude.

However, from the HAPS prospective, such high pfd levels could be required – if required at all –

only within their service areas (typically 50 km radius). Outside these service areas, pfd levels are

much lower, as the HAPS elevation as seen from the GSO FSS earth station decreases.

This is illustrated in the following figures which show – as an example – the maximum I/N

produced by System 4a at a typical GSO FSS earth station located at the same latitudes and with the

same pointing elevations than those considered in Fig. 90.

118 Rep. ITU-R F.2475-0

FIGURE 90

Maximum I/N produced at a GSO FSS earth station by System 4a

0°


0°


0°

LATITUDE, 80° ELEVATION 20° LATITUDE, 10° ELEVATION


Rep. ITU-R F.2475-0 119


The Figure above shows that the HAPS locations in the sky seen from the GSO FSS station where

the I/N may exceed the FSS GSO long term is very limited and restricted to the particular pointing

direction of the GSO FSS earth station with respect to the HAPS location in the sky.

The frequency range of consideration in this study (38-39.5 GHz) is not identified for use by

high-density applications in the Fixed-Satellite Service (see RR No. 5.516B). This means that FSS

earth stations are coordinated on a case-by-case basis with terrestrial services and between

Administrations.

Given the very particular geometry involved when the assessing sharing between HAPS and a

particular GSO FSS earth station (see Fig. 90 above), it is hence assumed that as any other station of

the Fixed Service, HAPS can be coordinated on a case-by-case basis. This coordination will be

done using the specific characteristics of the HAPS emissions in the direction of the GSO FSS earth

station and the specific pointing direction(s) of the GSO FSS earth station involved.

1.4.3.1.2 Proposed way forward to handle coordination between HAPS-to-ground emissions

and a FSS receiving earth station

As explained and illustrated in the above paragraph, as any other station of the Fixed Service,

HAPS can be coordinated on a case-by-case basis with individual GSO FSS earth stations in the

38-39.5 GHz.

For that, it is proposed to trigger that coordination on the basis of the minimum angle at the GSO

FSS earth station between the line to the HAPS and the lines to the GSO arc.

Indeed, the I/N and hence the required pfd at the GSO FSS earth station can be expressed as

follows:

𝐼𝑁⁄ = 𝑝𝑓𝑑(α) + 10log10 (

λ2

4π) + 𝐺𝑟𝐹𝑆𝑆(α) − 𝑁

𝑝𝑓𝑑(α) = 𝐼𝑁⁄ − 10log10 (

λ2

4π) − 𝐺𝑟𝐹𝑆𝑆(α) + 𝑁

where:

: minimum angle at the GSO FSS earth station between the line to the HAPS and

the lines to the GSO arc (degree)

pfdi(): required pfd at the GSO FSS earth station location by the HAPS

(dB(W/(m2· MHz))

120 Rep. ITU-R F.2475-0

I/N: FSS protection criteria (see § 1.4.2 above)

N: GSO FSS earth station receiver noise level (dB(W/MHz))

GrFSS(): maximum GSO FSS earth station antenna gain towards the HAPS (dBi).

As indicated in Table 7, the GSO FSS earth station antenna pattern conforms to Recommendation

ITU-R S.465-5 which is given below:

G = Gmax – 2.5 × 10–3 (D/)2 for 0 ≤ < m

G = 32 for m ≤ < r

G = 32 – 25 log for r ≤ < b

G = –10 for b ≤ ≤ 180°

where:

𝐷

𝜆= √10(

𝐺𝑚𝑎𝑥10

)

ηπ2

φ𝑚 = 20λ/𝐷√𝐺𝑚𝑎𝑥 − 𝐺1

G1 = 32 for D/ > 100,

= – 18 + 25 log (D/) for D/ ≤ 100.

r = 1° for D/ > 100,

= 100 /D for D/ ≤ 100.

φ𝑏 = 10(42

25)

Using a 68 dBi antenna gain, the GSO FSS antenna pattern of a 6.8 m antenna at 39 GHz is hence:

G = 68 – 1954 ² for 0 ≤ <

G = 32 for ≤ <

G = 32 – 25 log for 1° ≤ < 47.9°

G = –10 for 47.9° ≤ ≤ 180°

Hence the maximum pfd produced by a HAPS can be expressed as follows:

–169.9 + 1954 ² dB(W/(m2 · MHz)) for 0 ≤ <

–133.9 dB(W/(m2 · MHz)) for ≤ <

–133.9 + 25 log dB(W/(m2 · MHz)) for 1° ≤ < 47.9°

–91.9 dB(W/(m2 · MHz)) for 47.9° ≤ ≤ 180°

where:

: minimum angle at the GSO FSS earth station between the line to the HAPS and

the lines to the GSO arc (degrees).

To calculate the pfd produced by a HAPS, the following equation should be used:

pfdI/N = EIRP– 10log10(4d²) – Attgaz

where:

d : distance between the HAPS and the GSO FSS earth station (m)

Rep. ITU-R F.2475-0 121

Attgaz : attenuation to atmospheric gazes on the HAPS to GSO FSS earth station path

(dB)

pfdI/N : required pfd at the GSO FSS earth station location to meet the FSS protection

criteria (dB(W/(m² · MHz))

EIRP : Maximum e.i.r.p. spectral density in the direction of the GSO FSS earth station

(dB(W/MHz)).

1.4.3.1.3 Summary and analysis of the results for sharing with GSO FSS

According to the results shown in above, HAPS technology can coexist with GSO FSS in the

38-39.5 GHz band in case the pfd level produced at the Earth surface is below the proposed pfd

mask.

It is proposed that for the purpose of protecting GSO FSS earth station in neighbouring

administrations from co-channel interference, it is proposed that for coordination of a transmitting

HAPS station is required when, and using long term protection criteria (–10.5 dB), the pfd over any

point of an administration’s border exceeds the following values:

–169.9 + 1954 ² dB(W/(m² · MHz)) for 0 ≤ <

–133.9 dB(W/(m² · MHz)) for ≤ <

–133.9 + 25 log dB(W/(m² · MHz)) for 1° ≤ < 47.9°

–91.9 dB(W/(m² · MHz)) for 47.9° ≤ ≤ 180°

where is the minimum angle on the border between the line to the HAPS and the lines to the GSO

arc in degrees.

To calculate the pfd produced by a HAPS, the following equation should be used:

pfdI/N = EIRP– 10log10(4d²) - Attgaz

where:



(dB)



EIRP : maximum e.i.r.p. spectral density in the direction of the GSO FSS earth station

(dB(W/MHz)).

The pfd necessary to protect FSS Earth station use within the territory of an administration

deploying the HAPS is not specified. While conditions for the co-existence between HAPS and FSS

earth stations within the territory of an administration can be based on the same HAPS pfd

thresholds, further specific conditions would need to be addressed at a national level to avoid undue

constraints to existing Fixed Satellite Service.

1.4.3.2 Impact from transmitting HAPS into receiving NGSO FSS earth station

Some technical parameters were provided by the relevant group for NGSO FSS systems to be

considered in the sharing studies (see Table 7, Carrier #26), in particular NGSO FSS earth station

receiving parameters, the type of orbit of the constellation (circular) and its altitude (1 400 km) to

consider.

However, this information is incomplete for conducting sharing studies, no information is provided

regarding the constellation like:

122 Rep. ITU-R F.2475-0

– the number of planes of the constellation;

– the number of satellites per planes;

– the inclination of the planes;

– the tracking strategy of the NGSO FSS earth stations.

All these parameters are essential to adequately characterize interference at the NGSO FSS earth

station.

In the following sharing studies have been made using the following assumptions on these

parameters. These have been chosen in order to provide a “generic” sharing study case,

representative of NGSO constellations filed so far the maximum possible extent:

TABLE 34

Assessment on NGSO FSS constellation characteristics used in the following sharing studies

Number of planes of the constellation 18

number of satellites per planes 36

Inclination of the planes 90°

Tracking strategy of the satellites by the NGSO

FSS earth stations

Best elevation with a minimum elevation angle of

10° at the NGSO FSS Earth stations

1.4.3.2.1 Impact from transmitting HAPS into receiving NGSO FSS earth station

This study aims to define the maximum pfd levels from HAPS versus elevation angle in order to

protect NGSO FSS receiving earth stations.

To achieve that, the NGSO FSS constellation is run considering for 10 orbit periods, with a time

step of 1 second.


account the impact of a single HAPS emissions:

Step 1: Consider a NGSO FSS earth station located at 0° latitude and initiate the NGSO FSS

constellation based on the parameters detailed above.

Step 2: Divide the sky into cells of approximately equal solid angles as described in

Recommendation ITU-R S.1586-1 (see Fig. 91), and locate randomly a HAPS within each cell

considered.

Rep. ITU-R F.2475-0 123

FIGURE 91

Division of the sky into 2334 cells of approximately equal solid angle

Step 3: Calculate the pointing direction of the NGSO FSS earth station based on the constellation

parameters and the NGSO FSS earth station tracking strategy.

Step 4: For each cell, compute the NGSO FSS earth station antenna gain towards the HAPS

location.

Step 5: For each cell, compute and store the HAPS pfd level required at the NGSO FSS earth

station to meet the FSS protection criterion using the following equation:

𝑝𝑓𝑑𝑖(θ) = 𝐼𝑁⁄ + 𝑁 + 10 × log10 (

4π

λ2) − 𝐺𝑟(φ) + 𝐴𝑡𝑡𝑔𝑎𝑧(θ)

where:

i: index of the cell (1 to 2334)

θ: elevation angle at the GSO FSS earth station towards the HAPS (angle of

arrival above the horizontal plane) (degrees)

pfdi(θ): required pfd at the GSO FSS earth station location by the HAPS located in cell

i (dB(W/(m² · MHz)))

I/N: FSS protection criteria (see § 1.4.2 above)

N: NGSO FSS earth station receiver noise level (dB(W/MHz))

φ: angle between the vector NGSO FSS earth station to HAPS and the NGSO

FSS earth station antenna main beam pointing vector (degrees)

Gr(φ): NGSO FSS earth station antenna gain towards the HAPS (see Step 4), (dBi);

Attgaz(θ): gaseous attenuation (Rec. ITU-R SF.1395) for the slant-path of (dB).

Step 6: Redo steps 3 to 5, for each time step up to 10 orbit periods.

Step 7: For each cell, determine the maximum required pfd level of HAPS to ensure the NGSO FSS

protection criteria in all iterations considered using the following equation:

𝑝𝑓𝑑𝑖 𝑚𝑎𝑥(θ) = 𝑚𝑖𝑛𝑗(𝑝𝑓𝑑𝑖(θ))

124 Rep. ITU-R F.2475-0

where:

i: index of the cell

j: index of time step.

Step 7: Redo steps 2 to 7 considering a NGSO FSS earth station located 40° latitude.

Figure 92 provides the results depending on the FSS protection criteria.

FIGURE 92

REQUIRED MAXIMUM PFD LEVELS TO MEET THE FSS CRITERIA

0° LATITUDE, 1 M DIAMETER

-10.5 DB / 20% OF THE TIME

0°

LATITUDE, 1 M DIAMETER

-6 DB / 1% OF THE TIME

0°

LATITUDE, 1 M DIAMETER

8 DB / 0.02% OF THE TIME

40° LATITUDE, 1 M DIAMETER

-10.5 DB / 20% OF THE TIME

Rep. ITU-R F.2475-0 125

The above Figure shows that the pfd level required to protect the NGSO FSS station highly depends

on the statistics of the NGSO FSS earth station pointing directions relative to the HAPS, on the

relative locations of the HAPS with respect to the station and on the tracking strategy of the

satellites by the NGSO FSS earth stations.

Figure 92 also shows that the NGSO FSS earth station can tolerate quite high pfd levels when the

HAPS is seen at low elevation, i.e. when the earth station is located outside the HAPS service area

(typically 50 km, i.e. for elevation angles less than 21°). In particular, required pfd levels for

elevations equal or less than 10° (i.e. for HAPS which nadir are located at more than 100 km from

the NGSO FSS earth station) are always much higher than what would be effectively transmitted by

HAPS systems at these elevation angles.

The frequency range of consideration in this study (38-39.5 GHz) is not identified for use by high-

density applications in the Fixed-Satellite Service (see RR No. 5.516B). This means that FSS earth

stations are coordinated on a case-by-case basis with terrestrial services and between

Administrations.

