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Page 1: Alums- Gsm Rf - Student Guide

Do not delete this graphic elements in here:

All Rights Reserved © Alcatel-Lucent 2009

GSM RF Fundamentals for ALUMS

STUDENT GUIDEVolume 1

Page 2: Alums- Gsm Rf - Student Guide

Do not delete this graphic elements in here:

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Basic RF Engineering

Page 3: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks3

Module Objectives

Upon completion of this module, you should be able to:

Explain different propagation effects for Radio waves.Explain Radio propagation losses.Identify the Components of an Antenna system and explain the Antenna radiation patternElectrical and mechanical specifications of different types of antennaeDescribe types of cables and its parametersDescribe the process of Radio Network Planning.Identify the steps for network design.

Page 4: Alums- Gsm Rf - Student Guide

All Rights Reserved © Alcatel-Lucent 2009

RF Fundamentals for Cellular Networks4

Course Outline

1. Basic RF Engineering- Radio Propagation- Path Loss prediction- Antennae & Cable- Radio Network Planning

2. GSM/GPRS Overview

3. GSM Advanced Concepts

4. Network Dimensioning

5. Network Characteristics

6. RF Optimization and Case Studies

Page 5: Alums- Gsm Rf - Student Guide

All Rights Reserved © Alcatel-Lucent 2009

RF Fundamentals for Cellular Networks5

Radio Propagation

Page 6: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks6

Radio Propagation

Propagation effects

Reflection, Refraction, Scatteringin the atmosphereat a boundary to another material

Diffractionat small obstaclesover round earth

AttenuationRain attenuationGas absorption

Fading

Page 7: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks7

ϕ

P0

∆h

Propagation effects

Reflection

Reflection is the returning, or "bouncing" of a wave off a surface which resists that kind of wave

Pr = Rh/v ⋅ P0

Rh/v = f(ϕ, ε, σ, ∆h)horizontal reflection factorvertical reflection factorangle of incidencepermittivityconductivitysurface roughness

Rh

Rv

ϕεσ∆h

Pr

Page 8: Alums- Gsm Rf - Student Guide

All Rights Reserved © Alcatel-Lucent 2009

RF Fundamentals for Cellular Networks8

Propagation effects

Refraction

k = 4/3

k = 1 k = 2/3k =

true earth

Ray paths with different k over true

Refraction is the change in direction of a wave when it passes into a new substance.

Radio path plotted as a straight line by changing the earth's radius

k = 4/ 3k = 1

k = 2/ 3

k =

radio path

earth

Considered through an effective earth radius factor k

Page 9: Alums- Gsm Rf - Student Guide

All Rights Reserved © Alcatel-Lucent 2009

RF Fundamentals for Cellular Networks9

Propagation effects

Diffraction

Occurs at objects which sizes are in the order of the wavelength λRadio waves are ‘bent’ or ‘curved’ around objects

Bending angle increases if object thickness is smaller compared to λInfluence of the object causes an attenuation: diffraction loss

diffractedradio shadow

zone obstacle

radio

Page 10: Alums- Gsm Rf - Student Guide

All Rights Reserved © Alcatel-Lucent 2009

RF Fundamentals for Cellular Networks10

Propagation effects

Fading

Caused by delay spread of original signalMulti path propagationTime-dependent variations in heterogeneity of environmentMovement of receiver

Short-term fading, fast fadingThis fading is characterised by phase summation and cancellation of signal components, which travel on multiple paths. The variation is in the order of the considered wavelength. Their statistical behaviour is described by the Rayleigh distribution (for non-LOS signals) and the Rice distribution (for LOS signals), respectively.In GSM, it is already considered by the sensitivity values, which take the error correction capability into account.

Page 11: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks11

Propagation effects

Fading types

Mid-term fading, lognormal fadingMid-term field strength variations caused by objects in the size of 10...100m (cars, trees, buildings). These variations are lognormal distributed.

Long-term fading, slow fadingLong-term variations caused by large objects like large buildings, forests, hills, earth curvature (> 100m). Like the mid-term field strength variations, these variations are lognormal distributed.

Page 12: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks12

Propagation effects

Signal Variation due to Fading

-70

-60

-50

-40

-30

-20

-10

00.

1

2.8

5.4

8.0

10.6

13.2

15.9

18.5

21.1

23.7

26.3

29.0

31.6

34.2

36.8

39.4

42.1

44.7

47.3

49.9

Distance [m]

Rec

eive

d Po

wer

[dB

m]

Lognormal fadingRaleygh fading

Fading hole

Page 13: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks13

Propagation effects

Lognormal Fading

Lognormal fading (typical 20 dB loss by entering a village)

Fading hole

Lognormal fading (entering a tunnel)

Page 14: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks14

Path Loss Prediction

Page 15: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks15

Path Loss Prediction

Free Space Loss

The simplest form of wave propagation is the free-space propagationThe according path loss can be calculated with the following formulaPath Loss in Free Space Propagation

L free space lossd distance between transmitter and receiver antennaf operating frequency

L dkm

fMHzfreespace = + ⋅ + ⋅324 20 20. log log

Page 16: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks16

Path Loss Prediction

Fresnel Ellipsoid

The free space loss formula can only be applied if the direct line-of-sight (LOS) between transmitter and receiver is not obstructedThis is the case, if a specific region around the LOS is cleared from any obstaclesThe region is called Fresnel ellipsoid

Transmitter

Receiver

LOS

Page 17: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks17

Path Loss Prediction

Fresnel Ellipsoid

21

21

ddddr+⋅⋅

The Fresnel ellipsoid is the set of all points around the LOS where the total length of the connecting lines to the transmitter and the receiver is longer than the LOS length by exactly half a wavelengthIt can be shown that this region is carrying the main power flow from transmitter to receiver

Transmitter Receiver

LOS

LOS + λ/2

Fresnel zone

Page 18: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks18

Path Loss Prediction

Knife Edge Diffraction

1st Fresnel zone

r

BTS

MS

d1 d2

h0

line of sight

path of diffracted wave

d1 d2

h0

replaced obstacle (knife edge)

h0 = height of obstacle over line of sight

d1, d2 = distance of obstacle from BTS and MS

Knife-edge effect or edge diffraction is a redirection by diffraction of a portion of the incident radiation that strikes a well-defined obstacle such as a mountain range or the edge of a building.

Page 19: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks19

Path Loss Prediction

Knife Edge Diffraction Function

Knife-edge diffraction function

-5

0

5

10

15

20

25

30

35

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3

Clearance of Fresnel ellipsoid (v)

F(v)

[dB

]

Additional diffraction loss F(v)v: clearance parameter, v=-h0/rNote: h0 = 0 ⇒ v =0 ⇒ L = 6 dB

Page 20: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks20

Path Loss Prediction "Final Solution" for Wave Propagation Calculations?

Exact field solution requires too much computer resources!Too much details required for inputExact calculation too time-consumingField strength prediction rather than calculation

Requirements for field strength prediction modelsReasonable amount of input dataFast (it is very important to see the impact of changes in the network layout immediately)Accurate (results influence the hardware cost directly)Tradeoff required (accurate results within a suitable time)Parameter tuning according to real measurements should be possible

Page 21: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks21

Path Loss Prediction

CCIR Recommendation

The CCIR Recommendations provide various propagation curves

Based on Okumura (1968)Example (CCIR Report 567-3):

Median field strength in urban areaFrequency = 900 MHzhMS = 1.5 mDashed line: free space

How to use this experience in field strength prediction models?

Model which fits the curves in certain ranges → Hata's model

was modified later by the European Cooperation in Science and Technology (COST): COST 231 Hata/Okumura

Page 22: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks22

Path Loss Prediction

Mobile Radio Propagation

Free-space propagation (Fresnel zone not obstructed) → L ~ d2

Fresnel zone heavily obstructed near the mobile station → L ~ d3.7

d

Page 23: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks23

Path Loss Prediction

Terrain Modeling

TopographyEffective antenna heightKnife edge diffraction

single obstaclesmultiple obstacles

Surface shape/Morpho-structureCorrection factors for Hata-Okumura formula

Page 24: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks24

Path Loss Prediction

Effect of Morphostructure on Propagation Loss

Open area Open areaUrban area

Distance

Fiel

d st

reng

th

urban area

open area

Page 25: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks25

Antennae and Cables

Page 26: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks26

Antennae and Cables

The Antenna System

AntennaePower dividerCables (jumper)Feeder cablesConnectorsClampsLightning protectionWall glandsPlanning

Rxdiv

Tx

Rx

Feedercable

Earthingkit

Wallgland

Jumper cables

Feederinstallationclamps

Plugs7/ 16“

Sockets7/ 16“

Mountingclamp

Grounding

Lightningrod Antennas

Earthing kit

Jumpercable Jumper

cable

Mechanicalantennasupportstructure

Page 27: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks27

Antennae and Cables

Antenna Theory

50Ω is the impedance of the cable377Ω is the impedance of the airAntennae adapt the different impedancesThey convert guided waves, into free-space waves (Hertzian waves) and/or vice versa

Z =377ΩZ =50Ω

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RF Fundamentals for Cellular Networks28

Antennae and Cables

Antenna Data

The antenna parameters which are of interest for the radio network engineering are the following: Antenna directivity, efficiency, gainPolarization, near field and far field

Specification due to certain wave polarization (linear/elliptic, cross-polarization)

Half power beam width (HPBW)Related to polarization of electrical fieldVertical and Horizontal HPBW

Antenna pattern, side lobes, null directionsYields the spatial radiation characteristics of the antenna

Front-to-back ratioImportant for interference considerations

Voltage standing wave ratio (VSWR)Bandwidth

Page 29: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks29

Antennae and Cables

Antenna Pattern and HPBW

0 dB

-3 dB

-10 dB

0 dB

-3 dB

-10 dB

verticalhorizontal

sidelobe

null direction

main beam

HPB

W

What is HPBW?Half Power Beam Width. The angle across the main lobe of an antenna pattern between the two directions at which the antenna's sensitivity is half its maximum value at the center of the lobe.

Page 30: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks30

Antennae and Cables

EIRP

Pt = 45 dBm

Gain = 11dBi

Isotropic radiated Power Pt

Effective isotropicradiated power:EIRP = Pt+Gain

= 56 dBm

V1

V2 = V1

radiatedpower

Page 31: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks31

For the link between base station and mobile station, mostly linear antennae are used:

Monopole antennaeMS antennae, car roof antennae

Dipole antennaeUsed for array antennae at base stations for increasing the directivity of RX and TX antennae

Antennae and Cables

Linear Antennae

Page 32: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks32

Antennae and Cables

Panel Antenna with Dipole Array

Many dipoles are arranged in a grid layoutNearly arbitrary antenna patterns may be designed

Feeding of the dipoles with weighted and phase-shifted signalsCoupling of all dipole elements

Page 33: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks33

Antennae and Cables

Dipole Arrangement

Dipole arrangement

Typical flat panel antenna

Dipole element

Weightedandphaseshiftedsignals

Page 34: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks34

Antennae and Cables

Omni Antenna

Antenna with vertical HPBW for omni sitesLarge area coverage

AdvantagesContinuous coverage around the siteSimple antenna mountingIdeal for homogeneous terrain

DrawbacksNo mechanical tilt possibleClearance of antenna required

Page 35: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks35

Antennae Parameters

Page 36: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks36

Antennae Parameters

X 65°T6 900MHz 2.5m

Rural road coverage with mechanical up-tiltAntenna

RFS Panel Dual Polarized Antenna 872-960 MHzAPX906516-T6 Series

Electrical specificationGain in dBi: 17.1Polarization: +/-45°HBW: 65°VBW: 6.5°Electrical down-tilt: 6°

Mechanical specificationDimensions HxWxD in mm: 2475 x 306 x 120Weight in kg: 16.6

Horizontal Pattern

Page 37: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks37

Antennae Parameters

X 65°T6 900MHz 1.9m

Dense urban areaAntenna

RFS Panel Dual Polarized Antenna 872-960 MHzAPX906515-T6 Series

Electrical specificationGain in dBi: 16.5Polarization: +/-45°HBW: 65°VBW: 9°Electrical down-tilt: 6°

Mechanical specificationDimensions HxWxD in mm: 1890 x 306 x 120Weight in kg: 16.6

Vertical Pattern

Page 38: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks38

Antennae Parameters

X 90° T2 900MHz 2.5m

Rural area with mechanical up-tiltAntenna

RFS Panel Dual Polarized Antenna 872-960 MHzAPX909014-T6 Series

Electrical specificationGain in dBi: 15.9Polarization: +/-45°HPBW: 90°VBW: 7°Electrical down-tilt: 6°

Mechanical specificationDimensions HxWxD in mm: 2475 x 306 x 120Weight in kg: 15.5

Vertical Pattern

Page 39: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks39

Antennae Parameters

V 65° T0 900MHz 2.0m

HighwayAntenna

RFS CELLite® Panel Vertical Polarized Antenna 872-960 MHzAP906516-T0 Series

Electrical specificationGain in dBi: 17.5Polarization: VerticalHBW: 65°VBW: 8.5°Electrical down-tilt: 0°

Mechanical specificationDimensions HxWxD in mm: 1977 x 265 x 130Weight in kg: 10.9

Vertical Pattern

Page 40: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks40

Antennae Parameters

V 90° T0 900MHz 2.0m

Rural AreaAntenna

RFS CELLite® Panel Vertical Polarized Antenna 872-960 MHzAP909014-T0 Series

Electrical specificationGain in dBi: 16.0Polarization: VerticalHBW: 65°VBW: 8.5°Electrical down-tilt: 0°

Mechanical specificationDimensions HxWxD in mm: 1977 x 265 x 130Weight in kg: 9.5

Vertical Pattern

Page 41: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks41

Antennae Parameters

X 65° T6 1800MHz 1.3m

Dense urban areaAntenna

RFS Panel Dual Polarized Antenna 1710-1880 MHzAPX186515-T6 Series

Electrical specificationGain in dBi: 17.5Polarization: +/-45°HBW: 65°VBW: 7°Electrical down-tilt: 6°

