coverage and capacity planning

1

Radio Planning andDimensioning

2

Cellular Cellular EngineeringEngineering

3

Radio Network Planning Area

4

• Adequate coverage -Contiguous coverage of the required areas without appreciable holes

• Adequate depth of coverage (i.e. outdoor or indoor, 1 W or 8 W mobiles) to meet the companies marketing plans.

• Traffic handling capacity Accommodating traffic in the busiest hour with only a low probability of

blocking.• Quality of Service (QOS) -Adequate service quality across the

required areas (i.e. calldrop, congestion, setup success rate, voice quality levels) to meet the companies marketing plans.

• Network growth accommodation: -Extension of coverage to new areas -Expanding the network capacity so that the quality of service is maintained at all times.

• Cost effective design: Lowest possible cost over the life of the network while meeting the

quality targets.

Objectives of Cellular Engineering

5

Design Constraint

6

GSM Specific Parameters :The GSM-specific parameters have been taken from the European

Telecommunications Standards Institute (ETSI) recommendation dealing with radio transmission and reception:

Frequency bands Mobile Station (MS) transmit power Base Transceiver Station (BTS) transmit power Receiver sensitivities of the MS and BTS Carrier-to-Interference ratios (C/I)Equalizer performance.

Design Constraint (1)

7

• Manufacturer specific parameters The main manufacturer specific parameters are: BTS transmit power Receiver sensitivity Combiner performance Cable losses Antenna performance Availability of frequency hopping and power control functions Handover algorithms Capacity: number of transceivers (TRXs) provided per BTS.

Design Constraint(2)

8

• Radio communication Some of the fundamentals are: – Propagation loss – Shadowing – Multipath fading – Time dispersion – Power link budgets – Interference effects – The (un)predictability of radio wave propagation .

• Budgetary factors The following budgetary factors are important: – Governed by business plan – Limited by shareholders investment resources – Need to identify those areas for coverage which will maximize return

on investment

Design Constraints (3)

9

The radio planning methodology consists of: • Define design rules and parameters • Set performance targets • Design nominal plan • Implement cell plan • Produce frequency plan • Optimize the network • Expand the network.

Radio Planning Methodology

12

Mystery of Decibel

13

Power

VoltagesdB

PP

Plin

P dB

10 10

0

10log [ ].( )

dBEE

E lin

E dB

20 10

0

20log [ ].( )

Plin.=Elin.² / 2

deciBel Definition

14

• Calculations in dB (deciBel)• Logarithmic scale

• Always with respect to a reference– dBW = dB above Watt– dBm = dB above mWatt– dBi = dB above isotropic– dBd = dB above dipole– dBV/m = dB above V/m

• Rule-of-thumb: – +3dB = factor 2– +7 dB = factor 5– +10 dB = factor 10

-30 dBm = 1 W-20 dBm = 10 W-10 dBm = 100 W-7 dBm = 200 W-3 dBm = 500 W

0 dBm = 1 mW+3 dBm = 2 mW+7 dBm = 5 mW

+10 dBm = 10 mW+13 dBm = 20 mW+20 dBm = 100mW

+30 dBm = 1 W+40 dBm = 10W

+50 dBm = 100W

deciBel Conversion

15

Decibel is a relative comparison between numbers... whatever the numbers are!

Absolute comparison in decibel between numbers... whatever the numbers are!

APP

(dB) 10 log10 1

2

A PP

(dBunity) 10 log10 unity

dBm = dBW + 30

A P(dBW) 10 log10 1 Watt

AP

(dBm) 10 log10 1 milliWatt

Warming-up: The decibel definition

16

Multiplying numbers meansadding the numbers in decibels

3 • 2 = 6

Arithmetic operations Decibel operations

5 dB dB + dB

3 dB+ dB

8 dB=

Dividing numbers meanssubtracting the numbers in decibels

8 ÷ 4 = 2

9 dB dB - dB

6 dB- dB

3 dB=

The mystic of decibels

17

Power absolutelinear scale

13 dBm + 3 dB = 16 dBm dBm + dB dBm

1 mW

20 mW

40 mW

0 dBm

13 dBm

16 dBm

Power absolutelogarithmic scale

3 dB 3 dB

Decibel operations

16 dBm - 3 dB = 13 dBm dBm - dB dBm

16 dBm - 13 dBm = 3 dB dBm - dBm dB

13 dBm + 16 dBm = 29 dBm dBm + dBm

794 mW

18 dBm

Undefined!

20 mW + 40 mW = 60 mW

The mystic of decibels

18

- 74 dBm

- 74 dBm - 86 dBm -(74 dBm + 86 dBm )

Undefined!10-74/10 0.000000039 mW

10-86/10 0.0000000025 mW

- 86 dBm

Linear scale

+

0.0000000415 mW

Power - absolutelogarithmic scale

- 90 dBm

- 80 dBm

- 70 dBm

+

-

10 • log (0.0000000415) = -73.8 dBm

Logarithm scale

Struggling against decibels

19

Radio Propagation Aspects

20

Free Space Attenuation

Principle The free-space attenuation refers to the decay of the signal, travelling in free-space, as a function of the distance of the receiver from the transmitter.

21

Isotropic Power Radiation

22

Practical Path Loss

23

Steep Path Loss Slope

Typical path-loss slope In a mobile radio medium, n is usually assumed to be 4; which results in a typical path-loss slope of -40 dB/decade.

24

• Linear– In field strength

• Reciprocal• Dispersive

– In time (echo, multipath propagation)– In spectrum (wideband channel)

amplitud

e

delay time

direct pathechoes

Radio Channel Main Characteristics

25

Reflection, Diffraction and Scattering

26

Free-space propagation– Signal strength decreases exponentially

with distance

Reflection• Specular reflection

amplitude A a*A (a < 1)phase f - fpolarisation material dependant

phase shift

• Diffuse reflectionamplitude A a *A (a < 1)phase f random phasepolarisation random

specular reflection

diffuse reflection

D

Propagation Mechanisms (1/2)

27

Absorption– Heavy amplitude– Attenuation material– Dependant phase shifts– Depolarisation

Diffraction– Wedge - model– Knife edge– Multiple knife edges

A A - 5..30 dB

Propagation Mechanisms (2/2)

28

Scattering local to mobile– Causes fading – Small delay and angle spreads– Doppler spread causes time varying

effectsScattering local to base station

– No additional Doppler spread– Small delay spread– Large angle spread

Remote scattering– Independent path fading– No additional Doppler spread– Large delay spread– Large angle spread

Scattering to mobile

Scattering to base station

Remote scattering

Scattering Macrocell

29

• Echoes due to multipath propagation– 1 s 300 m path difference

• GSM equalizer in the receivers– Time window of 16 s (~ 4.8 km path difference)– 2-path-model as “worst case” situation– Standardized delay profiles in GSM specs:

• TU3 typical urban at 3 km/h (pedestrians)• TU50 typical urban at 50 km/h (cars)• HT100 hilly terrain (road vehicles)• RA250 rural area (highways)

– No hard limitation at 250 km/h

Time dispersion

30

t

P

4.3.2.

1.

”GSM window” = 16 sMaximum delay,based on equaliser

1.

2.=>

f1

f1f1

f1BTS

1st floor2nd floor3rd floor4th floor

Multipath propagation

Channel impulse response

<= Equaliser enables the use of DAS (Distributed antenna systems)

Delay Spread

31

Typical values

Environment Delay Spread (s)

Macrocellular, urban 0.5-3

Macrocellular, suburban

0.5

Macrocellular, rural 0.1-0.2

Macrocellular, HT 3-10

Microcellular < 0.1

Indoor 0.01...0.1

Delay Spread

32

• Average trend ~ 35 – 50 dB / decade (path loss)• Slow fading: Caused by shadowing. Typically log-normal distributed (σ

around 8 – 11 dB)• Fast fading: Caused by local scatters near mobile. Typically Rayleigh

distributed• Time-selective fading: Short delay + Doppler• Frequency-selective fading: Long delay• Space-selective fading: Large angle

Fading

33

Slow fading (Log-normal fading)

– Shadowing due to large obstacles on the way

Fast fading (Rayleigh fading)– Destructive interference of

several signals– “fading dips”, “radio holes”

+10

0

-10

-20

-300 1 2 3 4 5 m

level (dB)

920 MHzv = 20 km/h

Fading Slow & Fast

34

time

power

2 sec 4 sec 6 sec

+20 dB

mean value

- 20 dB

lognormal fading

Rayleighfading

Fading Slow & Fast (2)

35

• Most general form of distribution– Superposition of several processes with any distribution function will always

converge towards a Gaussian distribution– Applicable to all natural processes, also to slow fading

