NtwPlan&Optimi-Presentation 2

8/7/2019 NtwPlan&Optimi-Presentation 2

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NETWORK PLANNINGNETWORK PLANNING

ANDANDOPTIMISATIONOPTIMISATION


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Multipath propogation

Shadowing

Terrain structures

Reflections

Inerferences

RADIO CHANNEL


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PROPOGATION LOSS

Basic loss formula

Clutter loss factors

Land usage classes

Usually stated in dB/decade

e.g. :

Free space 20 dB/dec

Open country side 25 dB/dec

Suburban areas 30 dB/dec

Urban areas 40 dB/dec

Historic city centre >45 dB/dec

L = Lo + E log(d) Losses are exponential with distance

Loss at reference point (e.g. 1km) EIRP level

Coupling loss

= Lo

reference

distance

40 dB/de

c30 dB/dec

20 dB/dec

0.1km 1km 10km


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SIGNAL ATTENUATION

Mixed land usage types on propagation path

25 dB/dec

30 dB/dec 20 dB/dec

40..50 dB/dec

Path loss


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MIXED PATH LOSS

Path loss

distance

Open : 25 dB/dec Urban : 40..50 dB/dec Open : 25 dB/dec

Signal

level

Open area curve

Urban curve

actual

signal level


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DIVERSITY TECHNIQUES=> USED TO COMBAT LOSSES

Time diversity

Frequency diversity

Space diversity

Polarisation diversity

Multipath diversity

interleaving

frequency hopping

multiple antennas

crosspolar antennas

equaliser,

rake receiver

t

f

Diversity techniques are used for improving coverage. Diversity gain

depends on environment


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PROPOGATION MODELS

Propagation models that are being used in planning tools:

Okumara Hata

The most commonly used statistical model

Walfish - Ikegami

Statistical model especially for urban environments

Juul - Nyholm

Same kind of a prediction tool as Hata, this model has different

equation for predictions beyond radio horizon (~20 km)

Ray - tracing

Deterministic prediction tool for micro cellular environments


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ANTENNA SYSTEMS


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ANTENNA CHARACTERISTICS

Directional antennas

Lobes

main lobes

side / back lobes

front-to-back ratioH-plane : 65-90 E-plane : 6-13

Half power beam-width

(3 dB- beam width)

Polarisation

Antenna impedance

Mechanical size (wind load)

Antenna down tilting

Mechanical / Electrical tilt (Electrical tilt is preferred due to good

backlobe suppression and dispersion control capability)

improves spot coverage and reduces interference

Typical characteristics VSWR : < 1.3

Impedance : 50 ohm

Front-to-back-ratio : >25 dB

Max. power : 500 W

Gain : 221 dBi


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INSTALLATION EXAMPLES

Flat panel antennas

sectorised sites Three-sector cell with RX

diversity

Horizontal / vertical separation

Horizontal Separation

needs approx. 5-15 lambda (2..4 m) separation for sufficient decoupling

and to avoid superimposing of antenna patterns

Horizontal decoupling distance depends on antenna gain and horizontal

radiation pattern

Vertical Separation needs approx. 1 lambda separation for sufficient decoupling

good for RX / TX decoupling


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ANTENNA CABLES

Cable types

Coaxial cables : 1/2, 7/8, 1 5/8

Losses approx. 10..4 dB/ 100m

power dissipiation is exponential with

cable length !!

Connector losses approx. 1 dB per connection(jumper cables etc..)

Thick antenna cables

lower losses per length

large bending radii

much more expensive

Keep antenna cables short

Jumper(2 m)

Jumper

(2 m)


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ANTENNA CABLES

Typical values for antenna cables

Typediameter

(mm)

