wcdma fundamentals

Contents

Mobile Technology in Term of generation. Spectrum Allocation and N/W Architecture Approaches to 3G Radio Network Planning Link Budget What is CPICH,Ec and Ec/Io Handover Scrambling Code Planning Neighbour List Site Selection Criteria

Cellular Generations

Mobile Technology in terms of generations

1st Generation or 1G

2nd Generation or 2G

2.5G3rd Generation or

3G4th Generation 0r

4Gtime

Data rate

Progress of data rates with time and generation

Future of 3G – Projection

Spectrum Allocations– 3GPP rel4

3G(WCDMA 1900) for U.S

Uplink Uplink Downlink Downlink

SATELLITE FDDTDDFDDTDD SATELLITE

Duplex 190 MHz

22002025201019801920 21702110

60MHz 60MHz

3G(WCDMA) 2GHz frequency band for Europe and APAC

Uplink Downlink

FDDFDD

Duplex 80 MHz

Frequency MHz

19101850 19901930

60MHz 60MHz

UMTS Network Architecture

Circuit SwitchedCore Network

GGSN

3GSGSN

GPRS

USIM

card

WCDMA

mobile

GSM/WCDMAmobile

RAN

(Node B)

RNC

RNC

MSC

HLR

MGW

IN SCP

SRR

PS Core Network

(PSTN/ISDN)

InternetTCP/IP)

GSM/WCDMAmobile

CBC(Node B)

Scrambling Codes & CPICH

The Common Pilot Channel (CPICH) is broadcast from every cell It carries no information and can be thought of as a “beacon”

constantly transmitting the Scrambling Code of the cell It is this “Beacon” that is used by the phone for its cell

measurements for network acquisition and handover purposes (Ec, Ec/Io).

Beacon: A signaling or guiding device, such as a lighthouse, located on a coast. A radio transmitter that emits a characteristic guidance signal.

CPICH

Comments

Majority of the measurements are based on CPICH.

Thumb rule is that, if UE can’t see the CPICH, it can’t see the cell.

Initial optimisation is purely based on the CPICH measurements.

In the Downlink, WCDMA cells are identified by their SC.

Its like a BCCH in GSM but the difference is in using same frequency.

Concepts of RSCP and Ec/No

• Three Important Terms

– RSCP (Received signal code power)– Ec/Io ( Energy per chip/ Noise density)– Eb/No (Energy per bit/Noise density)

Total Received Power Io

• In a WCDMA network the User Equipment (UE) receives signals from many cells

• Io* = No = The sum total of all of these signals (dBm)

Io

Received Power of a CPICH

• Using the properties of SCs the UE is able to extract the respective CPICH levels from the sites received

• RSCP = The Received Power of a Particular CPICH (dBm) • Ec = Energy per Chip

Ec1 Ec2

The CPICH Quality (Ec/Io)

• From the previous two measures we can calculate a signal quality for each CPICH (SC) received

• Ec/Io = Ec - Io (dB)• Eb/No = Ec/Io+ Processing Gain

Ec1 Ec2

Handover Types

• Intra-Frequency Handovers Softer Handover

• Handover between sectors of the same Node B (handled by BTS) Soft Handover

• MS simultaneously connected to multiple cells (from different Node Bs) Hard Handover

• Arises when inter-RNC SHO is not possible (Iur not supported or Iur congestion)

• Decision procedure is the same as SHO (MEHO and RNC controlled)

• Inter-Frequency Handover– Can be intra-RAN, intra-RNC, inter-RNC

• Inter-RAT Handover – Handovers between GSM and WCDMA (NEHO)

MEHO- Mobile evaluated handover

NEHO- Network evaluated handover

Handovers in WCDMA - Softer HO

• Softer handover occurs between sectors of the same site

• Soft handover occurs between sectors of the different sites

• For both softer and soft it is the Ec/Io levels used to determine whether a cell should be added or removed from the active set

Handovers in WCDMA - Soft HO

Handovers - Inter frequency HO

Inter frequency handover occurs between two WCDMA carriers

Will be used once operator deploys its second carrier, for microcell layer or capacity purposes

Handovers - Inter system HO

• Inter system handover occurs between 3G and 2G sites• As with all handovers, accurate adjacencies will be required

3G 2G

UMTS CELL PLANNING

UMTS & GSM Network Planning

GSM900/1800: 3G (W CDM A):

Approaches to 3G Radio Network Planning

• There are two approaches to 3G radio network planning:

• Path loss based

• 3G simulation based.