• Mean value m, standard deviation

Fading Gaussian Distribution

36

• Applicable to fast fading in obstructed paths

p rr r

( ) exp( ) 2

2

22

Fading Rayleigh Distribution

37

• Basic loss formula

• Clutter loss factors• Land-usage classes (in

dB/decade)• e.g.:

free space 20 dB/dec

open countryside 25 dB/dec

suburban areas 30 dB/dec

urban area 40 dB/dec

historic city centre >45 dB/dec

L = L0 + *log(d)

loss at reference point (e.g. 1km)

losses are exponential with distance

0,1 km 10 km1 km

EIRP level

coupling loss = L0

referencedistance

20 dB/dec

30 dB/dec40 dB/dec

Path Loss

38

25 dB/dec30 dB/dec 20 dB/dec

40 ..50 dB/dec path loss

Path Loss Signal Attenuation

39

urban: 40 ..50 dB/decopen: 25 dB/dec open: 25 dB/dec

open area curveurban curve

actual signal level

signallevel

distance

• Mixed land usage types on propagation path

Path Loss Mixed Path Loss

40

RadioRadioNetwork Network Planning Planning ProcessProcess

41

DESCRIBE THE RADIO NETWORK PLANNING PROCESS

DESCRIBE THE MAJOR TASKS IN THE PLANNING PROCESS

DESCRIBE THE PLANNING TOOLS FOR DIFFERENT PHASES

DESCRIBE THE INPUT AND OUTPUT DOCUMENTS (DATA)

DESCRIBE THE PLANNING ENVIRONMENT

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

Module objectives

42

INTRODUCTION AND PRE-PLANNING DETAILED PLANNING POST-PLANNING DOCUMENTATION MEASUREMENTS

Content of Planning Process

43

Network planning team• data acquisition• site survey and selection• field measurement evaluation• NW design and analysis• transmission planning

Network design• number and configuration of BS• antenna systems specifications • BSS topology• dimensioning of transmission lines• frequency plan• network evolution strategy

Network performance• grade of service (blocking)• outage calculations• interference probabilities• quality observation

Customer requirements• coverage requirements• quality of service• recommended sites• subscriber forecasts

External information sources• topo- & morphological data• population data• bandwidth available• frequency co-ordination• constraints

Interactions with• external subcontractors• site hunting teams• measurement teams• Operator• switch planning engineers

Network Planning

44

CoveragePlanning andSite Selection

ParameterPlanning

PropagationmeasurementsCoverageprediction

SiteacquisitionCoverageoptimization

External Interference Analysis

NetworkConfigurationand

Dimensioning

PRE-PLANNING DETAILED PLANNING

Traffic distributionService distributionAllowed blocking/queuingSystem features

IdentificationAdaptation

Area / Cellspecific

Handoverstrategies

Maximumnetworkloading

Other RRM

NetworkOptimization

POST-PLANNING

Surveymeasurements

Statistical performance analysis

Quality Efficiency Availability

Capacity Requirements

Requirementsand strategyfor coverage,quality and

capacity,per service

Network Planning Process

45

external inputs:(traffic, subs. forecast,

coverage requirements...)

Initial NW dimensioning TRX, cells, sites

bandwidth needed NW topology

suggestions for site locations

cell parameters coverage achieved

coverage prediction signal strength

multipath propagation

Sitepre-validation

site accepted ?planningcriteria fulfilled?

go tofrequency planning

nominal cell plan

site inspectionreal cell planfield measurements

N

N

N

create celldata for

BSC field measurements

Network Planning Process

46

issue search area & requirements

find suitable

site candidates

calculate coverage range of each candidate

propagation measurements needed ?

transmission links available?

sign contract with site owner

get building permit

construction work

installing & testing

on air!

Network Planning Process : Site Building

47

radio planner

fixed networkplanner

measurementteams

architect

network operator

site acquisitionagent site owner

Network Planning Process Site Acquisition

48

• Key quantities for radio network dimensioning (EXCEL tool)– # of BS needed for coverage reasons– # of BS needed for capacity reasons– Outage probabilities/percentages– Frequency re-use rate (vs. interference)– Bandwidth used

• Design goals are inter-dependant– Network can only be optimised with respect to one single aspect

Design goals to be applied must be clearly agreed with customer!

Pre-planning: Dimensioning Key Quantities

49

AMOUNT OF TRAFFIC

NUMBER OF BASE STATIONS (CAPACITY)

ANTENNA HEIGHT (CAP. & COV.)

FREQUENCY BAND AND REUSE-

PROPAGATION PREDICTIONS

ANTENNA HEIGHT FOR PLANNING AREA MAXIMUM ANTENNA HEIGHT

NUMBER OF BASE STATIONS FORPLANNING AREA (CAPACITY OR COVERAGE LIMITED)

PROPAGATION PREDICTION

Antenna height?

Pre-planning: Dimensioning Target

50

• Before T0, the network is coverage limited• After T0, the network is capacity limited• The other constraint is automatically fulfilled

# of BS

time

coverage

capacity

T0

At the very beginning, just the coverage planning is needed

Pre-planning: Dimensioning Limiting factors

51

• When the network is coverage limited, the expansion consists of: – Adding new sites in not already covered areas

• When the network is capacity limited, the expansion consists of: – Adding TRX’s; – Adding new sites in already covered areas; – Adding software capacity...

Pre-planning: Dimensioning: Network Expansion

52

• Main purpose of the network?– 1st operator in country plain coverage?– 2nd operator competitive pricing?– 3rd operator replacing wire line phones?

• Roamer volumes expected?– Where?

• Neighbouring countries– Existing international regulations?

• Use of microwave links for transmission?

Each network philosophy calls for a different planning

approach

Dimensioning Input Data Preliminary Questions

53

Maps– Main cities– Important roads– Location of mountain ranges– Inhabited area– Shore lines

Local knowledge– City skylines– Typical architecture– Structure of city– Local habits

Dimensioning Input Data Morpho data

54

Statistical yearbook– Largest towns, cities– Population distribution– Where are expected customers?

Local knowledge– Population migration routes– Commuting traffic volumes– Subscriber concentration points

2 mill.pop.

300 000 pop.

400 000 pop.

400 000 pop.

250 000 pop.

Dimensioning Input Data Demographic Data

55

• Roll-out phases & time schedules

• Coverage level requirements• Indoor coverage areas• MS classes to plan for• Operator´s cell deployment

strategies– Omni-cells in rural areas?– 3-sector cells in urban areas?– Minimum of 2 TRX per cell?

phase 1NW launch

rolloutphase 2

rolloutphase 3

Dimensioning Input Data Coverage Requirements

56

INTRODUCTION AND PRE-PLANNING

DETAILED PLANNING POST-PLANNING DOCUMENTATION MEASUREMENTS

Planning Process

57

• Configuration planning• PBGT calculations (EXCEL tool)• BTS and antenna line equipment

• Coverage planning / Site selection• Coverage thresholds (NetAct Planner)• Coverage predictions (NetAct Planner)

• Prediction model tuning (NetAct Planner))• Propagation slope measurements (TOM/Nemo)• Antenna directions (NetAct Planner)

• Capacity planning• CS, PS traffic (NetAct Planner)• Signaling needs (NetAct Planner)

• Frequency planning• Reuse factor and C/I requirements (NetAct Planner)

• Parameter planning (BSSPAR course)• BSC, BTS, TRX, TSL parameters (NMS/NetAct)

load_vec ind2

dt

load ind2 start N N_start

12 12.2 12.4 12.6 12.8 130

2

4

6

8The cell load

Time / hours

Num

ber o

f res

erve

d tim

eslo

ts

.

RD

Detailed Planning

58

• Configuration planning

• PBGT calculations• DL: TX power, combiner, booster, duplexer, diplexer, cable, power amplifier, antenna• UL: antenna, diversity, LNA, cable, diplexer, duplexer, RX sensitivity

• BTS type (macro/micro, outdoor/indoor, GSM/EDGE/3G)• SW features (FH, IFH, ...)

Configuration Planning

59

• Coverage thresholds• DL Path loss: TX power (max.) - RX power (min.) -

margins • BTS type (macro/micro, outdoor/indoor, GSM/EDGE/3G)• SW features (FH, IFH, ...)

• Coverage predictions• Prediction model (Okumura-Hata)• BTS-MS distance (max.) = cell range = coverage

• Site selection (documentation)• Antenna height, location (x,y), direction • BTS location => cable length• PWR, TRS!!!

Coverage Planning

60

Radio criteria

• Good view in main beam direction

• No surrounding high obstacles• Good visibility of terrain • Room for antenna mounting• LOS to next microwave site• Short cabling distances

Non-radio criteria

• Space for equipment

• Availability of leased lines or microwave link

• Power supply

• Access restrictions?

• House owner

• Rental costs

Site Selection Criteria

61

• Proper site location determines usefulness of its cells• Sites are expensive• Sites are long-term investments• Site acquisition is a slow process• Hundreds of sites needed per network

Base station site is a valuablelong-term asset for the operator

Site Selection General Considerations

62

wanted cellboundary

uncontrolled, stronginterferences

interleaved coverage areas:weak own signal, strong foreign signal

• Avoid hill-top locations for BS sites– Uncontrolled interferences– Interleaved coverage– Awkward HO behaviours– But: good location for microwave links!