Given the very particular geometry involved when the assessing sharing between HAPS and a

particular NGSO FSS station (see Fig. 92 above), it is hence assumed that as any other station of the

Fixed Service, HAPS can be coordinated on a case-by-case basis. This coordination will be done

using the specific characteristics of the HAPS emissions in the direction of the NGSO FSS earth

station and on the statistics of pointing direction(s) of the NGSO FSS earth station involved in the

direction of the HAPS. These statistics highly depends on the constellation (number of satellite,

number of planes, number of satellites per planes, altitude), and on the tracking strategy of the

NGSO FSS earth station.

For the purpose of protecting NGSO FSS earth station in neighbouring administrations from co-

channel interference, it is proposed to use a predetermined coordination distance of 100 km between

the HAPS nadir and an administration’s border. This distance of 100 km corresponds to the

maximum distance between the sub-HAPS point and an NGSO FSS earth station when this NGSO

FSS earth station points to its minimum elevation angle (i.e. 10°).

1.4.3.2.2 Summary and analysis of the results for sharing with NGSO FSS

According to the results shown in above, HAPS technology can coexist with NGSO FSS in the

38-39.5 GHz band when taking into account the statistics of the NGSO FSS earth station pointing

directions relative to the HAPS, and on the tracking strategy of the satellites by the NGSO FSS

earth stations.

40° latitude, 1 m diameter

-6 dB / 1% of the time

40° latitude, 1 m diameter

8 dB / 0.02% of the time

126 Rep. ITU-R F.2475-0

It is proposed that for the purpose of protecting NGSO FSS earth station in neighbouring

administrations from co-channel interference, coordination of a transmitting HAPS is required

when, the distance between the HAPS nadir and any point of an administration’s border is less than

the predetermined coordination distance of 100 km.

1.4.4 Impact of transmitting FSS space stations into receiving HAPS ground stations

Sharing between transmitting FSS space stations and HAPS receiving ground stations is assessed to

be of particular concern in the cases where the FSS space stations can be seen in the main beam of

the receiving HAPS ground stations.

But this impact highly depends on the latitude of HAPS ground stations of consideration. Hence at

0° latitude a HAPS ground station would see about 120° GSO arc with elevations ranging from

21.5° to 90°, whereas at 60° latitude, only 20° GSO arc can be seen with elevations ranging from

21.5° to 22°. Above 60.5° latitude, the GSO arc is always seen with elevation angles less than

21.5°, which means that HAPS ground stations will never suffer main-beam interference from GSO

FSS stations.

As a consequence, the areas where HAPS ground stations could potentially suffer interference are

very different from one latitude to another.

This is illustrated in Fig. 93, which shows for different latitudes, within a HAPS service area

(typically 50 km radius) the locations where the GSO arc is seen with an off-axis angle less than 2°

with respect to the HAPS direction as seen from a HAPS ground station:

FIGURE 93

Within a HAPS service area, locations where the GSO arc is seen with an off-axis angle less than 2° with respect to the HAPS

direction, as seen from a HAPS ground station located at different latitudes

Rep. ITU-R F.2475-0 127

As illustrated above, the percentage of the HAPS service areas, where HAPS ground station could

potentially suffer important interference levels from GSO FSS station is very small and even

decreases as the HAPS station latitude increases. Furthermore, it should be noted that the location

of a HAPS ground station in this area does not necessarily imply that this HAPS receiving ground

station will suffer interference from a GSO FSS station, as the interference level will depend on the

exact location of GSO space stations on the GSO arc and on the pfd level from this FSS space

station in the direction of the HAPS service area.

Given the thinness of the areas of potential concern and the number of HAPS ground stations in a

given HAPS service area (only 16 for the proposed System 4a), it is anticipated that a careful choice

of the location of these HAPS ground stations should be possible to limit sharing issues to the

extent possible.

In the seldom cases where this would not be possible, mitigation techniques could be envisaged on

the HAPS side based on the following considerations:

– in this frequency range, FSS systems are expected to operate multi-spot beams with

frequency reuse. The size of these multi-spot beams is expected to be of the same order of

magnitude of a HAPS service area. It is hence expected that depending on the HAPS

ground station location with respect to the GSO spot-beams and on the frequency bands

effectively used within these FSS spot-beams, it will be possible to find frequency ranges

where interference could be manageable;

– in cases where the HAPS ground station location could not be changed, it could be

envisioned to slightly move the HAPS in order to mitigate the interference given the small

number of HAPS ground stations to accommodate in a given HAPS service area (only 16

for the proposed System 4a);

128 Rep. ITU-R F.2475-0

– in cases where the HAPS ground station location could not be changed, it could be

envisioned to use larger antenna in order to mitigate the interference given the small

number of HAPS ground stations to accommodate in a given HAPS service area (only 16

for the proposed System 4a).

As a consequence, it is anticipated that interference from transmitting FSS space stations into HAPS

receiving ground stations will be manageable.

1.4.5 Summary and analysis of the results of studies

1.4.5.1 Impact from transmitting HAPS into receiving FSS earth station

Study D shows that according to the results shown in above, HAPS technology can coexist with

GSO FSS in the 38-39.5 GHz band in case the pfd level produced at the Earth surface is below the

proposed pfd mask.

It is proposed that for the purpose of protecting GSO FSS earth station in neighbouring

administrations from co-channel interference, coordination of a transmitting HAPS is required

when, using the long term protection criteria, the pfd over any point of an administration’s border

exceeds the following values:

–169.9 + 1954 ² dB(W/(m² · MHz)) for 0 ≤ <

–133.9 dB(W/(m² · MHz)) for ≤ <

–133.9 + 25 log dB(W/(m² · MHz)) for 1° ≤ < 47.9°

–91.9 dB(W/(m² · MHz)) for 47.9° ≤ ≤ 180°

where is the minimum angle at the border between the line to the HAPS and the lines to the GSO

arc in degrees.


pfdI/N = EIRP– 10log10(4d²) – Attgaz

where:

d: distance between the HAPS and the GSO FSS earth station (m)

Attgaz: attenuation to atmospheric gazes on the HAPS to GSO FSS earth station path

(dB)

pfdI/N: required pfd at the GSO FSS earth station location to meet the FSS protection


EIRP: maximum e.i.r.p. spectral density in the direction of the GSO FSS earth station

(dB(W/MHz)).

The pfd necessary to protect FSS Earth station use within the territory of an administration

deploying the HAPS is not specified. While conditions for the co-existence between HAPSs and

FSS earth stations within the territory of an administration can be based on the same HAPS pfd

thresholds, further specific conditions would need to be addressed at a national level to avoid undue

constraints to existing Fixed Satellite Services.

Study D also shows that HAPS technology can also coexist with NGSO FSS in the 38-39.5 GHz

band when taking into account the statistics of the NGSO FSS earth station pointing directions

relative to the HAPS, and on the tracking strategy of the satellites by the NGSO FSS earth stations.

It is proposed that for the purpose of protecting NGSO FSS earth station in neighbouring

administrations from co-channel interference, coordination of a transmitting HAPS station is

required when the distance between the sub-HAPS point and any point of an administration’s

border is less than 100 km.

Rep. ITU-R F.2475-0 129

1.4.5.2 Impact from transmitting HAPS ground station into receiving FSS earth station

Study C shows that HAPS receivers will not be impacted and can accept interference from FSS

donwlink that are compliant with Table 21-4 of the RR Article 21.

Study C shows also that HAPS system ground stations can be considered as any FS station as the

result of the impact of HAPS ground station emissions into FSS Earth station receivers is less than

the impact of an FS emitting station into FSS receiving Earth station.

1.4.5.3 Impact from transmitting FSS space stations into receiving HAPS ground station

Study D shows that HAPS receiving ground stations can coexist with FSS space stations emissions

in the 38-39.5 GHz band given the percentage of HAPS service area where there could be

potentially a problem and given the mitigation techniques that could be implemented on the HAPS

side.

1.5 Study E

1.5.1 Introduction

This study investigates the sharing and compatibility between HAPS systems and FSS (s-E) in the

38-39.5 GHz frequency range. In this frequency range, the following directions are considered in

this study for HAPS.

– Gateway to HAPS Platform (UL).

– CPE to HAPS Platform (UL).

The proposed introduction of HAPS may provide diverse usage scenarios and applications with

different network requirements. At the same time, it is necessary to ensure continued operation of

services already allocated in the bands under consideration. Hence, simulation studies are required

to understand the impact of HAPS systems on existing services, especially satellite services in the

same bands.

1.5.2 Background

All studies consider the aggregate interference of a number of HAPS cells into the affected satellite

receiver and were performed by means of system-level static simulations. The simulations concern

the aggregate interference of a HAPS network consisting of several HAPS covering a large area.

The results are thus probabilistic, i.e. a certain probability that the interference exceeds a given level

is obtained for each scenario.

To contribute actively with ITU-R studies, the Spectrum, Orbit and Broadcasting Division of the

Brazilian National Telecommunication Agency (ANATEL) is developing, in cooperation with partners

in the industry and academia, an open-source simulation tool, named SHARC, to support SHARing

and Compatibility studies between radio communication systems. SHARC was originally developed to

study the interference to and from an IMT-2020, according to the framework proposed by

Recommendation ITU-R M.2101. For this study, the simulator was adapted to model a HAPS system.

HARC is a static system-level simulator using the Monte-Carlo method. It has the main features

required for a common system-level simulator, such as antenna beamforming, resource blocks

allocation, among other.The simulator is written in Python and the source code for the HAPS

simulator is available at GitHub (https://github.com/Ektrum/SHARC_HAPS).

In SHARC, the HAPS are located at fixed positions in a regular grid, and the gateways and CPEs are

randomly located at each drop within the HAPS coverage area. For each link, the coupling loss is

calculated between the GTW/CPEs and their nearest, including directional antennas and

beamforming. The coupling loss between HAPS network elements and the interfered receiver is also

https://github.com/Ektrum/SHARC_HAPS

130 Rep. ITU-R F.2475-0

calculated, enabling the interference calculation among the systems. Finally, system performance

indicators are collected, and this procedure is repeated for a fixed number of snapshots.

The main key performance indicator obtained from these simulations is the aggregate interference

generated by HAPS into the other system. Aggregate interference is a summation of interfering

signals sourced from all active HAPS, gateways or CPEs, depending on the investigated scenario.

In this contribution, a geo-stationary FSS is considered in the earth station (FSS Earth Station). The

aggregate interference power is calculated and compared with protection criteria for this frequency

range.

1.5.3 Technical characteristics

This section provides the specific parameters used in the study presented here. Tables 35 to 38 list

the main parameters and deployment characteristics of the HAPS (System 6) and satellite networks

that have been used in these studies. Note that the FSS parameters were provided by the relevant

group.

TABLE 35

HAPS characteristics (System 6)

Parameter Value

Load factor 100%

CPE Transmitter

Carrier frequency 38.75 GHz

Bandwidth 117 MHz

e.i.r.p. 40.3 dBW

Power control attenuation 25.3 dB

Nominal transmit power 4.5 dBm

Height 10 m

Antenna pattern ITU-R F.1245

Antenna gain 40.6 dBi

Antenna diameter 0.35 m

GW Transmitter

Carrier frequency 38.75 GHz

Bandwidth 1428.6 MHz

Max power 9 W

Power control attenuation 35 dB

Nominal transmit power 4.54 dBm

Feeder loss 1.5 dB

Height 10 m

Antenna pattern ITU-R F.1245

Antenna gain 56.5 dBi

Antenna diameter 2 m

Rep. ITU-R F.2475-0 131

TABLE 36

GSO FSS characteristics

Parameter Value

FSS Earth Station

Antenna height 5 m, 10 m

Elevation angle 10°

Bandwidth 600 MHz

Noise temperature 250 K

Antenna pattern ITU-R S.465

Antenna gain 68 dBi

Antenna diameter 6.8 m

TABLE 37

GSO FSS protection criteria

I/N value (dB) Percentage of time associated with

I/N value (%)

+8 0.02

–6 1.0

–10.5 20

TABLE 38

Channel Model

Parameter Value

HAPS to GSO FSS Earth Station

Channel model ITU-R P.452

Latitude of half-way point –23.3646°

Atmospheric pressure 935 hPa

Air temperature 300 K

Sea-level surface refractivity 𝑁0 352.58

Radio refractive Δ𝑁 43.127

Percentage path-loss not exceeded 20%

Distance over-land to the coast 70 km

Clutter Type Suburban (at one side only)

1.5.4 Methodology

It is considered that HAPS are located in a regular hexagonal grid, with a 100 km distance between

adjacent HAPS. A cluster of 19 HAPS is considered.

