3_cellularplanningprinciples.pdf

8/14/2019 3_CellularPlanningPrinciples.pdf

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Introduction to Mobile Communications


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Technologies (analog)

First generation first public mobile radio in Scandinavia(1974) mamually switched, radio-phones in vehicle

Second generation NMT 450, NMT 900 AMPS

TACS, E-TACS Trunked radio

"walkie-talkie" (military origin) "open channel" (police, fire brigades, taxi..) MPT 1327 : quasi-standard (UK)


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Technologies (digital)

"2nd generation" GSM900 (more than 100 countries now) GSM1800 (Europe,Asia; formerly know as "DSC1800")

GSM1900 (USA; formerly: "PCN") Trunked radio

EDACS (Erisson)

ASTRO (Motorola) Digicom7 (Alcatel) TETRA (ETSI-Standard)

Cordless DECT (ETSI-Standard)


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Why digital

Analog Digital

Digital signals can be reconstructed identically reproduced packetised encryted compressed stored


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Cellular Planning Principles


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Scope of NW Planning Customer requirements External information sources subscriber forecasts terrain & morphological data coverage requirement population data

quality of service bandwidth available

recommended sites frequency co-ordination constraints

Network design number and configuration of BS

antenna systems specification Network performance BSS topology grade of service (blocking) dimensioning of transmission line outage calculations

frequency plan interference probabilities

network evolution strategy quality observation

Network Planningdata acquisition

sites survey and selectionfield measurement evaluationNW design and analysistransmission planning

Network Planningdata acquisitionsites survey and selectionfield measurement evaluationNW design and analysistransmission planning


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Cellular Planning Principle

Transmissionplan

Transmissionplan Coverageplan

Coverageplan

Freq.&inter-

ference plan

Freq.&inter-

ference planFinal NWtopology

Final NWtopology

Parameter

plan

Parameter

plan

Initial NWdimensioningInitial NWdimensioning

marketing

Businessplan

Trafficassumptions


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Key Dimensioning Quantities

Dimensioning quantities for radio network:

number of BTS needed for coverage reasons

number of BTS needed for traffic reasons

outage probabilities/percentages

interference probability vs. Frequency Re-use Rate

bandwidth used


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Coverage Planning

Initial NW dimensioningTRX's,cells,sites

bandwidth neededNwtopology

External inputs :traffic,subs,forecast,

coverage,requirement... Suggestions for site locations

cell parameterscoverage achieved

Coverage predictionsignal strength

multipath propagation

Coverage ok?

Site accepted?Planning

criteria fulfilled?

Go tofrequencyplanning

Create celldata for

BSC

Filed measurements

CELLPLAN


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Frequency Planning

Aim: find solution with minimum interferences in total NW

Traditional approach hexagonal cell patterns "regular grid" "cluster sizes" "frequency re-use distance"

NW planning tools (NPS\X, ASSET, PlaNet) digital maps site information interference analysis interference prediction


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Macro Cell Network

Cost-effective solution

Good for covering large areas large cell ranges high antenna positions

Cell ranges 220km

(depends on geography)

Good with low traffic volumes typically rural areas road coverage

Commonly used with omnidirectional antennas

Optimize for coverageOptimize for coverage


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Small Cell Network

Capacity oriented network additional capacity by multiple cell coverage

Good for areas with high traffic

Mostly used with sectored cells most cost-efficient solution best usage of available cell sites

Typical applications medium towns suburbs

Typical cell ranges: 0.5..2km

Optimize for capacity Optimize for capacity


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Large Cells2 .. 30 kmlate 80s

Small Cells1.. 5 kmearly 90s

Microcells100m.. 1 kmmid 90s

Indoor cells10m .. 100 mlate 90s

Layered networkMacro cells

Increasing NW capacity calls for smaller cellsbut : increasing effort to maintain sites

Cell Size Evolution


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Traffic Planning

Estimation of traffic expected Number of subscribers in area? Traffic load per subscriber?

Geographical area to cover? Traffic per sq.km traffic per cell number of TRX needed per BS allow extra capacity for roamers and busy hour traffic

"Bottle-neck" of the system shallnot be in transmission lines

"Bottle-neck" of the system shallnot be in transmission lines


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carriers si te

= =total no. carrierscluster size

carriers ban dwid th

bandwid th

cluster size

BaseStationdensity

Frequencyreuse

Averagechannelutilization

TDMAslotsper

carrier

Spectrumfor

operator

Channelspacing

CapacityCapacitytrafficarea

trafficchannel

channelscarrier

sitesarea

= carriers site

traffic

area

traffic

channel

channels

carrier

carriers

bandw idth

1

cluster size bandw idth

sites

area=

Overview of Capacity Enhancement Methods


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Traffic A process of events related to demands for the utilization of

resources in a telecommunication network.