900 MHz

dB/100m

1800 MHz

dB/100m

1/2

7/8

5/8

1 5/8

12.5

25

17

47

7

4

5

2

10

6

8

3


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NETWORK PLANNING


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OBJECTIVES OF NETWORKOBJECTIVES OF NETWORK

PLANNINGPLANNING

MAXIMIZE CAPACITY(Erl/KmMAXIMIZE CAPACITY(Erl/Km22) WITH) WITH

LIMITED FREQUENCY BANDLIMITED FREQUENCY BAND

MINIMIZEMINIMIZE

NETWORKNETWORKELEMENTS,ELEMENTS,

REDUCEREDUCE

COSTCOST

BETTER QoS,BETTER QoS,MINIMUMMINIMUM

INTERFERENCEINTERFERENCE

& CALL DROPS& CALL DROPS

MAXIMUM RADIO COVERAGEMAXIMUM RADIO COVERAGE

OBJECTIVES OF NETWORK PLANNINGOBJECTIVES OF NETWORK PLANNING


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CELLULAR PLANNING PRINCIPLE

5 steps of Network Planning

1. NW Dimensioning

2. Coverage /Capacity

Planning

3. Transmission Planning

4. Frequency Planning

5. ParameterPlanning

Initial NW

dimensioning

marketing

Coverage /

capacityplan

Freq & inte-

rferenceplan

Transmissionplan Trafficassumptions

Business

plan

Parameterplanning

Final NW

topology


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FACTORS GOVERNING NETWORK PLANNINGFACTORS GOVERNING NETWORK PLANNING

TOPOLOGY OF THE AREATOPOLOGY OF THE AREA

MORPHOLOGY OF THE AREAMORPHOLOGY OF THE AREA

DEMOGRAPHY OF THE AREADEMOGRAPHY OF THE AREA

While Morphology and Topology of an area play an

important role in coverage planning, Demographyplays an important role in capacity planning


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SITE SELECTION / LOCATION

Proper site location determines usefulnessof its cell

Sites are expensive

Sites are long-term investments

Site acquisition is a slow process

Hundreds of sites needed per network

Basestationsiteisa valuable long-termassetforthe operatorand accountsfor

majority ofthenetworkcost


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BAD SITE LOCATION

Avoid hill-top locations forBS Sites

Uncontrolled interferences

Interleaved coverage

Awkward HO behaviours

But : good location for

microwave links!

Wanted cellboundary

Uncontrolled, stronginterferences

Interleaved coverage areas:

Weak own signal, strong foreign signal

Prefer sites off hill-tops

Use hills to separate cells

Contiguous coverage area Needs only low antenna heights if

sites are slightly elevated above

valley bottom

Wanted cellboundary

GOOD SITE LOCATION

SITE LOCATION CRITERIA


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COVERAGE PLANNING

Initial NW dimensioning

TRX, cells, sitesbandwidth neededNW topology

Preliminary exercise

Site locationsCell parametersLink Budgeting

Preliminary Coverage

grid using search circles

Coverage simulation

using planning tool

Signal strengthArea of coverage

Sitepre-validation

Siteaccepted ?

Siteinspection

real cellplan

Cell size determination

usingTx-Rx.equipment

N

NPlanningcriteria fulfilled?

Fieldmeasurements

N

Go tofrequencyplanning

Createcell dataforBSC

External inputs

(traffic, subs. Forecast, Covg./ capacity requirements..)


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CELL SIZES

Achievable cell sizes depend on

Frequency band used(450, 900,1800 MHz)

Surroundings, environment

Link budget figures

Antenna types

Antenna positioning

Minimum required signal levels


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LINK BUDGET PLANNINGLINK BUDGET PLANNING


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LINK BUDGET LOSS FACTORS

At base station

connectors

cables

isolator

combiner

filter

At mobile station

body loss

polarisation of antenna

~ 3..5 dB losses

50..70% of signal energy is

lost before even reachingthe transmit antenna


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LINK BUDGET GAIN FACTORS

Antenna gain

Half-power beam width

Mechanical size

Antenna types

Diversity gain

Diversity can be implemented in many ways

Frequency hopping

Improves average link quality, but is not typically

taken into account in link budget calculations


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POWER BUDGET : DOWNLINK

Combiner

loss = 3 dB

Tx Power

43dBm(20W)

Feeder

loss = 4 dB

40 dBm

36 dBm AntennaGain = 16 dBi

52 dBm

Path loss = 154 dB

-102 dBm

Rx sensitivity

-102 dBm


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POWER BUDGET : UPLINK

Rx Sensitivity

-105 dB

Feeder

loss = 4 dB

-105 dBm

-101 dBm

DiversityGain = 4 dB

-121 dBm

Path loss = 154 dB

33 dBm

Tx Power

33 dBm (2W)

Antenna

Gain = 16dBi


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POWER CONTROL, PC

GSM : 15 power steps (2 dB each) BSC in command

Level or quality-driven or both

Use power control in both uplink & downlink

Doesnt affect the Link Balance

Minimise interference in network

Save battery life-time

PC not allowed

on BCCH carrier

Signallevel Target level

e.g. 85 dBm


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CAPACITY PLANNINGCAPACITY PLANNING


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WHAT IS ERLANG ?

Erlang is the name of a Danish researcher.