In the case of the simulation of links between HAPS and gateways, for each HAPS, one single

gateway is randomly located within its coverage area, as seen, for example, in Fig. 94. The antennas

from the gateways and the HAPS are assumed to be perfectly pointed towards each other.

132 Rep. ITU-R F.2475-0

FIGURE 94

HAPS deployment scenario - Gateways

In the case of the simulation of links between HAPS and CPEs, for each HAPS, four separate non-

overlapping beams are generated for each HAPS at random angles, and within each beam, four

different CPEs are randomly located. Such a configuration can be seen in Fig. 95. The antennas

from the CPEs are assumed to be perfectly pointed towards the HAPS.

FIGURE 95

HAPS deployment scenario – CPEs

In case of simulation between HAPS and FSS Earth Station, the FSS Earth Station receiver is

assumed to be located randomly at each drop within the central cell of the HAPS network. Results

are compared with the protection criteria of maximum I/N for the satellite system for –10 dB

Rep. ITU-R F.2475-0 133

(for 20% of cases), –6 dB (for 1% of cases) and +8 dB (for 0.02% of cases) with and without an

apportionment value of 3 dB.

1.5.4.1 Ground CPE to FSS Earth Station in the 38-39.5 GHz band

For this study case, the 0.35 m diameter antenna was chosen for worst-case analysis. This is

because the CPE antenna with a larger diameter has a higher peak gain and lower side and back

lobe gains compared to a smaller dish, as seen in Fig. 96. However, the interference caused to the

ES is mostly from the CPE sidelobes, as the direct pointing of the CPE towards the ES is unlikely.

FIGURE 96

Antenna gain values for CPE 1.2 m and 0.35 m diameter dishes

Figure 97 shows the ground CPE to ES aggregate CDF I/N in the 38-39.5 GHz band, as well as the

protection criteria. Simulations with clutter (ES at 5 m height) and without clutter (ES at 10 m height)

were performed and in all the simulated cases the I/N is well below the protection criteria.

134 Rep. ITU-R F.2475-0

FIGURE 97

CPE to FSS Earth Station I/N in the 38-39.5 GHz band

1.5.4.2 Ground GW to FSS Earth Station in the 38-39.5 GHz band

Figure 98 shows the ground GW to ES aggregate CDF I/N in the 38-39.5 GHz band, as well as the

protection criteria. Simulations without clutter (ES at 10 m height) and with clutter (ES at 5 m height)

were performed and in all the simulated cases the I/N is well below the protection criteria.

FIGURE 98

GW to FSS Earth station I/N in the 38-39.5 GHz band

1.5.4.3 Worst case I/N values

Table 39 summarizes the achieved I/N values for the simulation cases shown above, including cases

when a 3 dB apportionment is taken into account. The column labelled as “Margin” indicates the

level of exceedance of the protection criteria (higher value corresponds to higher interference).

Rep. ITU-R F.2475-0 135

TABLE 39

Worst case I/N values

Interferer

station Clutter I/N criteria

Probability

of time

I/N result

(dB)

Margin without

apportionment

(dB)

Margin with

apportionment

(dB)

CPE

Without

–10 dB 20% –65.97 –55.47 –52.47

–6 dB 1% –48.94 –42.94 –39.94

+8 dB 0.02% –31.81 –39.81 –36.81

With

–10 dB 20% –79.39 –68.89 –65.89

–6 dB 1% –62.38 –56.38 –53.38

+8 dB 0.02% –42.96 –50.96 –47.96

GW

Without

–10 dB 20% –89.74 –79.24 –76.24

–6 dB 1% –69.61 –63.61 –60.31

+8 dB 0.02% –52.11 –60.11 –57.11

With

–10 dB 20% –103.75 –93.25 –90.25

–6 dB 1% –83.14 –77.14 –74.14

+8 dB 0.02% –65.15 –73.15 –70.15

1.5.5 Summary and analysis of the results of study E

Aggregated interference simulations from HAPS ground terminals towards FSS GSO earth station

has been performed using nominal power for the long term protection criteria (not to be exceeded

more than 20% time) and maximum power for the other protection criteria (not to be exceeded more

than 1% and 0.02% time respectively) in the 38-39.5 GHz frequency band. The results show that

the aggregate I/N level will always meet the FSS protection criteria (with and without

apportionment), based on the assumptions and input parameters used in this study.

1.6 Study F

In this study the HAPS system technical parameters are applied for System 5 of Report ITU-R

F.2439-0. The analysis focus on:

• Interference from the transmitting HAPS GW and HAPS CPE into receiving FSS earth

station.

• Interference from the transmitting HAPS into receiving earth station.

• Interference from the transmitting FSS space station to receiving HAPS CPE and HAPS

Gateway.

• Interference from the transmitting FSS space station to receiving HAPS.

The FSS (E-s) transmitter and receiver parameters assumed for this study are carriers 6 (GSO) and

26 (NGSO), respectively. The interference characteristics are modelled as recommended in

Recommendation ITU-R P.452-16.

1.6.1 Methodology – HAPS CPE/gateway to FSS ES

The methodology used in this study is to investigate the potential for coexistence between HAPS

and FSS, considering Minimum Coupling Loss (MCL) method (deterministic), for each interference

scenario.

136 Rep. ITU-R F.2475-0

Single HAPS interference

The interfering signal power density (I) at FSS ES receiver is determined by the following equation:

I (dB(W/MHz)) = Ptx + Gtx(α) + Grx(α) – LPL – Lf,rx – Lf,tx

where:

Ptx: HAPS ground terminal (GW/CPE) transmitted power spectral density

(dB(W/MHz))

Gtx(α): antenna gain of HAPS GW/CPE transmitter towards FSS ES receiver (dBi)

Grx(α): antenna gain of FSS ES receiver towards HAPS GW/CPE transmitter (dBi)

LPL: pathloss (P.452-16 propagation model)

Lf,tx: feeder loss of HAPS GW/CPE(dB) (assumed 0 dB)

Lf,rx: feeder loss of FSS ES (dB).


equation:


where:


T: System noise temperature of FSS ES (K)


For gateways, interference may be mitigated by taking advantage of site shielding (up to 30 dB) to

reduce side lobe radiation, while maintaining system performance as mentioned in

Recommendations ITU-R SF.1481 and ITU-R F.1609.

To calculate the separation distance, the propagation model is based on Recommendation ITU-R

P.452-16. For every step of distance, the propagation loss and I/N for all gateway/CPE elevation

angles is calculated. Therefore, for every HAPS gateway/CPE elevation angle, the minimum

separation distance is presented when the calculated I/N meets the protection threshold of the FSS

ES.

The MCL analysis determines a required separation distance. If the distance between the two

interfering services is greater than that required separation distance, then these services would not

interfere. However, below that required separation distance, there may be cases where the threshold

is exceeded.

1.6.2 Methodology –HAPS Platform to FSS ES

The methodology used in this study is based on the following methodology.

Static Model

The interfering signal power density (I) at satellite earth station receiver is determined by the

following equation:

I (dB(W/MHz)) = Ptx – Lf,tx + Gtx(Φ𝑇𝑥) – Ls + Grx(Φ𝑅𝑥) – Lf,rx

where:

Ptx: HAPS transmit power density (dB(W/MHz))

Lf,tx: feeder loss of HAPS in the transmit side (dB)

Gtx(Φ𝑇𝑥): antenna gain of HAPS transmitter towards FSS ES receiver (dBi)

Rep. ITU-R F.2475-0 137

Ls: free space path loss between FSS ES and HAPS (dB) shown in the following:

Ls = 92.45 + 20 log(fGHz) + 20 log10(dkm)

dkm: distance between FSS ES and HAPS (km)

fGHz: frequency (GHz)

Grx(Φ𝑅𝑥): receive antenna gain of FSS ES receiver towards HAPS (dBi)

Lf,tx: feeder loss of FSS ES in the receive side (dB).


equation:


where:


T: System noise temperature of HAPS (K)


This methodology is based on a minimum coupling loss (MCL) approach, which calculates the I/N

between FSS ES and HAPS nadir where the HAPS is pointing directly towards the FS terminal in

azimuth.

1.6.3 Methodology –FSS satellite to HAPS CPE/Gateway

The analysis addresses the following interference scenarios from satellite to the HAPS ground

terminal (GW/CPE):

1) Gateway/CPE bore sight pointing into a range of off-axis angles to the transmit antenna of

the satellite. For this case, it is assumed that the gateway/CPE, the HAPS and the satellite

are aligned. The satellite is not pointing at the Gateway/CPE and then sees the latter with an

off-axis angle which comes as a function of the elevation angle of the gateway/CPE

(see Fig. 99).

FIGURE 99

GW/CPE boresight to off axis satellite receiving angles (case 1)

2) This case considers the off-axis emissions from the satellite are received by HAPS

GW/CPE but through the boresight.

Therefore, as shown in Fig. 100, the off-axis angles (90-Ф) are calculated for both terminals.

Sat’s side lobe

ϕ

HAPS GW/CPE

Platform’s main lobe

FSS ES

HAPS

FSS Sat

Sat’s main lobe

138 Rep. ITU-R F.2475-0

FIGURE 100

Off axis to off axis transmission (Case 2)

3) This case is similar to Case 1 but assumes a NGSO satellite instead of a GSO.

4) This case is similar to Case 2 but assumes a NGSO satellite instead of a GSO.

The I/N at the HAPS receiver is calculated for a range of off axis angles, and compared with the

threshold, which are calculated using the following antenna parameters:

a) ITU-R S.672-4 for the GSO satellite.

b) ITU-R S.1528 for the NGSO satellite.

c) ITU-R F.1245 for the HAPS gateway terminal.

A more widely applicable antenna template of ITU-R F.1245 instead of Annex 1 in ITU-R F.1245

is used in this study.

For Case 1 and Case 3, the following method is used to calculate I/N:

I/N (dB) = Ptx (in 1 MHz) + Gtx – Floss – FSL + GSrx (90-Φ) – N.

For Case 2 and Case 4, the following method is used to calculate I/N:

I/N (dB) = Ptx (in 1 MHz) + Gtx(Φ) – Floss – FSL + GSrx (90-Φ) – N.

where:

Ptx: satellite peak power spectral density (dB(W/MHz))

Floss: feeder losses (dB)

Gtx: satellite peak gain (dBi)

Gtx(Φ): off axis satellite gain (dBi)

FSL: free space path loss (dB)

GSrx: peak HAPS gain (dBi)

GSrx(Φ): off axis HAPS gain (dBi)

N: HAPS noise power (dB(W/MHz)) = 10log(KTB).

1.6.4 Methodology –FSS satellite to HAPS Platform

The following methodology is used to calculate interference from satellite to HAPS.

The interference power level in 1 MHz (dB(W/MHz)), I(g,h,b,r), due to spot beams of a satellite

received by a HAPS (g) is calculated using equation below:

𝐼(𝑔, ℎ, 𝑏, 𝑟) = 𝑃𝐻(𝑏) − 𝐹𝑙𝑜𝑠𝑠 + 𝐺𝑡𝑥𝐻 ((𝑔, ℎ, 𝑏)) − 𝐹𝑆𝐿(𝑔, ℎ) + 𝐺𝑟𝑥

𝑆 ((𝑔, ℎ, 𝑏))

where:

Sat’s side lobe

Platform’s main lobe

HAPS

ϕ

HAPS GW/CPE FSS ES

FSS Sat

Sat’s main lobe

Rep. ITU-R F.2475-0 139

𝑃𝐻(𝑏) : transmit power density in 1 MHz (dB(W/MHz)) at the input of satellite antenna

for beam (b)

𝐹𝑙𝑜𝑠𝑠: satellite feeder loss (dB)

(𝑔, ℎ, 𝑏): discrimination angle (degrees) at the satellite (h) between the pointing direction

of a satellite spot beam (b) and the HAPS (g)

𝐺𝑡𝑥𝐻 ((𝑔, ℎ, 𝑏)): transmitter antenna gain (dBi) of the satellite (h) for off-axis angle (𝑔, ℎ, 𝑏)

𝐹𝑆𝐿(𝑔, ℎ): free space loss (dB) between HAPS (g) and satellite (h)

(𝑔, ℎ, 𝑏): discrimination angle (degrees) at the HAPS (g) between the pointing direction

of the HAPS reference point (r) and satellite (h)

𝐺𝑟𝑥𝑆 ((𝑔, ℎ, 𝑏)): receiver antenna gain (dBi) of the HAPS (g) for off axis angle (𝑔, ℎ, 𝑏).