• The path loss based approach:– is relatively simple and is the most commonly adopted

approach.– makes use of software tools which are relatively mature

and results which are easy to interpret.– makes use of maximum allowed path loss figures resulting

from 3G link budgets.– generates plots and statistics for 3G coverage, best server

areas and C/I analysis.• The 3G simulation based approach:

– is more complex and time consuming.– is often used for focused 3G system investigations rather

than wide area radio network planning.– uses software tools which are less mature and results

which are more difficult to interpret.– makes use of 3G parameter assumptions and a 3G traffic

profile.– generates plots and statistics for coverage, capacity, soft

handover, intercell interference, uplink load and downlink transmit power.

Approaches to 3G Radio Network Planning

3G Simulation based Approach

• The 3G simulation based approach to radio network planning requires the use of a 3G radio network planning tool. The majority of 3G radio network planning tools, including NetAct Planner make use of Monte Carlo simulations. Monte Carlo simulations are static simulation. This means that system performance is evaluated by considering many independent instants (snap shots) in time. In the case of static simulations, the population of UE are re-distributed across the simulation area for every simulation snap shot. For each snap shot the uplink and downlink transmit power requirements are computed based upon link loss, C/I requirement and the level of interference. UE which are not able to achieve their C/I requirements are categorized as being in outage. Outage may also be caused by factors such as inadequate baseband processing resources or reaching the maximum allowed increase in uplink interference. By considering a large number of instants in the time the simulation is able to provide an indication of the probability of certain events occurring, e.g. the probability that a UE will be able to establish a connection at a specific location. The simulation is also able to provide an indication of average performance metrics such as cell throughput and downlink transmit power.

3G Simulation based Approach

· 3G site candidates with their physical configuration (antenna type, antenna height, antenna tilt ,antenna azimuth, feeder type and feeder length)

· propagation model· digital terrain map• 3G parameter assumptions· 3G traffic profile

• service coverage• system capacity• soft handover overhead• Intercell interference• uplink and downlink transmit powers• uplink and downlink interference floors• connection establishment failure mechanisms

Input

Output

Simplified Network Planning Flowchart

Create nominal plan

Define search ring

Site selection

Detailed site design

Site acquisition

CW Measurement

Identify site options

Site construction

Initial network dimensioning

Link Budget Overview

Noise figure

Cable losses

Soft handover gain,

antenna gain

Building Penetration loss

Body loss

Margins

PATH LOSS (L)

Max AllowedPath Loss (L)

= Tx Signal + All Gains – Other Losses – Rx Sensitivity

Link Budget

• Uplink Service – Link Budget• Downlink Service – Link Budget• Downlink CPICH

(A step towards validating link budgets is to validate whether the uplink service, downlink service or CPICH is the limiting link.)