Erlang is the unit of traffic

1 Erlang is the max.traffic on one line.

The traffic is calculated using a simple formula:Erlangs =(calls per hour) x (average conversation time)

3600sec

There are two tables

Erlang B - for system that support no queuing Erlang C - for system that support queuing


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Cell capacity depends on No. ofTraffic Channels

No. ofTraffic Channelsisbased on:

Traffic in Cell = No. of Subscribers xTraffic per subscriber

Using thisTraffic figure,targeted GOSand Erlang BTable,

No. ofTraffic Channelsina Cell canbe calculated

TCH 7 15 22 30 37 45 53

Traffic 2.94 9.01 15 22 28 35.5 43

CELL CAPACITY


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TRAFFIC PATTERNS

Traffic is not evenly spread across the day (or week)

Dimensioning must be able to cope with peak loads

busy hour is typically twice the average hour load

8

A A A A

8

A A P

P

P

P

8

P

P

PEAK TIMEOFF-PEAK TIME


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TIMECOVERAGE BUILDING

ADDING TRX, CELL SPLITING

SOFT CAPACITY ( FH + UO )

CAPACITY

FLEXIBLE NETWORK EVOLUTION TO MEETFLEXIBLE NETWORK EVOLUTION TO MEET

THE CAPACITY DEMANDTHE CAPACITY DEMAND


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BASE BAND HOPPING (BB HOPPING)BASE BAND HOPPING (BB HOPPING)

0 4321 5 6 7RTSL

f1

f2

f3

f4

TRX-1

TRX-4

TRX-3

TRX-2

B

B = BCCH timeslot. It does not hop

Time slots 17 of all TRXshop over (f1,f2,f3,f4).

Time slot 0 of TRX-2,3,4 hop over f2,f3,f4.

BB hopping on 4 TRXs. The BCCHTRXis hopping except on RTSL-0.


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RF HOPPING (SYNTHESIZED HOPPING)RF HOPPING (SYNTHESIZED HOPPING)

B = BCCH timeslot. TRX1 does not hop

Non-BCCH TRXs are hopping overthe MA-list (f1,f2,f3,.fn) attached to the cell.

RFhopping in 3-TRXcell

TRX-2

TRX-1

TRX-3

B

f1,

f2,

f3,fn

f1,

f2,

f3,fn

....

f0 f0 f0 f0 f0 f0 f0

f0


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SUPER

SUPER

SUPER

REGULAR

BCCH

REGULARBCCH

REGULAR

BCCH

Co-channel and Adjacent channel interference is monitored continuously

Handover based on C/I Measurements

CONCEPT OF UNDERLAYCONCEPT OF UNDERLAY--OVERLAYOVERLAY


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BENCHMARKING THE QUALITY OF SERVICEBENCHMARKING THE QUALITY OF SERVICE

CALL SETCALL SET--UP RATEUP RATE

CALL DROP RATECALL DROP RATE

HANDOVER SUCCESS RATEHANDOVER SUCCESS RATE

INTERFERENCEINTERFERENCE

MARGINMARGIN

BLOCKED CALLBLOCKED CALL

QUALITY OF CALLQUALITY OF CALL

UPLINK INTERFERENCEUPLINK INTERFERENCE

95 TO 100 % CALL 95 TO 100 % CALL

< 6 SECWITHOUT< 6 SECWITHOUT

CONGESTIONCONGESTION

< 2 %

> 95 %> 95 %

COCO--CHANNEL 9 dBCHANNEL 9 dB

& ADJACENT& ADJACENT

CHANNELCHANNEL --9dB9dB

2% GRADE OF2% GRADE OF

SERVICESERVICE

97% OF CALLWITH IN QUALITY BAND97% OF CALLWITH IN QUALITY BAND--55

< 3% IN BAND< 3% IN BAND-- 0 (0 ( --110 TO110 TO --105 dBm).105 dBm).

QoSQoS


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INTERFERENCE

REDUC

TION

PROCESS OF NETWORK OPTIMISATIONPROCESS OF NETWORK OPTIMISATION

POWERCONTROLANTENNA TILTS

DISCONTINUOUS TX

FREQUENCY HOPPING

FREQUENCY

REALLOCATION


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A Pole Mounted BTS Site

GSM antennas

monuted on poles

Microwaveantennas

Cable tray /

ladder

Shelter(equipment)

room


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A Tower mounted BTS Site

Shelter with Security Guard

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NtwPlan&Optimi-Presentation 2

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