1.6.5 Results of studies

1.6.5.1 HAPS ground terminal to FSS ES (Interference from the transmitting HAPS

GW/CPE into receiving FSS earth station)

1.6.5.1.1 HAPS gateway to FSS ES

1.6.5.1.1.1 HAPS GW to GSO FSS ES

Figure 101 shows the required separation distance between FSS GSO ES receiver (carrier 6) and

HAPS gateway transmitter in rural scenario. The threshold for GSO FSS is set to I/N = 8 dB

(0.02%), –6 dB (1.0%), and –10.5 dB (20%), respectively.

FIGURE 101

Required separation distance vs. HAPS GW elevation angle, when GSO ES elevation angle is 10 degrees,

based on I/N = 8 dB (0.02%), –6 dB (1.0%), and –10.5 dB (20%), respectively

(a)

10 20 30 40 50 60 70 80 900.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

GW Elevation angle(deg)

Min

imum

separa

tion d

ista

nce(k

m)

Minimum separation distance VS. HAPS GW elevation

GSO ES elevation angle = 10 deg

140 Rep. ITU-R F.2475-0

(b)

(c)

10 20 30 40 50 60 70 80 900.1

0.15

0.2

0.25

0.3

0.35


Min

imum

separa

tion d

ista

nce(k

m)



10 20 30 40 50 60 70 80 90

0.2

0.25

0.3

0.35

0.4

0.45

0.5


Min

imum

separa

tion d

ista

nce(k

m)



Rep. ITU-R F.2475-0 141

Figure 101 above presents the required separation distance between FSS GSO ES receiver

(carrier 6) and HAPS gateway transmitter. The required separation distance (i.e. minimum elevation

angle of 10 degrees for the HAPS gateway) are at 0.17 km, 0.33 km, 0.50 km for I/N = 8 dB


1.6.5.1.1.2 HAPS GW to NGSO FSS ES

Figure 102 shows the required separation distance between FSS NGSO ES receiver (carrier 26) and

HAPS gateway transmitter in rural scenario. The threshold for the above result are set to I/N = 8 dB


FIGURE 102

Required separation distance vs. HAPS GW elevation angle, when NGSO ES elevation angle

is 10degrees, based on I/N = 8 dB (0.02%), –6 dB (1.0%), and –10.5 dB (20%), respectively

(a)

10 20 30 40 50 60 70 80 900.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18


Min

imum

separa

tion d

ista

nce(k

m)


NGSO ES elevation angle = 10 deg

142 Rep. ITU-R F.2475-0

(b)

(c)

10 20 30 40 50 60 70 80 90

0.2

0.25

0.3

0.35

0.4

0.45

0.5


Min

imum

separa

tion d

ista

nce(k

m)



10 20 30 40 50 60 70 80 90

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65


Min

imum

separa

tion d

ista

nce(k

m)



Rep. ITU-R F.2475-0 143

Figure 102 above presents the required separation distance between FSS ES NGSO receiver

(carrier 26) and HAPS gateway transmitter. The required separation distance (i.e. minimum

elevation angle of 10 degrees for the HAPS gateway) are at least 0.18 km, 0.41 km, 0.62 km for

I/N = 8 dB (0.02%), –6 dB (1.0%), and –10.5 dB (20%), respectively.

1.6.5.1.2 HAPS CPE to FSS ES

1.6.5.1.2.1 CPE to GSO FSS ES


HAPS CPE transmitter in rural scenario The threshold for the above result are set to I/N= 8 dB

(0.02%), –6 dB (1.0%), and –10.5 dB (20%).

FIGURE 103

Required separation distance vs. HAPS CPE elevation angle, when GSO ES elevation angle is 10 degrees,

based on I/N = 8 dB (0.02%), –6 dB (1.0%), and –10.5 dB (20%), respectively

(a)

10 20 30 40 50 60 70 80 90

0.2

0.25

0.3

0.35

0.4

0.45

0.5

CPE Elevation angle(deg)

Min

imum

separa

tion d

ista

nce(k

m)

Minimum separation distance VS. HAPS CPE elevation


144 Rep. ITU-R F.2475-0

(b)

(c)

10 20 30 40 50 60 70 80 900

0.5

1

1.5

2

2.5

3


Min

imum

separa

tion d

ista

nce(k

m)



10 20 30 40 50 60 70 80 900.5

1

1.5

2

2.5

3

3.5

4

4.5


Min

imum

separa

tion d

ista

nce(k

m)



Rep. ITU-R F.2475-0 145

Figure 103 above presents the required separation distance between FSS ES GSO receiver (carrier

6) and HAPS CPE transmitter. The required separation distance (i.e. minimum elevation angle of

10 degrees for the HAPS CPE) are at least 0.46 km, 2.97 km, 4.06 km for I/N = 8 dB (0.02%), –6

dB (1.0%), and –10.5 dB (20%), respectively.

1.6.5.1.2.2 CPE to NGSO FSS ES


HAPS CPE transmitter in rural scenario. The result are set to I/N = 8 dB (0.02%), –6 dB (1.0%),

and –10.5 dB (20%), respectively.

FIGURE 104

Required separation distance vs. HAPS CPE elevation angle, when NGSO ES elevation angle is 10 degrees, based on I/N = 8

dB (0.02%), –6 dB (1.0%), and –10.5 dB (20%), respectively

(a)

10 20 30 40 50 60 70 80 90

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65


Min

imum

separa

tion d

ista

nce(k

m)



146 Rep. ITU-R F.2475-0

(b)

(c)

10 20 30 40 50 60 70 80 900

0.5

1

1.5

2

2.5

3

3.5

4


Min

imum

separa

tion d

ista

nce(k

m)



10 20 30 40 50 60 70 80 900

0.5

1

1.5

2

2.5

3

3.5

4


Min

imum

separa

tion d

ista

nce(k

m)



Rep. ITU-R F.2475-0 147

Figure 104 above presents the required separation distance between FSS ES NGSO receiver

(carrier 26) and HAPS CPE transmitter. The required separation distance (i.e. minimum elevation

angle of 10 degrees for the HAPS gateway) are at least 0.57 km, 3.62 km and 4.93 km for I/N =

8 dB (0.02%), –6 dB (1.0%), and –10.5 dB (20%), respectively.

1.6.5.1.3 Summary of HAPS ground terminals to FSS ES

For the gateway uplinks to the HAPS, the studies show that: 0.18 km, 0.41 km, 0.62 km (for I/N =

8 dB (0.02%), –6 dB (1.0%), and –10.5 dB (20%), respectively) are sufficient separation distances

between a gateway terminal and a FSS Earth station. For the CPE uplinks to the HAPS, the studies

show 0.57 km, 3.62 km, 4.93 km (for I/N = 8 dB (0.02%), –6 dB (1.0%), and –10.5 dB (20%),

respectively) separation distances are required between a CPE and a FSS Earth Station.

1.6.5.2 HAPS to FSS ES (interference from the transmitting HAPS into receiving earth

station)

1.6.5.2.1 HAPS (gateway link) to FSS ES


HAPS (gateway link) transmitter. The I/N threshold considered for this study are 8 dB (0.02%),

–6 dB (1.0%), and –10.5 dB (20%), respectively.

FIGURE 105

I/N vs. distance of FSS GSO ES to HAPS nadir (GW downlink)

I/N was calculated for an array of distances from the FSS GSO ES (carrier 6) to the HAPS nadir and

for different elevation angles of the FSS GSO ES. As seen in Fig. 105 above, at the minimum

elevation angle of the FSS GSO ES (i.e. 10 degrees),

– I/N threshold of 8 dB is met for a worst case separation distance of 108 km;

– I/N threshold of –6 dB is met for a worst case separation distance of 109 km;

0 50 100 150 200-80

-60

-40

-20

0

20

40

Distance of FSS GSO ES to HAPS Nadir(km)

Calc

ula

ted I

/N(d

B)

I/N VS. distance of FSS GSO ES to HAPS nadir(GW DL)

ES elevation angle:10



I/N threshold(-10.5 dB)

I/N threshold(-6 dB)

I/N threshold(8 dB)

148 Rep. ITU-R F.2475-0

– I/N threshold of –10.5 dB is met for a worst case separation distance of 109 km.

These separation distances ensure that the FSS GSO ES would not receive any interference for any

given elevation angle.


HAPS (gateway link) transmitter.

FIGURE 106

I/N vs. distance of FSS NGSO ES to HAPS nadir (GW downlink)

I/N was calculated for an array of distances from the FSS NGSO ES (carrier 26) to the HAPS nadir

and for different elevation angles of the FSS NGSO ES. As seen in Fig. 106 above, at the 20°

elevation angle of the FSS NGSO ES,

– I/N threshold of 8 dB is met for a worst case separation distance of 55 km;

– I/N threshold of –6 dB is met for a worst case separation distance of 58 km;

– I/N threshold –10.5 dB is met for a worst case separation distance of 59 km.

At 10 degrees elevation angle of the FSS NGSO ES, the results of I/N would not exceed 8 dB and

−6 dB, but the I/N threshold −10.5 dB is met for a worst case separation distance of 111 km.

These separation distances ensure that the FSS NGSO ES would not receive any interference for

any given elevation angle.

1.6.5.2.2 HAPS (CPE link) to FSS ES


HAPS (CPE link) transmitter. The I/N threshold considered for this study are 8 dB (0.02%), −6 dB

(1.0%), and −10.5 dB (20%), respectively.

0 50 100 150 200-80

-60

-40

-20

0

20

40

Distance of FSS NGSO ES to HAPS Nadir(km)

Calc

ula

ted I

/N(d

B)

I/N VS. distance of FSS NGSO ES to HAPS nadir(GW DL)






I/N threshold(8 dB)

Rep. ITU-R F.2475-0 149

FIGURE 107

I/N vs. distance of FSS GSO ES to HAPS nadir (CPE downlink)

I/N was calculated for an array of distances from the FSS GSO ES (carrier 6) to the HAPS nadir and

for different elevation angles of the FSS GSO ES. As seen in figure above, at the minimum

elevation angle of the FSS GSO ES (i.e. 10 degrees),

• I/N threshold of 8 dB is met for a worst case separation distance of 114 km;

• I/N threshold of –6 dB is met for a worst case separation distance of 130 km;

• I/N threshold of –10.5 dB is met for a worst case separation distance of 139 km.




HAPS (CPE link) transmitter.

0 50 100 150 200-60

-40

-20

0

20

40

60

Distance of FSS GSO ES to Nadir(km)

Calc

ula

ted I

/N(d

B)

I/N VS. distance of FSS GSO ES to HAPS nadir(CPE DL)






I/N threshold(8 dB)

150 Rep. ITU-R F.2475-0

FIGURE 108

I/N vs. distance of FSS NGSO ES to HAPS nadir (CPE downlink)

I/N was calculated for an array of distances from the FSS NGSO ES (carrier 26) to the HAPS nadir

and for different elevation angles of the FSS NGSO ES.

• the I/N threshold of 8 dB is met for a worst case separation distance of 114 km;

• the I/N threshold of –6 dB is met for a worst case separation distance of 134 km;

• the I/N threshold of –10.5 dB is met for a worst case separation distance of 145 km.



1.6.5.2.3 Summary HAPS to FSS ES

The studies above describe a MCL analysis (i.e. deterministic approach) based on a single HAPS

and FSS GSO/NGSO ES pair. The MCL analysis assumes that the HAPS transmitter is pointing

directly towards the FSS ES receiver in azimuth. Note, the FSS ES (both GSO and NGSO) is

pointing with maximum gain towards HAPS. A worst case separation distance between HAPS nadir

and FSS ES receiver (GSO and NGSO) was calculated based on the FSS threshold (I/N = 8 dB

(0.02%), –6 dB (1.0%), and –10.5 dB (20%), respectively).

For the gateway downlinks from the HAPS, the studies show that the I/N are met at worst case

separation distances of 108km, 109 km, and 109 km for I/N threshold values of 8 dB (0.02%),

−6 dB (1.0%), and –10.5 dB (20%) respectively for GSO. In the case of NGSO, the required

separation distances is 11 km for I/N threshold value of –10.5 dB.

For the CPE downlinks from the HAPS, the studies show that the I/N are met at required separation

distances of 114 km, 130 km and 139 km for I/N threshold values 8 dB (0.02%), –6 dB (1.0%), and

–10.5 dB (20%) respectively for GSO. In the case of NGSO, the required separation distances are

114 km, 134 km and 145 km for I/N threshold values 8 dB (0.02%), –6 dB (1.0%), and –10.5 dB

(20%) respectively.

