1 © NOKIA 6-90212/ SPECIAL CASES: INDOOR AND TUNNEL ENVIRONMENTS/v 1.0
SpecialSpecialCasesCases: Indoor and Tunnel Environments
2 © NOKIA 6-90212/ SPECIAL CASES: INDOOR AND TUNNEL ENVIRONMENTS/v 1.0
Module objectives
DESCRIBE HOW TO IMPROVE INDOOR COVERAGE
EXPLAIN THE PRINCIPLES OF INDOOR PLANNING
DESCRIBE THE BASICS OF TUNNEL PLANNING
LIST THE BASICS OF REPEATERS
At the end of this module you will be able to …
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Content of Special Cases
INDOOR PLANNING
TUNNEL PLANNING
REPEATERS
4 © NOKIA 6-90212/ SPECIAL CASES: INDOOR AND TUNNEL ENVIRONMENTS/v 1.0
Special Cases
INDOOR PLANNING
TUNNEL PLANNING
REPEATERS
5 © NOKIA 6-90212/ SPECIAL CASES: INDOOR AND TUNNEL ENVIRONMENTS/v 1.0
Why Indoor Sites?• Normally two reasons to build an indoor site
• Improve poor indoor coverage
• Free capacity to outdoor cells
• Indoor cell's interference area vs outdoor cell's interference area is much more limited
• High buildings, interference come as far as tens of kms => partition indoor frequency plan from outdoor frequency plan
• Problem: Strong signals coming from outdoors to indoors
• Buildings• Public (shopping malls, railway stations etc.) => improves the network
quality and service => operator finance
• Private (companies etc.) => possibility to sell mobile services => possibility to offer special tariffing => tie up the company to operator
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Building LossesBasics
• Signal levels in buildings are estimated by a applying a “building penetration loss” margin
• Big differences between rooms with window and “deep indoor” (10..15 dB)
• Signal losses for building penetration vary greatly with building materials used, e.g.:
mean value sigmaconcrete wall, windows 17 dB 9 dBconcrete wall, no windows 30 dB 9 dBconcrete wall within building 10 dB 7 dBbrick wall 9 dB 6 dBarmed glass 8 dB 6 dBwood or plaster wall 6 dB 6 dBwindow glass 2 dB 6 dB
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• Penetration loss depends heavily on incident angle of radio wave
0
5
10
15
20
25
30
0 15 30 45 60 75 90 105
120
135
150
165
180
dB
deg
0
90
180
glass pane
incidence angleof radio wave
Building LossesIncident Angle
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Building LossesIn-Building Path Loss
• Simple path loss model for in-building environment• Outdoor losses: Okumura´s formula• Wall losses: Lwall = f(material; angle)• Indoor losses: linear model
for picocells: Lin = L0 + ad
building type losses application example
old house 0,7 dB/m (urban residential)
commercial type 0,5 dB/m (modern offices)
open room, atrium 0,2 dB/m (museum, train station)
Lout
Lwall
Lin
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Indoor System Planning ProcessA) Pre-planning phase (= nominal planning)
• Monitoring macro cell network (at office!!)• Traffic distribution (macro cell blocking) • Timing advance distribution (mobile locations)
B) Planning phase• Detailed planning (on site!!!)• Configuration and Coverage planning
• (field measurements + input info = #antenna locations!!!!)
• Capacity planning (based on monitoring + input info)• Frequency planning (manually, field measurements)• Parameter planning and Verification
• (indoor based modifications + field measurements)
C) Post-planning phase• Monitoring (key performance indicators, especially HOs!!) • Optimisation (field measurements)
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Indoor Propagation
• Three main propagation mechanisms• Reflection• Diffraction• Scattering
• Similar to microcellular propagation, except in smaller scale!• Delay spread very small => large coherence bandwidth!!