Service Type Nokia Specific Speech CS Data PS Data

Uplink bit rate No 12.2 64 64 kbps

Maximum transmit power UE dependant 21.0 21.0 21.0 dBm

Terminal antenna gain UE dependant 0.0 2.0 2.0 dBi

Body loss No 3.0 0.0 0.0 dB

Transmit EIRP UE dependant 18.0 23.0 23.0 dBm

Chip rate No 3.84 3.84 3.84 Mcps

Processing gain No 25.0 17.8 17.8 dB

Required Eb/N0 Yes 4.4 2.0 2.0 dB

Target uplink load No 50 50 50 %

Rise over thermal noise No 3.0 3.0 3.0 dB

Thermal noise power No -108.0 -108.0 -108.0 dBm

Receiver noise figure Yes 3.0 3.0 3.0 dB

Interference floor No -102.0 -102.0 -102.0 dBm

Receiver sensitivity Yes -122.6 -117.8 -117.8 dBm

Node B antenna gain No 18.5 18.5 18.5 dBi

Cable loss No 2.0 2.0 2.0 dB

Benefit of using MHA/TMA No 2.0 2.0 2.0 dB

Fast fading margin Yes 1.8 1.8 1.8 dB

Soft handover gain Yes 2.0 2.0 2.0 dB

Building penetration loss No 12.0 12.0 12.0 dB

Indoor location probability No 90 90 90 %

Indoor standard deviation No 10 10 10 dB

Slow fading margin No 7.8 7.8 7.8 dB

Isotropic power required Yes -121.5 -116.7 -116.7 dBm

Allowed propagation loss Yes 139.5 139.7 139.7 dB

UplinkLink Budget

Bit rate bit/s 64000 aTotal TX power available dBm 21 bTX antenna gain dBi 2 cBody loss dB 0 dTX EIRP per traffic channel dBm 23 e=b+c-dRX antenna gain dBi 18 fRX cable and connector losses dB 3 gReceiver noise figure dB 3 hThermal noise density dBm/Hz -174 jCell loading % 70 kNoise rise due to interference dB 5.23 l=10*log10(1/(1-(k/100)))Total effect of noise dBm/Hz -171 m=h+jInformation rate dBHz 48.06 n=db(a)Effective required Eb/No dB 2.54 oRX sensitivity dBm -115.40 p=l+m+n+o+correction factorSoft Handoff Gain dB 4.5 qFast fading Margin dB 2.5 rLog normal fade margin dB 11.6 sIn-building penetration loss (urban) dB 20 tMaximum path loss urban dB 123.80 pl=e+f+q-g-p-r-s-t

Path loss = Tx signal + all gains - losses - ( SNR + Noise)