Site Selection Bad Site Location

63

wanted cellboundary

• Prefer sites off the hill-tops– Use hills to separate cells– Contiguous coverage area– Needs only low antenna heights if sites are slightly elevated above

valley bottom

Site Selection Good Site Location

64

Collect all necessary information about site details– Site coordinates, height above sea level, exact address– House owner– Type of building– Building materials (photo)– Possible antenna heights– 360deg photo (clearance view)– Neighbourhood, surrounding environment– Drawing sketch of rooftop– Antenna mounting conditions– Access possibilities (truck?, road, roof)– BS location, approx. feeder lengths

Site Selection Site Info

65

• Map• (D)GPS• (Test) mobile• Digital camera• Binoculars• Compass• Clinometers and tape measure• LOS checking tools: lights, mirrors, flags, balloons

Site Selection & Site Survey Tools

66

• Capacity planning• TRXs/cell• TRX layer purposes

• BCCH, GPRS, ...• TSL reservations for

• signaling, HSCSD, GPRS, ...• Signaling needs

• SDCCH, PCH, AGCH, ...• Special SW features for TCH

• FH, extended cell, ...• Special SW features for signaling

• dynamic SDCCH, ...

load_vec ind2

dt


12 12.2 12.4 12.6 12.8 130

2

4

6

8The cell load

Time / hours

Num

ber o

f res

erve

d tim

eslo

ts

.

Capacity Planning

67

• Frequency planning• Reuse factor for speech and data (GPRS)• C/I requirements for BCCH/TCH TRX• Special requirements for intermodulation • Interference probability targets• Frequency band splitting needs• Automatic frequency planning (AFP)

• interference matrix• measurements • calculation areas

R

D

Frequency Planning

68

• Parameter planning (BSSPAR course)• BSC level parameters • BTS level parameters • TRX level parameters • TSL level parameters

• Signaling related parameters• RRM related parameters• MM related parameters• Measurement related parameters• Handover related parameters• Power control related parameters• Other SW feature related parameters

• HSCSD, GPRS• Extended cell• Dual band, Half rate, IUO/IFH

Parameter Planning

69



Planning Process

70

• Verification or pre-optimisation • Coverage tests (TOM/Nemo)• Call setups• Handover tests

• Monitoring• KPI values (Traffica)

• Drop call rates• Blocking percentages• Handover success rates• Traffic in Erlangs

• Optimisation • KPI values• Plan audit (configurations, ...)• Counters (Network doctor)• Observations (DX causes)• IMSI tracing

•BTS•HOC•POC

•BTS•HOC•POC

•BTS•HOC•POC

ADCEADCE

ADCE

MS BTS BSC

CH. REQUEST (RACH)IMMEDIATE

ASSIGN(AGCH)SERVICE REQUEST (SDCCH)

Phase 1 : Paging, initial MS

AUTHENTICATION (SDCCH) Phase 2 : MM signalling

CIPHERING MODE (SDCCH) Phase 8 : Ciphering

TMSI REALLOCATION (SDCCH)

SETUP (SDCCH) Phase 2 : MM signalling

CH.RELEASE Phase 4 : Release ALERTING & CONNECT (FACCH) Phase 2 : MM signalling

CONN. ACK. and MEASUREMENT Phase 15 : ConversationDISCONNECT & RELEASE (FACCH) Phase 4 : Release

ASSIGNMENT (SDCCH-FACCH) Phase 3 : Basic assignment

DX-cause

Post - Planning

71



Planning Process

72

• SARFSite Acquisition Request Form

• SIR/SARSite Information (Acquisition) Report

• TSS reportTechnical Site Survey Report

• TDRSTechnical Data for Radiating System

• ...

Site Selection / Site Survey Documentation

73

• SITE FOLDER– BTS configuration– Antenna line configuration

• PARAMETER SET– BTS ID, Frequency, NCC, BCC, LAC,

neighbours – Default parameters

• MONITORING REPORTS– Traffic history (TCH, signaling)– KPI values (DCR, blocking, ...)

Radio Network Plan Output Documentation

74

PRE-PLANNING DETAILED PLANNING POST-PLANNING DOCUMENTATION MEASUREMENTS

Planning Process

75

• Propagation measurements– Check coverage area of site,

propagation model tuning– Site candidate evaluations– Test transmitter, mast antenna– CW- signal

• Functional test– After commissioning of site– Coverage audit– Parameter checking (HO, power control ...)

• Performance measurements– Drive tests– Real network under live conditions – The user´s view

detailed planning

pre-optimisation phase “dry run”

commercial phase

Measurements Types

76

• Propagation measurements– Stay within coverage area of cell

• Functional tests– Radial from site into neighbouring cells– Check handovers in & out of cell

• Performance measurements– Define a random route once– Drive repeatedly

(comparable results !)

Measurements Choice of Routes

77

• Propagation measurements– Signal averaging– Lee´s criterium: min. 50 samples per 40 – Estimate accuracy of prediction

• database resolution• correct information

• Functional tests– Identify incorrect parameter settings– Check missing HO relations

• Performance measurements– Detect misbehaviour of network– Calculate call success rate– Key performance indicators– Evaluate network behaviour under nominal conditions

Measurements Results

78

ConfigurationConfigurationPlanning Planning

79

At the end of this module, the participant will be able to:• List the different elements used in the GSM network.• Calculate the power budget.• Describe how to balance uplink and downlink directions in the

power budget.

Objectives

80

• Base station transceiver•maintain synchronisation to MS•GMSK modulation•RF signal processing (combining,

filtering, coupling...)•diversity reception•radio interface timing•detect access attempts of

mobiles•de-/ encryption on radio path•channel de-/ coding & interleaving on radio path•perform frequency hopping•forward measurement data to BSC

typ. 1..4 TRX1..3 sectorsavg. 7,5 traffic channels per TRXsupports typ. 300 users

typ. 1..4 TRX1..3 sectorsavg. 7,5 traffic channels per TRXsupports typ. 300 users

BTS : Functions

81

Nokia MetroSiteBase Station

Connected to FXC RRI orFC RRI indoor unit.

Connected to FXC RRI orFC RRI indoor unit.

NokiaMetroHopper Radio

Nokia MetroHubTransmission Node

Nokia FlexiHopperMicrowave Radio

Nokia MetroSiteBattery Backup

Nokia MetroSiteAntennas

Citytalk6 TRX

Extratalk, SiteSupport System

Flexitalk2 TRX

Flexitalk+2 TRX

Intratalk6 TRX

Nokia BTS Family

82

RF Characteristics Metrosite PrimeSite InSite Flexitalk Intratalk Citytalk Ultrasite EDGE

Max. TRXs 4 1 1 2 6 6 6 Max. TRXs Special Cabinet

12 12 108

Max. Sectors 4 1 1 1 4+4+4 4+4+4 36+36+36 Max TX Power (dBm)

30 38 22 42 42 42 42

Dynamic sensitivity (dBm) single branch, RBER2<2%

-106.0 -106.0 -100 -102/-108 -102/-108

-102/ -108

-108.5/ -109

BTS Configurations

83

Antenna Systems

84

• Transport mechanismelectromagnetic energy transport by constant exchange between electrical and magnetic field : “E-wave” and “H-wave”

Poynting- vector (energy) : E x H• E- and H-wave are perpendicular at distances larger than

the far field distance (“plane wave”)

E- fieldH- field

rD

R 2 2

Far Field Distance

85

• Energy in antenna only partly converts to electromagnetic waves

• Radiated energy is only a fraction of received energy

• Radiated energy is measurable only in a “reference distance” from antenna (minimum = far field distance!)

• Coupling losses are ~ 50 ... 60 dB for first few meters, then use “free-space propagation” losses

Coupling Losses

86

• Antennas on base station– receiver antenna– receiver diversity antenna– transmit antenna

• Transition point to / from radio wave propagation

• “Best possible signal”

Take every effort to make optimum use of the available signal

Antenna Systems

87

• Omnidirectional antennas• same radiation patterns in all directions• useful in flat rural areas.

• Directional antennas• concentrate main energy into certain direction• larger communication range• useful in cities, urban areas, sectorised sites

Antenna Categories

88

AntennasEurocell panels mounted on a church.Eurocell F-Panels mounted on the wall of an industrial building.

89

• Dipoles– most general type: omnidirectional

• Arrays– combinations of many smaller elements– high gains, special radiation patterns,– “phased array” antennas ( ---> smart antennas )

• Yagi– very common, high gain, directional antennas– often used as TV- antennas

• Paraboles– very high gain, extremely narrow beam-widths – commonly used for line-of-sight paths (satellites...)