TX
RX
R
SD D
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Indoor Coverage Planning
• Indoor environment very difficult to model (as microcell)• Coverage planning based on measurements
• Two distinct types of survey• Existing coverage surveys• New cell surveys and Proposal
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Existing Coverage Survey
• To determine whether an in-building cell is required
• Survey of current digital networks, to show coverage level available
• Test mobile in dedicated mode while walking in the building
• Download measurement data to PC for analysis
• Post measurement tool, SAM are used to analyse measurement data
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Measurement showing RxQual & Event Types using NIB and SAM
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Measurement Methods
• Test transmitter emitting at a designated test frequency set up
• Antenna positioned to achieve the required coverage
• Data collected while walking around the building
• Test equipment will be• a calibrated GSM900/1800 test transmitter (InSite or any generic signal
generator) feeding via a• cable of measured attenuation and• either a omni or directional antenna mounted on a tripod
• Same data acquisition apparatus for exisitng coverage survey measurement will be used
• Using SAM, coverage level against position will be overlaid on the building plan
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Indoor Coverage Solutions
• Small BTS• FlexiTalk• PrimeSite, MetroSite, InSite
• Repeaters• Active, passive• Optical
• Antennas• Distributed antennas• Radiating cable
• Signal distribution• Power splitters• Optical fibre
Inconspicuous placing of BTS:hide antennas from public view!
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Directional antenna (wall-mounted)
Bi-directional antenna (wall-mounted)
Omni-directional antenna (ceiling-mounted)
Outdoor BTS
Outdoor cell
Distributed antenna system (RF signal splitters)
Coaxial antenna
RF repeater with optical interface
Indoor BTS
A-bis / BSC
BASE STATIONS SIGNAL DISTRIBUTION ANTENNAS
Distributed antenna system with amplifier (in line RF amplifiers)
RF outRF in
Opt Tx
Opt RxRF out
RF out
Optical RF Distribution
RF repeater for indoors
Passive repeaterDirect connection
Indoor Coverage Solutions
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• Distributed Antenna System (DAS)• Benefit: low equipment price
• Disadvantage: lack of control over antenna signal level, due to the variation in size of distribution network
• Use: shopping malls, airports, etc
• Leaky Cable• Benefit: evenly distributed coverage along the length of the cable
• Disadvantage: relatively small coverage area
• Use: tunnels
• Fibre Optical Distribution System (FODS)• Benefit: easy installation due to use of thin optical fibre
• Disadvantage: higher price and propagation delay within the fibre
• Use: when the cable runs are too long for a DAS
Indoor Coverage Transmission Media
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Indoor Coverage DAS
• Indoor antennas are connected to base station via coaxial feeder cable
• Choose antennas that match to the environment - i.e. hard to spot!
• Install high enough - prevent desensitization
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Symbolin systemdiagram
1/2"7/8"
1-1/4"
RFF 1/2"-50 SuperFlexible
RFX 1/2"-50 Cable Antenna
RFX 7/8"-50 Cable Antenna
RF 7/8"-50 Feeder Cable
Leaky feeders
Indoor Coverage Leaky Cable
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• Coaxial cable with perforated leads ⇒ “energy leak”
• Radiating losses 10 ..40 dB per 100m• Coupling loss typ. 55 dB (at 1m ref. dist.)
• Constant field strengths along cable runs
• Operate in wide frequency range• Radiating losses become higher with frequency
• Very large bending radii • Disturbs field distribution
• Formerly often used for tunnel coverage
• VERY EXPENSIVE
Indoor Coverage Leaky Cable
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Splitter
Combiner
OpticalConverter
OpticalConverter
Uplink
Downlink
OpticalConverter
OpticalConverter
• RF signal is converted to optical signal and fed into the optical fibre.
• Conversion from optical signal to RF signal takes place at the antenna end.