Service Type Nokia Specific Speech CS Data PS Data

Downlink bit rate No 12.2 64 64 128 384 kbps

Maximum transmit power Yes 34.2 37.2 37.2 40.0 40.0 dBm

Cable loss No 2.0 2.0 2.0 2.0 2.0 dB

MHA insertion loss Yes 0.5 0.5 0.5 0.5 0.5 dB

Node B antenna gain No 18.5 18.5 18.5 18.5 18.5 dBi

Transmit EIRP Yes 50.2 53.2 53.2 56.0 56.0 dBm

Processing gain No 25.0 17.8 17.8 14.8 10.0 dB

Required Eb/N0 UE dependant 7.9 5.3 5.0 4.7 4.8 dB

Target loading No 80 80 80 80 80 %

Rise over thermal noise No 7.0 7.0 7.0 7.0 7.0 dB

Thermal noise power No -108.0 -108.0 -108.0 -108.0 -108.0 dBm

Receiver noise figure UE dependant 8.0 8.0 8.0 8.0 8.0 dB

Interference floor No -93.0 -93.0 -93.0 -93.0 -93.0 dBm

Receiver sensitivity UE dependant -110.1 -105.5 -105.8 -103.1 -98.2 dBm

Terminal antenna gain UE dependant 0.0 2.0 2.0 2.0 2.0 dBi

Body loss No 3.0 0.0 0.0 0.0 0.0 dB

Fast fading margin UE dependant 0.0 0.0 0.0 0.0 0.0 dB

Soft handover gain UE dependant 2.0 2.0 2.0 2.0 2.0 dB

MDC gain UE dependant 1.2 1.2 1.2 1.2 1.2 dB

Building penetration loss No 12.0 12.0 12.0 12.0 12.0 dB

Indoor location probability No 90 90 90 90 90 %

Indoor standard deviation No 10 10 10 10 10 dB

Slow fading margin No 7.8 7.8 7.8 7.8 7.8 dB

Isotropic power required Yes -90.5 -90.9 -91.2 -88.5 -83.6 dBm

Allowed propagation loss Yes 140.7 144.1 144.4 144.5 139.6 dB

DownlinkLink Budget

Downlink CPICH

Service Type Nokia Specific CPICH

Maximum transmit power Yes 33.0 dBm

Cable loss No 2.0 dB

MHA insertion loss Yes 0.5 dBi

Node B antenna gain No 18.5 dBi

Transmit EIRP Yes 49.0 dBm

Required Ec/I0 UE dependant -15 dB

Target loading No 80 %

Rise over thermal noise No 7.0 dB

Thermal noise power No -108.0 dBm

Receiver noise figure UE dependant 8.0 dB

Interference floor No -93.0 dBm

Receiver sensitivity UE dependant -108.0 dBm

Terminal antenna gain UE dependant 0.0 dBi

Body loss No 3.0 dB

Fast fading margin No 0.0 dB

Building penetration loss No 12.0 dB

Indoor location probability No 90 %

Indoor standard deviation No 10 dB

Slow fading margin No 7.8 dB

Isotropic power required Yes -85.2 dBm

Allowed propagation loss Yes 134.2 dB

Service Type Speech CS Data PS Data

Bit rate 12.2 64 64 128 384 kbps

Uplink allowed propagation loss (original)

139.5 139.7 139.7 - - dB

Downlink allowed propagation loss 140.7 144.1 144.4 144.5 139.6 dB

CPICH allowed propagation loss 134.2 dB

Scrambling Code Planning

• The 512 downlink primary scrambling codes are organized into 64 groups of 8.

• Each cell within the radio network plan should be assigned a primary scrambling code.

• Scrambling code planning strategies can be defined that maximize the number of neighbors belonging to the same code group or that maximize the number of neighbors belonging to different code groups. The difference between the two strategies has not been quantified in the field but is likely to be dependant upon the UE implementation.

Neighbor List

• Maximum NBR list for Nokia is 46• Intra-Frequency Cells (ADJS) - 32• Inter-Frequency Cells (ADJI) - 32• Inter-System Cells (ADJG) – 32

(If an operator has both GSM900 and DCS1800 networks then it is possible to define inter-system neighbors only for the GSM900 layer or only for the DCS1800 layer.)

Site Selection Criteria

Site Selection Criteria

Proper site location determines usefulness of its cells

Sites are expensive

Sites are long-term investments

Site acquisition is a slow process

Hundreds/thousands of sites needed per network

Base station sites are Base station sites are valuablevaluablelong-term assets for the long-term assets for the operatoroperator

How do I assess a site option?

Each site needs to be assessed on several grounds.

RadioTransmissionAccessPowerPlanning

Ideally every site option reported by the surveyor would pass in each of the areas listed above.

Bad GSM Sites

In GSM, there were two types of bad sites. Donkeys - Low sites which provide very little coverage.

Donkeys carry so little traffic that they often never pay for themselves.

Boomers - High sites which propagate much further than is needed.

A boomer will cause localised interference and prevent capacity being added to some other sites in the area.

Small “Donkey” site Large “Boomer” site

Bad UMTS Sites

Good radio engineering practice doesn’t change much for UMTS.

It just becomes more important. In UMTS

A “Donkey” will never pay for itself. A “Boomer” will reduce the range and capacity of

surrounding sites. Two major factors determine whether a site is

considered good, a “Donkey” or a “Boomer”, They are: Site location. Antenna height.

Other parameters can be used in an attempt to control booming sites but it is far better to avoid building them in the first place.

Importance of Controlling 'Little i'

WCDMA is an interference-limited network. I.e. capacity of the network is directly linked to how interference is maintained/controlled.

From the Radio Network Planning point of view, the "little i" - other-to-own cell interference- is the only thing that can really be influenced by the Planner during the site selection and planning stage. WCDMA RF planning is all about having good dominance in the desired coverage area.

