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Copyright ©2008 Telefocal Asia Pte Ltd. All rights reserved.1
Radio Network Optimisation
Principles
Instructor: Dr Tony Vernon
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Overview of entire five day courseWhat will be learned over the next five days
Why this is important in the context of radio networkoptimisation
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Overview of Day 1
First, Second and Third Generation Networks
Introduction to Generic Radio Access Networks
Radio Propagation Theory
Multiple Access Schemes
The GSM 2G Air Interface
UTRAN – The UMTS 3G Radio Access Network
The Upgrade Migration Path 2G > 2.5G > 2.75G > 3G
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Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks
1st Generation Analog NetworksCoverage on Regional Basis
Out of Town High Sites
Cell Radii 5-20km
Mobile coverage targeted
No express indoor coverage
Later deployments reduced
cell size and emphasisedindoor reliability (1990-)
Town 1 Town 2
Town 3
Town 4
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Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks
2nd Generation Digital NetworksSmaller cell size
Sectorisation to reduceinterference
Tighter frequency reuse
More robust, digital modul-ation schemes
Advanced understanding of differing requirements for Urban,Suburban and Rural/Road coverage
Town 1
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Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks
2nd Generation Digital Networks (cont.)The ‘Air Interface Wars’
IS-95 CDMA advocated by Qualcomm + acolytes
GSM advocated by LM Ericsson + acolytes
Claim & counter-claim for spectral efficiency,immunity from interference, adaptability to differentcoverage scenarios etc.
GSM now by far the dominant 2G standard, 80.79%of all connections to cdmaOne (=IS95 CDMA) 0.22%*
*source: GSM Association http://www.gsmworld.com/news/statistics/pdf/gsma_stats_q2_08.pdf
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Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks
3rd Generation Mobile Networks3G rollout less driven by coverage scenario, moreoriented toward usage scenario
Source: Morawek, R and Özcelik, H “General UMTS Network Architecture” http://www.morawek.at/roman/papers/umts.pdf
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Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks
3rd Generation Mobile Networks (cont.)Development of 3G standards started in early ’90s, atlaunch of the first 2G GSM and cdmaOne networks
Another air interface ‘Holy War’ with wideband CDMA
prevailing for the air interface and GSM RAN behind this A number of multiple access schemes standardised bythe ITU, of which 3GSM (UMTS) and the CDMA 2000variants are most widespread
China, which adopted GSM in the 2G era, has mandatedTD-SCDMA as its preferred 3G standard, which may aidthe rollout of this air interface to other territories
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144kb/s
384kb/s
Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks
2G Standards offered a single (low) data rate everywhereThe ITU mandated “graceful degradation”, or graduallyfalling bit rate for 3G, with increasing distance from theRadio Base Station
Up to 2Mb/s close to site (~10m)Up to 768kb/s in vicinityof site (~100m)
Up to 384kb/s in general
area of site (~1km)Up to 144kb/s (2B+D ISDN)elsewhere
768kb/s
2Mb/s
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Day 1 Section 2 – Introduction to Radio Access Network
Section OverviewObjective of Radio Network Planning (RNP)
Operator Perspective of RNP
RNP Technology and Automation
Relationship between RNP and Frequency Planning
Radio Propagation Principles (Reflection, Refraction,Diffraction, Absorbtion, Multipath)
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Day 1 Section 2 – Introduction to Radio Access Network
The Radio Access Network governs one third of theusers’ overall experienceand 100% of users’ qualityof service
The operator inter-acts with the network and users via theOperations Subsystem
Both users and the operatorinteract with external networksvia the Network Subsystem
Operator
E x t e
r n a l
N e t w o r k s