Antenna Types

90

• 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 Aw4

2

microwave ant. : w ~ 50 .. 60 %optical ant. : w ~ 80 .. 85 %

Antenna Characteristics

91

• Lobes– main lobes– side / back lobes– front-to-back ratio

• Halfpower beam-width (3 dB- beam width)

• Antenna downtilting• Polarisation• Antenna bandwidth• Antenna impedance• Mechanical size

– windload

InputConnector positionFrequency rangeVSWRGainImpedancePolarisationFront-to-back-ratioHalf-power beam width

Max. powerWeightWind load

Max. wind velocityPacking sizeHeight / width / depth

7 /16” femalebottom

870 - 960 MHz< 1,3

15,5 dBi50 Ohmvertical> 25 dB

H-plane: 65° / E-plane: 13°

500 Watt (50 °C ambient temp.)6 kg

frontal : 220 N (at 150 km/h)lateral: 140 N (at 150 km/h)rear : 490 N (at 150 km/h)

1410 x 270 x 140 mm1290 / 255 / 105 mm

H- plane E- plane

Antenna Characteristics

92

Radiation Patterns• Example: patterns for high-gain directional antenna

Horizontal pattern Vertical pattern

93

Antenna Down Tilting• Antenna (down-) tilting

– improve spot coverage– signal attenuation – 30 .. 40dB/decade

– reduce interference– signal attenuation – ~20dB/decade

• What is the difference between electrical and mechanical down tilt?

5..8 deg

94

Coupling Between Antennas• Horizontal separation

– needs approx. 5 distance for sufficient decoupling

– antenna patterns superimposed if distance too close

• Vertical separationdistance of 1 provides good decoupling valuesgood for RX /TX decoupling

• Minimum coupling loss

main lobe

5 .. 10

1

95

• Recommended decoupling– TX - TX: ~20dB– TX - RX: ~40dB

• Horizontal decoupling distance depends onantenna gainhorizontal rad. pattern

• Omnidirectional antennas– RX + TX with vertical separation (“Bajonett”)– RX, RX div. , TX with vertical separation (“fork”)

Vertical decoupling is much more effective

0,2m

omnidirectional.: 5 .. 20mdirectional : 1 ... 3m

Installation Examples

96

• Directional antennas– sectorised sites– three-sector cell with RX

diversity– horizontal separation

Installation Examples

97

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 cables etc..)

• Thick antenna cables lower losses per length

large bending radii much more expensive

jumper(2 m)

40 ..

70m

jumper(2 m)

Keep antenna cables short

98

Antenna Cables

Type diameter 900MHz 1800MHz (mm) dB/100m dB/100m

3/8” 10 10 145/8” 17 6 97/8” 25 4 61 5/8” 47 2 3

•Typical values for antenna cables

99

Nearby Obstacles Requirement (1/3)

100

Height Clearance vs Antenna Tilt

0,01,02,03,04,05,06,07,08,09,0

5 10 15 20 25 30 35 40 45 50Roof Edge d (m)

h (m)

From 0 up to 6 down tilt

T y p e U n i t O r D e p a r t m e n t H e r eT y p e Y o u r N a m e H e r e

h

h


101


102

•Time diversity

•Frequency diversity

•Space diversity

•Polarisation diversity

•Multipath diversity

interleaving

frequency hopping

multiple antennas

crosspolar antennas

equaliser,rake receiver

t

f

Diversity Techniques

104

• Selection diversity

• Maximum ratio combining– pre-detector

combining:

– ==> add signals in correct phasing

• C/I- improvement

C/N measuring

Phase measuring

2

1

G3

G2

G1

+

3

Diversity Reception

105

• Diversity gain depends on environment• Is there coverage improvement by diversity ?

– antenna diversity• equivalent to 5dB more signal strength• more path loss acceptable in link budget• higher coverage range

R

R(div) ~ 1,3 RA 1,7 A ??70% more coverage per cell ??needs less cells in total ??

True only (in theory)if environment is infinitely large and

flat

Coverage Improvement?

106

Link Budget

107

• Link budget calculations consist of two parts:– 1) Power budget calculations– 2) Cell size evaluations

• Communication must be two-way

Power budget must

be balanced

Link Budget

108

• In addition to BTS and MS powers and sensitivities, several other factors need to be taken into account when doing Link Budget calculations

• These factors can be classified into three categories:– 1) Link Budget loss factors

– 2) Link Budget gain factors

– 3) Link Budget margins

Link Budget Factors

109

• At base station• connectors• cables• isolator• combiner• filter

• At mobile station• body loss• polarisation of antenna

man

y m

eter

s

cables &connectors

filter

combiner

BS output

~3..5 dB losses==> 50 ..70% of signal energy is lost before even reaching the transmit antenna

Link Budget Loss Factors

110

• Antenna gain• half-power beamwidth• 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

Link Budget Gain Factors

111

• Fast fading margin– Fast variations in field strength levels that are caused by

multipath reception has to be taken into account in calculating the maximum allowable path loss

• Slow fading margin– Slow fading that is caused by shadowing has a direct effect

on the location probability; this has to be taken into account in evaluating cell sizes

• Penetration losses

Link Budget Margins

112

WLL subscribers

path loss = 154 dB

combiner loss = 5 dB

Feeder Loss = 4 dB

Rx Sensitivity- 102 dBm

Tx Power45 dBm (20W)

AntennaGain = 16dBi

- 102 dBm

52 dBm

36 dBm

40 dBm

Power Budget: Downlink

113

WLL subscribers

path loss = 154 dBFeeder Loss = 4 dB

Tx Power33 dBm (2W)

AntennaGain = 16 dBi Diversity

Gain = 4 dB

33 dBm

- 121 dBm

- 101 dBm

- 105 dBm

Rx Sensitivity -105 dB

Power Budget: Uplink

114

RADIO LINK POWER BUDGET MS CLASS: 1

GENERAL INFOFrequency (MHz): 1800 System: GSM1800 set starting parameters hereRECEIVING END: BS MSRX RF-input sensitivity dBm -106,00 -100,00 AFast fading margin dB 3,00 3,00 BCable loss + connector dB 4,00 0,00 CRx antenna gain dBi 15,00 0,00 DDiversity gain dB 4,00 0,00 EIsotropic power dBm -118,00 -97,00 F=A+B+C-D-EField strength dBµV/m 24,00 45,00 G=F+Z*

* Z = 77.2 + 20*log(freq[MHz])TRANSMITTING END: MS BSTX RF output peak power W 1,00 25,00(mean power over RF cycle) dBm 30,00 44,00 KIsolator + combiner + filter dB 0,00 4,00 LRF-peak power, combiner output dBm 30,00 40,00 M=K-LCable loss + connector dB 0,00 4,00 NTX-antenna gain dBi 0,00 15,00 OPeak EIRP W 1,00 125,90(EIRP = ERP + 2dB) dBm 30,00 51,00 P=M-N+OIsotropic path loss dB 148,00 148,00 Q=P-F

path loss shall be balanced

can BS provideoutput power needed ?

Power Budget Calculations

115

Coverage Coverage Planning Planning

116

DEFINE COVERAGE THRESHOLD DESCRIBE DIFFERENT COVERAGE PLANNING

MARGINSLOCATION PROBABILITYPENETRATION LOSS

CALCULATE COVERAGE AREAS


Module objectives

117

• Based on the calculated maximum allowed path loss in PBGT, the coverage threshold can be defined

• Coverage threshold depends on margins related to • Location probability (= slow fading)• Fast fading / Interference degradation • Polarization / Antenna orientation loss• Body loss• Penetration losses (vehicle or building)

Coverage Threshold Basics

118

“Real” maximum allowed path loss

function (location probability)

From power budget calculations

function (morphological area)

Okumura-Hata

function (morphological area)

= Maximum allowed path loss => Coverage threshold

Cell radius

Cell area

EIRP - Minimum allowed receiving level –

Slow fading and other margins – Building penetration loss

Coverage Threshold DL Calculation Process

119

Full coverage of an area can never be guaranteed!