Mechanical specificationDimensions HxWxD in mm: 1310 x 198 x 50Weight in kg: 5.6

Vertical Pattern

Page 42: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks42

Antennae Parameters

X 65° T2 1800MHz 1.3m

Dense urban areaAntenna

RFS Panel Dual Polarized Antenna 1710-1880 MHzAPX186515-T2 Series

Electrical specificationGain in dBi: 17.5Polarization: +/-45°HBW: 65°VBW: 7°Electrical down-tilt: 2°

Mechanical specificationDimensions HxWxD in mm: 1310 x 198 x 50Weight in kg: 5.6

Vertical Pattern

Page 43: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks43

Antennae Parameters

X 65° T2 1800MHz 1.9m

HighwayAntenna

RFS Panel Dual Polarized Antenna 1710-1880 MHzAPX186516-T2 Series

Electrical specificationGain in dBi: 18.3Polarization: +/-45°HBW: 65°VBW: 4.5°Electrical down-tilt: 2°

Mechanical specificationDimensions HxWxD in mm: 1855 x 198 x 50Weight in kg: 8.6

Vertical Pattern

Page 44: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks44

Antennae Parameters

V 65° T2 1800MHz 1.3m

HighwayAntenna

RFS CELLite® Panel Vertical Polarized Antenna 1710-1880 MHzAP186516-T2 Series

Electrical specificationGain in dBi: 17.0Polarization: VerticalHBW: 65°VBW: 7.5°Electrical down-tilt: 2°

Mechanical specificationDimensions HxWxD in mm: 1310 x 198 x 50Weight in kg: 4.7

Horizontal Pattern

Page 45: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks45

Antennae Parameters

V 90° T2 1800MHz 1.9m

HighwayAntenna

RFS CELLite® Panel Vertical Polarized Antenna 1710-1880 MHzAP189016-T2 Series

Electrical specificationGain in dBi: 17.0Polarization: VerticalHBW: 90°VBW: 5.5°Electrical down-tilt: 2°

Mechanical specificationDimensions HxWxD in mm: 1855 x 198 x 50Weight in kg: 6.0

Vertical Pattern

Page 46: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks46

Cable Parameters

Page 47: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks47

Cable Parameters

7/8" CELLFLEX® Low-Loss Coaxial Cable

Feeder Cable7/8" CELLFLEX® Low-Loss Foam-Dielectric Coaxial CableLCF78-50J StandardLCF78-50JFN Flame Retardant

Installation temperature >-25°C

Electrical specification 900MHzAttenuation: 3.87dB/100mAverage power in kW: 2.45

Electrical specification 1800MHzAttenuation: 5.73dB/100mAverage power in kW: 1.79

Mechanical specificationCable weight kg\m: 0.53Minimum bending radius

Single bend in mm: 120Repeated bends in mm: 250

Bending moment in Nm: 13.0Recommended clamp spacing: 0.8m

Page 48: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks48

Cable Parameters

1-1/4" CELLFLEX® Coaxial Cable

Feeder Cable1-1/4" CELLFLEX® Low-Loss Foam-Dielectric Coaxial CableLCF114-50J StandardLCF114-50JFN Flame Retardant

Installation temperature >-25°C

Electrical specification 900MHzAttenuation: 3.06dB/100mAverage power in kW: 3.56

Electrical specification 1800MHzAttenuation: 4.61dB/100mAverage power in kW: 2.36

Mechanical specificationCable weight kg\m: 0.86Minimum bending radius

Single bend in mm: 200Repeated bends in mm: 380

Bending moment in Nm: 38.0Recommended clamp spacing: 1.0m

Page 49: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks49

Cable Parameters

1-5/8" CELLFLEX® Coaxial Cable

Feeder Cable1-5/8" CELLFLEX® Low-Loss Foam-Dielectric Coaxial CableLCF158-50J StandardLCF158-50JFN Flame Retardant

Installation temperature >-25°C

Electrical specification 900MHzAttenuation: 2.34dB/100mAverage power in kW: 4.97

Electrical specification 1800MHzAttenuation: 3.57dB/100mAverage power in kW: 3.26

Mechanical specificationCable weight kg\m: 1.26Minimum bending radius

Single bend in mm: 200Repeated bends in mm: 508

Bending moment in Nm: 46.0Recommended clamp spacing: 1.2m

Page 50: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks50

Cable Parameters

1/2" CELLFLEX® Jumper Cable

CELLFLEX® LCF12-50J JumpersFeeder Cable

LCF12-50J CELLFLEX® Low-Loss Foam-Dielectric Coaxial Cable

Connectors7/16” DIN male/femaleN male/femaleRight angle

Molded version available in 1m, 2m, 3m

Mechanical specificationMinimum bending radius

Repeated bends in mm: 125

Electrical specification 900MHzAttenuation: 0.068db/mTotal losses with connectors are 0.108dB, 0.176dB and 0.244dB

Electrical specification 1800MHzAttenuation: 0.099dB/mTotal losses with connectors are 0.139dB, 0.238dB and 0.337dB

Page 51: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks51

Radio Network Planning

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RF Fundamentals for Cellular Networks52

RNP Process Overview

Definition of RN Requirements

The Request for Quotation (RfQ) from the customer prescribes the requirements mainlyCoverage

Definition of coverage probabilityPercentage of measurements above level threshold

Definition of covered areaTraffic

Definition of Erlang per square kilometerDefinition of number of TRX in a cellMixture of circuit switched and packed switched traffic

QoSCall success rateRxQual, voice quality, throughput rates, ping time

Page 53: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks53

RNP Process Overview

Preliminary Network Design

The preliminary design lays the foundation to create the Bill of Quantity (BoQ)

List of needed network elements

Geo data procurementDigital Elevation Model DEM/Topographic mapClutter map

Definition of standard equipment configurations dependent on

clutter typetraffic density

Coverage PlotsExpected receiving level

Definition of roll out phasesAreas to be coveredNumber of sites to be installedDate, when the roll out takes place.

Network architecture designPlanning of BSC and MSC locations and their links

Frequency spectrum from license conditions

Page 54: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks54

RNP Process Overview

Project Setup and Management

This phase includes all tasks to be performed before the on site part of the RNP process takes place.This ramp up phase includes:

Geo data procurement if requiredSetting up ‘general rules’ of the projectDefine and agree on reporting scheme to be used

Coordination of information exchange between the different teamswhich are involved in the project

Each department/team has to prepare its part of the projectDefinition of required manpower and budgetSelection of project database

Page 55: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks55

RNP Process Overview

Initial Radio Network Design

Area surveysAs well check of correctness of geo data

Frequency spectrum partitioning designRNP tool calibration

For the different morpho classes:Performing of drive measurementsCalibration of correction factor and standard deviation by comparison of measurements to predicted received power values of the tool

Definition of search areas (SAM – Search Area Map)A team searches for site locations in the defined areasThe search team should be able to speak the national language

Selection of number of sectors/TRX per site together with project management and customerGet ‘real’ design acceptance from customer based on coverage prediction and predefined design level thresholds

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RF Fundamentals for Cellular Networks56

RNP Process Overview

Site Acquisition Procedure

Delivery of site candidatesSeveral site candidates shall be the result out of the site location search

Find alternative sitesIf no site candidate or no satisfactory candidate can be found in the search areaDefinition of new SAM (Search Area Map)Possibly adaptation of radio network design

Check and correct SAR (Site Acquisition Report)Location informationLand usageObject (roof top, pylon, grassland) informationSite plan

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RF Fundamentals for Cellular Networks57

RNP Process Overview

Site Acquisition Procedure [cont.]

Site candidate acceptance and rankingIf the reported site is accepted as candidate, then it is rankedaccording to its quality in terms of

Radio transmissionHigh visibility on covered areaNo obstacles in the near field of the antennasNo interference from other systems/antennas

Installation costsInstallation possibilitiesPower supplyWind and heat

Maintenance costsAccessibilityRental rates for objectDurability of object

Page 58: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks58

RNP Process Overview

Technical Site Survey

Agree on an equipment installation solution satisfying the needs of

RNE Radio Network EngineerTransmission plannerSite engineerSite owner

The Technical Site Survey Report (TSSR) defines

Antenna type, position, bearing/orientation and tiltMast/pole or wall mounting position of antennasEMC rules are taken into account

Radio network engineer (RNE) and transmission planner check electro magnetic compatibility (EMC) with other installed devices

BTS/Node B locationPower and feeder cable mountTransmission equipment installationFinal Line Of Site (LOS) confirmation for microwave link planning

E.g. red balloon of around half a meter diameter marks target location

If the site is not acceptable or the owner disagrees with all suggested solutions

The site will be rejectedSite acquisition team has to organize a new date with the next site from the ranking list

Page 59: Alums- Gsm Rf - Student Guide

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RF Fundamentals for Cellular Networks59

RNP Process Overview

Basic Parameter Definition

After installation of equipment the basic parameter settings are used for

CommissioningFunctional test of BTS and VSWR check

Call testsRNEs define cell design dataOperations field service generates the basic software using the cell design CAE data

Cell design CAE data to be defined for all cells are for example:

CI/LAC/BSCIFrequenciesNeighborhood/cell handover relationshipTransmit powerCell type (macro, micro, umbrella, …)

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RF Fundamentals for Cellular Networks60

RNP Process Overview

Turn On Cycle

The network is launched step by step during the TOCA single step takes typically two or three weeks

Not to mix up with rollout phases, which take months or even yearsFor each step the RNE has to define ‘TOC Parameter’

Cells to go on airDetermination of frequency planCell design CAE parameter

Each step is finished with the ‘Turn On Cycle Activation’Upload PRC/ACIE files into OMC-RUnlock sites

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RF Fundamentals for Cellular Networks61

RNP Process Overview

Site Verification and Drive Test

RNE performs drive measurement to compare the real coverage withthe predicted coverage of the cells.If coverage holes or areas of high interference are detected

Adjust the antenna tilt and orientationVerification of cell design CAE dataTo fulfill heavy acceptance test requirements, it is absolutely essential to perform such a drive measurement.Basic site and area optimization reduces the probability to haveunforeseen mysterious network behavior afterwards.

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RF Fundamentals for Cellular Networks62

RNP Process Overview

HW / SW Problem Detection

Problems can be detected due to drive tests or equipment monitoringDefective equipment

will trigger replacement by operation field serviceSoftware bugsIncorrect parameter settings

are corrected by using the OMC or in the next TOCFaulty antenna installation

Wrong coverage footprints of the site will trigger antenna re-alignments

If the problem is seriousLock BTSDetailed error detectionGet rid of the faultEventually adjusting antenna tilt and orientation

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RF Fundamentals for Cellular Networks63

RNP Process Overview

Basic Network Optimization

Network wide drive measurementsIt is highly recommended to perform network wide drive tests before doing the commercial opening of the networkKey performance indicators (KPI) are determinedThe results out of the drive tests are used for basic optimization of the network

Basic optimizationAll optimization tasks are still site relatedAlignment of antenna systemAdding new sites in case of too large coverage holesParameter optimization

No traffic yet -> not all parameters can be optimizedBasic optimization during commercial service

If only a small number of new sites are going on air the basic optimization will be included in the site verification procedure

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RF Fundamentals for Cellular Networks64

RNP Process Overview

Network Acceptance

Acceptance drive testCalculation of KPI according to acceptance requirements in contractPresentation of KPI to the customerComparison of key performance indicators with the acceptance targets in the contractThe customer accepts

the whole networkonly parts of it step by step

Now the network is ready for commercial launch

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RF Fundamentals for Cellular Networks65

RNP Process Overview

Further Optimization

Network is in commercial operationNetwork optimization can be performedSignificant traffic allows to use OMC based statistics by using optimization tools such as NPOEnd of optimization depends on contract and mutual agreement between Network provider and customer

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RF Fundamentals for Cellular Networks66

Module Summary

You should now be able to:

Explain different propagation effects for Radio wavesExplain Radio propagation lossesIdentify the Components of an Antenna system and explain the Antenna radiation patternElectrical and mechanical specifications of different types of antennaeDescribe types of cables and its parametersDescribe the process of Radio Network PlanningIdentify the steps for network design

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This slide is intentionally left blank.