Erlang The unit of traffic One Erlang traffic means continously holding time on a

circuit for specific time.

No.1

No. 29.00 9.30 10.00

1 hour

Traffic Theory


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Circuit and Packet Switched Systems

Circuit switched systems

Packet switched systems

circuit switched channel

packet switched channel

-restricted by acceptable packet delay

-mainly use Erlang C to calculate-Erlang C assumptions are additionally:*amount of queuing states are not limited*First-In, First-out-principle

-restricted by acceptable blocking rates-mainly use Erlang B to calculate-Erlang B assumptions are:

*amount of subscr. (independent traffic sources)is very large which means a constant flow ofrequired connections

*busy-time is exponential distributed


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Circuit Switched System

Blocking System Probability that a call will be lost due to congestion Erlang-B formula

Example: Speech channels on GSM

GOS,BTraffic offered Traffic carried

Traffic lost

Traffic carried = Traffic offered - Traffic lost


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Erlang-B formula

Blocking systems users experiencing blocked calls are not willing to wait and give up the

call attempt immediately.

Often use lookup table

B: Blocking rate

A: Traffic demand N: No. of circuits


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Traffic Theory

Erlang-B formula Applications:

No. of circuits N (TCH, SDCCH, TRX per cell, BTS ) needed tosupport a traffic offered, given a maximum blocking rate B?

No. of subscribers that can be supported by network with Ncircuits, given maximum blocking rate B?

Mean blocking rate B for a given traffic load and configuration


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Erlang B Table

1% 2% 3% 5%1 0.01 0.02 0.03 0.05

2 0.15 0.22 0.28 0.38

3 0.46 0.60 0.72 0.90

4 0.87 1.09 1.26 1.52

5 1.36 1.66 1.88 2.22

6 1.91 2.28 2.54 2.96

7 2.50 2.94 3.25 3.74

8 3.13 3.63 3.99 4.54

9 3.78 4.34 4.75 5.37

10 4.46 5.08 5.53 6.2211 5.16 5.84 6.33 7.08

12 5.88 6.61 7.14 7.95

13 6.61 7.40 7.97 8.83

14 7.35 8.20 8.80 9.73

15 8.11 9.01 9.65 10.63

16 8.88 9.83 10.51 11.54

17 9.65 10.66 11.37 12.46

18 10.44 11.49 12.24 13.38

19 11.23 12.33 13.11 14.31

20 12.03 13.18 14.00 15.25

N Blocking rateErlangs

1% 2% 3% 5%21 12.84 14.04 14.89 16.1922 13.65 14.90 15.78 17.13

23 14.47 15.76 16.68 18.0824 15.30 16.63 17.58 19.0325 16.13 17.50 18.48 19.9926 16.96 18.38 19.39 20.9427 17.80 19.26 20.30 21.9028 18.64 20.15 21.22 22.8729 19.49 21.04 22.14 23.83

30 20.34 21.93 23.06 24.8031 21.20 22.80 23.99 25.7732 22.10 23.70 24.91 26.7533 22.90 24.60 25.84 27.7234 23.80 25.50 26.77 28.7035 24.60 26.40 27.71 29.6836 25.50 27.30 28.64 30.6637 26.40 28.30 29.58 31.6438 27.30 29.20 30.51 32.6339 28.10 30.10 31.45 33.6140 29.00 31.00 32.39 34.60

Blocking rateErlangs

N


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Theory of Wave Propagation


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Mobile Communications

What is special about Mobile communications? Multi-path propagation

radio path is a miserable propagation medium

Limited transmit energy transmitting power of mobiles determines service ranges battery life-time

Limited spectrum sets upper limit for data rates (Shannon's theorem) additional effort needed for channel coding

frequencies need to be re-used Many mobile users


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Radio Channel

signal bendsaround obstacles

Scattering

ReflectionReflection

Reflection

Diffraction

Refraction

near mobile short term fading

atmospheric h t > 90m d > 23 km

multipath

Propagation phenomena


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distanceVariations dueto shadowing

Variations dueto Rayleigh fading

Receive Leveld

Long term fading due to shadowing (e.g. building

obstructing signal) log-normal distribution local mean value

Short term fading due to scatterers nearby Rayleigh distribution (if no

direct path) Rician distribution (direct +

reflected components)

Glo al meanb

Local mean

Fading


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Caused by shadowing buildings, trees etc.