• Outages• due to coverage gaps Pno_cov• due to interferences Pif

• Total location probability in a cell (1- Pno_cov) * (1- Pif)

• Both time and location probability• Typical required values are 90-

95%

Coverage Threshold Location Probability

120

• When calculating cell radius, LP is 50% by the cell edge and ~75% over the cell area

• To get 90% LP, the cell radius has to be reduced

00,10,20,30,40,50,60,70,80,9

1-3 -2 -1 0 1 2 3

90% of the area

Slow fading margin

Coverage Threshold Slow Fading Margin

121

• ETSI specific margin

Power budget

GENERAL INFORMATIONFrequency (MHz):1800 System: DCS1800Case description: MS Class: 1

RECEIVING END: BS MSRX RF- Input Sensitivity dBm -108.00 -100.00 A

Interference Degradation Margin dB 3.00 3.00 BBody Proximity Loss dB 0.00 2.00 CCable Loss + Connectors dB 3.00 0.00 DRx Antenna Gain dBi 18.00 0.00 EDiversity Gain dB 4.00 0.00 FIsotropic Power dBm -124.00 -95.00 G=A+B+C+D-E-FField Strength dBµV/m 18.31 47.31 H=G+Z*TRANSMITTING END: MS BSTX RF Output Peak Power W 1.00 29.50(mean power over RF cycle) dBm 30.00 44.70 KBody Proximity Loss dB 2.00 0.00 L

Isolator + Combiner + Filter dB 0.00 2.20 MRF-Peak Power, Combiner Output dBm 28.00 42.50 N=K-L-MCable Loss + Connectors dB 0.00 3.00 OTX Antenna Gain dBi 0.00 18.00 PPeak EIRP W 0.63 562.11

(EIRP = ERP + 2dB) dBm 28.00 57.50 Q=N-O+P* Z = 77.2 + 20*log(freq[MHz])

BT99 - AFE with combiner bypass (equiv. to

Coverage Threshold Interference Degrade Margin

122

• Body loss happens because of the existence of the human body • Typical loss 3 dB depending on the distance between mobile and

human body• Typically taken into account in coverage threshold

Coverage Threshold Body Loss

123

• Penetration losses have to be added as mean value, and standard deviation need to be taken into account as well

• type mean sigma

• urban building 15 dB 7 dB• suburban 10 dB 7 dB• in-car 8 dB 5 dB

Coverage Threshold Penetration Loss

124

COMMON INFO DU U SU F OMS antenna height (m): 1,5 1,5 1,5 1,5 1,5BS antenna height (m): 30,0 30,0 30,0 45,0 45,0Standard Deviation (dB): 7,0 7,0 7,0 7,0 7,0BPL Average (dB): 15,0 12,0 10,0 6,0 6,0Standard Deviation indoors (dB): 10,0 10,0 10,0 10,0 10,0OKUMURA-HATA (OH) DU U SU F OArea Type Correction (dB) 0,0 -4,0 -6,0 -10,0 -15,0WALFISH-IKEGAMI (WI) DU U SU F ORoads width (m): 30,0 30,0 30,0 30,0 30,0Road orientation angle (degrees): 90,0 90,0 90,0 90,0 90,0Building separation (m): 40,0 40,0 40,0 40,0 40,0Buildings average height (m): 30,0 30,0 30,0 30,0 30,0INDOOR COVERAGE DU U SU F OPropagation Model OH OH OH OH OHSlow Fading Margin + BPL (dB): 22,8 19,8 17,8 13,8 13,8Coverage Threshold (dBµV/m): 59,1 56,1 54,1 50,1 50,1Coverage Threshold (dBm): -77,2 -80,2 -82,2 -86,2 -86,2Location Probability over Cell Area(L%): 90,0% 90,0% 90,0% 90,0% 90,0%

Cell Range (km): 1,33 2,10 2,72 5,70 7,99OUTDOOR COVERAGE DU U SU F OPropagation Model OH OH OH OH OHSlow Fading Margin (dB): 4,5 4,5 4,5 4,5 4,5Coverage Threshold (dBµV/m): 40,8 40,8 40,8 40,8 40,8Coverage Threshold (dBm): -95,5 -95,5 -95,5 -95,5 -95,5Location Probability over Cell Area(L%): 90,0% 90,0% 90,0% 90,0% 90,0%

Cell Range (km): 4,39 5,70 6,50 10,69 14,99

Cell range: Example of Dimensioning (EXCEL based calculation)

125

• After cell radius has been determined, cell area can be calculated• When calculating cell area, traditional hexagonal model is taken

into account

R

OmniA = 2,6 R1

2Bi-sectorA= 1,73 R2

2Tri-sectorA = 1,95 R3

2

R

R

Coverage Area: Coverage Area in Dimensioning

126

• Three hexagons • Three cells

Coverage Area : Hexagons vs. Cells

127

Example of Planning Tool CalculationCoverage Area

128

Cell Area Terms• Dominance area• Service area• Coverage area

6dB hysteresis margin

coverage limit

cell coverage range

cell service range

dominance range

Coverage Area

129

• Achievable cell size depends on– Frequency band used (450, 900, 1800 MHz)– Surroundings, environment– Link budget figures– Antenna types– Antenna positioning– Minimum required signal levels

Coverage Area : Conclusion

130

Coverage Coverage Predictions Predictions

131

DESCRIBE DIFFERENT PREDICTION MODELS DESCRIBE PREDICTION MODEL TUNING TOPICS CALCULATE CELL RANGE


Module objectives

132

• Okumura-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, but with

different equation for predictions beyond radio horizon (~20km)

• Ray-tracing– Deterministic prediction tool for

microcellular environments

Statistical

to be tuned!

Determinis

tic

Propagation Models Used in Nokia tools

133

additional attenuation dueto land usage classes

• Adapted for 900 MHz and 1800 MHz• Different land usage classes

f frequency in MHzh BS antenna height [m]a(hm) function of MS antenna heightd distance between BS and MS [km]

A = 69.55 B = 26.16 (for 150 .. 1000 MHz) A = 46.3 B = 33.9 (for 1500 ..2000MHz)

L A B f h a hh d L

b m

b morpho

log . log ( )( . . log )log

1382449 655

Propagation Models: Okumura-Hata

134

• Urban– Small cells, 40..50 dB/dec attenuation

• Forest– Heavy absorption; 30..40 dB/dec; differs with season (foliage losses)

• Open, farmlands– Easy, smooth propagation conditions

• Water– Signal propagates very easily interference !

• Mountain faces– Strong reflections, long echos

• Etc…– Many morpho types have been defined

Propagation Models: Okumura-Hata

135

• Model for urban microcellular propagation• Assumes regular city layout (“Manhattan grid”)• Total path loss consists of two parts:

hwb

d

NLOS • roof-to-street diffraction and scatter

loss • mobile environment losses

LOS • line-of-sight loss

Propagation Models: Walfish-Ikegami

136

• Line-of-sight path (LOS)– Use free space propagation– Applicable for microwave & satellite links

• “Non-line-of-sight” path (NLOS)– Heavy diffraction, refraction situations– Many models exist in literature, none is satisfying– Great uncertainties in modeling– Needs detailed building databases (vectorial information)– Use ray-tracing models?

“Manhattan grid”model

Propagation Models: Walfish-Ikegami

137

• Deterministic model for microcellular environments– Launch rays into every direction of space– Certain number of rays calculated– Reflections calculated based on dielectric coefficients– Very high computational load

• Mirror image method also possible

r

“single point”signal source

Propagation Models: Ray Tracing

138

• It’s aimed to get a more realistic propagation model• It should be done at the very beginning of a planning project,

before any dimensioning activity• How?

– Select typical sites for measurements– Define measurement routes– Tune propagation model to make its predictions match the measurements data

Model Tuning: Basics

139

• What antenna height should be used?• Typical for the area?• Model restrictions? • Okumura-Hata stay above 24 m!

• Keep away from existing antennas• Mark LOS situations, tunnels, bridges etc.

• Take these out of the measurement file• A power budget is needed. Note down:

• TX power, cable and connector losses• Antenna type, height, direction, tilt• Site coordinates

Model Tuning: Measurements

140

• Measure only interference free frequencies• Measure only in the main lobe of the transmitting antenna • Avoid or erase line-of-sight measurement points• Use differential GPS if possible or match the coordinates with the

map• Check coordinate conversion parameters• Measure all the cable losses (both in transmitting and receiving

end)• Measure the output power of the transmitter• Check transmitter antenna installation and ensure that there are

no obstacles nearby• Document the measurements very carefully

Model Tuning: Measurements

141

• Measured field strength should be between – 95 dBm and – 60 dBm

– Stay in the main coverage area of the selected cell– Not too close to cell edges– Not too close to TX antenna

• Route long enough – Minimum 100 samples are needed

• O-H does not predict LOS situations– Avoid routes with LOS situations

• Make sure all wanted morpho classes and topo types are included• Which coordinate system?

Model Tuning: Okumura-Hata Measurements

142

• Import measurement results to a planning tool

– min. distance > 500 m to filter out too close samples

• Tune morpho corrections to best fit

• Tune only factors, which have more than 3%

• Mean value +/- 1 dB• If a lot of LOS negative mean• Standard deviation 8 dB• Correction factor for urban ~ 0

dB

Model Tuning: Okumura-Hata Model Tuning

143

• Why are the predictions and measurements different?– Is the digital map accurate enough?– What is the resolution of the map? – Is the morpho data correct?– Does the measured route match the roads?– Do the measured routes have a lot of LOS situations?

Model Tuning: Measurements Predictions?