0 50 100 150 200-60

-40

-20

0

20

40

60

Distance of FSS NGSO ES to Nadir(km)

Calc

ula

ted I

/N(d

B)

I/N VS. distance of FSS NGSO ES to HAPS nadir(CPE DL)






I/N threshold(8 dB)

Rep. ITU-R F.2475-0 151

1.6.5.3 FSS satellite to HAPS ground terminals (Interference from the transmitting FSS

space station to receiving HAPS CPE/Gateway)

In this frequency band, carrier 6 (GSO case) and carrier 26 (NGSO case) for FSS satellite

transmitter were selected from the information provided by the relevant group as these carriers were

considered the worst case.

1.6.5.3.1 FSS satellite to HAPS gateway

Tables 40 and 41 show the calculated I/N at HAPS CPE perceived from a GSO satellite (carrier 6)

for Cases 1, 2.

TABLE 40

Calculated I/N for Case 1 Carrier 6

Case 1 – Elevation of gateway with boresight pointing into a range of off-axis angles to the transmit antenna of

the FSS GSO satellite

Gateway

elevation to

GSO (degree)

20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

I/N (dB) –28.7 –28.7 –28.7 –28.7 –28.7 –28.7 –28.7 –28.7 –28.7 –28.7 –28.7 –28.7 –24.3 –16.8 29.6

Threshold Elevation Angle (degree)

87.9 (I/N = 10 dB)

85.7 (I/N = –10 dB)

TABLE 41


Case 2 – Gateway terminal receiving at varying off-axis angles to varying off-axis transmission angles,

assumed equal, from the FSS GSO satellite

Gateway off-

axis to GSO

(degree)

70 65 60 55 50 45 40 35 30 25 20 15 10 5 0

I/N (dB) –74.2 –74.2 –74.1 –74.1 –74.1 –73.4 –72.1 –70.1 –66.7 –62.8 –57.9 –51.7 –42.9 –27.9 39.1

Threshold off-axis angle (degree)

2.2 (I/N = 10 dB)

3.7 (I/N = –10 dB)

Tables 42 and 43 show the calculated I/N at HAPS GW perceived from a NGSO satellite

(carrier 26) transmitter for Cases 3, 4.

152 Rep. ITU-R F.2475-0

TABLE 42


Case 3 – Elevation of gateway with boresight pointing into a range of off-axis angles

to the transmit antenna of the FSS NGSO satellite

Gateway

elevation to

NGSO

(degree)

20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

I/N (dB) –36.5 –36.5 –36.5 –36.5 –36.5 –36.5 –36.5 –36.5 –36.5 –36.5 –36.5 –36.5 –36.5 –30.5 8.5

Threshold Elevation Angle (degree)

None (I/N = 10 dB)

87.6 (I/N = –10 dB)

TABLE 43


Case 4 – Gateway terminal receiving at varying off-axis angles to varying off-axis transmission angles,

assumed equal, from the FSS NGSO satellite

Gateway off-

axis to NGSO

(degree)

70 65 60 55 50 45 40 35 30 25 20 15 10 5 0

I/N full power

(dB)

–102.0 –102.4 –101.7 –102.3 –102.0 –101.1 –100.8 –98.4 –96.9 –95.5 –92.2 –89.7 –85.0 –70.9 8.5


none (I/N = 10 dB)

1.17 (I/N = –10 dB)

1.6.5.3.2 FSS satellite to HAPS CPE

Tables 44 and 45 show the calculated I/N at HAPS CPE perceived from a GSO satellite (carrier 6)

transmitter for Cases 1, 2.

TABLE 44


Case 1 – Elevation of CPE with boresight pointing into a range of off-axis angles

to the transmit antenna of the FSS GSO satellite

CPE

elevation

to GSO

(degree)

20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

I/N (dB) –39.0 –39.0 –39.0 –39.0 –39.0 –39.0 –39.0 –39.0 –39.0 –39.0 –39.0 –39.0 –34.6 –27.1 19.3

Threshold elevation angle (degree)

89.0 (I/N = 10 dB)

86.8 (I/N = –10 dB)

Rep. ITU-R F.2475-0 153

TABLE 45


Case 2 – CPE terminal receiving at varying off-axis angles to varying off-axis transmission angles,

assumed equal, from the FSS GSO satellite

CPE off-axis

to GSO

(degree)

70 65 60 55 50 45 40 35 30 25 20 15 10 5 0

I/N (dB) –94.2 –94.6 –93.9 –94.5 –94.2 –93.3 –93.0 –90.6 –89.1 –87.7 –84.4 –81.9 –77.2 –65.7 19.3


0.5 (I/N = 10 dB)

1.7 (I/N = –10 dB)

Tables 46 and 47 show the calculated I/N at HAPS CPE perceived from a NGSO satellite

(carrier 26) transmitter for Cases 3, 4.

TABLE 46


Case 3 – Elevation of CPE with boresight pointing into a range of off-axis angles

to the transmit antenna of the FSS NGSO satellite)

CPE

elevation to

NGSO

(degree)

20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

I/N (dB) –46.8 –46.8 –46.8 –46.8 –46.8 –46.8 –46.8 –46.8 –46.8 –46.8 –46.8 –46.8 –46.8 –40.8 –1.8

Threshold elevation angle (degree)

None (I/N = 10 dB)

88.9 (I/N = –10 dB)

TABLE 47


Case 4 – CPE terminal receiving at varying off-axis angles to varying off-axis transmission angles,

assumed equal, from the FSS NGSO satellite

CPE off-axis

to NGSO

(degree)

70 65 60 55 50 45 40 35 30 25 20 15 10 5 0

I/N (dB) –102.0 –102.4 –101.7 –102.3 –102.0 –101.1 –100.8 –98.4 –96.9 –95.5 –92.2 –89.7 –85.0 –70.9 –1.8


none (I/N = 10 dB)

0.59 (I/N = –10 dB)

1.6.5.3.3 Summary of FSS satellite to HAPS ground terminals

In terms of I/N threshold = 10 dB and –10 dB:

For the FSS GSO satellite transmitting (carrier 6) to HAPS gateway:

154 Rep. ITU-R F.2475-0

• Case 1: The I/N threshold is exceeded for any GW elevation higher than 87.9 degrees

(10 dB) and 85.7 degrees (–10 dB).

• Case 2: When the satellite is transmitting from off-axis to the off-axis beam of the satellite,

a mutual off-axis viewing angle of both interfering and interfered-with antennas of

approximately 2.2 degrees (10 dB) and 3.7 degrees (–10 dB) are required in order to satisfy

the threshold at the HAPS gateway terminal.

For the FSS NGSO satellite transmitting (carrier 26) to HAPS gateway:

• Case 3:The I/N threshold is exceeded for any GW elevation higher than none (10 dB) and

87.6 degrees (–10 dB).

• Case 4: The I/N threshold is exceeded for high elevation angles for both carriers. For carrier

26, a mutual off-axis viewing angle of both interfering and interfered-with antennas of none

(10 dB) and 1.17 degrees (–10 dB) are required to meet the I/N value.

For the FSS GSO satellite transmitting (carrier 6) to HAPS CPE:

• Case 1: The I/N threshold is exceeded for any CPE elevation higher than 89.0

degrees(10 dB) and 86.8 degrees (–10 dB).

• Case 2: The I/N threshold is satisfied if the mutual off-axis viewing angle of both

interfering and interfered-with antennas is 0.5 degrees(10dB) and 1.7 degrees

(–10 dB).

For the FSS NGSO satellite transmitting (carrier 26) to HAPS CPE:

• Case 3: The I/N threshold is exceeded for any CPE elevation higher than none (10 dB) and

88.9 degrees (–10 dB).

• Case 4: a mutual off-axis viewing angle of both interfering and interfered-with antennas

separation of none(10 dB) and 0.59 degrees (–10 dB) for carrier 26 is required in order to

satisfy the I/N criteria received at the CPE.

The above analysis assumes there is no azimuth off-axis for the HAPS link and the FSS link. This

scenario is considered as the worst case.

1.6.5.4 FSS satellite to HAPS (interference from the transmitting FSS space station to

receiving HAPS)

1.6.5.4.1 FSS satellite to HAPS (gateway uplink)

Table 48 shows the I/N from FSS GSO satellite transmitter to HAPS gateway beam receiver that

would receive the highest interference level.

TABLE 48

Total I/N from FSS GSO Satellite to HAPS GW beam

I/N (dB)

FSS GSO Satellite Transmitter:

Carrier 6


System 5 –21.9dB

The above analysis shows that I/N level is below the HAPS threshold (I/N = –10 dB) for the

gateway links.

Rep. ITU-R F.2475-0 155

Table 49 shows the I/N from FSS NGSO satellite receiver to HAPS gateway beam receiver that

would receive the highest interference level.

TABLE 49

Total I/N from FSS NGSO Satellite to HAPS GW beam

I/N (dB)

FSS NGSO Satellite Transmitter:

Carrier 26


System 5 −43 dB

The above analysis shows that I/N level is below the HAPS threshold (I/N = –10 dB) for the

gateway links.

1.6.5.4.2 FSS satellite to HAPS (CPE uplink)

Table 50 shows the I/N from FSS GSO satellite transmitter to HAPS CPE beam receiver that would


TABLE 50

Total I/N from FSS GSO Satellite to HAPS CPE beam

I/N (dB)


Carrier 6


System 5 −24 dB

The above analysis shows that I/N level is below the HAPS threshold (I/N = –10 dB) for the CPE

links.

Table 51 shows the I/N from FSS NGSO satellite receiver to HAPS CPE beam receiver that would


TABLE 51

Total I/N from FSS GSO Satellite to HAPS CPE beam

I/N (dB)


Carrier 26


System 5 −45.7 dB

The above analysis shows that I/N level is below the HAPS threshold (I/N = –10 dB) for the CPE

links.

1.6.5.4.3 Summary of FSS satellite to HAPS (CPE uplink)

The calculated I/N value is below the threshold I/N = –10 dB of the HAPS receiver for NGSO and

GSO satellite cases, respectively.

156 Rep. ITU-R F.2475-0


2.1 Impact from transmitting HAPS ground station into receiving FSS Earth station

Study A presented a deterministic approach to analyse the interference from HAPS uplink to FSS

Earth station receivers. For the long-term protection of FSS earth station receiver, a required I/N

value was assumed as –15.2 dB (–12.2 dB5 with a 3 dB apportionment). The separation distances

between HAPS ground terminals and FSS Earth stations were calculated. To comply with the

required long-term I/N value, HAPS gateways would need to be located at a distance of 4.7 km

from FSS Earth stations, and HAPS CPEs would need to be located at a distance of 15 km, noting

that these distances are based on a worst case main beam coupling scenario and that, for other

scenarios, distances may be lower. This study considered the interference from an individual HAPS

earth station towards an individual FSS Earth Station. The case of aggregate interference from all

co-frequency HAPS GWs and HAPS CPEs was not addressed in this study. This study did only

consider free space loss and did not take into account terrain model.

Study B (§ 1.2.3) presented two analyses. The first analysis provides pfd limits to ensure protection

of FSS GSO and NGSO Earth station receivers. A range of pfd limits are provided for satellite

receiver I/N criteria as presented in Table 52.

TABLE 52

pfd limits in dB(W/(m2 ‧ MHz)) at the FSS earth station receivers

FSS I/N values Time Percentage pfd limt at GSO earth station pfd limit at NGSO earth

station

I/N = –6 dB 1% –104.4 dB(W/(m2 ‧ MHz)) –106.6 dB(W/(m2 ‧ MHz))

I/N = –10.5 dB 20% –108.9 dB(W/(m2 ‧ MHz)) –111.1 dB(W/(m2 ‧ MHz))

I/N = +8 dB 0.02% –90.4 dB(W/(m2 ‧ MHz)) –92.6 dB(W/(m2 ‧ MHz))

Taking the worst-case assumption of an I/N value of –10.5 dB, a pfd level of

–111.1 dB(W/(m2 · MHz)) should not be exceeded for more than 20% of time, to protect the FSS

earth station receivers. A separation distance of 320 metres to 3.9 km between HAPS ground

stations and satellite Earth station receivers may be applied when using the I/N criteria listed in the

above Table.

The second analysis uses a statistical methodology to determine a separation distance between

HAPS ground stations and satellite receivers. This second analysis shows that the separation

distance between an FS terminal and an FSS earth station is greater compared to the separation

between a HAPS ground station and an FSS earth station.

Study C provides an assessment of potential interference from HAPS ground stations using the

same process that would be used in assessing interference from an FS station. The study shows that

the impact of HAPS ground station emissions is less than the impact of an FS emitting station into

FSS receiving Earth station.

