EXPLAIN M12 - 1 Special Cases Indoor and Tunnel Environments

1 © NOKIA 6-90212/ SPECIAL CASES: INDOOR AND TUNNEL ENVIRONMENTS/v 1.0

SpecialSpecialCasesCases: Indoor and Tunnel Environments


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 …


Content of Special Cases

INDOOR PLANNING

TUNNEL PLANNING

REPEATERS


Special Cases

INDOOR PLANNING

TUNNEL PLANNING

REPEATERS


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


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


• 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


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


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)


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


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


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


Measurement showing RxQual & Event Types using NIB and SAM


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


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!


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


• 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


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


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


• 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


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


• 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


RF DAS System Diagram

Basement

Floor 1

Floor 3

Floor 2

15dB dB

10dB

BTS

A1

A5

A4

A3

A2

1/2"


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


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


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


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


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


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


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?


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


Special Cases

INDOOR PLANNING

TUNNEL PLANNING

REPEATERS


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


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


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


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


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 -- + +++


Special Cases

INDOOR PLANNING

TUNNEL PLANNING

REPEATERS


• 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


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


RepeatersOverview

Donor SiteDonor Antenna Repeater Antenna

Location Site of a CRDonor Cell

Combined Coverage

Cell Repeater

MS

MS


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


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


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 ?


References

1. S. Saunders, “Antennas and Propagation for Wireless Communication Systems,” John Wiley & Sons, 1999.

Documents

EXPLAIN M12 - 1 Special Cases Indoor and Tunnel Environments