Distribution has been determined from measurements log-normal distribution

determined by ,

Typical values

Urban: 7 dBSuburban: 6 dBRural: 5 dB

Long Term Fading

Shadowing

( ) ( )

=2

2

2

exp

2

1

m x x p dB

meanlocaluemedian valmean value ===m

deviationstandard=


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Short Term Fading

Received signal is a combination of several reflectedcomponents - multipath components

each multipath wave hasdifferent phase

combination of signal components in phasestrengthening of composite signal

combination of signal components out of phaseweakening of composite signal

worst case: zero if mobile and surroundings are stationary

signal strength constant if mobile or surroundings move

signal strength varies the radius of the region in which active scatterers affecting

received signal can be found is roughly 100 wavelengths

+

=


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Mi d P h L


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Mixed Path Loss

Path loss

Signallevel

Actualsignal level Urban curve

Open area curve

Open area Urban area Forest area


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The Mobile Radio Link

L d U g T


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Land Usage Types

Urban small cells, high attenuation Forest heavy absorption

Open, farmlands easy, smooth propagation condition

Water signal propagation very easy, dangerous!

Mountain face strong reflection, long echoes

Hilltops can be used as barrier between cells do NOT use as antenna sites locations

Propagation Models


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Propagation Models

Okumura-Hata empirical model measured and estimated additional attenuation

estimations for larger distances (range: 5..20 km) don't use for small distances (


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Okumura-Hata

The general equation of a statistical prediction model interpreted as a transformedHata model, is the following:

PRX = PTX + K1 + K2log(d) + K3log(Heff) + K4D + K5log(Heff)log(d) + K6log(Heffm) + Kclutter

where :

PRX = measured receiving power (dBm)

PTX = transmitting power EIRP (dBm)

K1 = constant offset, comprehensive of the term log(frequency) (dB)

K2 = multiplying factor for log(d); slope

K3 = multiplying factor for log(Heff), compensates for gain due to antenna height

K4 = multiplying factor for diffraction calculation

K5 = Okumura-Hata type of multiplying factor for log(Heff)log(d)

K6 = Correction factor for the effective mobile antenna height gain

Kclutter = clutter correction factor (dB)

d = Tx Rx distance (m)

Heff = test site antenna effective height (m)

Heffm = test mobile effective height (m)

D = diffraction loss (dB)

Antenna Types


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Antenna Types

Omnidirectional antenna same radiation patterns in all directions useful in flat rural areas Low Antenna gain

Directional antenna

concentrate main energy into certain direction large communication range use in cities, urban area, sectored sites High Antenna gain

Antenna Characteristics


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Antenna Characteristics

Antenna gain the measure for the antenna's capability to transmit/ extract energy to/ from the propagation medium (air) dB over isotropic antenna (dBi) dB over Hertz dipole (dBd)

Antenna gain depends on mechanical size: A effective antenna aperture area :W frequency band Antenna gain: G= 4 Aw/


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Coupling Between Antennas


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Coupling Between Antennas

Horizontal separation needs approx. 5

distance for sufficient decoupling

antenna patterns superimposed if distance too close

Vertical separation

distance of 1

provides good decoupling values good for RX/TX decoupling

Antenna Cables


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Antenna Cables

Cable types coaxial cables: 1/2", 7/8", 1 5/8" losses approx. 10..4 dB/100m power dissipation is exponential with cable length

Connector losses approx. 1 dB per connection (jumper cableetc..)

Think antenna cables lower losses per length large bending radii much more expensive

Keep antenna cables short Keep antenna cables short


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Radiation PatternRadiation Pattern Horizontal and vertical patterns are specified for

antennas.

Down (positive) and Up (negative) tilting of antenna is

possible if the vertical pattern is specified.