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RF Fundamentals for Cellular Networks68

End of ModuleBasic RF Engineering

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Do not delete this graphic elements in here:

All Rights Reserved © Alcatel-Lucent 2009

GSM/GPRS Overview

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RF Fundamentals for Cellular Networks2

Module Objectives

Upon completion of this module, you should be able to:

Describe the history of GSM and other Communication SystemsList the GSM and other Cellular Network featuresDescribe the GSM architectureIdentify the GSM interfaces and protocolsList the radio interfaces in a GSM networkDescribe the Physical ChannelsDescribe the Logical ChannelsExplain the steps for speech processingDescribe GPRS architecture

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RF Fundamentals for Cellular Networks3

Course Outline

1. Basic RF Engineering

2. GSM/GPRS Overview- History of GSM and other

communication systems- GSM and other cellular network

features- GSM Architecture- GSM Interfaces and Protocols- GSM Identities- GSM Radio Interface- Speech Processing- GPRS Overview

3. GSM Advanced Concepts

4. Network Dimensioning

5. Network Characteristics

6. RF Optimization and Case Studies

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RF Fundamentals for Cellular Networks4

History of GSM and other Communication Systems

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RF Fundamentals for Cellular Networks5

History of GSM and other Communication Systems

History of Cellular Networks

Mobile network "Prehistory":1946: St Louis (Missouri)1970 - 80: NATEL (Switzerland)

1st Generation: Analog cellular networks1979: Chicago: AMPS1981: Sweden: NMT1985: UK: TACS

2nd Generation: Digital networks1992: Europe: GSM 1995: US: IS95 (CDMA)

3rd Generation: Universal Standards2001: JapanIMT-2000: UMTS

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RF Fundamentals for Cellular Networks6

History of GSM and other Communication Systems

GSM key dates

1979 World Administrative Radiocommunications Conference (WARC): 900 MHz band reserved

1982 Stockholm - Creation of the "Groupe Spécial Mobile" within CEPT (Post & Telecom European Conference)

1986 Creation of a GSM "Standing Committee”CNET Paris: Comparative trials of 8 prototypes

1987 "Broad Avenue": Choice of main techniques:Medium Band - Digital Transmission < 16 kbit/s - 8 x Time-division multiplexing, subsequent development to 16 x - Slow frequency hopping

1988-89 GSM taken over by ETSIFirst publication of the (Draft) "recommendations"

1990 Beginning of studies for adaptation to 1800 MHz (at UK's request)1990-91 "Phase 1" recommendations fixed (GSM, then DCS)

First GSM prototypes in service (Télécom'91 Geneva)1992 First commercial GSM networks placed in service1995 "Phase 2" recommendations issued (upward compatibility)

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RF Fundamentals for Cellular Networks7

GSM - MoU: Memorandum of Understanding

signed in 1987 between Europeanoperators

1991: acceptation of non-Europeansignatories (UAE, Hong Kong,New Zealand, Australia)

Scope:

-System deployment schedule

-Routing and numbering plancompatibility

-Joint introduction of new services

-Harmonization of tariff setting principles

-Definition of billing procedures

History of GSM and other Communication Systems

International agreements

European GSM-MoU signatories (operators) in 1999

323 4

3

42

33

2

4

3 34

5

2

33

42

3

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RF Fundamentals for Cellular Networks8

History of GSM and other Communication Systems

Contribution of GSM standard

Pan-European standard + MoU

GLOBAL system (standardized infrastructure)

New concept: SIM card ("SIM-roaming")

Digital transmission, speech encoding

Introduction of state of the art techniques

Integrated security procedures

Considerable potential market

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RF Fundamentals for Cellular Networks9

GSM and other Cellular Network features

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RF Fundamentals for Cellular Networks10

Standard CT2 GSM DCS DECT IS95System type cordless cellular cellular cordless satellite

Frequencyband (MHz) 864 – 868 890 - 915 (↑) 1710 -1785 (↑) 1880 –1900 1610 -1626.5 (↑)

935 - 960 (↓) 1805 -1880 (↓) 2483.5 -2500 (↓)

Commercial Pointel Orange Bouygues Digital Globalstarnames Bi-bop SFR Telecom domestic

cordlesstelephonesCompanymobiles

GSM and other Cellular Network Features

Overview of current standards

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RF Fundamentals for Cellular Networks11

GSM and other Cellular Network Features

GSM Success Factors

Large handset base

Short message Services (SMS)

Global roaming

Open standard environment

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RF Fundamentals for Cellular Networks12

GSM and other Cellular Network Features

Limits of GSM systems

public

residential

office PABX

PABX

Small Cells Medium Cells Large Cells

GSM

PSTN PSTN PSTN

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RF Fundamentals for Cellular Networks13

GSM and other Cellular Network Features

GSM 900 MHz and 1800MHz

Channel spacing 200kHz

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RF Fundamentals for Cellular Networks14

GSM and other Cellular Network Features

GSM 900 MHz and 1800MHz [cont.]

GSM 900 and GSM 1800 are twins

GSM 900 GSM 1800Frequency band 890 - 960 MHz 1710 - 1880 MHzNumber of channels 124 (125) 372 (375)Channel spacing 200 kHz 200 kHzMultiplex technologies TDMA/FDMA TDMA/FDMAMobile power 0.8 / 2 W 0.25 / 1 W

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RF Fundamentals for Cellular Networks15

GSM Architecture

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RF Fundamentals for Cellular Networks16

GSM Architecture

Overview

Operators

Users

ExternalNetworks

MSBSS NSS

OSS

GSM

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RF Fundamentals for Cellular Networks17

Users:The Mobile Station (MS) is used by the subscriber for calling another subscriber either in the fixed network or in the mobile network.The Base Station System (BSS) is the part of the GSM network used for access.

External Networks:The Network Sub-System (NSS) is used for all the call and mobility functions. The actual name used in the standards is Switching and Management Sub-System (SMSS). It is interfaced with other network such as Public Switched Telephone Network (PSTN) or Public Data Network (PDN).

Operators:The Operation Sub System (OSS) is composed of all the resources used by the operator to manage the network (BSS+NSS).

GSM Architecture

Overview [cont.]

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RF Fundamentals for Cellular Networks18

GSM Architecture

Types of Mobile Stations

SIM card

(includingTAF)

TAR

SMT1

MT0

MT2

TE2

TE2

TE1

Um"plug-in" SIM

ISDN

ISDN concepts GSM concepts

MT = Mobile TerminationTE = Terminal Equipment

TE1 = ISDNTE2 = V or X type

TA(F) = Terminal Adaptor (Function)

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RF Fundamentals for Cellular Networks19

GSM Architecture

Base Station System

PSTN/ISDN

BTS

NSSBSC with

TRAU

BTS

CBC

OtherBSCs

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RF Fundamentals for Cellular Networks20

The main entities of the Base Station System (with the corresponding functions) are:BTS: Base Transceiver Station

Physical Channel Management

BSC: Base Station ControllerLogical Channel ManagementManagement of interfaces with NSS and OSSBTS monitoring

CBC: Cell Broadcast Center (optional)Generation, storage of Cell Broadcast Short Messages

GSM Architecture

Base Station System

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RF Fundamentals for Cellular Networks21

NSS?

AuC

HLR

VLR

GSM Architecture

Network and Switching System

PSTN/ISDN

MSC

BSS

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RF Fundamentals for Cellular Networks22

VLR

GSM Architecture

Network and Switching System [cont.]

PSTN/ISDN

MSC

BSS

AuC

HLR

SMS-C

EIR

GCR

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RF Fundamentals for Cellular Networks23

Concept of Intelligent Network:The introduction of new services and access to the GSM service are based on the concept of Intelligent Network (IN). This is because of the independence between:

Conventional call processing handled by the exchange,Mobile radio functions handled by a dedicated server.

Dialog between these two is managed by an IN interface.

Advantages of this architecture:Separation between applications:

switching functions handled by the SSP,radio control functions handled by GSM servers (Radio Control Processor - RCP).

Functions can be developed independently.

The MSC handles all mobile radio network access functions.The RCP handles all mobile radio functions:

Mobility management and radio frequencies (Radio Control Function - RCF).It incorporates the VLR function (Visitor Location Register).

GSM Architecture

Network and Switching System [cont.]

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RF Fundamentals for Cellular Networks24

GSM Architecture

MSC (Mobile Switching Centre)

Exchange where calls are established, maintained and releasedDatabase for all subscribers and their associated features.Communicates with the BSCs on the A interface and with PSTN on fixed line.MSC is weighted on the number of subscribers it can support. Forexample, an MSC of 1 lakh subscribers means one MSC is enough till subscriber base increases up to 1 lakh, beyond which another MSC is required.

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RF Fundamentals for Cellular Networks25

BSC

BSC

MSC

MSC

GMSC PSTN

GSM Architecture

Multiple MSCs

When there is more capacity, there are more than one MSCs.All MSCs have to communicate with one another and to the outside world.Very complicated to connect each MSC to each other and each MSC to PSTNSo there is a concept of GMSC (Gateway MSC)

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RF Fundamentals for Cellular Networks26

GSM Architecture

HLR – Home Location Register

MSC has all subscriber database stored in HLRHLR has all permanent subscriber databaseHLR has a database which describes the subscriber’s profile i.e. basic features and supplementary servicesMSC communicates with the HLR to get data for subscribers on callHLR contains the addresses of the VLR in which subscriber is presently located

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RF Fundamentals for Cellular Networks27

MSCVLR

HLR

GSM Architecture

VLR – Visiting Location Register

A subscription when activated is registered in VLRVLR has all the subscriber numbers which are active.VLR has a temporary database of all active subscribers (on/off, location information)

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RF Fundamentals for Cellular Networks28

MSC MSCVLR

HLR

VLR

GSM Architecture

VLR [cont.]

MSC communicates with HLR for subscribers coming from different MSCs. If the subscriber is found valid, then it registers the subscriber in the VLR

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RF Fundamentals for Cellular Networks29

MS MSC HLR AUC

GSM Architecture

AUC – Authentication Centre

Authentication is a process by which a SIM is verifiedSecret data and the verification process algorithm are stored in AUCAUC is the element which carries out the verification of the SIMAUC is associated with the HLR

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RF Fundamentals for Cellular Networks30

GSM Architecture

EIR (Equipment Identity Register)

EIR is the Mobile Equipment Database which has a series of IMEIsMSC asks the Mobile to send its IMEIMSC then checks the validity of IMEI with the EIRAll IMEIs are stored in EIR with relevant classifications

EIRMSCMS

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RF Fundamentals for Cellular Networks31

BC Generates the billing statement for each subscriberBC may be directly connected to the MSC or through a mediation deviceMSC sends CDRs (Call Detail Records) to the BCAccording to the template of pulse rates and units set, BC creates a bill according to the destination called and the call duration

GSM Architecture

Billing Centre (BC)

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RF Fundamentals for Cellular Networks32

GSM Architecture

GPRS Network Architecture

Packet SwitchingMSC/VLR

GSM+GPRS

BSS withPCU

PSTN/ISDN

GPRSBackbone

SGSN

Internet

GGSN

GPRSGPRSMobileMobile

Circuit Switching

BSS

HLR

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RF Fundamentals for Cellular Networks33

MediationDevice(MD)

ConfigurationFault

PerformanceSecurity

Accounting

GSM Architecture

Operation and Maintenance

MD

OperationSystem

(OS)

Data Communications Network(DCN)

MSC/VLR SGSNGGSN

BSSHLRNetwork

Elements (NE):

TMN

Data Communications Network(DCN)

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RF Fundamentals for Cellular Networks34

GSM Interfaces and Protocols

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RF Fundamentals for Cellular Networks35

GSM Interfaces and protocols

GSM Interfaces

NMS

NSSBSS

BSCHLR/AC/EIRMSC/VLR

BTS

AbisInterface

AterInterface

AInterface

AirInterface

TC

Ater’Interface

O&MInterface

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RF Fundamentals for Cellular Networks36

GSM Interfaces and protocols

GSM Interfaces [cont.]

Abis interface PROPRIETARY13 kb/s traffic channelsone TRXSIG signaling channel / TRX16, 32 or 64 kb/s signaling rates

A interface OPEN64 kb/s traffic channels64 kb/s channels for X.25 NMS connection

Air interface OPEN13 kb/s traffic channels8 channels / TRXsome channels reserved for signaling blocking

Ater interface PROPRIETARY16 kb/s traffic channels64 kb/s CCS#7 signaling64 kb/s channels for X.25 NMS connection

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RF Fundamentals for Cellular Networks37

HLR GCR

GSM Interfaces and protocols

GSM Interfaces and Protocols

AuC

E

B C

D

F

G H

I

Abis

BCDEFGHI

PSTNISDN

BTS - BSC

MSC-VLR(SM-G)MSC-HLR

HLR-VLR(SM-G)MSC-MSC (SS7 basic) +

MAPMSC-EIRVLR-VLRHLR-AuCMSC-GCR

MSC-PSTN (SS7 basic) + TUP or ISUPMSC-ISDN

LAPD(ISDN type)

GSM Circuit-switching:

(BSSAP = BSSMAP + DTAP)

A BSC - MSC (SS7 basic) + BSSAP

BTSLAPDm

(GSM specific)Um (Radio) MS - BTS

BSCBSC

MSCMSC

BTS

PSTN /ISDN

MS

VLR VLR EIR

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RF Fundamentals for Cellular Networks38

GSM Interfaces and protocols

(Um) Air Interface

This is the interface between the mobile station and the Base station. The Air interface uses the Time Division Multiple Access (TDMA) technique to transmit and receive traffic and signaling information between the BTS and MS.The TDMA technique is used to divide each carrier into eight time slots. These time slots are then assigned to specific users, allowing up to eight conversations to be handled simultaneously by the same carrier.

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GSM Interfaces and protocols

Abis Interface

The A-bis interface is responsible for transmitting traffic and signaling information between the BSC and the BTS.The transmission protocol used for sending signaling information on the A-bis interface is Link Access Protocol on the D Channel (LAPD)

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RF Fundamentals for Cellular Networks40

GSM Interfaces and protocols

A Interface

A interface between the BSC and the MSC The A interface provides two distinct types of information, signaling and traffic, between the MSC and the BSC.The speech is transcoded in the TRC and the SS7 (Signaling system) signaling is transparently connected through the TRC or on a separate link to the BSC.

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RF Fundamentals for Cellular Networks41

Gc GGSN-HLR IP/SS7

LAPDm(GSM specific)

GSM Interfaces and protocols

GPRS Interfaces and Protocols

Gs

Gb

Um (Radio)

Gi GGSN-Data Network IP

MS

BSS - SGSN

Gr SS7SGSN-HLR

Gf SS7SGSN-EIRSGSN-MSC/VLR

GnSGSN-GGSN IP

IPSGSN-SGSN

MS - BTS

Gs

GfGr

Gn

Gn

Gc SS7

GSM Packet-switching (GPRS):

BSSGP

BSS withPCU

BSS withPCU

HLR EIR

DataNetwork

SGSN

GGSN

SGSN MSC

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RF Fundamentals for Cellular Networks42

GSM Interfaces and protocols

Position of Transcoding Unit (TRAU) [cont.]

Abis interface A interface

2 Mb link, each channel = 16 Kbps2 Mb link, each channel = 64 Kbps

MSC Site

MSC/VLRBSC

MSC/VLR

MSC/VLR

TRAUBTS

TRAUBTS

BTS TRAU BSC

BSC

BSC SiteBTS Site

BTS Site

BTS Site

BSC Site

BSC Site

MSC Site

MSC Site

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RF Fundamentals for Cellular Networks43

GSM Identities

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RF Fundamentals for Cellular Networks44

Identifications Concepts within a GSM Network

Subscriber Identifications

IMSI MS - ISDN

( International Mobile Subscriber Identity )

International IdentityE.212 compliantNature

( Mobile Station - Integrated Service Digital Network n° )

Directory Number ISDN type, E.164/E.213 compliant

MCC MNC MSINH1 H2 x x x ........ x x x

Mobile Country

Code

Mobile NationalCode

Mobile Subscriber Identity Numberincluding H1 H2 identifying the HLR

Format

Meaning

N° of digits

Examples

Characteristics

3 2 max 10

234

208 01

10

Stored in SIM module and AuC

CC NDC SNM1 M2 x x x x x x x x

CountryCode

National

Code*Destination

Subscriber Number( national identity )

including M1 M2 identifying the HLR

1 to 3 2 to 4

44 802 Cellnet GSM44 385 Vodafone GSM44 956 Mercury DCS44 973 Hutchinson DCS33

33

607/8

609

61 MC DU to 69 MC DU LYON01 MC DU to 09 MC DU MASSENA

11 xxxx to 3x xxxx LA FOURCHE

Allocated to an IMSI (by MMC) in the HLR

69 xx xx xx xx LYON94 xx xx xx xx MASSENA

?