The antennas used for both HAPS ground stations and FSS stations are directional, therefore, the

required separation distance between the two systems can be reduced by appropriate site-

configuration. Protection by HAPS ground stations of FSS Earth stations can be managed on a case-

by-case basis by coordination amongst administrations or usual link/planning method and

procedures used at national level for conventional FS stations.

5 It should be noted that the relevant group in ITU-R indicated the use of I/N of –10.5 dB.

Rep. ITU-R F.2475-0 157

Study E considers the effects of aggregated interference from HAPS ground stations towards FSS

GSO earth station. The study uses I/N values for satellite receivers of –6 dB and –10 dB. The results

show that the aggregate I/N value will always meet the FSS protection criteria (with and without an

allowance for apportionment of 3 dB).

Study F shows that 1 km is a sufficient separation distance between a HAPS gateway uplink and a

FSS Earth station receiver. For the HAPS CPE uplinks, the studies show 5 km separation distance is

sufficient between a CPE and a FSS Earth station. These results are based on the use of satellite

Earth station receiver I/N value of 8 dB (0.02%), –6 dB (1.0%) and –10.5 dB (20%).

2.2 Impact from transmitting HAPS into receiving FSS Earth station

Study D provides pfd levels to facilitate co-existence between HAPS and FSS GSO Earth station

receivers in the 38-39.5 GHz band.

Under this study and for the purpose of protecting GSO FSS earth station in neighbouring

administrations from co-channel interference, coordination of a transmitting HAPS station would be

required when, the pfd over any point of an administration’s border exceeds the following values:

–169.9 + 1954 2 dB(W/(m2 · MHz)) for 0 ≤ <

–133.9 dB(W/(m2 · MHz)) for ≤ <

–133.9 + 25 log dB(W/(m2 · MHz)) for 1° ≤ < 47.9°

–91.9 dB(W/(m2 · MHz)) for 47.9° ≤ ≤ 180°

where is the minimum angle at the border between the line to the HAPS and the lines to the GSO

arc in degrees.


pfdI/N = EIRP – 10log10(4d2) – Attgaz

where:



(dB)


criteria (dB(W/(m2 · MHz))

EIRP : Maximum e.i.r.p. spectral density in the direction of the GSO FSS earth station

(dB(W/MHz)).

The pfd necessary to protect GSO FSS Earth station use within the territory of an administration

deploying the HAPS is not addressed in this Report. Coordination for the co-existence between

HAPSs and GSO FSS Earth stations within the territory of an administration could be based on the

same HAPS pfd levels.

HAPS technology can also coexist with NGSO FSS in the 38-39.5 GHz band when taking into

account the statistics of the NGSO FSS earth station pointing directions relative to the HAPS, and

on the tracking strategy of the satellites by the NGSO FSS earth stations.

For the purpose of protecting NGSO FSS earth stations from co-channel interference, coordination

of a transmitting HAPS station should be undertaken when the distance between the HAPS nadir

and any point of an administration’s border is less than 100 km.

One deterministic study (Study F) provides a minimum coupling loss analysis based on a single

HAPS and FSS GSO/NGSO Earth station pair. The analysis assumes that the HAPS transmitter is

pointing directly towards the FSS Earth station receiver in azimuth. Note that the FSS Earth station

158 Rep. ITU-R F.2475-0

receive antenna (both GSO and NGSO) is pointing with maximum gain towards the HAPS. The

required separation distance between HAPS nadir and FSS Earth station receiver (GSO and NGSO)

was calculated based on the FSS threshold I/N values of 8, dB, –6 dB, and –10.5 dB).

For the gateway downlinks from the HAPS, the studies show that for a satellite Earth station

receiver with an I/N value of –10.5 dB, the required separation distance from the HAPS nadir is

109 km for GSO and 111 km for NGSO satellite Earth station receivers.

For the CPE downlinks from the HAPS, the studies show that for a satellite Earth station receiver

with an I/N value of –10.5 dB, the required separation distance from the HAPS nadir is 139 km for

GSO and 145 km for NGSO satellite Earth station receivers.

This study considers that the FSS earth station is always pointing in the direction of the HAPS,

which gives maximum separation distances.

The range of distances for which the FSS protection criteria is not met, depends on the relative

configuration between the HAPS and the FSS earth station, and on the FSS earth station pointing

elevation.

2.3 Impact from transmitting FSS space station Satellite into receiving HAPS

Study B (§ 1.2.4) provides an analysis to determine whether the I/N value at the HAPS receiver is

exceeded by emissions from FSS (GSO and NGSO) satellites. The calculated I/N value at the HAPS

receiver does not exceed –25.39 dB.

The analysis shows that the I/N value is below the HAPS protection criteria of I/N = –10 dB for

worst case analysis.

Study F shows that HAPS receivers will not be impacted and can accept interference from FSS

downlink that are compliant with Table 21-4 of the RR Article 21.

2.4 Impact from transmitting FSS space station into receiving HAPS ground station

Study D shows that HAPS receiving ground stations can coexist with FSS space stations emissions

in the 38-39.5 GHz band given the percentage of HAPS service area where there could be

potentially a problem and given mitigation techniques that could be implemented by HAPS.

Study F, using an I/N value of –10 dB for the HAPS receiver, shows the following:

For the FSS GSO and NGSO satellite transmitting to HAPS gateway and CPE, at worst case:

• The I/N threshold is exceeded for any elevation higher than 85.7 degrees.

• An off-axis angular separation of 3.7 degrees between the satellite beam and the HAPS

beam is required in order to satisfy the threshold at the HAPS receiver.

This analysis assumes there is no azimuth off-axis for the HAPS link and the FSS link.

By employing appropriate mitigation, HAPS ground stations can coexist with FSS transmissions

that are at the RR Article 21 pfd levels.

Rep. ITU-R F.2475-0 159

Annex 4

Compatibility study of Space Research service in the adjacent band 37-38 GHz

and HAPS systems operating in 38-39.5 GHz frequency range


TABLE 53

Summary of scenarios considered in Studies A, B, C and D

Study A Study B Study C Study D

HAPS ground terminal to SRS X X X

HAPS to SRS X X X

1.1 Study A

1.1.1 Summary

This study investigates the compatibility between HAPS and SRS. This study will first present a

compatibility study. Then the impact of the various mitigation techniques will be assessed.

In this frequency range, the flowing directions are considered for HAPS:

– gateway to HAPS (UL);

– CPE to HAPS (UL).

1.1.2 Introduction

The parameters for the SRS systems are based on Recommendation ITU-R SA.1014. This

Recommendation also lists the SRS earth stations that require protection. The antenna gain pattern

for large diameter earth station was based on Recommendation ITU-R SA.1811. The maximum

gain considered for the SRS earth station is 86 dBi.

The protection criterion is specified in Recommendation ITU-R SA.1396 as I0/N0 = –6 dB. Using

SRS system noise temperature of 60 K, the protection criterion is specified as –217 dB (W/Hz) not

to be exceed 0.001% for manned SRS missions and 0.1% for unmanned SRS missions.

The HAPS parameters (gateway and CPE links) used in this study are from System 6 of Report

ITU-R F.2439-0.

1.1.3 Methodology and results – HAPS CPE/Gateway to SRS

1.1.3.1 SRS pfd limit

This section defines the required pfd levels at the input of the SRS earth station antennas to protect

them from interference caused by the HAPS ground terminals.

Therefore, the worst-case should be considered whereby the victim SRS site is located close-by and

is facing the HAPS ground terminals with minimum elevation angle.

The maximum possible HAPS ground terminal pfd level at the SRS earth station is defined by the

following equation:

𝑝𝑓𝑑𝑚𝑎𝑥 = 𝐼𝑅𝑥 + 10 × log10 (4π

λ2) − 𝐺𝑟 𝑀𝑎𝑥(Horizon)

160 Rep. ITU-R F.2475-0

where:

IRx: SRS earth station protection level (dB(W/Hz))

Gr Max: maximum gain of the SRS receiver towards the horizon (dBi).

To protect the SRS service, the out of band pfd level in the frequency band 37-38 GHz should not

exceed the value –183.3 dB(W/(m2 ‧ Hz)) at the input of the SRS earth station antenna for 0-degree

interference arrival angle, calculated using propagation loss for 0.001% exceedance probability.

To verify the compliance with the above propose pfd limits, the following equation should be used:

𝑂𝑂𝐵𝐸𝑝𝑓𝑑(𝑒𝑙) = 𝐸𝐼𝑅𝑃𝑑𝐵𝑊

𝑀𝐻𝑧

(𝑒𝑙) + P. 452(𝑑, %𝑡𝑖𝑚𝑒) − 10 ∗ log10 (4π

λ2)

where:

Att: propagation loss based on Recommendation ITU-R P.452-16 propagation

model

EIRP: maximum HAPS e.i.r.p. density level in dB(W/Hz) (dependent on the elevation

and pointing angles of HAPS station and SRS earth station)

d: distance between the HAPS and the SRS earth station

%𝑡𝑖𝑚𝑒: 0.001% is used for the P.452-16 propagation model.

1.1.3.2 Statistical method

This section gives the results of statistical studies to assess the percentage of HAPS deployments

that will cause interference to SRS earth stations if HAPS operate at closer distances than the

coordination distance. The following steps have been performed to derive the minimum separation

distance CDF between a single HAPS ground (interferer) stations and SRS ES (victim). The

coordination distance established using maximum interference scenario, where SRS earth station

and HAPS ground terminal will point to each other at minimum elevation angles would ensure the

protection of any SRS station for any HAPS deployment. In practice, for specific HAPS and SRS

deployments shorter separation distances could ensure the protection of the SRS. The following

analysis studies these deployment cases.

Step 1: Compute the SRS antenna gain towards the HAPS GW/CPE based on the following input

parameters:



– SRS station antenna pointing azimuth: random variable with a uniform distribution between

−180° to 180°;

– SRS terminal could be pointing a randomised point in the sky with elevations between 5

and 90 and it is therefore more likely to be pointing at low elevations than higher ones as

shown with the elevation distribution in Fig. 109.

Rep. ITU-R F.2475-0 161

FIGURE 109

Elevation distribution

– SRS maximum antenna gain: 86 dBi (for a 70 metre antenna diameter);

– SRS antenna pattern: Recommendation ITU-R SA.1811.

Step 2: Compute the HAPS GW/CPE antenna gain towards the SRS based on the following input

parameters:

– 0° is taken for the elevation angle towards the SRS;

– 180° is taken for the azimuth towards the SRS;



– HAPS station antenna pointing elevation: random variable with a uniform distribution

between 20 and 90 degrees;



Step 3: Compute the minimum separation distance needed to meet the SRS protection criteria

– Analysis done with the following range of SRS I protection criteria: -217 dB(W/Hz) not be

exceeded more than 0.001% of the time;

– HAPS station maximum e.i.r.p. density: 33 dB(W/MHz) for the GW and 30.3 dB(W/MHz)

for the CPE (equivalent –27 dB(W/Hz) and –29.7 dB(W/Hz));

– Propagation model used: Recommendation ITU-R P.452.


The following plots present the separation distance CDF for GW and CPE into SRS and FS Point-

to-Point into SRS.

162 Rep. ITU-R F.2475-0

FIGURE 110

HAPS GW/CPE and FS (Point-to-Point) to SRS earth station, minimum separation distance CDF

It can be seen from Fig. 110 above that the separation distance between a HAPS ground terminal

and an SRS earth station is about 30 km, which is much smaller compared to the separation between

an FS terminal and an SRS earth station.



such as:

– The positioning of ground terminals and HAPS to increase angular separation.



1.1.3.4 Summary of HAPS ground terminal (gateway/CPE) to SRS

Two types of analysis were presented:

1) pfd limit based on SRS protection criteria. To protect the SRS service, the out of band pfd

level in the frequency band 37-38 GHz should not exceed the value

−183.3 dB(W/(m2 ‧ Hz)) at the input of the SRS earth station antenna for 0.deg interference

arrival angle, calculated using propagation loss for 0.001% exceedance probability.