Indoor Coverage FODS
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• Signal from in-building BTS
• Fibre optic distribution system• Very low cabling losses (2 dB/ 1000m)• >50 remote antennas possible• Signal amplification and distribution at remote end• Easy cabling (very thin fibres)
• Application examples• Multi-level offices, shops• Airport halls (large distances!)• Industrial plants
Indoor PanelAntenna
Indoor BTS
Remote Unit
Master Unit
Optical Fiber RF Cable
Indoor Coverage Optical Repeater
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RF DAS System Diagram
Basement
Floor 1
Floor 3
Floor 2
15dB dB
10dB
BTS
A1
A5
A4
A3
A2
1/2"
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InSite
• Capacity is always 1 BTS & 1 TRX (Combined CCCH/SDCCH/4 + 7 TCH)
• If there is a need for 2 TRX in the same area, 2 InSites can be installed near each other
• ’Direct Retry’ -parameter needed
• If many InSites are used in a building, frequencies are reused more tightly
• Planner can plan frequency manually or use APP (Automatic PicocellPlanning)
• Interference area and coverage area has to be verified so that the same frequency can be reused
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InLite• One option to provide coverage if cable length from BTS to antenna
comes long
• Fiber optic cables up to 1.5 km without any remarkable attenuation (optical link budget < 3 dB)
• Flexible & easy integration with MetroSite
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InLite• InLite is a system for indoor cellular coverage, based on use of fiber optics
and remote antennas• Consists of two main parts, main unit MU and remote unit RU• MU is a central unit for RF transmission and reception
• Main function is to convert RF-signal to optical mode and vice versa• Each LU can support and continuously monitor up to 4 RUs• Can expand up to 8 LU → 32 RU → 64 output ports• Two optical fibres for each RU one for DL and one for UL• In DL, a laser in LU is modulated by the RF electrical signals to generate optical
carrier• LU carries out 1:4 optical splitting at DL• In UL, LU optically combines the optical signals from RU and a PIN photo diode
converts the optical signals into RF electrical signals• A LNA is used to increase the received power from the RU in the UL path
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InLite Architecture
SWITCH MATRIX 8:4
Optical Converters
BTS Interface
32 fibre opticRemote Units
Air Interface
NokiaInLite RU
Antenna(Panel)
Antenna(Omni)
BTS BTS
eo
eo
Dual band
RF
module#3
eo
eo
Dual band
RF
module#2
eo
eo
Dual band
RF
module#1
eo
eo
Dual band
RF
module#4
Multi-fibre cable
RU
Multi-fibre cable
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Outdoor AntennaGain: 18 dBi
Indoor AntennaGain: 9dBi
Target Indoor Coverage Building
7/8'' Cable Loss: 4dB / 50mCable length : 25m
-50 dBm
4th Floor
3rd Floor
1st Floor
Ground Floor
2nd Floor
1:1
50m
50m
1:1
50m
50m
1:1
50m
50m
1:1
50m
50m
1:1
50m
50m
1:1
1:1:1
1:1
4th floor
3rd floor
2nd floor
1st floor
ground floor
• With repeater• Relay outdoor signal into target building• Needs “donor” cell; adds coverage, no capacity
• With indoor BTS and distributed antennas• Heavy losses by power splitting and cabling
Indoor Coverage Example
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Indoor Cell Frequency Planning
• Target to find “clear enough” channel• Planning tool cannot predict accurate interference in upper floors in high
buildings• Channel can be optimised by indoor measurement• Quality HOs typically problem
• Frequency re-use can be high if antenna planning good• Minimised leaking outside
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Indoor Cell Parameter Planning• In general no need to do many changes to the Nokia's default
parameter set before implementation• Idle mode
• C2-per cell basis parameter in idle mode (phase 2 mobiles)• Can be used to guide call setup in indoor cell when moving indoors• Measurements needed for fine tuning
• Dedicated mode• PBGT HO can be disabled from indoor cell in order to keep traffic indoors. Good
indoor plan with uniform coverage needed.• Important that mobiles are using an indoor cell(s) inside a building and handovers
at building entrance work as wanted. PBGT HO margin optimization from other cells.
• Umbrella HO-parameter?
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Summary of Indoor Planning
• Cost efficient solution, repeater/insite/ultrasite
• Indoor solution should be planned to cover whole building
• Minimize leaking outdoors in antenna location selection -> reduce interference
• When planning site minimize # of HOs due to level/quality
• Use parameters to keep indoor traffic in indoor site
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Special Cases
INDOOR PLANNING
TUNNEL PLANNING
REPEATERS
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Tunnel PlanningBasics
• Extraordinary propagation environment• Tunnel coverage planning differs greatly from the conventional planning
• Reliable simulation/prediction is impossible• Test measurements usually difficult to conduct• Planning has to be based on known propagation properties and common sense
• Signal can be generated by BTS or repeater (optical or RF)• BTS needed if the tunnel is very long or high capacity is needed
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Propagation inside tunnels depends on
• Tunnel shape• Circular tunnel has higher propagation loss than rectangular
• Wall structure• Newer tunnel ⇒ more steel in concrete ⇒ better propagation
• Filling factor• How big part of the tunnel's cross-section is blocked? • Depend on cross-section size and number of tubes
• Tunnel curvature• In most cases the curvature is meaningless, not always
• Location of the antenna• Simulations has been made, but it is very difficult to adapt the results into real world
Tunnel PlanningPropagation
35 © NOKIA 6-90212/ SPECIAL CASES: INDOOR AND TUNNEL ENVIRONMENTS/v 1.0
Rules of thumb concerning propagation when using regular antenna.