France

U.K.

Orange

Cegetel

total up to 15

* instead of identifying a geographical area, the NDC identifies an OPERATOR

( national identity )NMSI

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Identifications Concepts within a GSM Network

Subscriber Identification

International Mobile Subscriber Identity (IMSI)IMSI is the primary identity of the subscriber within the mobile networkIMSI is permanently assigned to that subscriber.

Temporary Mobile Subscriber Identity (TMSI)TMSI is assigned to the subscriber by the GSM network.TMSI is assigned after the initiation of IMSI.TMSI can be used for sending backward and forward across the network to identify the subscriber.TMSI is automatically changed at regular intervals to protect the subscriber’s identity.TMSI is a local number and is always transmitted with the Location Area Identification (LAI) to avoid ambiguities.

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RF Fundamentals for Cellular Networks46

Identifications Concepts within a GSM Network

Subscriber Identification Module (SIM)

GSM PLMN routes calls and perform billing based on the identity of the subscriber rather than the mobile equipment being used. The identity of a subscriber is a removable SIM. A ”smart card” is one possible implementation of a SIM module.

SummaryIMSI is transmitted at initialization of the mobile equipment.TMSI is updated periodically by the PLMN.MSISDN is made up of a country code, a national code and a subscriber number.LAI identifies the current location of the subscriber.Subscriber Authentication Key is used to authenticate the SIM

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Identifications Concepts within a GSM Network

Mobile Equipment Identification

IMEI / IMEISV

( International Mobile Equipment Identity )

TAC FAC SNR SP

Type Approval CodeFinal Assembly Code

Serial NumbeR

(SPare)

Stored in the Equipment (Terminal)Used to replace the IMSI or TMSI if they cannot be used(example: emergency calls with no SIM card) or at the network's request (maintenance)Can be used to update the EIR database (if there is one)

( International Mobile Equipment Identity and Software Version number) (Phase 2+)

TAC FAC SNR SVN

Software Version Number

IMEI:

IMEISV:

...……...

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RF Fundamentals for Cellular Networks48

Identifications Concepts within a GSM Network

Equipment Identity Number

International Mobile station Equipment Identity (IMEI)IMEI is used to identify the mobile equipment.IMEI number is permanently stored in the mobile equipment. IMEI is sent by the MS to the MSC upon request by the MSC.IMEI can be used to identify mobile stations that are reported stolen or operating incorrectly.

Equipment Identity Register (EIR)A listing of the allowed IMEI is maintained by the PLMN’s in the EIR to validate

the mobile equipment.

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RF Fundamentals for Cellular Networks49

Identifications Concepts within a GSM Network

Geographic Identification

LAI: Location Area IdentificationMCC = Mobile Country CodeMNC = Mobile Network CodeLAC = Location Area Code

Use of LAI:PagingLocation Area UpdatingSecurity

CGI Cell Global IdentifierCI = Cell Identity

MCC MNC LAC CI

LAI

CGI

For GSM:

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RF Fundamentals for Cellular Networks50

Identifications Concepts within a GSM Network

Geographic Identification [cont.]

RAI: Routing Area IdentityMCC = Mobile Country CodeMNC = Mobile Network CodeLAC = Location Area CodeRAC = Routing Area Code

Use of RAI:PagingRouting Area Updating

MCC MNC LAC RAC

RAI

For GPRS:

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GSM Radio Interface

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RF Fundamentals for Cellular Networks52

Introduction

Importance of the Radio Interface

RADIO INTERFACE: essential part of GSM specifications because of:

Inter-PLMN COMPATIBILITY==> Complete Specification(to the nearest bit)

Very elaborate SPECTRUM EFFICIENCY optimization techniques:Reduction of INTERFERENCE to manage a large number of Mobiles per km²

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RF Fundamentals for Cellular Networks53

GMSK = Gaussian Minimum Shift Keying:

convolution of an MSK ramp (π/2 - width: 1 bit),by a Gaussian function:0-1 or 1-0 bit transition => smooth transition of ± π/2:

PROPERTIES:

Gradual transitions avoid the needto filter signal harmonics which are very weak

Spectrum efficiency ~ 1 bit/Hertz(270.8 kbits/200 kHz)

Modulation spectrum:==> To prevent catastrophic interference,it is essential to avoid usingadjacent frequencies in adjacent cells.

Introduction

GMSK Modulation

π/2

t

0-Tb

θ(t)

Tb

MSK

Tb/2-Tb/2

GMSK

dB0

-10-20

-30

-70

0 100 200 300 400-100-200 kHz

200 kHz

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RF Fundamentals for Cellular Networks54

Introduction

8-PSK Modulation

A new modulation Scheme : 8-PSK200 kHz Channel spacing:

unchangedSymbol rate unchanged

- 270.8k symbol/sBUT- 3 bits/symbol

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RF Fundamentals for Cellular Networks55

IntroductionTraffic and Signalling

Traffic: Information interchanged from user-to-user, after setting up the call, requiring dedicated radio resource allocation.In GSM, Traffic can be an interchange of SPEECH or DATA.

Signaling:Information interchanged (in some cases, without the user's

knowledge) between the Mobile Equipment and Network Machines.

Out of Call: required for managing mobiles, eg.: location updateDuring a Call: required for various reasons, eg.: handover,

access to a supplementary service, call release

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RF Fundamentals for Cellular Networks56

Switch-offSwitch-on

"Connected"

"Power Off"

"Idle"

Introduction

MS status (Circuit and Packet Switching Mode)

End of

transactionNetwork Access

Circuit Switching Mode (GSM)

MS not reachable

MS reachable

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RF Fundamentals for Cellular Networks57

"Idle" Attachment to

network

Detachment

Out of Time

Packet Tx or Rx

Deta

chmen

t or O

ut of

Tim

e

"Ready""Stand-by"

Introduction

MS status (Circuit and Packet Switching Mode) [cont.]

Packet Switching Mode (GPRS)

MS not reachable

MS reachable

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RF Fundamentals for Cellular Networks58

Introduction

Radio Resources

Typical Mobile - Network Transaction (GSM) :

Mobilepre-synchronization

"Idle" state "Connected" state

Network Access Out of callsignaling phase

TRAFFIC phase

Access

procedure

(Optional)

Dedicated Signaling Channels

Common Access

Channels

Common Broadcast Channels

Channels to be used

DedicatedTraffic

Channels

Main Tasks

&Types of

Inter-change

Frequency search

Timing Synchro

System Parameter Analysis

(Paging)

Access Request

Dedicated Channel Assignment

Same dedicated channel used for:- Authentication- Signaling:

.Location Updating. Short Messages. (Traffic Channel

Assignment)

Traffic

Signaling

Frequency

Monitoring

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RF Fundamentals for Cellular Networks59

Physical Channels: Time Multiple Access

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RF Fundamentals for Cellular Networks60

Frequencyaxis

Physical Channels: Time Multiple Access

Frequencies

UPLINKBand

MS -> BTS

DOWNLINKBand

(BTS ->MS)

900 bands

possible extension of GSM bands

(2 x 25 MHz: 124 carriers)

(2 x 35 MHz: 174 carriers)

1800 bands(2 x 75 MHz: 374 carriers)

MHz

MHz

200 kHz

890

935

960

915

880 1710

1785

1805

1880

915

960

925

ARFCN

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RF Fundamentals for Cellular Networks61

GSM 900 and GSM 1800 are twinsGSM 900 GSM 1800

• Frequency band 890 - 960 MHz 1710 - 1880 MHz

• Number of channels 124 (125) 372 (375)

• Channel spacing 200 kHz 200 kHz

• Multiplex technologies TDMA/FDMA TDMA/FDMA

• Mobile power 0.8 / 2 W 0.25 / 1 W

There are no major differences between GSM 900 and GSM 1800

Physical Channels: Time Multiple Access

GSM Bandwidth & Main Parameters Summary

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RF Fundamentals for Cellular Networks62

UPLINKBand

MS -> BTS

DOWNLINKBand

(BTS ->MS)

Physical Channels: Time Multiple Access

TDMA Frame

1 BTS (eg. 3 carriers)

Frequency spacing45 MHz in 90095 MHz in 1800

22

17

7

Cell"beacon”frequency

22

17

7

ARFCN

Frequencyaxis

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RF Fundamentals for Cellular Networks63

Physical Channels: Time Multiple Access

TDMA Frame [cont.]

1 BTS (eg. 3 carriers)

TDMA frame = 4.615 ms

1 "CHANNEL" (in 1 direction)

Same "CHANNEL" (if bidirectional)

time axis

Time slot (or burst window)

1 2 3 4 5 6 70 1 2 3 4 5 6 70 1 2 3 4 5 6 70

1 2 3 4 5 6 70 1 2 3 4 5 6 70 1 2 3 4 5 6 70

22

17

7

22

17

7

Time shift betweentransmit and receive: 3 TS

Frequencyaxis

UPLINKBand

MS -> BTS

DOWNLINKBand

(BTS ->MS)

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RF Fundamentals for Cellular Networks64

Physical Channels: Time Multiple Access

Normal Burst

TDMA frame = 4.615 ms

CHANNEL

time axis

guard time

Training sequence

577 µs

Time Slot (TS) or Burst Period (BP)

1 2 3 4 5 6 70 1 2 3 4 5 6 70 1 2 3 4 5 6 70

22

17

7

Burst

”Data” (114 symb)

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RF Fundamentals for Cellular Networks65

Physical Channels: Time Multiple Access

Normal Burst [cont.]

Training Sequences:8 different bit patterns, chosen so that:

They are easily recognizable (very accurate auto-correlation function)

They are easily distinguishable from one another (little correlation between each pattern)

Stealing Flags:

26 symb

"Stealing Flags“ GMSK ONLY

S = 0

S = 1

57 symb 57 symb+

+

Traffic (or Signaling out of call)

Signaling during call

Training sequence

57 symb 57 symb

GMSK: 1 bit / symbol

8-PSK: 3 bits / symbol

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RF Fundamentals for Cellular Networks66

Logical Channels

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RF Fundamentals for Cellular Networks67

Logical Channels

Analogy of Physical & Logical channels

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RF Fundamentals for Cellular Networks68

Logical Channels

Mapping with the Physical Channels

1 2 3 5 6 7TS

Frequency Correction

Timing synchronization

System information

Subscriber paging

Response to access request

Out of call signaling -> MSi

Power Control -> MSi

Traffic samples -> MSj

In call signaling -> MSj

BTS MS

Example: "Beacon" frequency, downlink:

FCCH

SCH

BCCH

PCH

AGCH

SDCCH

SACCH

TCH

FACCH

0 4

FCCH

BCCH

PCH

AGCH

SDCCH

SACCH

TCH

FACCH

SCH1

2

3

4

Traffic sample decoding

In call signaling receipt

Power Control

Out of call signaling receipt

Mobile presynchronization

Subscriber paging

Response to access request

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RF Fundamentals for Cellular Networks69

Logical Channels

Mapping with the Physical Channels [cont.]

SACCH FACCH

PCH RACH SDCCH + SACCHAGCH TCH / FACCH + SACCH

1 2 3 4 5

Use of Logical Channelsduring transactions between Network and MS

1 If Terminating Call (TC), the MS must be paged P= Paging

2 The MS accesses the PLMN network RA = Random Access

3 The Network allocates (or grants)a dedicated channel to the MS for signaling AG = Access Grant

4 Signaling interchange (SDCCH and SACCH).If necessary, the Network allocates a Traffic channel to the MS

5 Traffic interchange (speech or data) on the TCH, with associated signaling in a SACCH (background tasks) and an FACCH if required

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RF Fundamentals for Cellular Networks70

Logical Channels

Time Division Multiplexing on a Physical Channel

0 1 2 3 4 5 6 7TS

1 2 3 4 5 6 7 8 9 10 20 30 40 50 0 1

1 2 3 4 5 6 7 8 9 10 20 232425

Multiframe: 51 frames (= 235 ms approx.)

"TRAFFIC" type Multiframe:

"SIGNALING" type Multiframe:

1 TDMA frame = 120/26 ms (4.615 ms)

1 2 3 4 5 6 7 8 9 10 20 232425 0

Multiframe: 26 frames = 120 ms

GSM (Circuit Switching)

0

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RF Fundamentals for Cellular Networks71

1 2 3 4 5 6 7 8 9 10 20 30 40 5051 0

Multiframe : 52 frames (= 240 ms)

52 Frame - Multiframe on PDCH:

Logical Channels

Time Division Multiplexing on a Physical Channel [cont.]

0 1 2 3 4 5 6 7TS

1 TDMA frame = 120/26 ms (4.615 ms)

GPRS (Packet Switching) (1)

Block 0 Block 1 Block 2 Block 3 Block 4 Block 5 Block 6 Block 7 Block 8 Block 9 Block 10 Block 11

0

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RF Fundamentals for Cellular Networks72

1 2 3 4 5 6 7 8 9 10 20 30 40 5051 0

Multiframe : 52 frames (= 240 ms)

Logical Channels

Time Division Multiplexing on a Physical Channel [cont.]