To verify the compliance with the above propose pfd the following equation should be

used:

𝑂𝑂𝐵𝐸𝑝𝑓𝑑(𝑒𝑙) = 𝐸𝐼𝑅𝑃𝑑𝐵𝑊

𝑀𝐻𝑧

(𝑒𝑙) + 𝑃. 452(𝑑, %𝑡𝑖𝑚𝑒) − 10 ∗ log10 (4π

λ2)

where:

Att: attenuation based on P.452-16 propagation model with p = 0.001%, calculated

using the maximum SRS and HAPS antenna heights

EIRP: maximum HAPS e.i.r.p. density level in dB(W/MHz) (dependent on the

elevation and pointing angles of HAPS antenna and SRS earth station antenna)

d: distance between the HAPS and the SRS earth station;

2) a statistical method presenting a minimum separation CDF to compare the following

scenarios:

Rep. ITU-R F.2475-0 163

– HAPS ground terminal (CPE and gateway) to SRS earth station

– FS to SRS earth station.

The studies show that the required separation distances are of the order of 30 km between HAPS

ground terminals and the SRS earth stations. As a comparison, the second analysis shows that the

separation distance between an HAPS ground terminals and an SRS earth stations are much smaller

than the separation between an FS terminal and an SRS earth station.


HAPS ground into SRS earth stations

The studies show that the required separation distances are of the order of 30 km between the HAPS

ground terminals and the SRS earth stations. In comparison, the analysis shows that the separation

distance between a HAPS ground terminal and SRS earth station is much smaller than the

separation between HAPS ground terminal and SRS earth station.

1.2 Study B

Interference Scenario:

This study provides results of a parametric analysis that calculates the required separation distances

to protect the SRS earth stations operating in the 37-38 GHz band from out-of-band emissions of

HAPS operating in the 38-39.5 GHz band. The e.i.r.p. density for the out-of-band emissions from

HAPS is assumed to vary between –88 dB(W/Hz) to –48 dB(W/Hz) at the 38 GHz band edge.

1.2.1 Technical parameters and protection criteria for SRS (s-E) systems operating in the

37-38 GHz band

The telecommunication requirements and parameters for manned and unmanned SRS systems are

given in Recommendation ITU-R SA.1014. This recommendation also includes a list of SRS earth

stations that need to be protected. Reference gain pattern for large earth station antennas is given in

Recommendation ITU-R SA.1811 for the 37-38 GHz band. The maximum gain of the SRS earth

station antenna is 86 dBi.

The protection criterion is specified in Recommendation ITU-R SA.1396 as Io/No = –6 dB. Using

SRS system noise temperature of 60 K, the protection criterion is specified as –217 dB (W/Hz) not

to be exceeded 0.001% for manned SRS missions and 0.1% for unmanned SRS missions. This

protection criteria is intended to protect unique operations during critical mission events in the

space research service from unexpected interference. Levels in excess of the protection criteria may

be acceptable on a case-by-case basis.

Interference scenario and parameters for HAPS/SRS compatibility in the 37-38 GHz band

Figure 111 shows the interference scenario studied in this analysis. HAPS is at 20 km altitude with

a service area of radius 50 km. In this scenario, smooth earth model is used.

164 Rep. ITU-R F.2475-0

FIGURE 111

HAPS/SRS interference scenario

The HAPS gateway is located at the perimeter of the service area in the direction of the SRS earth

station. HAPS antenna is pointed towards the gateway station. The SRS earth station antenna is

pointed in the direction of the HAPS with an elevation angle at least 6 degrees. Thus, if the HAPS

has an elevation angle greater than 6 degree at the SRS earth station, it is assumed that SRS antenna

is pointed at the HAPS.

The following parameters are assumed for the HAPS transmitter operating in the 38-39.5 GHz

band.

TABLE 54

HAPS parameters

Parameter Value

Transmit frequency (GHz) 38.5

Transmit power (total) (dBW) 15.4

Transmit antenna gain (dB) 28.1

Transmit e.i.r.p. (dBW) 43.5

Transmit bandwidth (MHz) 1 428.6

Transmit e.i.r.p. density (dB(W/Hz)) –48.1

Tmt power density (before antenna) (dB(W/Hz)) –76.2

Transmit antenna gain pattern Rec. ITU-R F. 1891

Antenna height above ground (km) 20

Service area radius (km) 50

Antenna beam elevation angle = -atan(20/50) (Ddeg) –21.8

Range of transmit e.i.r.p. density @ 38 GHz (dB(W/Hz)) –88 to –48

Note that the HAPS transmit e.i.r.p. density at the 38-GHz band edge is assumed to vary between

−88 dB(W/Hz) and −48 dB(W/Hz).

The following receiver parameters are assumed for the SRS earth station receiver.

HAPS Platform

SRS Earth Station

SRS antenna

boresight

HAPS antenna

boresight20 km

HAPS service area

R = 50 km

0 d

Rep. ITU-R F.2475-0 165

TABLE 55

SRS earth station receiver parameters

Parameter Value

Antenna diameter (m) 70

Antenna height above ground (m) 39

Antenna boresight gain (dBi) 86

Antenna gain pattern Rec. ITU-R SA. 1811

Antenna min elevation angle (degree) 6

SRS protection p.s.d. (ddB(W/Hz)) –217

SRS protection exceedance percentage (%) 0.001

Using the transmitter and receiver parameters above, the required minimum propagation loss needs

to be:

𝐿𝑟𝑒𝑞 = 217 − 76.2 + 𝐺𝑡 + 𝐺𝑟 = 140.8 + 𝐺𝑡 + 𝐺𝑟 (𝑑𝐵)

where Gt and Gr are the transmitter and receiver antenna gains towards each other. Gt and Gr change

as a function of off-boresight angles of the interference signal at the HAPS transmitter and SRS

earth station receiver.

1.2.2 Results of Study B

Using the propagation loss recommendations included in Recommendation ITU-R P.1409, the

required separation distance between SRS earth station and HAPS is calculated to satisfy the

required propagation loss. Figure 112 shows interference power density received by the SRS earth

station from an HAPS transmitter with –48 dB(W/Hz) e.i.r.p. density as a function of separation

distance. This is the maximum interference power density at the SRS earth station, since it assumes

no HAPS spectral mask to limit the out-of-band emissions.

FIGURE 112

SRS interference power density from HAPS with -48 dB(W/Hz) e.i.r.p. density vs separation distance

-500

-450

-400

-350

-300

-250

-200

-150

-100

-50

100 200 300 400 500 600 700 800 900

Rcv

In

terf

ere

nce P

ow

er

Den

sit

y, d

BW

/Hz

Separation Distance, km

SRS earth station protection = -217 dBW/Hz

HAPS tmt eirp densityat boresight = -48 dBW/Hz

166 Rep. ITU-R F.2475-0

From this Figure, three cases for interference can be easily identified:

Case 1: line-of-sight with HAPS elevation greater than 6 degrees,

Case 2: line-of-sight with HAPS elevation less than 6 degrees, and

Case 3: non-line-of sight.

For Case 1, the interference enters the SRS antenna through boresight with maximum gain.

Therefore, interference p.s.d. exceeds the SRS protection.

For Case 2, the interference enters the SRS antenna through side-lobes of the antenna with reduced

gain. This reduces the interference p.s.d., and at about 200-km separation distance meets the SRS

protection.

For Case 3, the HAPS is below the horizon and interference to SRS earth station comes through the

diffracted rays. The interference p.s.d. is further reduced due to diffraction losses.

1.2.2.1 Aggregate interference

To assess the aggregate interference to SRS earth station from multiple HAPS, the study also

considered additional HAPS on the left, on the right, and behind the original HAPS. The results

showed that the additional interference from the surrounding HAPS was very small compared to the

interference received from the main HAPS. Thus, in calculating interference to an SRS earth

station, it is enough to consider the closest HAPS in the direction of SRS antenna pointing with the

HAPS antenna pointing towards the SRS earth station.

1.2.2.2 Parametric out-of-band e.i.r.p. study

Figure 113 gives the required separation distance between HAPS and SRS earth station as a

function of HAPS transmit e.i.r.p. density ranging from –88 to –48 dB(W/Hz) at 38-GHz band

edge.

FIGURE 113

Separation distance between HAPS and SRS earth station vs out-of-band e.i.r.p. density @ 38 GHz

From Fig. 113 it can be seen that the required separation distances vary from 173 km to 200 km. If

it is assumed that the out-of-band emissions at 38 GHz band edge is attenuated by 20 dB to

−68 dB(W/Hz), the required separation distance is 176.5 km.

165

170

175

180

185

190

195

200

205

210

-95 -90 -85 -80 -75 -70 -65 -60 -55 -50 -45 -40

Sep

ara

tio

n D

ista

nce,

km

Eirp Density @ 38GHz, dBW/Hz

Rep. ITU-R F.2475-0 167

If the HAPS altitude increases to 50 km with a service area of radius 200 km, then the required

separation distance would be expected to increase also. This case needs to be analysed in the future

depending on changes in the HAPS deployment scenario and parameters considered.


Study B used a static analysis to determine the required separation distance between an SRS earth

station and HAPS nadir point to protect the SRS operating in 37-38 GHz band from the out-of-band

emissions of HAPS GW downlink in the 38-39.5 GHz band. The results indicate that, as the HAPS

GW out-of-band e.i.r.p. density vary from -88 dB(W/Hz) to –48 dB(W/Hz), the required separation

distance vary from 173 km to 200 km.

1.3 Study C

1.3.1 Impact of transmitting HAPS ground station in the 38-39.5 GHz band into SRS

receiving station in the 37-38 GHz band and comparison with the FS to SRS scenario

1.3.1.1 Impact of transmitting HAPS ground station in the 38-39.5 GHz band into SRS

receiving station in the 37-38 GHz


a single HAPS system ground station (interferer) and SRS Earth station (victim).

Step 1: Compute the HAPS system 2, 4a and 4b transmitting ground station antenna gain towards

the SRS impacted station based on the following input parameters:

– 0° is taken for the elevation angle towards the SRS impacted station;

– 0° is taken for the azimuth angle towards the SRS impacted station;





• 33.3° and 90° for the HAPS system 2 Gateways;

• 21° and 90° degrees for the HAPS system 2 CPE and for System 4a and 4b CPE and

Gateways that are shown in Fig. 114.


FIGURE 114

Elevation computation

168 Rep. ITU-R F.2475-0


• for HAPS System 2: 55 dBi for the GW and 49 dBi for the CPE;

• for GW of HAPS Systems 4a and 4b: 57.4 dBi;

• for CPE of HAPS System 4a: 49.8 dBi;

• for CPE of HAPS System 4b: 47.2 dBi and 39.3 dBi.


• For System 2: ITU-R F.1245-2;

• For Systems 4a and 4b: ITU-R S.580-6.

Step 2: Compute the SRS impacted Earth station antenna gain towards the HAPS System 2

transmitted ground station based on the following input parameters:



– SRS Earth station antenna pointing azimuth: random variable with a uniform distribution


– SRS station antenna pointing elevation: 10°

– SRS maximum antenna gain: 86 dBi;

– SRS antenna pattern: ITU-R SA.1811.

Step 3: Compute the propagation loss needed to meet the SRS protection criteria:

𝐼𝑚𝑎𝑥 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐻𝐴𝑃𝑆 − 𝐺𝑚𝑎𝑥𝐻𝐴𝑃𝑆+ 𝐺𝐻𝐴𝑃𝑆→𝑆𝑅𝑆 − 𝐴𝑡𝑡𝑃−452−16 + 𝐺𝑟𝑆𝑅𝑆

𝐴𝑡𝑡𝑃−452−16 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐻𝐴𝑃𝑆 − 𝐺𝑚𝑎𝑥𝐻𝐴𝑃𝑆+ 𝐺𝐻𝐴𝑃𝑆→𝑆𝑅𝑆 + 𝐺𝑟𝑆𝑅𝑆 − 𝐼𝑚𝑎𝑥

where:

EIRPmaxHAPS : HAPS station maximum e.i.r.p. density (in the main beam) (dB(W/MHz)):

TABLE 56

GW and CPE for the systems and weather conditions

GW CPE


System 2 –1.8 33.2 9.2 33.5

System 4a 11 26

15 30

System 4b 19 / 14.5 35.5 / 26.5

GmaxHAPS : maximum HAPS station antenna gain (dBi)

GHAPS→SRS : HAPS transmitted ground station antenna gain towards the SRS impacted

station (dBi)

GrFS : SRS impacted Earth station antenna gain towards the HAPS transmitting

station (dBi)

AttP-452-16 : propagation loss (dB) needed to meet the SRS protection criteria based on

P.452-16 propagation model with p = 0.001% for man SRS missions and

p = 0.1% for unmanned SRS missions. The land path type is used, the typical


Rep. ITU-R F.2475-0 169

Imax: maximum allowable interference level:

–217 dB(W/Hz) (I/N of –6 dB) not to be exceeded by more than 0.001% for

manned SRS missions and 0.1% for unmanned SRS mission.

