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GSM RF Fundamentals for ALUMS
STUDENT GUIDEVolume 1
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Basic RF Engineering
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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.
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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
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RF Fundamentals for Cellular Networks5
Radio Propagation
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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
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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
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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
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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
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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.
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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.
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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
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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)
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RF Fundamentals for Cellular Networks14
Path Loss Prediction
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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
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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
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RF Fundamentals for Cellular Networks17
Path Loss Prediction
Fresnel Ellipsoid
21
21
ddddr+⋅⋅
=λ
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
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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.
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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
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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
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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
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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
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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
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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
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RF Fundamentals for Cellular Networks25
Antennae and Cables
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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
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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
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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.
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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
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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
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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
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RF Fundamentals for Cellular Networks33
Antennae and Cables
Dipole Arrangement
Dipole arrangement
Typical flat panel antenna
Dipole element
Weightedandphaseshiftedsignals
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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
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RF Fundamentals for Cellular Networks35
Antennae Parameters
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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RF Fundamentals for Cellular Networks46
Cable Parameters
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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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RF Fundamentals for Cellular Networks67
This slide is intentionally left blank.
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RF Fundamentals for Cellular Networks68
End of ModuleBasic RF Engineering
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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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RF Fundamentals for Cellular Networks39
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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RF Fundamentals for Cellular Networks45
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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RF Fundamentals for Cellular Networks47
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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RF Fundamentals for Cellular Networks51
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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RF Fundamentals for Cellular Networks91
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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RF Fundamentals for Cellular Networks92
GPRS Overview
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RF Fundamentals for Cellular Networks93
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
Do not delete this graphic elements in here:
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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
...……...
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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...……...
All Rights Reserved © Alcatel-Lucent 2009
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
...……...
All Rights Reserved © Alcatel-Lucent 2009
RF Fundamentals for Cellular Networks20
GSM Handover
All Rights Reserved © Alcatel-Lucent 2009
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.]
All Rights Reserved © Alcatel-Lucent 2009
RF Fundamentals for Cellular Networks25
INTRA-CELL HandoversINTER-CELL HandoversINTRA-BSC HandoversINTER-BSC HandoversINTER-MSC Handovers
GSM Handover
Types of Handovers
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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)
...……...
All Rights Reserved © Alcatel-Lucent 2009
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)
All Rights Reserved © Alcatel-Lucent 2009
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)
All Rights Reserved © Alcatel-Lucent 2009
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)
All Rights Reserved © Alcatel-Lucent 2009
RF Fundamentals for Cellular Networks38
AMR
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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.]
All Rights Reserved © Alcatel-Lucent 2009
RF Fundamentals for Cellular Networks45
AMR Benefits
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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.]
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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:
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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
All Rights Reserved © Alcatel-Lucent 2009
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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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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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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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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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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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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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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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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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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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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End of ModuleGSM Advanced Concepts