144

Site and cell data Digital map System information

Calculate measurement route

Map matching

Measurement data

Coordinates

Model tuning

Compare

Analysis

Satisfactory model

End

Field strenght

No

Yes

Model Tuning: Detailed Process

145

Prediction model tuning areas

– Propagation slope– Effective antenna height– Morphographic corrections– Calculation distance


146

Assessment of propagation slope

• Okumura-Hata correction factor C:

dhChDfBA bb 10101010 log)log55.6(loglogL

propagation slope,parameter C has to be changedas a function of antenna height andenvironment


147

Effective antenna height definition

• 0 – 3 km: the average terrain height is calculated from base station to mobile station. The effective antenna height is the difference between the absolute antenna height and the average terrain height.

• 3 – 6 km: the average terrain height is calculated as a sliding average over 3 km from the mobile station towards to the base station.

• 6 – 15 km: the average terrain height is calculated from 3 km (from base station) to the mobile station.

• over 15 km: effective antenna height is the difference between the transmitting antenna and the average terrain height between 3 and 15 km


148

302928272625242322212019181716151413121110987654321

Terrain type UUUOOUUUOOOOSSSSPPPPWWWWWSSSSS

Correction factor [dB] 000-15-15000-15-15-15-15-5-5-5-5-8-8-8-8-23-23-23-23-23-5-5-5-5-5

Pixel size: 50 m x 50 m

Morphographic corrections

Example: Morphographic corrections • The distance between the base station and the mobile station is 1.5 km. On the digital map there are 30 pixels (50 m x 50 m) between the base station and the mobile. Each pixel presents the terrain

type within the 50 m x 50 m area.

The following notations are used: U = Urban, S = Suburban, P = Park, O = Open and W = Water.


149

Morphographic corrections

• The morphographic correction calculated as an average of the pixels between the mobile station and base station

• The average of the correction factors in this example is –9.4 dB

• The basic propagation model is corrected by adding the calculated correction to the prediction result (correction factor Lmorpho in Okumura-Hata model).


150

Calculation distance

• It is not very likely that the area close to the base station has a great impact on the received power of the mobile station

• The areas close to the mobile are more important for the prediction thus there are ways to weight the areas close to the mobile station

• The calculation distance can be shorter than the distance between the mobile station and the base station

• Only the pixels close to the mobile stations are considered • In the previous example the calculation distance is changed from 1.5

km down to 500 meters the average of the correction factors is –14 dB. Difference between the corrections is 4.6 dB.


151


1.01.0

1.02.0

10 9 8 7 6 5 4 3 2 1

Terrain type W W W W W S S S S S

Correction factor [dB] -23 -23 -23 -23 -23 -5 -5 -5 -5 -5

Weights 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Normalized weights 0.67 0.73 0.80 0.87 0.93 1.00 1.07 1.13 1.20 1.27

Normalized correction factors -15 -17 -18 -20 -21 -5 -5.3 -5.7 -6 -6.3


Linear weights for terrain type correction factors (example). The average of the normalized correction factors is –12.33 dB.


152

-100

-90

-80

-70

-60

-50

-40

1 51 101 151 201 251 301 351 401 451 501Measurement points

Sign

al le

vel [

dBm

]

MeasuredPredicted

0

10

20

30

40

50

60

70

80

90

-15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

dB

Example: Morpho Corrections Tuning

153

-100

-90

-80

-70

-60

-50

-40

100 1000 10000

Distance [m]

Sign

al le

vel [

dBm

]

Example: Quality of Tuning

154

Morpho Class Value [dB]

Open -20

Water -25

Forest -11

Quasi-Open -5

Houses -12

Sub-Urban -10

Urban -2

Buildings 7

Industrial buildings -4

High rise buildings 18

Example: Tuning Results

155

CapacityCapacityPlanningPlanning

156

DESCRIBE TRAFFIC THEORY PRINCIPLES CALCULATE CAPACITY OF DIFFERENT

CONFIGURATIONS DESCRIBE SIGNALLING CHANNELS AND

CALCULATE SIGNALLING CAPACITY DESCRIBE MAIN FEATURES OF CAPACITY

ENHANCEMENT


Objectives

157

TRAFFIC

SIGNALLING

CAPACITY ENHANCEMENTS

Capacity Planning

158

• Estimate number of subscribers over time– Long-term predictions– Numbers available from marketing people?

• Expected traffic load per subscriber– Different subscriber segments?– Expected behaviour of user segments

• Particular phone habits of subscribers– e.g. mainly heavy indoor usage– Phoning while in traffic jams?

• Busy hour conditions– Time of day– Traffic patterns

Traffic: Traffic Estimations

159

• 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

0102030405060708090

100

0 2 4 6 8 10 12 14 16 18 20 22 24hr

%peak timeoff-peak

Traffic: Traffic Patterns

160

load_vec ind2

dt


12 12.2 12.4 12.6 12.8 130

2

4

6

8The cell load

Time / hours

Num

ber o

f res

erve

d tim

eslo

ts

.

Cell load

161

M potential customers

m available resourcesM >> m

• Problem: many customers, limited number of resources• How many resources do we need to satisfy the demand?

Trunking Basics

162

• Trunking increases effective usage of limited resources– When we increase the traffic, we may not need that many new lines

• Main parameter: accepted blocking probability• Blocking depends on

– Number of available resources– Traffic statistical distribution

Trunking: Trunking Effect

163

time

CH 1CH 2CH 3CH 4

CH ...CH 5

CH n-2CH n-1CH n

Offered newtraffic

Trunking: Trunking Effect

164

• Erlang is the unit of traffic– Definition

• 2 formulas– Erlang B: for systems that support no queuing – Erlang C: for systems that support queuing

Seconds 3600)()( Erlangs timeonconversatiaveragehourpercallsx

Agner Krarup Erlang (1878-1929)

Erlang Definition

165

• Erlang B– No queuing: blocked calls are

dropped– Depends on call lengths &

statistical distribution of calls– Applicable in mobile systems

(e.g. air interface)

• Erlang C– Queuing– Applicable in trunking systems

M

i

i

k

k

i

kp

0

!/

!/

1

0 !1!

)0(Pr C

k

kC

C

kA

CACA

Adelayob

Erlang: Erlang Formulas

166

• Erlang B– No queuing: blocked calls are

dropped– Depends on call lengths &

statistical distribution of calls– Applicable in mobile systems

(e.g. air interface)

• Erlang C– Queuing– Applicable in trunking systems

M

i

i

k

k

i

kp

0

!/

!/

1

0 !1!

)0(Pr C

k

kC

C

kA

CACA

Adelayob

Erlang: Erlang Formulas

167

Blocking Probability Blocking ProbabilityChannels 1% 2% 3% 5% Channels 1% 2% 3% 5%

1 0,01 0 ,02 0 ,03 0 ,05 21 12 ,80 14 ,00 14 ,90 16 ,202 0 ,15 0 ,22 0 ,28 0 ,38 22 13 ,70 14 ,90 15 ,80 17 ,103 0 ,46 0 ,60 0 ,72 0 ,90 23 14 ,50 15 ,80 16 ,70 18 ,104 0 ,87 1 ,09 1 ,26 1 ,52 24 15 ,30 16 ,60 17 ,60 19 ,005 1 ,36 1 ,66 1 ,88 2 ,22 25 16 ,10 17 ,50 18 ,50 20 ,006 1 ,91 2 ,28 2 ,54 2 ,96 26 17 ,00 18 ,40 19 ,40 20 ,907 2 ,50 2 ,95 3 ,25 3 ,75 27 17 ,80 19 ,30 20 ,30 21 ,908 3 ,13 3 ,63 3 ,99 4 ,54 28 18 ,60 20 ,20 21 ,20 22 ,909 3 ,78 4 ,34 4 ,75 5 ,37 29 19 ,50 21 ,00 22 ,10 23 ,80

10 4 ,46 5 ,08 5 ,53 6 ,22 30 20 ,30 21 ,90 23 ,10 24 ,8011 5 ,16 5 ,84 6 ,33 7 ,08 31 21 ,20 22 ,80 24 ,00 25 ,8012 5 ,88 6 ,61 7 ,14 7 ,95 32 22 ,00 23 ,70 24 ,90 26 ,7013 6 ,61 7 ,40 7 ,97 8 ,83 33 22 ,90 24 ,60 25 ,80 27 ,7014 7 ,35 8 ,20 8 ,80 9 ,73 34 23 ,80 25 ,50 26 ,80 28 ,7015 8 ,11 9 ,01 9 ,65 10 ,60 35 24 ,60 26 ,40 27 ,70 29 ,7016 8 ,88 9 ,83 10 ,50 11 ,50 36 25 ,50 27 ,30 28 ,60 30 ,7017 9 ,65 10 ,70 11 ,40 12 ,50 37 26 ,40 28 ,30 29 ,60 31 ,6018 10 ,40 11 ,50 12 ,20 13 ,40 38 27 ,30 29 ,20 30 ,50 32 ,6019 11 ,20 12 ,30 13 ,10 14 ,30 39 28 ,10 30 ,10 31 ,50 33 ,6020 12 ,00 13 ,20 14 ,00 15 ,20 40 29 ,00 31 ,00 32 ,40 34 ,60