S u b
s c r i b
e r s
OSS
N S S
B S S / R A N
M S / U E
Adapted from Mouly & Pautet, ‘The GSM System’
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Day 1 Section 2 – Introduction to Radio Access Network
Operator view of RNPBase Station Subsystem defines 100% of users’ technicalexperience with the operator (ignoring NSS faults)
Operator can differentiate itself from other mobile
networks in the territory by investing in the RANCAPEX sunk into RAN precedes operating profits with nodirect ‘return on investment’
Many 3G networks built on top of existing 2G properties
2G site topology not necessarily suitable for 3G
Operators in mature markets outsourcing their RNP
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Day 1 Section 2 – Introduction to Radio Access Network
RNP Technology – RudimentaryCalculate approximatecell radius for differing
‘clutter’ types
Clutter maps commonfor at least rural,suburban, urban anddense urban
Perform ‘best fit’ of cellcoverage areas to cluttermap, bearing in mindhandover overlap
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Day 1 Section 2 – Introduction to Radio Access Network
RNP Technology – SophisticatedSignal from each sectorcomputed from clutter typein which it is located
Not necessary to maintainsite raster or orientation
Software fits sites so thatentire region to be servedhas coverage at least tominimum field strength
Town 1 Town 2
Town 3
Town 4
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Day 1 Section 2 – Introduction to Radio Access Network
Simple (Omni) Frequency PlanningGSM900 = 124 ARFCNs
Operator allocation =e.g 45 ARFCNs
Divide up into 7 ‘reuse’ groups
6 ARFCNs per site= (6 x 7) + 3 spare
for special purposes A connection suffers inter-ference from up to 6 neighbours
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Day 1 Section 2 – Introduction to Radio Access Network
Simple (Sector) Frequency PlanningOperator allocation =e.g. 45 ARFCNs
Divide frequencies
per site by numberof sectors, e.g.(2 x 3 x 7) + 3
Connection is nowinterfered by only3 other neighbours
Sectorisation reduces capacity
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Day 1 Section 2 – Introduction to Radio Access Network
-14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Distance from Site (km)
S i g n a l S t r e n g t h
Serving SiteAdjacent Site Adjacent Site
+
+
=
Interferenceapproximatelyconstant over
service area of site
Reuse Site Reuse Site
Interference ‘wash’ from more distant reuse sites
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Day 1 Section 2 – Introduction to Radio Access Network
Direct Path
Diffraction
Reflections
Refrac-tionThe
signal arrivesat the mobileterminal via avariety of paths
Interferer
Man-madeand
NaturalInterference
Sourcesof inter-
ference areless welldefined.
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Day 1 Section 3 Radio Propagation Theory
IntroductionRadio Propagation Environment
Frequency Division
Fast and Slow Fading
Propagation Loss
Propagation Models
Doppler Effect
Fresnel Zone
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Day 1 Section 3 Radio Propagation Theory
Introduction
SimpleDipole
Antenna
I
I
R
Rr
Current flow in the antennafor a given electrical stimulusis determined by the real and‘radiation’ resistance of the
antenna
H
EPower expended againstthe radiation resistance
flows away from theantenna in the form oflines of electric potential, Eand magnetic induction, H,
i.e. ElectromagneticRadiation
V ~
I
I
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Day 1 Section 3 Radio Propagation Theory
Radio Propagation EnvironmentElectromagnetic energyis scattered from objectsin the area of the terminalknown as DominantSecondary Scatterers
Close to the terminal, e.g.30-40m, smaller objectsreflect signal, linking to the
terminal’s antenna. Theseare called Primary Scatterers
Base site
PrimaryscatterersWater
tower
Dominant secondaryscatterers
Othermast
Tallbuilding
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Frequency DivisionSecondary scatterers link signal from the base sitefar outside its main service area
Pool of frequencies used by the operator is subdivided sothat e.g. (f1,f2,f3) are not used within 3 cell radii etc.