Coupling loss
~60 dB
First km
~30 - 50 dB
Next km
~20 - 30 dB
Tunnel PlanningPropagation
36 © NOKIA 6-90212/ SPECIAL CASES: INDOOR AND TUNNEL ENVIRONMENTS/v 1.0
Power splitter
X dBm
G=85 dB
X+13dBm
50m 7/8",
L=2 dB L=3,5 dB
X+98dBm
20m 1/2",
L=2 dB
X+96dBm X+92,5dBm
20m 1/2",
L=2 dB
X+90,5dBm
G=9,5dBi
EIRP = X+100 dBm
G=15 dBi
Tunnel PlanningExample
• Typical maximum output power for a channel selective repeater is about +31 dBm• In order to have this max power, we'd need -67 dBm by the pick-up antenna.• Then the EIRP from the tunnel antennas would be +33 dBm• Cable thickness need to be selected based on installation- and loss properties
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Tunnel PlanningSolution Summary
• Following table summarizes the feasibilities of different coverage solution types for highway tunnels of different lengths
Highwaytunnels
RF repeater BTS FOD
< 1000m +++ ++ ---
1000 – 2000 m ++ +++ -
2000 – 3000 m ++ ++ ++
3000 – 5000 m - ++ ++
> 5000 m -- + +++
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Special Cases
INDOOR PLANNING
TUNNEL PLANNING
REPEATERS
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• Advantages:• Easy and fast way to expand coverage or capacity• Abis transmission is not needed
• Disadvantages:• Uses BTS capacity -> congestion• Output power decreases if number of channels increases
• Future swap over to dedicated BTS when traffic increases, so design with the idea of maintaining the same EIRP with new BTS
• DL: Repeater picks up the signal coming from BTS via donor antenna, amplifies it and re-radiate it via coverage antenna
• UL: Receives signal from mobile, amplifies it and re-transmits the signal to the BTS
• Serving BTS handles call initiation, power control messages, HO requests etc.
• Incoming signal should be at least -70…-75 dBm• To achieve sufficient TX power for the repeater• To achieve good signal quality
RF-repeater
40 © NOKIA 6-90212/ SPECIAL CASES: INDOOR AND TUNNEL ENVIRONMENTS/v 1.0
RepeatersBasics
• Passive repeater• Needs strong external signal• Useful only with very short cables • Seldom used
• Active repeater• Amplifies and re-transmits all received signals
• Wideband or narrowband repeater
• Application examples• Places with coverage need and little traffic• Remote valleys• Tunnels• Underground coverage (e.g. garages)
needsdecoupling > amplification
41 © NOKIA 6-90212/ SPECIAL CASES: INDOOR AND TUNNEL ENVIRONMENTS/v 1.0
RepeatersOverview
Donor SiteDonor Antenna Repeater Antenna
Location Site of a CRDonor Cell
Combined Coverage
Cell Repeater
MS
MS
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RepeatersInterference Caused by Delay
• Signal to the MS can travel directly from the donor cell (delay0) or through a CR
• ∆delay= (delay1 + delayR + delay2) - delay0
• If ∆delay > equaliser window⇒ interferences
Donor SiteDonor Antenna Repeater Antenna
Location Site of a CR
Donor CellCell Repeater
delay0
MobileInterference Area
delay1
delay2
delayR
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BTS RepeaterCost • Expensive • Cheap
Coverage Expansion
• New Frequency • Allocation needed
• Easy Way to Expand • Coverage
CapacityExpansion
• Higher Frequency Reuse • Uses Radio Resources from Regular BTS•
RF Characteristics
• High C/I • Higher O/P Power
• Decoupling• Donor Antenna Required
Limitation • E1/T1 Required • No use in High Density • Traffic Areas
• BSC Features Not • Available
RepeatersBTS vs. Repeater
44 © NOKIA 6-90212/ SPECIAL CASES: INDOOR AND TUNNEL ENVIRONMENTS/v 1.0
Exercises / Questions
Why to use indoor sites?
List different methods to build indoor coverage!
What is different betweenthe indoor planning process and the normal planning process?
Which factors affect signal propagation in tunnels?
When is it feasible to use a repeater ?
45 © NOKIA 6-90212/ SPECIAL CASES: INDOOR AND TUNNEL ENVIRONMENTS/v 1.0
References
1. S. Saunders, “Antennas and Propagation for Wireless Communication Systems,” John Wiley & Sons, 1999.