Erlang: Erlang B Table

168

TRAFFIC

SIGNALLING


Capacity Planning

169

• TDMA Frame = 8 Time Slots (0.577 ms each)• Physical Channel = 1 TS of the TDMA Frame on 1 specific carrier• Logical Channel = the "purpose" a physical channel is used for

0 0

TDMA frame 4.615 msBURST PERIOD

0 7 0

Logical Channels: Definitions

170

0 7TDMA frame 4.615 ms

26 Multiframe = 120 ms 51 Multiframe 235 ms

TCH SIGN.0 1 2 24 25 0 1 2 49 50

Hyperframe = 2048 Superframes 3.5 h

Superframe = 26x51 or 51x26 Multiframes= 6.120 sec

Logical Channels Structure

171

• Same in GSM900 and GSM1800

FCH

Traffic Channels (TCH)

TCH/9.6FTCH/ 4.8F, HTCH/ 2.4F, H

Dedicated Channels

(DCH)

Broadcast Channel(BCH) Control ChannelsCommon Control

Channel (CCCH)

SCH BCCH(Sys Info)

TCH/FAGCH RACH SDCCH FACCH/ Bm

FACCH/ Lm

TCH/HPCH

Common Channels (CCH)

Logical Channels

SACCH

Overview of Logical Channels

172

Frequency Correction Channel (FCCH)– Unmodulated carrier: like a flag for the MS which enables it to find the frequency

among several TRXsSynchronisation Channel (SCH)

– Contains the Base Station Identity Code (BSIC) and a reduced TDMA frame number

Broadcast Control Channel (BCCH)– Contains detailed network and cell specific information as: Frequencies,

Frequency hopping sequence, Channel combination, Paging groups, Information on neighbour cells

– Careful frequency plan needed– BCCH is not allowed to involve in FH, PC

Broadcast Channels (BCH)

173

Paging Channel (PCH)– It is broadcast by all the BTSs of a Location Area in the case of a mobile

terminated callRandom Access Channel (RACH)

– It is used by the mobile station in order to initiate a transaction, or as a response to a PCH

Access Grant Channel (AGCH)– Answer to the RACH. Used to assign a mobile a SDCCH

Common Control Channels (CCCH)

174

Stand Alone Dedicated Control Channel (SDCCH)– System signalling: call set-up, authentication, location update, assignment of

traffic channels and transmission of SMSSlow Associated Control Channel (SACCH)

– Transmits measurement reports (UL)– Power control, time alignment, short messages (DL)

Fast Associated Control Channel (FACCH)– Mainly used for handover signalling– It is mapped onto a TCH and replaces 20 ms of speech

Traffic Channels (TCH)– Transfer user speech or data, which can be either in the form of Half rate traffic

(6.5 kbit/s) or Full rate traffic (13 kbit/s).

Dedicated Channels (DCH)

175

FCCHSCH

SDCCHPCH

AGCH

BCCH

CCCH

Common Channels

Dedicated Channels

Logical ChannelsDownlink

SACCHFACCHSDCCHTCH/FTCH/H

DCCH

TCH

176

RACH CCCH Common Channels

SDCCHSACCHFACCHTCH/FTCH/H

DCCH

TCH

Dedicated Channels

Logical ChannelsUplink

177

Search for frequency correction burst FCCHSearch for synchronisation sequence SCHRead system informations BCCH

Listen for paging PCHSend access burst RACHWait for signalling channel allocation AGCHCall setup SDCCH

FACCHTraffic channel is assigned TCHConversation TCHCall release FACCH

idle mode

'off' state

dedicated mode

idle mode

Logical Channels Use

178

Beware of "home-made" bottlenecks

• Example of mapping: – combined CCCH/SDCCH/4 configuration

Downlink 51 TDMA frames = 235 ms

1. 2. 3. 4.

f s bb bbc fc fc scccc cc cc fc fs t t t t tt t t f ft t t t tt t t fs fssss ss s ss i

t t tt r r s fs ss sssr r rr r r rs fr r r r r rr r r r fr r r r tr t t tr ft t t r tr t tt t

Uplink 51 TDMA frames = 235 ms

Logical Channels: Mapping - 1 Example

179

• Mainly realised by Stand-alone Dedicated Control CHannel (SDCCH)

• SDCCH is mainly used in 5 cases:– Call set-up– SMS– Location updates– Emergency call– Call re-establishment

• SDCCH channel is key in achieving successful & efficient call set-up

Cell Capacity Signalling

180

• TS0 of BCCH TRX always for BCCH + CCCH• TS0 may be configured to carry DCCH• SDCCH channels may be configured in any other TS. Convention

(but not law!) is to put it on TS1• 2 basic configurations

– Combined – Non-combined

Combined configuration

0 7

ts0=bcch/sdcch/4/pch/agch

Non-combined configuration

0 7

ts0=bcch/pch/agchts1=sdcch/8

Cell Capacity: SDCCH Configurations

181

• Efficient network design is required to achieve 2 goals– An appropriate signalling dimensioning strategy, on a cell per cell basis– An appropriate upgrade philosophy

• SDDCH channels may be dimensioned in 3 ways– On a cell per cell basis– On a generic macro layer (not linked to macro/ micro cell layer definitions)– On both of the above

Cell Capacity: SDCCH Dimensioning

182

1 TRX and 7 Traffic channels means that• There can be 7 simultaneous GSM data or speech calls• The total traffic over a hour period (=busy hour) is 2.5 Erl and 1% of call attempts is blocked• Extra capacity of 64% (= (7-2.5)/7) is needed to guarantee 1% blocking

(compare to the situation of 2 TRX => trunking effect!!) 1 TRX and 1 signalling channel means that

• All signalling channels (BCCH, PCH, AGCH, SDCCH) are sent on the 1st time slot• PCH and SDCCH capacities are the possible bottlenecks!

Capacity Planning: Conclusion

183

Traffic channel capacity need is calculated / estimated

1. Based on the average traffic per subscriber (= 25 mErl = 90 s) and number of subscribers (250 Subs) and the total traffic need = 250 Subs x 25 mErl/Subs = 6.25 Erl

2. Next the required number of traffic channels will be found from the Erlang-B table based on the quality criteria that is usually 1% blocking in GSM.

3. Erlang-B shows that 13 channels give 6.61 Erl @ 1% blocking which exceeds the capacity demand 6.25 Erl.

4. Next it can be noted that 2 TRX equals 14 TCHs and 2 SCHs (= 7.35 Erl = 6.25 + 1.1 extra capacity for the future).

5. 2 TRX will be implemented to the cell!

Example: to estimate the Service for Subscribers

184

TRAFFIC

SIGNALLING


Capacity Planning

185

Dual Band

186

• Dual Band means combining both GSM 900 and GSM 1800 (previously DCS) in the same network

• GSM 900 and GSM 1800 are twins from the technical point of view

BSCGSM900/1800

GSM1800

GSM900/1800

GSM900

Dual Band Network Basics

187

• Capacity with GSM900 is limited: – Subscriber growth– Increased usage

• Quality and capacity required: New services

– WLL– Wireless Office– Data Services

• Roaming: High revenue from roaming traffic

Dual Band Network Basics

188

• Traffic management– First priority is to camp on GSM 1800 cells– Transferring the Dual Band mobiles from GSM 900 cells to GSM 1800 cells is the

key process– Setting special BSS parameters.

• Planners should pay more attention to:– Careful set of HO parameters– Dualband network configuration– LAC planning

Dual Band Network Effect on RNP

189

• Typically BSC and LAC areas are compact and bounded to geographical location

• Microcells connected to same BSC with surrounding macrocells

• Compact BSC areas enable the effect use of Nokia features e.g. AMH and traffic reason HO

• Intra BSC HO success rate better than Inter BSC HO success rate

– Better candidate evaluation in Intra BSC HO• Optimised LAC borders decrease signalling load

– User mobility– Highways and railroads– Geographical areas

LAC/BSC Borders

190

MSC

BSCa BSCb

GSM900

GSM1800

GSM900

GSM1800

GSM900

GSM1800

GSM900

GSM1800

LACa LACb

Dual Band Network: Same LAC and BSC

191

If you need to provide capacity for 20 Erlangs, 2 % blocking, how many TRXs do you need?

How many TRXs do you need to provide capacity for 10 Erlangs, 1 % blocking?

How many subscribers can you serve with 2 TRX/cell, 1% blocking, with average usage 20 mErl?

How many cells would you therefore need to give capacity for Helsinki area (49.2 % penetration, population 1 million)?

In China the average usage is 30 mErl. How many subscribers can you serve with 2 TRX/cell (1% blocking)?