Horizontal Pattern(Top View)

Vertical Pattern(Side View)

Diversity Techniques


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Diversity Techniques

Time diversity Coding, interleaving

Frequency diversity frequency hopping

Space diversity multiple antennas

Polarization diversity crosspolarised antennas

Multipath diversity equalizer

Advantage of Diversity


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Advantage of Diversity

Equivalent to 5 dB more signal strength

More path loss acceptable in radio link budget

Higher coverage range

Diversity gain depends on environment Diversity gain depends on environment

Interference Reduction Methods


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Interference Reduction Methods

Frequency allocation Frequency planning (menul or Frequency Planning Tool)

Proper choice of site location

proper site location choice according to environment Antenna installation planning

proper site height wall mounted downtilting

Frequency hopping interference averaging

Power control evaluate signal level and quality

DTX silent transmitter in speech pauses


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Link Plan


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Maximize allowablepath loss to obtaingreatest servicerange

T X o u t

p u t

C o m b i n

e r l o s s

F i l t e r, c

o n n e c t i

o n l o s s

A n t e n

n a c a

b l e l o s

s

Antenna gain

Diversity gain

Coverage margin

Cable & connectorloss

Fast fading marginRX sensitivity

Maximum allowable path loss~145.. 150 dB

-110

-100

-90

-80

+50

+40

+30

+20

Link Budget calculation


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g

General information Frequency (MHz) System: 1800

Receiving end BS MS RX RF-input sensitivity dBm -106 -100 A Fast fading margin dB 3.00 3.00 B Cable loss + connector dB 4.00 0.00 C Rx antenna gain dBi 15.00 0.00 D Diversity gain dB 4.00 0.00 E Isotropic power dBm -118.00 -97.00 F=A+B+C-D-E Field strength dBuV/m 24.00 45.00 G=F+Z

Transmitting end MS BS TX RF output peak power W 1.00 25.00 K (mean power over RF cycle) dBm 30.00 44.00 L Isolator + combiner + filter dB 0.00 4.00 M=K-L RF-peak power, combiner output dBm 30.00 40.00 N Cable loss + connector dB 0.00 4.00 O TX-antenna gain dBi 0.00 15.00 Peak EIRP W 1.00 125.00 (EIRP= ERP + 2Db) dBm 30.00 51.00 P=M-N+O Isotropic path loss dB 148.00 148.00 Q=P-F

Z=77.2+20log(freq)

Set starting parameter hereSet starting parameter here

Path loss shall be balancedPath loss shall be balanced

P B dg t D li k


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WLL subscribers

Power Budget: Downlink

path loss = 154 dB

combinerloss = 4dB

FeederLoss = 3 dB

Rx Sensitivity- 102 dBm

Tx Power 43 dBm (20W)

AntennaGain = 16

- 102 dBm

52 dBm

36 dBm

39 dBm

Po er B dget: Uplink


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WLL subscribers

Power Budget: Uplink

path loss = 154 dBFeederLoss = 3 dB

Tx Power 33 dBm (2W)

AntennaGain = 16 Diversity

Gain = 4

33 dBm

- 121 dBm

- 101 dBm

- 104 dBm

Rx Sensitivity-104 dB

Cell Sizes


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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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Indoor Coverage Solutions


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Outdoor BTS near important building(s) Combined indoor / outdoor site

Indoor Repeater

Micro BTS

Coaxial antenna feeder network

Fibre optical antenna feeder network Pico BTS

Leaky cable

Outdoor BTS Near Important Building(s)


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BTS

Direct one antenna to the building(s)Traffic shared between indoor and outdoor No dedicated traffic for the buildingDifficult to cover top floors in urban areas

Combined Indoor / Outdoor Site


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BT S

Distributedindoorantennas

1 sector dedicated

for indoor coverage

Other sectors foroutdoor coverage

Various solutions

for indoor coverage

possible (as

described below)

Indoor Repeater


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BT

S

Amplifiedsignals

Easy installation

No transmission

Cost effective

No extra traffic

offered

May be used as

a temporarysolution

Micro BTS


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Small and non-intrusive

Transmission required

Extra traffic offered

Traffic limited to smallareas (limited trunking gain)

BTS

BTS

BTS

Coaxial Feeder Network


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Single BTSCascaded BTSs

Better dynamic capacityReduce no. of BTSsLow costLimited feeder lengths

BTS

BTS

BTS

BTSAntenna system

BTS

Antenna system

Bidir.Ampl.

Optical Fibre Repeater


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Base Station Fibre Optic Master Unit

Antenna Antenna

Fibre-optic repeater

Antenna Antenna


Antenna


Antenna

Antenna

2waysplitter

Antenna


AntennaAntenna

Good dynamic capacity

Reduce no. of BTSs

Long feeders possible

Relatively expensive

May be used with

a normal repeater


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END

&&&

QUESTION

3_cellularplanningprinciples.pdf

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