GPRS (Packet Switching) (2)

Block 0 Block 1 Block 2 Block 3 Block 4 Block 5 Block 6 Block 7 Block 8 Block 9 Block 10 Block 11

TFI: Temporary Flow Identifier:created when data has to be transmitted and until all data have been transmittedBSN: Block Sequence Number

Data Flow to User BData Flow to User A Data Flow to User C

TFI 28 TFI 2 TFI 19

TFI =28

Data

BSN =21

TFI =28

Data

TFI =28

Data

BSN =22 BSN =23

TFI =28

Data

BSN =24

TFI =28

Data

TFI = 2

Data

BSN =25 BSN =12

TFI = 2

Data

BSN =13

TFI = 2

Data

TFI = 2

Data

BSN =14 BSN =15

TFI = 19

Data

BSN =75

TFI = 19

Data

TFI = 19

Data

BSN =76 BSN =77

0

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RF Fundamentals for Cellular Networks73

Logical Channels

Channel Mapping

0 1 2 3 4 5 6 7TS

0 1 2 3 4 5 6 7

0 1 2 3 4 5 6 7

0 1 2 3 4 5 6 7

"Beacon" frequency

Otherfrequencies

FCCH + SCH + BCCH + PCH + AGCH

uplink direction

downlink direction

RACHTS 0: :

TS 1: 8 SDCCH/8 + 8 SACCH/8 in each direction

other TSs: TCH (+ SACCH / FACCH) in each direction

BTS

Examples: Number of Frequencies Number of TCH Channels ERLANGS (formula B, blocking 2%)

3 22 154 30 22

5 38 29

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RF Fundamentals for Cellular Networks74

Logical Channels

Channel Mapping [cont.]

0 1 2 3 4 5 6 7TS

0 1 2 3 4 5 6 7

”Beacon”frequency

Otherfrequency

(FCCH + SCH + BCCH) + (PCH + AGCH + RACH) + (4 SDCCH/4 + 4 SACCH/4)TS 0 of beaconfrequency:

other TSs: TCH + SACCH (+ FACCH))BTS

Structure of the Multiframe in "Time Slot" 0 (Config. n° 1: combined BCCH):

DOWNLINK (Multiframes of 51 frames)

F = FCCH S = SCH B = BCCH C = CCCH (PCH or AGCH) R = RACH Dn/An = SDCCH / SACCH/4

UPLINK

F S B C F S F S F S -F SC C D0 D1 D2 D3 A0 A1

F S B C F S F S F S -F SC C D0 D1 D2 D3 A2 A3

R R R RR R R R R R R RR R R R R R RR R R R R RR RD3 A2 A3 D0 D1 D2

R R R RR R R R R R R RR R R R R R RR R R R R RR RD3 A0 A1 D0 D1 D2

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RF Fundamentals for Cellular Networks75

Logical Channels

Timing Advance

BTS

MS

Pre-synchronized

BTSTxRx

Tx

RxMS1

TS iTS i

Timing Advance measured by BTS

Access Burstforward propagation time

BTSTxRx

Tx

RxMS1

TS iTS i

(after TA)- TA

forward propagation time

return propagation time

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RF Fundamentals for Cellular Networks76

Logical Channels

Subscriber Paging

The Network knows the LOCATION AREA (LA) in which the mobile is travelling. An LA can cover more than one cell.

The PCH channel is used to signal a Call to a mobile. The same "Paging" message is transmitted to all cells in the area (shaded areas above).

Only a mobile in "IDLE" state (pre-synchronized) can respond to paging.

BSC

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RF Fundamentals for Cellular Networks77

Logical Channels

Access to the Network

An access request is always initiated by the MS(when an MS is called, the "paging" procedure is used).The RACH channel is used to transmit the "CHANNEL REQUEST" message.

The channel is called "random" since the mobile chooses the call TSsrandomly.This means that there is a risk of collision.

Collisions are resolved by retransmission after pseudo-random delays.

MS1

MS5

MS2 MS3 MS4 MS4

MS5

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RF Fundamentals for Cellular Networks78

BCCH(Broadcast Control Channels)Downlink Only.Broadcast information of the serving cell (System Information).Transmitted on timeslot zero of BCCH carrier.Read only by idle mobile at least once every 30 secs.

SCH (Synchronization Channels)Downlink OnlyCarries information for frame synchronization.Contains frame number and BSIC (Base Station Identity Code).

FCCH (Frequency Correction Channels)Downlink Only.Enable MS to synchronize to the frequency.

Logical Channels

BCH (Broadcast Channels)

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RF Fundamentals for Cellular Networks79

RACH(Random Access Channel)Uplink only.Used by the MS when making its first access to the Network.The reason for access could be initiation of a call or a page response.

AGCH (Access Grant Channel)Downlink only.Used for acknowledgement of the access attempt sent on RACH.Used by the network to assign a signaling channel upon successful decoding of access bursts.

PCH (Paging Channel)Downlink only.The network will page the MS ,if there is a incoming call or a short Message.It contains the MS identity number, the IMSI or TMSI.

Logical Channels

CCCH (Common Control Channel)

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RF Fundamentals for Cellular Networks80

SDCCH (Stand-alone Dedicated Control Channel)Uplink and Downlink.Used for call setup, authentication, ciphering location update and SMS.

SACCH (Slow Associated Control Channel)Downlink and Uplink.Used to transfer signal while MS have ongoing conversation on traffic or while SDCCH is being used.On the forward link, the SACCH is used to send slow but regularly changing control information to each mobile on that ARFCN, such as power control instructions and specific timing advance instructionsThe reverse SACCH carries information about the received signal strength and quality of the TCH, as well as BCH measurement results from neighboring cells.

FACCH (Fast Associated Control Channel)Downlink and uplink.Associate with TCH only.It is used to send fast message like hand over message.Work by stealing traffic bursts.

Logical Channels

DCCH (Dedicated Control Channel)

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RF Fundamentals for Cellular Networks81

Logical Channels

Logical Channels Summary

Abbreviation Name Type Role/Info carried Burstformat

Frequency Correction CHannel MP -- > MS Frequency for synthesizer alignment Frequency

Synchronization CHannel MP -- > MS Timing sync - Frame N° Sync

Broadcast Common CHannel MP -- > MS Broadcastsystem information Normal

Random Access CHannel PP < -- MS Network access (Channel request) Access

Paging CHannel PP -- > MS Subscriber paging (paging) Normal

Access Grant CHannel PP -- > MS SDCCH channel assignment (Imm.Ass) Normal

Cell Broadcast Control CHannel MP -- > MS Broadcast short messages (SMS/CB) Normal

Notification CHannel MP -- > MS Accessibilitynotification (VGCS/VBS) Normal

DedicatedSignaling

(out of call)

Standalone Dedicated Ctrl CH. PP < ----> Out of call signaling Normal

Slow Associated Control CH. PP < ----> Measurements - P Contr. - Timing adv. Normal

Traffic/ Full Rate CHannel PP < ----> 13 kbit/s traffic Normal

Traffic/ Half Rate CHannel PP < ----> 5.6 kbit/s traffic (phase 2) Normal

Slow Associated Control CH. PP < ----> Measurements - P Contr. - Timing adv. Normal

Fast AssociatedControl CH. PP < ----> In call signaling (cycle stealing) Normal

Family

FCCHSCH

BCCH

Broadcast

CommonControl

DedicatedTraffic + Signaling

(during call)

RACHPCH

AGCHCBCHNCH

SDCCHSACCHTCH/FTCH/HSACCHFACCH

Abbreviation Name Type Role/Info carried Burstformat

Frequency Correction CHannel MP -- > MS Frequency for synthesizer alignment Frequency

Synchronization CHannel MP -- > MS Timing sync - Frame N° Sync

Broadcast Common CHannel MP -- > MS Broadcastsystem information Normal

Random Access CHannel PP < -- MS Network access (Channel request) Access

Paging CHannel PP -- > MS Subscriber paging (paging) Normal

Access Grant CHannel PP -- > MS SDCCH channel assignment (Imm.Ass) Normal

Cell Broadcast Control CHannel MP -- > MS Broadcast short messages (SMS/CB) Normal

Notification CHannel MP -- > MS Accessibilitynotification (VGCS/VBS) Normal

DedicatedSignaling

(out of call)

Standalone Dedicated Ctrl CH. PP < ---- > Out of call signaling Normal

Slow Associated Control CH. PP < ---- > Measurements - P Contr. - Timing adv. Normal

Traffic/ Full Rate CHannel PP < ---- > 13 kbit/s traffic Normal

Traffic/ Half Rate CHannel PP < ---- > 5.6 kbit/s traffic (phase 2) Normal

Slow Associated Control CH. PP < ---- > Measurements - P Contr. - Timing adv. Normal

Fast Associated Control CH. PP < ---- > In call signaling (cycle stealing) Normal

Family

FCCHSCH

BCCH

Broadcast

CommonControl

Channels

DedicatedTraffic + Signaling

(during call)

RACHPCH

AGCHCBCHNCH

SDCCHSACCHTCH/FTCH/HSACCHFACCH

GSM (circuit switching)

CCCH

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RF Fundamentals for Cellular Networks82

Logical Channels

Multiple CCCH

Need and transported information

Why a such feature:Due to the increasing signaling load of cells with high CS and PS traffic throughput, the Common Control CHannel (CCCH) the channel has reached its throughput limit: a second CCCH is needed

As seen in previous table, CCCH carries important logical channels for call establishment and MS localization:- Uplink : RACH, - Downlink: AGCH and PCH,

CCCH

Cell with high CS and PS trafficBase Station

CCCHAir

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RF Fundamentals for Cellular Networks83

Logical Channels

Multiple CCCH [cont.]

BCCH forCELL INFORMATION

CCCH 2 CCCH 4 CCCH 6 CCCH 8

CCCH 7CCCH 5CCCH 3CCCH 1 CCCH 9TS0

Fram

e 1

TS0

Fram

e 11

TS0

Fram

e 21

TS0

Fram

e 31

TS0

Fram

e 41

FCCH

SCH

FCCH

SCH

FCCH

SCH

FCCH

SCH

FCCH

SCH

TS0

Fram

e 51

51-multi-frame

51 TS multi-frame structure

A 51-multiframe describes the TS0 organization. A cell configured with the BCC mode conveys 9 CCCHs.

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RF Fundamentals for Cellular Networks84

Logical Channels

Multiple CCCH [cont.]

TS0 content;

Example of implementation

TS0

CCCH 1 AGCHCCCH 2 AGCHCCCH 3 AGCHCCCH 4 AGCHCCCH 5 PCHCCCH 6 PCHCCCH 7 PCHCCCH 8 PCHCCCH 9 PCHRACH

BCCHSCHFCCH

CCCH

CCCH 7

CCCH 6

CCCH 8

CCCH 9

CCCH 5

CCCH 4

CCCH 3

CCCH 2

CCCH 1

BCCH

51-multiframe

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RF Fundamentals for Cellular Networks85

Logical Channels

Multiple CCCH [cont.]

Implementation on the air interface:

To increase the signaling bandwidth on the Air interface, 3GPP defines up to 4 time slots to carry the CCCH information (TS0, TS2, TS4 and TS6). The GSM solution supports multiple CCCH on TS0 and TS2 in G2 BSCs and MX BSCs.

Duplicationof the

System Information SI messages

The cell paging capacity reaches up to 60 paging messages per second.

With multiple CCCH,the System Information message

is broadcasted on bothTS0 and TS2.

TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7

SI

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RF Fundamentals for Cellular Networks86

Speech Processing

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RF Fundamentals for Cellular Networks87

ChannelEncoding

Speech Processing

Radio Channel Generation

Speech Digitization

and Encoding

InterleavingBurst

Formatting Encryption Modulation Transmission

ReceptionDemodulationDecryptionBurst

DeformattingDe-

interleavingChannelDecoding

SpeechDecoding

POWER CONTROL

260 bits / 20 ms:13 kbit/s 22.8 kbit/s(per channel)

270.8 kbit/sFR Speech frames:

...……...

(modulated)

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RF Fundamentals for Cellular Networks88

Speech Processing

Radio Channel Generation [cont.]

Bit Rate on Um interfaceGSM circuit-switched

Full Rate (FR) / Enhanced Full Rate (EFR) speech: 13 Kbps / 12.2 Kbps Half rate (HR) speech: 5.6 KbpsAdaptive Multi-Rate (AMR): variable speech coding rate from 4.75 to 12.2

GSM packet-switched (GPRS): 4 Coding Schemes (CSs)

Rate Code RateCS1 9.05 kb/s 0.5CS2 13.4 kb/s 0.66CS3 15.6 kb/s 0.75CS4 21.4 kb/s 1.0GMSK (1 bit per symb)

GPRSGPRSGMSK

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RF Fundamentals for Cellular Networks89

EGPRS : 9 Modulation and Coding Schemes (MCSs)

8-PSK

8-PSK (3 bits per symb)

Rate CodeMCS5 22.4 kb/s 0.37MCS6 29.6 kb/s 0.49MCS7 44.8 kb/s 0.76MCS8 54.4 kb/s 0.92MCS9 59.2 kb/s 1.00

GMSK (1 bit per symb)

Rate Code RateMCS1 8.8 kb/s 0.53MCS2 11.2 kb/s 0.66MCS3 14.8 kb/s 0.80MCS4 17.6 kb/s 1.00

EGPRSEGPRS

Speech Processing

Radio Channel generation [cont.]

GMSK

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RF Fundamentals for Cellular Networks90

Speech Processing Radio Channel generation [cont.]

Speech coding: Adaptive Multi-Rate (AMR)Voice quality benefits:

It provides the best voice quality according to radio conditionsIt increases in the same time the offered capacity due to the provision of half-rate channels2 extensive sets of “codec modes”:

6 possible rates in HR channels: 4.75, 5.15, 5.9, 6.7, 7.4, 7.95 Kbps8 possible rates in FR channels: 4.75, 5.15, 5.9, 6.7, 7.4, 7.95, 10.2,12.2 Kbps

Channel coding = speech protectionSpeech coding = speech information

Medium radioconditions

Bad radioconditions

Good radioconditions

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Speech Processing Discontinuous Transmission

Principles (Mandatory in the mobile and on the BTS uplink path):Discontinuous Transmission (DTX): reduced rate transmission (~ 500 bit/s) during silencesVoice Activity Detection (VAD): Measurement of signal strength for detecting moments of silence (neither speech nor tone) - adaptive-threshold FILTERComfort Noise Generation:In receive mode, reconstitution of background noise based on thecharacteristics received in Silence Descriptor (SID) frames, to avoid giving the receiving user the impression that the line has been cut off

SS S S S S S S S S

480 ms

BTS

TRAU --> BTS

MS <--> BTS

Speech

Silence

SID Frame

TRAU

MS

...……...