Unlike in GSM, that there is no frequency plan to "play" with in order to minimise the effects of bad sites.

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Uplink Load Uplink Load EquationEquation

Uplink Load Uplink Load EquationEquation Downlink Load Downlink Load

EquationEquationDownlink Load Downlink Load

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Importance of Controlling 'Little i'

• Planners have to select the sites diligently so that the other-to-own cell interference ratio is MINIMIZED by planning clear dominance areas during site selection / planning phase.

0 500 1000 1500140

145

150

155

160

165

170

DL throughput in kbps

Max

imum

pro

paga

tion

loss

(dB

)

128 kbps

i = 0.2i = 0.2i = 0.4i = 0.4i = 0.6i = 0.6i = 0.8i = 0.8

BTS TX power 43 dBm

MS TX power 21 dBm

Ec/Io -16.5 dB

BTS Eb/No 1.5

MS Eb/No 5.5

Other to own cellinterference ratio i

0.2, 0.4, 0.6,

0.8

Orthogonality 0.6

Channel profile ITU VehicularA, 3 km/h

MS speed 3 km/h

MS/BTS NF 8 dB / 4 dB

Antenna gain 16 dBi• RESULT: Doubling of the "little i" will

cause throughput to decrease to 70% of the original value

i = Coverage Overlap

Some overlap is required to allow soft handover to occur

Need to control amount of interference since the network capacity is directly related to it.

Soft handover helps to reduce interference. (Soft HO Gain)

Too much overlap:• Increases interference to other cells -->

reduce capacity• Increases Soft Handover overhead --> reduce

capacity

Bad Site Location

wanted cellboundary

uncontrolled, stronginterferences

interleaved coverage areas:weak own signal, strong foreign signal

• Avoid hill-top locations for BS sites (same for GSM) uncontrolled interference interleaved coverage no sharp dominance areas awkward Soft/Hard HO behaviours BUT: good location for microwave links ! (TNP jurisdiction)

wanted cellboundary

Good Site Location

• Prefer sites off the hill-tops use hills/high rise buildings to separate cells contiguous coverage area well defined dominance areas needs only low antenna heights if sites are slightly

elevated above valley bottom

Characteristics of a good site

It has good clearance, no obstacles around, and it overlooks the surrounding rooftops. This site will give good macro coverage.

Bad site; blocked by neighbour building

Characteristics of a good site

BAD: In a urban/dense urban area, too high a site is a bad site since it will introduce too much interference to other sites in the network(remember the little i)

while for a rural area it's a good site.

Uplink Load EquationUplink Load EquationUplink Load EquationUplink Load Equation

Downlink Load Downlink Load EquationEquation

Downlink Load Downlink Load EquationEquation

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Examples of Bad Sites

Typical mess! =>GSM1800 antennas with space div. between CDMA (IS-95) antennas and pointing directly at the high building

GSM1800 and GSM900 antennas are too close=> Not enough isolation => Intermodulation and spurious emission.

These situations can easily be avoided!!

Time consuming and costly to fix.

Arghhh… note how far you can see -roughly 10km = TOO FAR. There is a riveras well, so interference is enormous. Sitedistance is about 700meters in thisphase!! Site was good in phase 1when distance between sites was 4km!

Well shit happens … who could have known that they were going to build this high building one year after installation ?

Planners should have anticipated this during initial site surveys!

Examples of Bad Sites

Little i, Little i, Little i !!!

Examples of Bad Sites

The TX/RX and Rx div antennas are not pointing in the same direction! Installation problem.

Is this installation OK? The satellite dish is in near field of the GSM900 antennas -> some effects for sure. Definite interference to satellite system. But could not be tested because the satellite system was not in use!

Avoid installing antennas in close proximity to other objects since its radiation pattern will be altered.

Examples of GOOD Sites

Enough space between the two Tx/Rx and Rx Div., AND pointing in the same direction! Site survey point of view: Provides clear dominance to the desired coverage area.