Day 1 Section 3 Radio Propagation Theory
Minimum distance at which ‘red’frequency can be reused
Coverage Zone
Interference Zone
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Day 1 Section 3 Radio Propagation Theory
Fading Effects
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Frame Number
-92
-90
-88
-86
-84
-82
-80
Power(dBm)
Acknowledgement: University of Bristol TSUNAMI II Testbed
Fast Fading
Slow FadingVerySlow
Fading
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Day 1 Section 3 Radio Propagation Theory
Fading Effects (cont.)Fast Fading – due to primary scatterers near MS
Slow Fading – caused by secondary scatterers randomlybecoming obstructions that cause signal loss
Very Slow Fading – used to be relevant when cell sizeswere 20km+, caused by random losses when signaldiffracts over landscape.
Very Slow Fading now absorbed into ‘propagation model’
or factored out as small cell size in modern networksmeans that topography does not vary significantly withincell coverage area
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Day 1 Section 3 Radio Propagation Theory
Fast Fading
Object within 30-40mof the terminal link
signal in to the antenna
Many random, smallE-field contributions
R e c e i v e d P
o w e r
Distance/Time
|| (rand[-1..1] + rand [-j..j]) ||
rand[-1..1]
rand[-j..j]
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Day 1 Section 3 Radio Propagation Theory
Slow Fading
A large number of objects, either primary or secondaryscatterers, obstruct the path between base site and MS.Each has a random loss between 0dB and Lmax dB
‘Propagation’ LossLoss 1 Loss 2
Loss 3
Loss 4
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Day 1 Section 3 Radio Propagation Theory
Slow Fading (cont.)
BS MSL1 L2 L3 L4 L5 L6 L7 L8 L9 L10
rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax]
Slow fading isthe outcome ofa large numberof linked fadingprocesses, andthe overall lossis Sum(L1..L10)
For L=5dB
and 10000
samples
0
100
200
300
400
500
600
700
800
900
1 3 5 7 9 1 1 1 3 15 1 7 19 21 2 3 25 27 2 9 31 33 3 5 37 3 9 41 43 4 5 47 4 9 51
Slow Fading Loss (dB)
N u
m b e r o f S a m p l e s
Classic‘Lognormal’distribution
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Day 1 Section 3 Radio Propagation Theory
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Day 1 Section 3 Radio Propagation Theory
Propagation Model As terminal moves away from base station, an increasingaverage number of objects obstruct the signal
Total propagation loss = free space loss (≥ 1/r²) +obstruction loss (1/[r→r²])
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Day 1 Section 3 Radio Propagation Theory
Propagation Model (cont.)Huygens Principle: each point on a wavefront can beregarded as a source of secondary ‘wavelets’
The envelope of these wavelets, at a later instant, gives
a divergent wave with the BS antenna at its centre.
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Day 1 Section 3 Radio Propagation Theory
Propagation Model (cont.)The space between BS and MS antenna can be dividedup into a number of ‘Fresnel Zones’, the edges of whichcorrespond to a path length increment of half awavelength over the direct path between BS and MS
p+λ /2
p
p+2λ /2
p+3λ /2
Resultant
Huygens wavelets over oddnumber zones contribute to
an increasing resultantamplitude until their edge-to-edge phase difference is λ /2
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Day 1 Section 3 Radio Propagation Theory
Propagation Model (cont.)