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GPRS Overview

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General Packet Radio Service

End User (compared to 9.6 data & HSCSD): Service differentiation opportunitiesAlways connectedPay per bit transferredHigher speedsFaster session set up

Operator:Service differentiation opportunitiesCatch Corporate business (including speech)Additional revenue for contentGet more use out of network investmentPath to 3rd Generation

New Applications & Uses Feasible

GPRS

Basics

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RF Fundamentals for Cellular Networks94

Packet SwitchingMSC/VLR

GSM+GPRS

BSS withPCU

PSTN/ISDN

GPRSBackbone

SGSN

Internet

GGSN

GPRSGPRSMobileMobile

Circuit Switching

BSS

HLR

GPRS

Network Architecture

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RF Fundamentals for Cellular Networks95

StrengthsIP ConnectivityPacket DataAlways “ON” AbilityCompatibilityOther Advantages

GPRS

Strengths and Weakness

WeaknessLimited ResourcesLow practical speedSub optimal ModulationTransit DelaysNo Store & Forward

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RF Fundamentals for Cellular Networks96

SW Upgrade in MSC/VLR and HLR

GPRS capable MS

MSC

ISDN/PSTNNetwork

EIR

HLR/AuC

SMSC

BSCBTS

Um

HW and SW Upgrade in BSC

SW Upgrade in BTS

Internet or

Corporate LAN

GPRS Core

Network

GPRS Core Network Elements

New Services (APNs. WAP)

GPRS

GPRS H/W and S/W upgrade from GSM

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RF Fundamentals for Cellular Networks97

TRX 1

TRX 2

CCCH TS TS TS TS TS TS TS

TS TS TS TS TS TS TSTS

Dedicated GPRS

Capacity

Circuit Switched Territory

Packet Switched Territory

Territory border moves dynamically based on

Circuit Switched traffic load

Circuit Switched capacity not affected

by introducing GPRS

Circuit Switched traffic has priority

In each cell Circuit Switched & Packet Switched territories are defined

Territories consist of consecutive timeslots

GPRS

Territory Method

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RF Fundamentals for Cellular Networks98

CS1 & CS2: implemented in BTS without HW changeCS3 & CS4: future release (with added HW in the BTS’s)

More DataLess ErrorCorrection

GPRS

Coding Schemes and Multiple TS

Channel Coding Scheme CS1 CS2 CS3 CS4Single TS Data Rate 9.05 kbit/s 13.4 kbit/s 15.6 kbit/s 21.4 kbit/s8 TS Data Rate 72.0 kbit/s 107.2 kbit/s 124.8 kbit/s 171.2kbit/s

GPRS release 1

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RF Fundamentals for Cellular Networks99

GPRS

GPRS Specific Parameters

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RF Fundamentals for Cellular Networks100

Module Summary

You should now be able to:

Describe the history of GSM and other Communication SystemsList the GSM and other Cellular Network featuresDescribe the GSM architectureIdentify the GSM interfaces and protocolsList the radio interfaces in a GSM networkDescribe the Physical ChannelsDescribe the Logical ChannelsExplain the steps for speech processingDescribe GPRS architecture

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RF Fundamentals for Cellular Networks101

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RF Fundamentals for Cellular Networks102

End of ModuleGSM/GPRS Overview

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GSM Advanced Concepts

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RF Fundamentals for Cellular Networks2

Module Objectives

Upon completion of this module, you should be able to:

Explain GSM Call flow scenarioExplain Mobile Origination and Mobile Terminating callsExplain the types of Handovers in GSM networkDescribe Adaptive Multi Rate (AMR) coding and its benefitsDescribe the benefits of Power control in GSMExplain the techniques involved in Frequency Planning

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RF Fundamentals for Cellular Networks3

Course Outline

1. Basic RF Engineering

2. GSM/GPRS Overview

3. GSM Advanced Concepts- GSM Call flow- GSM Handover- AMR- Power Control- Frequency Planning

4. Network Dimensioning

5. Network Characteristics

6. RF Optimization and Case Studies

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RF Fundamentals for Cellular Networks4

GSM Call flow

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RF Fundamentals for Cellular Networks5

GSM Call flow

Call Processing

MOBILE

CHANNEL REQUESTIMMEDIATE ASSIGNMENT

CM SERVICE REQUEST

AUTHENTICATION REQUESTAUTHENTICATION RESPONSE

CIPHERING MODE CMDCIPHERING MODE COMPLETE

SET UPCALL PROCEEDING

ASSIGNMENT CMDASSIGNMENT COM

ALERTING

CONNECTCONNECT ACK

SET-UP of anRR CONNECTION (MO)

SERVICE INDICATION

AUTHENTICATION

TRANSITION to CIPHERING MODE

START of CALL

TRAFFIC CHANNEL

CALL CONFIRMATION

CALL ACCEPTED

ASSIGNMENT

...……...

GSMNetwork

PSTN or ISDN

Typical Sequence in Call Origination

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RF Fundamentals for Cellular Networks6

Level 3 GSM Procedures

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RF Fundamentals for Cellular Networks7

Level 3 GSM Procedures

Setting up the Radio Connection

SDCCH N°

MM CM_SERVICE REQUEST

SDCCH N°

RACH

MSCHANNEL REQUEST

IMMEDIATE ASSIGN.

BTS BSC MSC

Um A bis A

CHANNEL REQUIRED

ASSIGNMENT of anSDCCH Channel

CHANNEL ACTIV.

ACTIVATION ofChannel indicated CHANNEL ACTIV. ACK

AGCHCONNECTION to the

SDCCH Channel

SDCCHSABM ESTABLISH INDIC.

SCCP CONNECT REQUEST

SCCP CONNECT CONFIRM

T3101

T9105

IMM. ASSIGN. CMD

RR

RR

MM CM_SERVICE REQUEST

RR

BTSM

BTSM

BTSM

SDCCH UA

MM CM_SERVICE REQUEST

MM CM_SERVICE REQUEST

...……...

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RF Fundamentals for Cellular Networks8

Level 3 GSM Procedures

Security Functions

Authentication

Checks that the Mobile Station is the required station and not an intruder

Ciphering

All Information (Signaling, Speech and Data) is sent in ciphered mode, to avoid monitoring and intruders (who could analyze signaling data)

Temporary Identification (TMSI)

Used instead of IMSI for safety reason: “tracing” an MS is not so easy on the air interface

Allocated at least when the MS is registered in a new VLR(but can be allocated at each transaction)

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RF Fundamentals for Cellular Networks9

Level 3 GSM Procedures

Security Functions [cont.]

SIM card

A3

AuCRadio Channel

A8

Ki Ki

Random number selection

A3

A8

A3 A3

A8A8

A5A5

= ?

Identification key (128 bits)

RAND (128 bits)

RAND

Signed ref. (32 bits) SRES SRES

Cipher command

OK

Kc: Cipher key

for the call (64 bits)Kc

Speech - Data - Signaling Speech - Data - SignalingCiphered data

Ciphering/Deciphering Ciphering/Deciphering

BTS

A5A5

...……...

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RF Fundamentals for Cellular Networks10

Level 3 GSM Procedures

Security Functions [cont.]

MS BTS HLRMSC / VLR AuC

SIM cardIMSI

KiA3A8

RAND

SRES

Kc

CipheringFunction

A5

CipheringFunction RAND

SRESKc

RANDSRES

Kc

Kc

= ?

TripletsTriplet

Generation

RAND

Ki

KiIMSI

A4Ki

IMSI

(ciphered)

A4

A2

SpeechData

Sign°

SpeechData

Sign°

(ciphered)

RAND

SRES

A8A3Ki

IMSI

IMSIA8A3Ki

IMSIIMSITMSI

A5 Kc

TMSI

A5

Kc

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RF Fundamentals for Cellular Networks11

Level 3 GSM Procedures

Mobile Originating Call (MO)

MOBILE

CHANNEL REQUESTIMMEDIATE ASSIGNMENT

CM SERVICE REQUEST

AUTHENTICATION

CIPHERING

SET UP

ASSIGNMENT CMDASSIGNMENT COM

ALERTING

CONNECTCONNECT ACK

VEA: Very Early Assignment:

CALL CONFIRMATION

CALL ACCEPTED

or SET UP if VEA

ASSIGNMENT CMDASSIGNMENT COM

1/2 OACSU:

ASSIGNMENT CMDASSIGNMENT COM

OACSU complete

Immediate assignment of a TCH:No authentication or ciphering(Signaling carried on FACCH)

EA: Early Assignment:TCH allocated BEFORE call confirmation

omitted if VEA

TCH allocated after called party ringing

TCH allocated after called party answer

...……...

GSMNetwork

PSTN or ISDN

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RF Fundamentals for Cellular Networks12

Level 3 GSM Procedures

Mobile Originating Call (MO) [cont.]

TCH allocation

CHANNEL ACTIV.

DATA REQUEST

MS BTS BSC MSC/VLR

A bis A

CALL PROCEEDING

DATA INDICATION

SCCP DATASCCP DATA

SET - UP

ASSIGNMENT CMD

PHYS. CTX REQ. SCCP DATA CIC selection

AUTHENTICATION

CIPHERING

CHANNEL REQUEST

IMMEDIATE ASSIGN.RACH

AGCHSDCCH N°

SDCCH

Ciphered

SABMUA

ESTABLISH INDIC. SCCP CONNECT REQUEST

SCCP CONNECT CONFIRM

SDCCH

PHYS. CTX CONF.TCH

CHANNEL ACTIV. ACK

DATA REQUESTAssignment Cmd

TCH

T3107RELEASE REQ * Local End

Um

RR

RR

CM Serv. Req.MMCM Serv. Req.MM

CM Serv. Req.MM

CC

CC

Set - UpCC

Call Proceeding.CC Call Proceeding.CC

Set - UpCC

Assignment RequestBSSMAPBTSMBTSM

BTSMBTSM

RRRR

*: if no answer from the MS

IAMISUP

...……... PSTN or ISDN

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RF Fundamentals for Cellular Networks13

Level 3 GSM Procedures

Mobile Originating Call (MO) [cont.]

Off-hooking

Called P. ringing

ConnectConnect

Alerting

Assign. compl.Assign. compl.

DATA REQUEST

MS BTS BSC MSC/VLR

Um A bis A

ALERTING

DATA INDICATION

SCCP DATA

SCCP DATAASSIGNMENT COMPL.

RF CHANNEL REL.

SCCP DATA

FACCH SABMUA

ESTABLISH INDIC.

RF CHANNEL REL. ACK

DATA REQUESTCONNECTSCCP DATA

ACM

ANM

DATA IND.CONNECT ACK ConnectAck

CONVERSATION PHASE

Alerting

ConnectAck

...……... PSTN or ISDN

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RF Fundamentals for Cellular Networks14

Level 3 GSM Procedures

Mobile Terminating Call (MT)

GMSC

VMSC VLR

HLR

1

4

5

6

7

8

2

...……...

PSTN

PLMN9

Signalling

Traffic

1 Called party number: MSISDN 2 Detection of a mobile number, call directed to the PLMN concerned3 HLR interrogation: transmission of the mobile MSISDN4 VLR interrogation: IMSI used5 Temporary routing number allocation by VLR: MSRN (roaming number)6 MSRN forwarded to the GMSC7 Call rerouted to the visited MSC8 The VMSC asks for paging information and the VLR replies9 Subscriber paging with TMSI

3

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RF Fundamentals for Cellular Networks15

Level 3 GSM Procedures

Mobile Terminating Call (MT) [cont.]

MOBILE

CHANNEL REQUESTIMMEDIATE ASSIGNMENT

PAGING RESULT

AUTHENTICATION REQUESTAUTHENTICATION RESPONSE

CIPHERING MODE CMDCIPHERING MODE COMPLETE

SET UPCALL CONFIRMED

ASSIGNMENT CMDASSIGNMENT COM

ALERTINGCONNECT

CONNECT ACK

SET-UP of anRR CONNECTION (MT)

SERVICE INDICATION

AUTHENTICATION

TRANSITION to CIPHERING mode

START OF CALL

TRAFFIC CHANNEL

CALL CONFIRMATION

CALL ACCEPTED

ASSIGNMENT

PSTN or ISDN

PAGING REQUEST

...……...

GSMNetwork

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RF Fundamentals for Cellular Networks16

Level 3 GSM Procedures

Example of an International Call

GMSC

PSTN

VMSC VLR

HLR

Visited PLMN

interrogation

Home PLMN

COUNTRY 1COUNTRY 2

COUNTRY 3

Incoming

Incoming

Outgoing

Outgoing

International SCCPGateways...……...

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RF Fundamentals for Cellular Networks17

Level 3 GSM Procedures

Location Updating

GeneralThis procedure is always initiated by the Mobile Station and involves providing the VLR (and HLR if required) with its current position.

The visited VLR stores the Location Area (LA).

The LA n° (LAI) received is updated dynamically in the SIM non-volatile memory.

Normal Location UpdateWhen the mobile is switched on without having stored the LAI (e.g.: initial use of SIM).

When the mobile is switched on in an LA different from the LA stored in the SIM.

When the pre-synchronized mobile moves from one LA to another (same or different VLR).

Periodic Location UpdateWhen the SIM internal counter overflows (based on BCCH broadcasted value)

(This counter is automatically incremented by the mobile when it is switched on)

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RF Fundamentals for Cellular Networks18

Level 3 GSM Procedures

Location Updating [cont.]

MOBILE

CHANNEL REQUESTIMMEDIATE ASSIGNMENT

LOCATION UPDATING REQUEST old TMSI or IMSI

AUTHENTICATION REQUESTAUTHENTICATION RESPONSE

CIPHERING MODE CMDCIPHERING MODE COMPLETE

LOCATION UPDATING ACCEPT new

TMSI REALLOCATION COMPLETE

CHANNEL RELEASE

Set-up of an RR Connection (MO)

Service Indication

Authentication (*)

Transition toCiphering Mode (*)

Allocation of a newTemporary Identification

RR Connection release

TMSI

...……...

GSMNetwork

(*) option

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RF Fundamentals for Cellular Networks19

Level 3 GSM Procedures

Location Updating [cont.]

