Explain M12 - 1 Special Cases Indoor And Tunnel Environments 23535r

Special Cases: Indoor and

Tunnel Environments

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

Module objectives At the end of this module you will be able to … 9

DESCRIBE HOW TO IMPROVE INDOOR COVERAGE

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EXPLAIN THE PRINCIPLES OF INDOOR PLANNING

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DESCRIBE THE BASICS OF TUNNEL PLANNING

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LIST THE BASICS OF REPEATERS

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Content of Special Cases 9

INDOOR PLANNING

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TUNNEL PLANNING

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REPEATERS

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Special Cases 9 INDOOR PLANNING 9 TUNNEL PLANNING 9 REPEATERS

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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

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•

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 Losses Basics

• 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 concrete wall, windows concrete wall, no windows concrete wall within building brick wall armed glass wood or plaster wall window glass

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17 dB 30 dB 10 dB 9 dB 8 dB 6 dB 2 dB

sigma 9 dB 9 dB 7 dB 6 dB 6 dB 6 dB 6 dB

Building Losses Incident Angle

• Penetration loss depends heavily on incident angle of radio wave

30

dB

25

incidence angle of radio wave 90

20 15 10

glass pane

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180

165

150

135

120

105

90

75

60

45

30

15

0

0

7

180

0

deg

Building Losses In-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

Lout Lwall Lin

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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)


Indoor System Planning Process A) 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) 9

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Indoor Propagation • Three main propagation mechanisms • • •

Reflection Diffraction Scattering

R TX

S D

D

RX

• Similar to microcellular propagation, except in smaller scale! • Delay spread very small => large coherence bandwidth!!

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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 • •

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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 • 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 14

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Indoor Coverage Solutions

• Small BTS • •

FlexiTalk PrimeSite, MetroSite, InSite

• Repeaters Active, ive • Optical •

• Antennas Distributed antennas • Radiating cable •

• Signal distribution Power splitters • Optical fibre •

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Inconspicuous placing of BTS: hide antennas from public view!

Indoor Coverage Solutions

SIGNAL DISTRIBUTION

BASE STATIONS

Direct connection

ANTENNAS

ive repeater

RF repeater for indoors Coaxial antenna

Indoor BTS RF repeater with optical interface Op t T x

A-bis / BSC

RF in

Op t Rx

RF out

RF out

RF out

Optical RF Distribution Outdoor BTS Outdoor cell

Distributed antenna system (RF signal splitters) Distributed antenna system with amplifier (in line RF amplifiers)

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Directional antenna (wall-mounted) Bi-directional antenna (wall-mounted) Omni-directional antenna (ceiling-mounted)

Indoor Coverage Transmission Media

• 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)

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•

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

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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Indoor Coverage Leaky Cable

RFX 1/2"-50 Cable Antenna RFF 1/2"-50 SuperFlexible

RF 7/8"-50 Feeder Cable RFX 7/8"-50 Cable Antenna

1/2" 7/8" 1-1/4" Symbol in system diagram

Leaky feeders 19

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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

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Indoor Coverage FODS

• 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.

Downlink

Uplink

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Splitter

Combiner


Optical Converter

Optical Converter

Optical Converter

Optical Converter

Indoor Coverage Optical Repeater

• 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 BTS Indoor Antenna

Optical Fiber

Remote Unit

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Master Unit

RF Cable

RF DAS System Diagram A5 Floor 3

A4 10dB

A3 A2

15dB dB

1/2" BT S 23

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A1

Floor 2

Floor 1

Basement

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 Picocell Planning) • 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 • • • • • • • •

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Main function is to convert RF-signal to optical mode and vice versa Each LU can 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

Air Interface Antenna ()

Nokia InLite

Antenna RU Multi-fibre cable

Optical Converters e

o

e

o

e

o

e

o

e

o

e

o

e

o

e

o

RU Dual band

Dual band

Dual band

Dual band

RF

RF

RF

RF

module#1

module#2

module#3

module#4

Multi-fibre cable

SWITCH MATRIX 8:4

32 fibre optic Remote Units BTS Interface

BTS

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BTS


(Omni)

Indoor Coverage Example

• 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

-50 dBm

50m

1:1

1:1

50m

4th floor

50m

1:1

1:1

50m

3rd floor

1:1:1

1:1

50m 50m 50m

2nd floor 1st floor

50m

1:1

50m

7/8'' Cable Loss: 4dB / 50m Cable length : 25m

4th Floor 3rd Floor

50m

1:1

Outdoor Antenna Gain: 18 dBi

ground floor

2nd Floor 1st Floor Ground Floor Indoor Antenna Gain: 9dBi

Target Indoor Coverage Building 28

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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 •

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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 • •

•

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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

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Tunnel Planning Basics

• 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) •

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BTS needed if the tunnel is very long or high capacity is needed


Tunnel Planning Propagation

Propagation inside tunnels depends on • • •

• •

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Tunnel shape •

Circular tunnel has higher propagation loss than rectangular

•

Newer tunnel ⇒ more steel in concrete ⇒ better propagation

• •

How big part of the tunnel's cross-section is blocked? Depend on cross-section size and number of tubes

•

In most cases the curvature is meaningless, not always

•

Simulations has been made, but it is very difficult to adapt the results into real world

Wall structure Filling factor

Tunnel curvature

Location of the antenna


Tunnel Planning Propagation

Rules of thumb concerning propagation when using regular antenna.

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Coupling loss

First km

Next km

~60 dB

~30 - 50 dB

~20 - 30 dB


Tunnel Planning Example

G=15 dBi X+90,5dBm

X dBm X+13dBm

• • • •

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X+98dBm

50m 7/8",

20m 1/2",

L=2 dB

L=2 dB

G=85 dB

X+96dBm Power splitter L=3,5 dB

X+92,5dBm

EIRP = X+100 dBm

G=9,5dBi

20m 1/2", L=2 dB

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 Planning Solution Summary

• Following table summarizes the feasibilities of different coverage solution types for highway tunnels of different lengths

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Highway tunnels

RF repeater

BTS

FOD

< 1000m

+++

++

---

1000 – 2000 m

++

+++

-

2000 – 3000 m

++

++

++

3000 – 5000 m

-

++

++

> 5000 m

--

+

+++



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• Advantages: • •

RF-repeater

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 • •

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To achieve sufficient TX power for the repeater To achieve good signal quality


Repeaters Basics

• ive repeater • • •

Needs strong external signal Useful only with very short cables Seldom used

• Active repeater

Amplifies and re-transmits all received signals

•

• Application examples

Places with coverage need and little traffic • Remote valleys • Tunnels • Underground coverage (e.g. garages) •

• Wideband or narrowband repeater needs decoupling > amplification

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Repeaters Overview

Donor Site

Donor Antenna

Repeater Antenna Location Site of a CR

Donor Cell MS

Combined Coverage

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Cell Repeater

MS

Repeaters

Interference 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 delay1

delayR Repeater Antenna Donor Antenna

Donor Site

delay0 Donor Cell Interference Area

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delay2

Location Site of a CR Cell Repeater

Mobile


Repeaters BTS vs. Repeater

BTS

Repeater

Cost

• Expensive

• Cheap

Coverage Expansion

• New Frequency • Allocation needed

• Easy Way to Expand • Coverage

Capacity Expansion

• 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

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Exercises / Questions 9

Why to use indoor sites?

9

List different methods to build indoor coverage!

9

What is different betweenthe indoor planning process and the normal planning process?

9

Which factors affect signal propagation in tunnels?

9

When is it feasible to use a repeater ?

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References 1.

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

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