In a small town A, with 1000 residents, the collected statistic data shows that the average air-time in busy hour is 90 seconds. If we want to cover this town by one cell, how many TRXs do we need to achieve the blocking probability of 1%?

192

FrequencyFrequencyPlanningPlanning

193

DESCRIBE FREQUENCY PLANNING CRITERIA

CALCULATE THE FREQUENCY REUSE FACTOR

DESCRIBE FREQUENCY ALLOCATION METHODS


Module objectives

194

• Tighter re-use of own frequencies more capacity more

interference• Target

• to minimise interferences at an acceptable capacity level

• First when a complete area has been finalised

• Automatic frequency planning tools

R

D

Frequency Plan: Basics

195

• Why frequency re-use ?– 8 MHz = 40 channels à 7 traffic timeslots = 280 users– max. 280 simultaneous calls??!

• Limited bandwidth available – Re-use frequencies as often as possible– Increased capacity– Increased interferences

• Trade-off between interference level and capacity• Allocate frequency combination that creates least overall

interference conditions in the network

Interference is unavoidable minimise total interferences in network

Frequency Plan: Basics

196

Criteria

The frequency planning criteria include the configuration and frequency allocation aspects. The configuration aspects consider the:

• Frequency band splitting between the macro and micro base stations, • Frequency band splitting between the BCCH and TCH layers,• Frequency band grouping and• Different frequency reuse factors for different TRX layers.

Frequency allocation aspects includefrequency planning thresholds (QOS requirements)

• C/I requirements• Percentage of co-channel and adjacent channel interference

Frequency Plan : Frequency Planning Criteria

197

Macro - Micro

• needed because of inaccurate coverage predictions between macro and micro layers • not needed if accurate coverage predictions available in the future

BCCH - TCH

• needed to ensure a good quality on BCCH frequency (in order to ensure signalling)

Frequency Plan: Frequency Band Splitting

198

Frequency grouping

+ Frequency hopping (coherence bandwidth)+ Intermodulation + Frequencies assigned to all TRX layers at one time+ Frequencies evenly used - Limitations for automatic frequency planning algorithms - Fixed frequency reuse factor

f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 f13 f14BCCH 1 2 3 4 5 6 7 8 9 10 11 12 13 142. TRX 15 16 17 18 19 20 21 22 23 24 25 26 27 283. TRX 29 30 31 32 33 34 35 36 37 38 39 40 41 42

Frequency Plan: Frequency Band Grouping

199

f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 f13 f14 f15BCCH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 152. TRX 16 17 18 19 20 21 22 23 24 25 26 27 28 29 301. Micro 31 32 33 34 35 36 31 32 33 34 35 36 31 32 332. Micro 37 38 39 40 41 42 37 38 39 40 41 42 37 38 39

Frequency planning for different TRX layers

• different freqency reuse factors for different TRX layers • frequency planning for different layers

Different Frequency Reuse Factors for Different TRX Layers

200

C/I requirements

- C/Ic = 15 dB, C/Ia = -6 dB (Note Overlay-Underlay concepts)

Interference probability

- 2% co-channel and 5% adjacent channel interference

Frequency separations

- cell/site separations- combiner limitations

Frequency Allocation Thresholds

201

• Do not use– Hexagon cell patterns– Regular grids– Systematic frequency allocation

• Use– Interference matrix calculation– Calibrated propagation models– Minimise total interference in

network

RD

f2

f3f4f5

f6f7

f3f4f5

f6

f2

f3f4f5

f6f2

f3f4f5

f6f7

f2

f3f4f5

f7

f2

f3f4f5 f2

f3f4f5

f6f7

Best Method

202

• RuF– Average number of cells that have different frequencies – Measure for effectiveness of frequency plan– Trade-off: effectiveness vs. interferences

• Multiple RuFs increase effectiveness of FP– Compromise between safe, interference free planning and effective resource

usage

1 3 6 9 12 15 18 21

safe planning(BCCH layer)

normal planning(TCH macro layer)

tight re-use planning (IUO layer)

same frequencyin every cell(“spread spectrum”)

Re-Use-Factor

203

• Capacity increase with multiple RuFs– e.g. network with 300 cells– Bandwidth : 8 MHz (40 radio channels)

• Single RuF =12– NW capacity = 40/12 * 300 = 1000 TRX

• Multiple RuF– BCCH layer: re-use =14, (14 frq.)– Normal TCH: re-use =10, (20 frq.)– Tight TCH layer: re-use = 6, (6 frq.)– NW cap. = (1 +2 +1)* 300 = 1200 TRX

Multiple Re-Use-Factor

204

• Co-cell separation– e.g. 3 (4 for GSM1800)– 600 (800 ) kHz spacing between frequencies in the same cell

• Co-site separation– e.g. 2– 400 kHz spacing between frequencies on the same site

• Co-channel interferences from neighbouring sites• Adjacent channel interferences from neighbouring sites

Frequency Plan: Constraints

205

A1 B1 C1 D1 E1 F1 G1 H1 A2 B2 C2 D2BCCH 1 26 3 28 5 30 7 32 9 34 11 36TCH 25 2 27 4 29 6 31 8 33 10 35 12

E2 F2 G2 H2 A3 B3 C3 D3 E3 F3 G3 H3BCCH 13 38 15 40 17 42 19 44 21 46 23 48TCH 37 14 39 16 41 18 43 20 45 22 47 24

• With Frequency Groups: 8 groups, 6 ARCFN each

A1 B1 C1 D1 E1 F1 G1 H1 I1 L1 A2 B2 C2 D2 E2 F21 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

G2 H2 I2 L2 A3 B3 C3 D3 E3 F3 G3 H3 I3 L3 M3 N317 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

O3 P3 Q3 R3 M4 N4 O4 P4 Q4 R4 M5 N5 O5 P5 Q1 R533 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

BCCH

BCCH TCH

TCH

• With Separated Bands: 10 groups BCCH, 6 TCH, 3 ARCFN each

Frequency Plan: Manual Allocation

206

Allocation Criteria

– Take into account both:• theoretical dominance area and• planner's knowledge of the site

– Starting point:• critical site or• critical area

– "cluster approach"?– "dynamic" BCCH allocation– No more than 60-70 sites!!!

Conclusion

– Method 1 is simpler than method 2

– Method 2 is more accurate (RuFBCCH > RuFTCH, intracell HO)

C/I C/A C/I C/Agroups x x x x

sub-bands x

TCHBCCHsimplicity

Frequency Plan: Manual Allocation

207

• Frequency allocation algorithms implemented in planning tools

• Compute compatibility matrix across total cell area (heavy computing!)

• Allocate same frequencies in “sufficiently separated” cells

• Allocate frequencies until traffic needs of all cells are satisfied

• Boundary condition: minimise total network interferences

• No closed solution available for this problem

• Iterative procedure

Frequency Plan: Automatic Allocation

208

Interference parameters

settingSeparation parameters

setting

Interference matrix calculation

Separation matrix calculation

Frequency allocationAnaly

ze result

s

• Choose the following parameters for all network layers– Co-cell separation– Co-site separation– Target level for co-channel + adj channel interference– Frequency band allowed

• Algohorithm:


209

• Interference matrix– Element (i,j) = amount of interference caused on cell i by cell j– Comparison parameter = co-channel (adj channel) C/I

• Separation matrix– Element (i,j) = minimum channel separation between cell i and cell j– Comparison parameter = maximum C/I (C/A) probability– Co-site, co-cell and adj-cell separations manually set


210

Evaluation criteria– Check the avg co-channel

interference parameter– Check the channel distribution– Check the contraints violation

list– Use the Interference Analisys

tool

Automatic frequency plan

Manual analysis and error correction

Final result


211

A

BC

15km

internationalborderline

• Regulations for international boundaries– 18 dB V/m at borderline– 18 dB V/m at 15km distance from border for preferential frequencies

• Set of preferential and reserved frequencies must be mutually agreed between operators

Frequency Plan: Frequency Coordination

212

Intermodulation interference can be avoided by

• Ensuring that the base station site equipment quality is such high that the

intermodulation does not exist,• Grouping the frequencies such that the intermodulation products do not cause interference or• Allocating the frequencies such that the intermodulation products do not cause interference or

it’s complex influence on the frequency planning can be made easier by

• Preventing the power control (only for the downlink intermodulation products) or• Directing the intermodulation products to the BCCH frequencies (there is no downlink power control on the BCCH).

Frequency Plan: Intermodulation

213

Is the frequency grouping of the reuse factor 15 enough to maximise the performance of the frequency hopping?

Does the 1800 MHz GSM network cause interference to the 900 MHz networks?

Why does the frequency band have to be split?

Exercises / Questions

coverage and capacity planning

Documents

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dbm dbm db dbm16 dbm

db dbm dbm db13 dbm

decibeis29 db db db

dbeeeline db

watt dbm

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frequency plan