RACH

AGCH

SDCCH

CHANNEL REQUEST

IMMEDIATE ASSIGN.

CHANNEL REQUIRED

CHANNEL ACTIV.

CHANNEL ACTIV. ACK

SABM

UA

ESTABLISH INDIC. SCCP CONNECT REQUEST

SCCP CONNECT CONFIRM

IMM. ASSIGN. CMD

MS BTS BSC MSC

Um A bis A

VLR

SCCP DATADATA REQUESTLOCATION UPDATING

ACCEPT

TMSITMSI REALLOC COMPLETEDATA INDICATION SCCP DATA

HLR

UPDATE LOCATION AREA UPDATE LOCATION

UPDATE LOCATION ACC

INSERT SUBSCR. DATA

LOC. AREA UPD. ACC.INSERT SUB. DATA ACK

TMSI Alloc.

RR

RR

MM

Loc. Upd. Req.MM

RR

BTSM

BTSM

BTSM

MAP MAP

MAP

MAP

MAPMAP

MM

TMSI Realloc. compl.MMTMSI Realloc. compl.MM

Loc. Upd. Req.MM Loc. Upd. Req.MM Loc. Upd. Req.MM

Loc. Upd. Acc.MMLoc. Upd. Acc.MM

...……...

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RF Fundamentals for Cellular Networks20

GSM Handover

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RF Fundamentals for Cellular Networks21

Cell 1 Cell 2

Handover is a GSM feature by which the control/communication of a Mobile is transferred from one cell to another if certain criteria’s are met. It is a network initiated process.

GSM Handover

Handover

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RF Fundamentals for Cellular Networks22

Receive Quality (RXQUAL) on uplink and downlinkReceive Signal Strength (RXLEV) on uplink and downlinkDistance (Timing Advance)Interference LevelPower Budget

GSM Handover

Criteria for Handover

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RF Fundamentals for Cellular Networks23

BSC process the measurements reported by Mobile and the BTS

BTS

BTS

BTS

BTS

BTS

BTS

Mobile has measurements of six neighbors

GSM Handover

Handover Decision

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RF Fundamentals for Cellular Networks24

BSS performs averaging function on these measurements every SACCH frame (480ms)

Handover Decision algorithm is activated after a set number of SACCH frame periods by comparison against thresholds

GSM Handover

Handover Decision [cont.]

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RF Fundamentals for Cellular Networks25

INTRA-CELL HandoversINTER-CELL HandoversINTRA-BSC HandoversINTER-BSC HandoversINTER-MSC Handovers

GSM Handover

Types of Handovers

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RF Fundamentals for Cellular Networks26

C0

C1

GSM Handover

Intra-Cell Handover

Handover between timeslots of same frequencyHandover between different frequencies of the same cell (to reduce interference)MSC is not aware about this

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RF Fundamentals for Cellular Networks27

Handover between cells of the same BTS

BTSCell 1 Cell 2

GSM Handover

Inter-Cell Handover

MSC is told about Handover (HO)BTS -> BSC -> MSC

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RF Fundamentals for Cellular Networks28

MSC BSC

BTS

BTS

This HO takes place if the cell to which handover is to be done belongs to the same BSC

GSM Handover

Intra-BSC Handover

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RF Fundamentals for Cellular Networks29

MSC

BSC BTS

BTSBSC

The MSC is completely involved in this Handover

GSM Handover

Inter-BSC Handover

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RF Fundamentals for Cellular Networks30

BSC

BSC

MSC

MSC

BTS

BTS

GMSC/PSTN/

Backbone

In this case the handover takes place through the interconnecting element which can be GMSC or PSTN or private Backbone between the MSCs

GSM Handover

Inter-MSC Handover

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RF Fundamentals for Cellular Networks31

Better cell HOEmergency HO

Level QualityPBGT

Traffic causesInterferenceDistance

GSM Handover

Different causes of Handover

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RF Fundamentals for Cellular Networks32

GSM Handover

Change of Cell during the Call (“Handover”)

3 Phases:Identification of requirement, Selection of a new cell, Execution

Mobile Station:Continuous Quality and Received Power ControlContinuous adjacent cell Power monitoringTransmission of measurement reports to the BTS (every 0.5s)

Network:The BTS measures the Quality and the received Power from the mobileThe BSC runs the Power Control and Handover central algorithmThe BSC controls the handover operation

Handover Types:Intra-BSC / Inter-BSC, Intra-MSC / Inter-MSC / Inter-PLMN / Inter-Network (2G <-> 3G)Internal (within the same BTS) if there is uplink or downlink interferenceSynchronized / non-synchronized

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RF Fundamentals for Cellular Networks33

GSM Handover

Change of Cell during the Call (“Handover”) [cont.]

BSC

BSC

BSC

BSC

BTS 1

BTS 2 MSC / VLR

MSC / VLR

MSC / VLR

PSTN

(Intra-BSC)

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RF Fundamentals for Cellular Networks34

GSM Handover

Change of Cell during the Call (“Handover”) [cont.]

PSTN or ISDN

FACCH

Release of old channel

Changeover to new channel

Internal Handover decision

MEASUREMENT REPORT

HANDOVER COMMAND

CHANNEL ACTIV.

CHANNEL ACTIV. ACK

SABM

UAESTABLISH INDIC.

MS BTS 1 BSC MSCUm A bis A

SCCP DATA

DATA REQUEST

DATA INDICATION

Handover Cmd

H.O. PerformedHandover. compl.

BTS 2

(RELEASE REQUEST)Local End

HANDOVER ACCESS(access burst) HANDOVER DETECTION

PHYSICAL INFO

HANDOVER COMPLETE

T8

RF CHANNEL RELEASE

RF CHANNEL RELEASE ACK

RRMEASUREMENT REPORT

MEASUREMENT REPORTMEASUREMENT REPORTRR

BTSM

BTSM

RRRR

RR

RR

RR

BTSM

BTSM

BSSMAPRR

FACCH

SACCH

SACCH

FACCH

(old)(new)

...……...

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RF Fundamentals for Cellular Networks35

GSM Handover

Change of Cell during the Call (“Handover”) [cont.]

BTS 2

BTS 1 MSC / VLR

MSC / VLR

MSC / VLR

PSTNBSC 1

BSC 2

BSC

BSC

(Inter-BSC)

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RF Fundamentals for Cellular Networks36

GSM Handover

Change of Cell during the Call (“Handover”) [cont.]

BTS 2

BTS 1

MSC / VLR1

MSC / VLR2

MSC / VLR

PSTNBSC

BSC 1

BSC 2

BSC

(Inter-MSC)

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RF Fundamentals for Cellular Networks37

GSM Handover

Change of Cell during the Call (“Handover”) [cont.]

BTS 1

BTS 2

MSC / VLR1

MSC / VLR2

MSC / VLR3

PSTNBSC

BSC

BSC 1

BSC 2

(Inter-MSCsubsequent)

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RF Fundamentals for Cellular Networks38

AMR

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RF Fundamentals for Cellular Networks39

Hard blocking

The whole radio resource is in use - no more calls can be established due to lack of free radio timeslots.

Hard blocking

The whole radio resource is in use - no more calls can be established due to lack of free radio timeslots.

Soft blocking

The capacity of individual cells is limited by the level of the interference rather than the number of TRXs available

Soft blocking

The capacity of individual cells is limited by the level of the interference rather than the number of TRXs available

Dominates with large reuse factors = Wideband deployment

Is dominating with tight reuse patterns = Narrowband deployments

AMR Introduction

Hard/Soft Blocking

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RF Fundamentals for Cellular Networks40

Standard Measure: Erl/km²/MHzNokia Measure: Effective Frequency Load (∝ Erl/MHz)Spectral Efficiency is equivalent to performanceAssuming no lack of radio resources or HW blocking

Dropped calls due to coverage gaps

Targeted quality level

TrafficLoad

Key PerformanceIndicator – CDR, BQS

Capacity Increase is measuredin terms of additional loadat the same quality level

Two alternative solutions

OperatingPoint

Quality Enhancementis measured in terms of

increased qualityfor the same load

Increased performance (spectral efficiency) delivers

improved quality and/or higher capacity for the same

quality criteria

Increased performance (spectral efficiency) delivers

improved quality and/or higher capacity for the same

quality criteria

Performance is a trade-offbetween

capacity AND quality

AMR Introduction

Spectral Efficiency & Performance

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RF Fundamentals for Cellular Networks41

EFL is a measure of the average frequency utilization in the area ⇒ Represents how loaded each frequency can be across the systemEFL is proportional to spectral efficiencyEFL is directly proportional to the carried traffic ⇒ x % higher EFL = x % more carried traffic

)(#

1#

TRXTCHAvefreqTot

ErlEFL BH ×=

Busy hour area level average Erlangs/cell

Total number of frequencies used

to carry the traffic

Average number of timeslots/TRX

AMR Introduction

Effective Frequency Load Defined

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RF Fundamentals for Cellular Networks42

EFL is a measure of the average frequency utilization in the area ⇒ Represents how loaded each frequency can be across the systemAssume 1.2 Mhz (6 x 200 kHz carriers) of hopping frequencies in addition to the BCCH carrierAssume in each cell 5 simultaneous voice users on the averageIn this case the Effective frequency load is ~ 5 Erlangs / 48 timeslots = 10.4%Thus, in each hopping frequencies we can have 8 (timeslots per carrier) x 10.4% = 0.83 Erlangs or 6 X 0.83 = 4.98 Erlangs in hopping layer

Time

Frequency200 kHz 200 kHz 200 kHz 200 kHz 200 kHz 200 kHz

5 tim

eslots

per ca

rrier

6 frequencies @ 200 kHz each

AMR Introduction

Effective Frequency Load Explained

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RF Fundamentals for Cellular Networks43

Adaptive Multi-Rate (AMR) codec consists of a family of codecs (source and channel codecs with different trade-off bit-rates) operating in the GSM FR and HR channels modes

The AMR system exploits the channel performance and robustness added by the coding rates by adapting the speech and channel coding rates according to the quality of the radio channel

AMR adapts its error protection level (select its optimum channel mode and codec mode) to the local radio channel and traffic load conditions to deliver the best possible combination of speech quality and system capacity

Codec mode adaptation for AMR is based on received channel quality estimation in both MS and BTS, followed by a decision on the most appropriate speech and channel codec mode to apply at a given time

The basic AMR codec mode sets for MS and BTS are provided by BSC via layer 3 signaling

MS shall support all speech codec modes, although only a set of up to 4 speech codec modes is used during a call

AMR Introduction

Adaptive Multi-Rate Codec

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RF Fundamentals for Cellular Networks44

0

5

10

15

20

25

FR12.2

FR10.2

FR7.95

FR 7.4 FR 6.7 FR 5.9 FR5.15

FR4.75

HR7.95

HR 7.4 HR 6.7 HR 5.9 HR5.15

HR4.75

AMR codec mode

Cha

nnel

bit-

rate

(kbi

t/s) Channel coding

Speech coding

SpeechSpeech QualQual

RobustnessRobustness

GSM FR/EFR channel gross bit-rate is 22.8 kbit/s in GSM FR/EFR: 13 kbit/sspeech coding and 9.8 kbit/channel coding (HR channel gross bit rate 11.4 kbit/s)For AMR case, different codecs use different bit rate to encode speech (source coding). The rest of the gross bit-rate is used for channel protection

AMR Introduction

Adaptive Multi-Rate Codec [cont.]

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RF Fundamentals for Cellular Networks45

AMR Benefits

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RF Fundamentals for Cellular Networks46

Link level results show very high improvement in the terms of TCH FER when robust AMR modes are usedAs high as 6 dB improvement at 1% FER in C/I can be achieved ⇒Therefore, high capacity gain can be expected when robust AMR modes are utilizedIn addition, increased robustness to channel errors can be utilized in the cell coverage, i.e. lower C/I can be allowed at the cell edgeHowever, in the mixed traffic case the cell coverage has to be planned according to EFR mobilesWith respect to signaling channels, the retransmissions schemes used by SACCH and FACCH channels maintain the probability of signalling success even for very degraded conditions

AMR Benefits

Capacity and Coverage Gain

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RF Fundamentals for Cellular Networks47

Due to robust AMR codec modes, very low TCH FER compared to EFRIn 850 MHz case all mobiles are AMR capable, but this comparison illustratesthe capacity gain AMR provides when it is introduced in a typical network

ONE-LAYER (RF-hopping 2/2, no BCCH included)

012

34567

89

10

5 7.5 10 12.5 15

Effective Frequency load (%)

Rela

tive

Fre

quen

cy

TCH

FER

> 5

.4 %

(%

)AMR MS penetration: 0%

AMR MS penetration: 25%

AMR MS penetration: 50%

AMR MS penetration: 75%

AMR MS penetration: 100%

Capacity gain based on the 2%

outage of the bad TCH FER

samples

~150% gain

relative to EFR

AMR Benefits

Capacity Increase with AMR

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RF Fundamentals for Cellular Networks48

Since the average C/I found in a cell area can be measurably less than that used in a non-AMR network and still provide comparable quality to EFR, the existing clean BCCH layer can be tightened, potentiallyreleasing frequencies to be used on the non-BCCH layer

This offers improved speech quality and extra capacity for TCH, especially in the narrow band deployment (frequency band less than 5 MHz)

However, if EFR roaming mobiles are to be taken care of, the BCCH will have to be planned accordinglyHow to plan networks to ensure the quality for the old EFR mobiles?