Summary of Site Selection Guidelines

The objective is to select a site location which covers the desired area but keeps emissions to a minimum.

The site should be located as close to the traffic source as possible.

• The closer the site is to the traffic, the less output power will be required by the user equipment and node B. This will minimize the noise affecting other users on both the serving cell as well as other nearby cells.

The antenna height selected will depend largely on the type of environment in which the site is to be located. Eg Dense Urban, Urban, Suburban, Rural.

The key factor to be considered is how well can the emissions be controlled.

Summary of Site Selection Guidelines

You can "feel" the site only if you are there! If one or more of these characteristics are not

fulfilled by the examined site, the Field Planner should REJECT the site and choose another site

Be flexible, even creative! Try to think of all the possible implementation solutions that the site could support: different pole heights, split poles for different sectors, etc.

Always check neighbouring sites, to be sure your chosen candidate is "fitting" well into the surrounding, e.g. for coverage, SHO zones,etc.

Using Existing Cellular Sites

Most UMTS networks will be built around an existing GSM network.

Many GSM networks were built around existing analogue sites.

In the early days of analogue cellular sites were often located to give maximum coverage. No thought was given to capacity issues.

Despite causing problems in high capacity networks, many of these high sites are still in operation today.

Most cellular networks contain these nightmare sites.

When rolling out UMTS around an existing network it is vital to avoid these sites.

UMTS Configurations

• Most vendors support the same basic configurations.– Omni– 3 sector– 6 sector

• Each vendor supports their own variations on these configurations.– Some require similar amounts of equipment to a

GSM BTS.– Some increase the number of antennas on a site.

• The configuration can be affected by the wide variety of UMTS antennas.

Co-locating a Node B at a GSM site

Isolation requirements between UMTS and GSM systems can be derived from UMTS and GSM specifications. In many cases equipment performance will exceed

the requirements in the specifications. Each vendor should be able to provide information

which can be used to improve the isolation requirements.

The isolation requirements will affect• Choice of antenna configuration• Filtering at both the GSM and UMTS sites.

Isolation is the attenuation from the output port of a transmitter to the input port of the receiver.

Interference Issues

Wideband Noise - unwanted emissions from modulation process and non-linearity of transmitter

Spurious Emissions - Harmonic, Parasitic, Inter-modulation products

Blocking - Transmitter carriers from another system Inter-modulation Products - Spurious emission,

specifications consider this in particular• Active: non-linearities of active components - can be

filtered out by BTS• Passive: non-linearities of passive components - cannot

be filtered out by BTS Other EMC problems - feeders, antennas, transceivers

and receivers

Interference Issues• Nonlinear system transfer function can be expressed as a

series expansion

In the case of one input frequency, vin = cos 1t, output will consist of harmonics, m1

• Fundamental (m = 1) frequency is the desired one.• If m > 1, there are higher order harmonics in output =>

harmonic distortion.• Can be generated both inside an offender or a victim

system. In the case of two input frequencies, vin = cos 1t + cos 2t ,

output will consist of harmonics m1 + n2, where n and m are positive or negative integers.

• Intermodulation is the process of generating an output signal containing frequency components not present in the input signal. Called intermodulation distortion (IMD).

• Most harmful are 3rd order (|m| + |n| = 3) products.• Can be generated both inside an offender or a victim

system.

x y = a0 + a1x + a2x2 + a3x3 + ...System

Interference from Other System

GSM spurious emissions and intermodulation results of GSM 1800 interfere WCDMA receiver sensitivity

WCDMA spurious emissions interfere GSM receiver sensitivity

GSM transmitter blocks WCDMA receiver

WCDMA transmitter blocks GSM receiver

GSM GSM 1800 1800

ULUL

GSM GSM 1800 1800

DLDL

1710-1785 MHz

1805-1880 MHz

UMTS UMTS UL UL

UMTS UMTS DLDL

1920-1980 MHz

2110-2170 MHz

40 MHz

M Distortion from GSM1800 DL to WCDMA UL

• GSM1800 IM3 (3rd order intermodulation) products hits into the WCDMA FDD UL RX band if:

• 1862.6 f2 1879.8 MHz

• 1805.2 f1 1839.6 MHz

WCDMADL

WCDMAUL

GSM1800DL

GSM1800UL

1710 - 1785 MHz1805 - 1880 MHz 1920 - 1980 MHz2110 - 2170 MHz40 MHz

f1 f2

fIM3

fIM3 = 2f2 - f1

X dBc

• For active elements IMproducts levels are higherthan IM products producedby passive components• Typical IM3 suppressionvalues for power amplifiers are -30 … -50 dBc depending on frequencyspacing and offset• Typical values for passiveelements are -100 … -160 dBc

Harmonic distortion

Harmonic distortion can be a problem in the case of co-siting of GSM900 and WCDMA.

GSM900 DL frequencies are 935 - 960 MHz and second harmonics may fall into the WCDMA TDD band and into the lower end of the FDD band.

GSM900935 - 960 MHz

WCDMATDD

WCDMA FDD1920 - 1980

...

2nd harmonics

fGSM = 950 - 960 MHz

1900 -1920 MHz

2nd harmonics can be filtered out at the output of GSM900

BTS.

f

Isolation Requirements

GSM 900 GSM 1800 UMTSReceiving band

(UL)890 – 915 MHz 1710 – 1785 MHz 1920 – 1980 MHz

Transmitting band(DL)

935 – 960 MHz 1805 – 1880 MHz 2110 – 2170 MHz

GSM 1800 TxGSM 1800 Tx

1805 MHz1805 MHz 1880 MHz1880 MHz

UMTS RxUMTS Rx

1920 MHz1920 MHz 1980 MHz1980 MHz

GSM 1800 RxGSM 1800 Rx

1710 MHz1710 MHz 1785 MHz1785 MHz

UMTS RxUMTS Rx

2110 MHz2110 MHz 2170 MHz2170 MHz

For example - To prevent UMTS BTS blocking: with transmit power = 43 dBm For example - To prevent UMTS BTS blocking: with transmit power = 43 dBm

Max level of interfering signal for blocking = -15 dBm in UMTSMax level of interfering signal for blocking = -15 dBm in UMTS

Isolation required = 58 dBmIsolation required = 58 dBm

Achieving Isolation Requirements

• Isolation can be provided in a variety of different ways.

By antenna selection and positioning.

By filtering out the interfering signal.

By using diplexers and triplexers with shared feeder and multiband antennas.

UMTSUMTS

GSMGSM

FilterFilter

UMTSUMTS

GSMGSM

DiplexerDiplexer

UMTSUMTS

GSMGSM

Co-siting - Antenna Installations Difficult to calculate isolation between two antennas and

measurements are required. Best configurations - antennas pointing in different

directions or where there is vertical separation between antennas

The following configurations will should all give 30dB isolation.

dddd

dd

90º90º 120º120º

dd

dd180º180º

dd

d = 0.3 - 0.5 md = 0.3 - 0.5 m d = 1 - 3 md = 1 - 3 m d = 0.5 - 2 md = 0.5 - 2 m

Site sharing with third party systems Some UMTS sites might be co-

located with other non GSM operators.

PMR (Private mobile radios) Broadcast Navigation

Some of these systems use older equipment which might be more vulnerable to EMC issues.

Need to define minimum antenna separations between systems

Better to avoid sites used for safety critical applications.

UMTS antennas

Other systems

Minimum separation

Antenna installation issues: Clearance angle

h (meters)

d (meters)Clearance angle

• Rules of thumb: – h d/2, d < 10 m– h d/3, 10 < d < 20 m– h d/4, d > 30 m

Antenna

d (meters)

Top view

Side view

Antenna installation

d has to be >3.2 m

• Safety margin of 15 between the reflecting surface and the 3 dB lobe