Step 4: Compute the separation distance needed to meet the SRS protection criteria based on the


Step 5: Store the calculated separation distance and repeat Steps 1 through 4 sufficiently to obtain a

stable CDF.

1.3.1.2 Impact of transmitting FS station into SRS receiving Earth station at 38-39.5 GHz


a single FS station (interferer) and SRS Earth station (victim).

Step 1: Compute the FS transmitting station antenna gain towards the SRS impacted Earth station


– 0° is taken for the elevation angle towards the SRS impacted Earth station;

– 0° is taken for the azimuth towards the SRS impacted Earth station;


−180° to 180°;


−0.004° and standard deviation 3.6°);


46 dBi;


Step 2: Compute the SRS impacted Earth station antenna gain towards the FS transmitting station




– SRS station antenna pointing azimuth: random variable with a uniform distribution between

–180° to 180°;

– SRS Earth station antenna pointing elevation: 6°;

– SRS Earth maximum antenna gain: 86 dBi;

– SRS antenna pattern: ITU-R SA.1811.


𝐼𝑚𝑎𝑥 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐹𝑆 − 𝐺𝑚𝑎𝑥𝐹𝑆+ 𝐺𝐹𝑆→𝑆𝑅𝑆 − 𝐴𝑡𝑡𝑃−452−16 + 𝐺𝑟𝑆𝑅𝑆

𝐴𝑡𝑡𝑃−452−16 = 𝐸𝐼𝑅𝑃𝑚𝑎𝑥𝐹𝑆 − 𝐺𝑚𝑎𝑥𝐹𝑆+ 𝐺𝐹𝑆→𝑆𝑅𝑆 + 𝐺𝑟𝑆𝑅𝑆 − 𝐼𝑚𝑎𝑥

where:

EIRPmaxFS : is the FS station maximum e.i.r.p. density (in the main beam): random variable

with a uniform distribution between –15.7 and 17 dB(W/MHz)

GmaxFS : is the maximum FS station antenna gain (dBi)

GFS→SRS : is the FS transmitting station antenna gain towards the SRS impacted Earth

station (dBi)

GrSRS : is the SRS impacted Earth station antenna gain towards the FS transmitting

station (dBi)

170 Rep. ITU-R F.2475-0

AttP-452-16 : is the propagation loss (dB) needed to meet the SRS protection criteria based

on P.452-16 propagation model with p = 0.001% (manned SRS missions) and

p = 0.1% (unmanned SRS missions). The land path type is used, the typical


Imax : is the maximum allowable interference level:

–217 dB(W/Hz) (I/N of –6 dB) that not to be exceeded by more than 0.001%

(manned SRS missions) and 0.1% (unmanned SRS missions).

Step 4: Compute the separation distance needed to meet the SRS protection criteria based on the



stable CDF.

1.3.1.3 Results


FIGURE 115

Results in the long and short term

From the above results it can be concluded that HAPS System 2, 4a and 4b ground stations can be

considered as any FS station as the result of the impact of HAPS ground station emissions into SRS

Earth station receivers is less than the impact of an FS emitting station into SRS receiving earth

station.

Rep. ITU-R F.2475-0 171

1.3.2 Impact of transmitting HAPS in the 38-39.5 GHz band into receiving SRS earth

stations in the 37-38 GHz adjacent band

This study aims to assess the sharing between HAPS downlink emissions in the frequency band

38-39.5 GHz and SRS receiving stations in the 37-38 GHz adjacent band.

In this study, specific SRS site locations are considered in order to take into account the terrain

profile around the SRS site in the calculations. Goldstone and Madrid SRS site are taken as

examples in the following study.

In order to calculate the maximum worst case separation distances required to meet SRS protection

threshold between the SRS antenna site and the nadir of a HAPS, the following assumptions are

made:

– the HAPS is supposed to always transmit at it maximum transmit power in the direction of

the SRS receiving antenna. In practice this corresponds to situations where the HAPS to

ground link is facing severe rain attenuation, whereas no rain is present on the HAPS to

SRS site link. This represents a worst case calculation;

– the SRS antenna is supposed to always point directly in the direction of the HAPS station,

with a minimum elevation angle of 6° at the SRS site. If the HAPS station is seen with an

elevation angle less than 6°, then antenna discrimination is taken into account using the

SRS antenna pattern. Such assumption is a worst case made to ensure that calculated

separations distances are maximum worst case;

– as a worst-case assumption, no filtering is considered for the HAPS in the SRS 37-38 GHz

receiving band. This implies that resulting separation distances are maximum values, and

that in reality separation distances are expected to be much lower

– HAPS parameters used are those of System 4a.

Calculations are made using the following methodology:

Step 1: Consider Goldstone and Madrid SRS receiving earth station with the following parameters:

– antenna diameter: 70 m;

– antenna height above ground: 39 m;

– antenna maximum gain: 86 dBi;

– antenna pattern: ITU-R SA.1811;

– protection threshold: –217 dB(W/Hz);

– minimum elevation angle: 6°.

Step 2: Upload the real terrain model for each SRS Earth station considered.

Step 3: Upload the real terrain model surrounding each SRS Earth station considered up to a

distance of 500 km, which corresponds to the visibility area of a HAPS located at 20 km.

Step 4: Generate a grid of HAPS over the area obtained in Step 3 and compute the elevation angle

of the SRS earth station with respect to each HAPS location.

Step 5: Compute the interference received by the SRS earth station from each HAPS location

generated, taking into account the HAPS System 4a pfd envelope:

𝐼(θ) = 𝑝𝑓𝑑(θ) − 10 log10 (4π

λ2) + 𝐺𝑟(φ) − 𝐴𝑡𝑡𝑔𝑎𝑧(θ)

where:

θ: is the elevation angle at the SRS earth station towards the HAPS (angle of

arrival above the horizontal plane) (degrees);

172 Rep. ITU-R F.2475-0

pfd(θ): is the pfd generated by System 4a transmissions in the frequency band

38-39.5 GHz (dB(W/(m2 · MHz))).

Step 5: Get the HAPS locations for which the interference generated is less or equal to the SRS

earth station protection threshold.

Figure 116 provides results for Goldstone and Madrid SRS earth stations:

FIGURE 116

Results for Goldstone and Madrid SRS earth stations

Rep. ITU-R F.2475-0 173

The maximum distance obtained in order to meet SRS Earth station protection threshold is about

160 km.

Note that given the interference scenarios considered above, the calculations are made assuming

that interference occurs in the same frequency band (and not in adjacent bands) and also is present

100% of the time.

In reality, the level of interference and the distances computed will decrease, considering the

tracking strategy of SRS earth stations and the time percentages associated to the protection

threshold and also the attenuation due to the HAPS ‘structure’, the HAPS transmissions rejection

filtering, and guard bands with the upper boundary of the frequency band 37-38 GHz.

1.3.3 Summary and analysis of the results of study C

1.3.3.1 Transmitting HAPS into receiving SRS earth stations

Study C shows that HAPS technology operating in the 38-39.5 GHz in the HAPS-to-ground

direction can coexist with SRS earth station in the 37-38 GHz band if appropriate separation

distances are ensured between HAPS stations nadir and SRS receiving sites and/or filtering and

guard band.

1.3.3.2 Transmitting HAPS ground station into receiving SRS earth stations

Study C shows that HAPS technology operating in the 38-39.5 GHz in the ground-to-HAPS

direction can coexist with SRS earth station in the 37-38 GHz band as the result of the impact of

HAPS ground station emissions into SRS Earth station receivers is less than the impact of an FS

emitting station into SRS receiving earth station.

1.4 Study D

This study is addresssing the derivation of pfd limits to protect the SRS earth stations in the

37-38 GHz band.

1.4.1 Introduction

The interference power density, Pr, received by an SRS antenna can be expressed as:

𝑃𝑟 = 𝑃𝐹𝐷 ⋅λ2

4π∙ 𝐺𝑟

where:

pfd : is the interference power flux density at the antenna input in W/m2 in a

reference bandwidth of 1 Hz, λ is the wavelength of the interfering signal in

meters, and Gr is the SRS antenna gain. Thus, the pfd can be obtain from:

𝑃𝐹𝐷 =𝑃𝑟

λ2

4π∙𝐺𝑟

or in decibels from:

⟨𝑃𝐹𝐷⟩ = ⟨𝑃𝑟⟩ − ⟨λ2

4π⟩ − ⟨𝐺𝑟⟩

where: ⟨𝑥⟩ = 10log (𝑥). For a 38-GHz interference signal, using the SRS protection criteria of

−217 dB(W/Hz), the above equation gives:

⟨𝑃𝐹𝐷⟩ = −217 + 53 − ⟨𝐺𝑟⟩ = −164 − ⟨𝐺𝑟⟩ dB(W/m2) in 1 Hz

It is clear that the required power flux density to protect the SRS earth stations depends on the SRS

antenna gain pattern.

174 Rep. ITU-R F.2475-0

1.4.2 Gain patterns for different SRS antennas

The gain pattern for SRS antennas operating in 37-38 GHz band is given Recommendation

ITU-R SA.1811. It should be noted that the antenna patterns given in this Recommendation include

a surface roughness parameter and that the antenna side-lobe gains increase as the surface

roughness increases.

Figure 117 shows three sets of gain patterns for SRS antennas with diameters 15 m, 34 m, and 70 m

and surface roughness parameter varying from λ/60 to λ/20 corresponding to a very good antenna

and a fairly good antenna, respectively.

FIGURE 117

Gain patterns for SRS antennas with diameters 15 m, 34 m, and 70 m

and varying surface roughness

Figure 117 also shows an envelope gain pattern that covers all the different types of SRS antennas,

which can be expressed as follows:

⟨𝐺𝑟⟩ = {

+86 0 ≤ θ < θ1

+34 − 21 ∙ log (θ) θ1 ≤ θ < θ2

−5 θ2 ≤ θ ≤ 180

where:

θ : off-boresight angle in degrees, and the corner angles θ1 and θ2 are given by:

θ1 = 10−52 21⁄ ≈ 0.003 degrees

θ2 = 1039 21⁄ ≈ 72 degrees

1.4.3 Required pfd limits to protect SRS earth stations in the 37-38 GHz band

The pfdlimits to protect the SRS antenna can now be obtained by using the envelope gain given in

Section 2 in the pfd equation given in section 1, which can be written as:

10-3 10-2 10-1 100 101 102-20

-10

0

10

20

30

40

50

60

70

80

90

Gai

n, d

B

Off-boresight angle, Deg

Rep. ITU-R F.2475-0 175

⟨𝑃𝐹𝐷⟩ = {

−250 0 ≤ θ < θ1

−198 + 21 ∙ log (θ) θ1 ≤ θ < θ2

−159 θ2 ≤ θ ≤ 180

where:

⟨𝑃𝐹𝐷⟩ : required pfd at the SRS antenna input in W/m2 in a reference bandwidth of 1

Hz, θ is the off-boresight angle in degrees, and the corner angles θ1 and θ2 are

given as follows:

θ1 = 10−52 21⁄ ≈ 0.003 degrees

θ2 = 1039 21⁄ ≈ 72 degrees

Note that the required power flux density ⟨𝑃𝐹𝐷⟩ given above can be written using the angle of

arrival of the interfering signal, ϕ, above the local horizontal plane at the SRS antenna as follows:

⟨𝑃𝐹𝐷⟩ = {−198 + 21 ∙ log (5 − φ) 0 ≤ φ < 5 − θ1

−250 5 − θ1 ≤ φ ≤ 90

using the fact that the minimum tracking elevation angle for SRS antenna is 5 degrees, and above

5 degrees the interference will be received at the boresight of the SRS antenna.


The studies show that the protection of sensitive receiving earth stations operating in the SRS in the

band 37-38 GHz may be achieved through a combination of separation distance and attenuation of

unwanted emissions for HAPS stations operating in the band 38-39.5 GHz.

An unwanted emission pfd mask to be applied at the SRS earth station location at the relevant earth

station antenna height has also been proposed to address the protection of SRS in adjacent band:

𝑃𝐹𝐷 (𝑑𝐵𝑊

𝑚2 ∗ 𝐻𝑧) = {

−198 + 21 ∙ log(5 − φ) 0 ≤ φ < 5 − θ1

−250 5 − θ1 ≤ φ ≤ 90

where the corner angle θ1 = 10−52 21⁄ ≈ 0.003 deg and φis the interference arrival angle above the

horizontal plane. The interference pfd should be calculated using propagation losses for

p = 0.001%.

______________

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