One method is to use more aggressive power adjustment for AMR mobiles in order to decrease the average interference level in the networkDue to better error correction capability against the channel errors lower C/I target can be set for AMR mobiles hence lower PC thresholds can be usedTherefore, the overall interference decreases in the network (smaller average transmission power) and thus the quality of the existing EFR connections increase

AMR Benefits

Improved BCCH Plan

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RF Fundamentals for Cellular Networks49

Half-rate is an efficient way to increase capacity in the case of limited number of TRXs per cellAMR HR codec obtains remarkable better speech quality than previous GSM EFR HR codecAMR FR obtains better quality than AMR HR only when higher FR modes than 7.4 are used (due to higher number of speech coding bits)

AMR FR 7.4 kbit/s mode and AMR HR 7.4 kbit/s mode have the same speech quality when the C/I is high (error free case)AMR HR channels can be then used in high C/I conditions without noticeably speech quality loss

In theory for ideal frequency hopping about 11-12 dB C/I is required for AMR HR to obtain the evaluated good speech quality limit (in real networks, depending on the BTS configuration and on FH mode used, it might be necessary 1-4 dB higher)

Based on this, all connections having at least 12 dB C/I could be handed over to HR channel remaining the good speech quality

AMR Benefits

Half-Rate Utilization in AMR Codec

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RF Fundamentals for Cellular Networks50

MOS vs. CIR

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

C/I (dB)

MO

S FR 12.2 MOSFR 7.4 MOSFR 5.9 MOSFR 4.75 MOSHR 7.4 MOSHR 5.9 MOSHR 4.75 MOS

Spee

ch Q

ualit

y G

ains

A user in good radio conditions perceives the same quality as EFR.

However, a user in bad radio conditions still receives acceptable speech quality while with EFR it would not received satisfactory speechquality.

AMR Benefits

Benefits For End User

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RF Fundamentals for Cellular Networks51

Approx. 5.5 dB link level gain in hopping layer

This turns into approx. 140% capacity gain for AMR-FR

Coverage enhancement (>4dB)

Tighter BCCH reuse schemes.

Saving of resources by deploying AMR-HR

0%

1%

10%

100%

0246810C/I [dB]

TCH

FER

fs475iFHfs515iFHfs590iFHfs670iFHfs740iFHfs795iFHfs102iFHfs122iFH

Capa

city

/

Cove

rage

Gai

ns

AMR Benefits

Benefits For Operator

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RF Fundamentals for Cellular Networks52

Speech quality enhancement: AMR maintains good speech quality in the situation where the connection faces low C/I or low signal levelCapacity and coverage gain: Link level simulation results illustrated improvement in terms of TCH FER (up to 5.5dB at 1% FER in C/I)Signaling channel performance: due to retransmissions schemes used by these channels the probability of signaling success maintain very high even for very degraded conditionsImproved BCCH plan: tighter frequency reuse or better quality with same frequency reuse, potentially releasing frequencies to be used on the non-BCCH layer.Half Rate utilization increases the hardware capacity of the cell since two half-rate connections can be allocated to fill only one timeslot.

When compare AMR HR to previous GSM HR codec, it is noticed that AMR HR obtains remarkable better speech quality

AMR Benefits

Benefits For AMR- Summary

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RF Fundamentals for Cellular Networks53

Power Control

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RF Fundamentals for Cellular Networks54

REASONSOptimize Uplink and Downlink QOS Decrease power consumption of the Mobile

STRATEGY

Handled by the BSCHO has always higher priority than POCControlled by intervalIncrease and decrease act independently (can be fixed or variable step size)BTS and MS apply Power Control independentlyBCCH TRX doesn't use Power ControlDL/UL Power Control can be disabledInitial POC level used by MS in new cell after HO, is determined by BSC(default is max permitted level, MsTXPwrMaxCell)Optionally POC/HOC processes can optimize the initial RF power in case of intra BSC HO

Power Control

Reasons and Strategy

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RF Fundamentals for Cellular Networks55

powerControlInterval 0 … 30 secpowerIncrStepSize 2, 4, 6 dBpowerRedStepSize 2, 4 dBpowerControlEnabled Y / N

Parameter Value

Uplink Level

Uplink Quality AV_RXQUAL_UL_PC

AV_RXLEV_UL_PC

Downlink Level

Downlink Quality AV_RXQUAL_DL_PC

AV_RXLEV_DL_PC

POWER CONTROL

UPLINK

POWER CONTROL

UPLINK

THRESHOLD COMPARISON

Separate Averaging Parameters For Handover and for Power Control

POWER CONTROL

DOWNLINK

POWER CONTROL

DOWNLINK

POCINTERVAL

Power Control

Overview

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RF Fundamentals for Cellular Networks56

LowerLEV UpperLEV

UpperQUAL

LowerQUAL

Applicable in both Downlink and Uplink Directions

Power Control

Safety Region

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RF Fundamentals for Cellular Networks57

Frequency Planning

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RF Fundamentals for Cellular Networks58

Cell Structures

Cell Structures and Quality

Frequency re-use in cellular radio networksallow efficient usage of the frequency spectrumbut causes interference

Interdependence ofCell sizeCluster sizeRe-use distanceInterference levelNetwork Quality

interfererregion

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RF Fundamentals for Cellular Networks59

Cell Structures

Cell Re-use Cluster (Omni Sites)

1

2 3

47

6 5 1

2 3

47

6 5RD

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RF Fundamentals for Cellular Networks60

Cell Structures

Cell Re-use Cluster (Omni Sites) [cont.]

5 64

1 2 3

7 8 9

10 11 12

D

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RF Fundamentals for Cellular Networks61

Cell Structures

Cell Re-use Cluster (Sector Site)

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RF Fundamentals for Cellular Networks62

Cell Structures

4x3 Cell Re-use Cluster (Sector Site) [cont.]

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RF Fundamentals for Cellular Networks63

Cell Structures

Irregular (Real) Cell Shapes

12 3

4

56

5

7Network Border

CoverageHole Island

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RF Fundamentals for Cellular Networks64

Frequency Reuse

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RF Fundamentals for Cellular Networks65

Frequency Reuse

GSM Frequency Spectrum

GSM 900DL: 935-960 MHz UL: 890-915 MHz200 kHz channel spacing -> 124 channelsARFCN 1 - 124

E-GSMDL: 925-935 MHz UL: 880-890 MHz200 kHz channel spacing -> Additional 50 channelsARFCN 0, 975 - 1023200 kHz channel spacing ->124 channels

GSM 850DL: 869-894 MHz UL: 824-849 MHzARFCN: 128 - 251

GSM 1800DL: 1805-1880 MHz UL: 1710-1785 MHz200 kHz channel spacing -> 374 channelsARFCN 512 - 885

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RF Fundamentals for Cellular Networks66

Frequency Reuse

Impact of limited Frequency Spectrum

Bandwidth is an expensive resource

Best usage necessary

Efficient planning necessary to contain good QoS when the traffic in

the network is increasingsmaller reuse Multiple reuse pattern (MRP) usageimplementation of concentric cells / microcells/dual bandimplementation of Frequency Hopping

BasebandSynthesized

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RF Fundamentals for Cellular Networks67

Frequency Reuse

What is frequency reuse?

As the GSM spectrum is limited, frequencies have to be reused toprovide enough capacity

The more often a frequency is reused within a certain amount of cells, the smaller the frequency reuse

Aim:Minimizing the frequency reuse for providing more capacity

Reuse Cluster:Area including cells which do not reuse the same frequency (or frequency group)

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RF Fundamentals for Cellular Networks68

Frequency Reuse

RCS and ARCS

Reuse Cluster Size - RCSIf all cells within the reuse cluster have the same amount of TRXs, the reuse per TRX layer can be calculated:

cellTRXBRCS

/#=

cellTRXBARCS

/#=

Average Reuse Cluster Size - ARCSIf the cells are different equipped, the average number of TRXs has to be used for calculating the average reuse cluster size:

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RF Fundamentals for Cellular Networks69

Frequency Reuse

RCS and ARCS [cont.]

The ARCS is giving the average reuse of the network when using the whole bandwidth and all TRXs per cell

For Example: If we want to have the reuse of all non hopping TCH TRXs, we have to use the dedicated bandwidth and the average number ofnon hopping TCH TRXs per cell to get the ARCS of this layer type.

Each cell has only one BCCH. Therefore the BCCH reuse is an RCS and not an ARCS!

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RF Fundamentals for Cellular Networks70

Frequency Reuse

Reuse Cluster Size

Sectorized sites4 sites per reuse cluster3 cells per site

Reuse Cluster Size:4X3 =12

1 2

3

4 5

6

7 8

9

10 11

12

1 2

3

4 5

6

7 8

9

10 11

12

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RF Fundamentals for Cellular Networks71

Frequency Reuse

Reuse Cluster Size [cont.]

Sectorized sites3 sites per reuse cluster3 cells per site

Reuse Cluster Size3X3 = 9

1 2

3

4 5

6

7 8

9

1 2

3

4 5

6

7 8

9

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RF Fundamentals for Cellular Networks72

Frequency Reuse

Reuse Distance

RCSRfD ⋅⋅⋅= 3

= cells sectorized-three32

cells ionalomnidirect1f

re-use distancecell A

cell B

interfererregion

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RF Fundamentals for Cellular Networks73

Frequency Reuse

Frequency Reuse Distance

site A site B

distance DR

D = distance between cell sites with the same frequenciesR = service radius of a cellB = number of frequencies in total bandwidthRCS = reuse cluster size, i.e. one cell uses B/RCS frequencies

In hexagonal cell geometry: D/R = f · 3 RCS

omni cells: f=1; sector cells: f= 2/3

Examples (omni):RCS = 7:D/R = 4.6RCS = 9:D/R = 5.2RCS =12: D/R = 6.0

Received Power

Frec

σC/I

Frec, A Frec, B

0

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RF Fundamentals for Cellular Networks74

Frequency Reuse

Frequency Reuse: Example

No sectorization7 cells per cluster

BCCH RCS = 7TCH Reuse: Depending on BW and Number of installed TRXs per cellExample:

B= 264TRXs per cell

interfererregion

63

1726=

−−=

GuardBCCHRCSTCH

RCSTCH

RCSBCCH

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RF Fundamentals for Cellular Networks75

Cell Planning

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Cell Planning

Cell Planning - Frequency Planning

Bad cell planningIsland coverage → Disturbs the reuse patternBig overlap areas → Bigger reuse necessary

Good cell planningSharp cell borders → Good containment of frequencySmall overlap areas → Tighter reuse possible

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RF Fundamentals for Cellular Networks77

Cell Planning

Influencing Factors on Frequency Reuse Distance

Topography

Hilly terrain, increases usage of natural obstacles to define sharp cell borders, increases tighter frequency reuse possible

Flat terrain, achievable reuse much more dependent on the accurate cell design

Morphology

Water low attenuation, high reuse distance

City high attenuation, low reuse distance

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RF Fundamentals for Cellular Networks78

Cell Planning

Conclusion

In cellular mobile networks, the frequency reuse pattern has a direct influence on the interference and hence the network qualityRegular hexagonal patterns allow the deduction of engineering formulasIn real networks, cell sizes and shapes are irregular due to

Variation in traffic densityTopographyLand usage

Engineering formulas allow the assessment of the network quality and worst-case considerations, but the real situation must be proved!

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RF Fundamentals for Cellular Networks79

Cell Planning

Examples for different frequency reuses

Big city in the south of Africa:BCCH reuse 26

Irregular cell designMixed morphologyLots of waterFlat terrain plus some high sites

Big city in eastern EuropeBCCH reuse 12

Regular cell designFlat areaOnly urban environment

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RF Fundamentals for Cellular Networks80

Interference Probability

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Interference Probability

Interference Theory

C/I restrictions9dB for co-channel interference-9 dB for adjacent channel interference

dista nce DR

Received PowerP rec

σC/ I

Prec, A Prec, B

0

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RF Fundamentals for Cellular Networks82

Interference Probability

Interference Theory [cont.]

Probability density function [%]

0,0%

1,0%

2,0%

3,0%

4,0%

5,0%

C/I [dB] →C/ImedC/Ithr

Margin

Interferer probability [%]

0%

20%

40%

60%

80%

100%

-20 -15 -10 -5 0 5 10 15 20

C/I - C/Ithr[dB]

Interference probabilityC/Imed is the calculated carrier to interference ratio at a certain location (pixel)

ARCS Pint[%]6.5..9.0 107.0..9.5 7.58.5..11.0 5.012.0..16.0 2.5

3.6 Interference Probability

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RF Fundamentals for Cellular Networks83

Interference Probability

CPDF - Cumulative Probability Density Function

Pint = P ( C/I < C/I thr)

00,10,20,30,40,50,60,70,80,91

P int

Distance from serving cell

DR

CPDF - Cumulative Probability Density Function

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RF Fundamentals for Cellular Networks84

Interference Probability

Interference Probability dependent on Average Reuse

ARCS =# of frequencies in used bandwidth

average # of carriers per cellPint [%]

ARCS0

3

6

9

12

5 10 15 20 25

Examples:Pint[%] ARCS10 6.5...97.5 7...9.55 8.5...112.5 12...16

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RF Fundamentals for Cellular Networks85

Manual frequency planning

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Manual Frequency Planning

Frequency planning

No fixed method

Free frequency assignment possible, but very time consuming for larger networks

For easy and fast frequency planning: use group assignment

Example:18 channels, 2TRX per cell ARCS 9

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RF Fundamentals for Cellular Networks87

Manual Frequency Planning

Frequency planning [cont.]

GSM restrictions are automatically fulfilled, if on one site only groups A* or only B* are used

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

A1B1A2B2A3B3A4B4A5

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Manual Frequency Planning

Subdivide frequency band?

Any subdivision of the frequency band is reducing the spectrum efficiencySeparations should be avoided if possibleAs the BCCH has to be very clean, it is nevertheless recommended to use a separated band and select a bigger reuse

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RF Fundamentals for Cellular Networks89

Manual Frequency Planning

Hint for creating a future proofed frequency plan

If a frequency plan is implemented, using all available frequencies in the most efficient way, it is very difficult to implement new sites in the future!

New sites would make a complete re-planning of the surrounding area or the whole frequency plan necessary

To avoid re-planning every time when introducing new sites, it is recommended to keep some frequencies free

These Joker frequencies can be used for new sites (especially BCCH TRXs) unless it is impossible to implement new sites without changing a big part of the frequency plan

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RF Fundamentals for Cellular Networks90

Module Summary

You should now be able to:

Explain GSM Call flow scenarioExplain Mobile Origination and Mobile Terminating callsExplain the types of Handovers in GSM networkDescribe Adaptive Multi Rate (AMR) coding and its benefitsDescribe the benefits of Power control in GSMExplain the techniques involved in Frequency Planning

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This slide is intentionally left blank.

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End of ModuleGSM Advanced Concepts