Obstruction
a
b
c
d
e
a
b
c
d
e
As an obstruction intrudes into the pathbetween BS and MS, the main Fresnel
Zones are obstructed and receivedamplitude at the MS reduces
Receivedamplitude
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Day 1 Section 3 Radio Propagation Theory
Propagation Model (cont.)Overall progation loss = free space loss (1/r²) +obstruction loss (1/r) + Fresnel loss (1/[/[r→r²])
Free Space Loss A + Br²
Free Space + Obstruction LossC + Dr[2-3]
Free Space + Obstruction + Fresnel LossE + Fr[3.5-5]
Distance from Site
PowerReceivedat MS
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Day 1 Section 3 Radio Propagation Theory
Doppler Effect
Primaryscatterers
Dominant secondaryscatterers
MS/UE Locus
f
Doppler effect increasesbit error rate and reduceshandover reliability
f f-f d f+f d
Frequency domainis spread by
Doppler
Time domain is‘smeared’ by
Doppler
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Day 1 Section 4 Multiple Access Schemes
A ‘multiple access scheme’ determines how mobileterminals and base stations share the transmissionresources to send and receive voice and packet data
Four multiple access schemes dominate (in order of increasing complexity
CSMA Carrier Sense Multiple Access
FDMA Frequency Division Multiple Access
TDMA Time Division Multiple Access
CDMA Code Division Multiple Access
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Day 1 Section 4 Multiple Access Schemes
CSMA Carrier Sense Multiple AccessBase stations and mobiles shareall network resources in common
Before transmitting, a base station
scans and listens on F1-Fn for othersites transmitting on that frequency.If a ‘clash’ is detected, the BS waitsa random interval before trying again
Mobile Terminals do the same, possibly
on a different set of frequencies f 1-f n
Commonest example - Ethernet
F1-Fn
F1-Fn
F1-Fn
f 1-f m
f 1-f m
f 1-f m
f 1-f m
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Day 1 Section 4 Multiple Access Schemes
Frequency Division Multiple Access
FDMA tries to solve the ‘distant clash’ problem of CSMA by setting a minimum
spacing at which a givenfrequency is used
The handset receiving on F1,F2,F3 should not be able to hear or be interfered bythe base stations where this frequency group is reused, as a number of cell spacings now intervene
F1,F2,F3
F4,F5,F6
F7,F8,F9
F10,F11,F12F13,F14,F15
F16,F17,F18F1,F2,F3
F1,F2,F3
F1,F2,F3f 1,f 2 ,f 3
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Day 1 Section 4 Multiple Access Schemes
Time Division Multiple AccessFn+Fn+1+Fn+2 combined into a digital allocation
Where in FDMA each MSused F1, F2 or F3 100%of the time, in TDMA all
three MSs use F A 33.3%of the time.
FA
FB
FC
FDFE
FGFA
FA
FAf A
f A
f A
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Day 1 Section 4 Multiple Access Schemes
Time Division Multiple Access (cont.)
Frequency
F1 F2 F3
Frequency
FA
In TDMA a numberof narrow FDMA allocations
are combined into a muchwider bandwidth TDMA channel
The wider frequency allocationpermits a higher digital modulationrate, and therefore a highercarrier bit rate. Each MS shares
the frequency resource for apercentage of the time, thereforea TDMA ‘channel’ is a combinationof frequency, start and stop times,known as a ‘timeslot’.
MS1 MS2 MS3 MS1 MS2 MS3
Time
T r a n s m
i t P o w e r
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Day 1 Section 4 Multiple Access Schemes
Time Division Multiple Access (cont.) Advantages:
Reduced Base Station complexity – many FDMA trans-ceivers (TRXs) channels replaced by single TDMA TRX,
also reduced combiner complexityExtra data can be incorporated in each TDMA timeslotto permit ‘channel estimation’ on uplink and downlink
Digital modulation schemes much more robust against
interference, e.g. 8dB margin for GMSK vs 25dB for FM As all information streams are digital, circuit and packetswitched data can much more easily be incorporated
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Day 1 Section 4 Multiple Access Schemes
Time Division Multiple Access (cont.)Disadvantages:
TDMA modulation schemes (usually a variant of MSK for2G systems) are much more complex than simple FM
modulation and demodulationCapacity can only be added in blocks corresponding tothe number of timeslots in a single TDMA carrier, or
Absolute Radio Frequency Channel Number (ARFCN).This may be inappropriate for low-traffic rural sites.
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Day 1 Section 4 Multiple Access Schemes
Code Division Multiple AccessF A +FB+..+FG combined into one allocation, F
In CDMA all BSs sharea single frequencyallocation. Voice or packet
data in low bitrate digitalform is multiplied with amuch higher bitrate ‘spreadingcode’. At the receiver the incomingsignal is multiplied by a synchronised versionof the spreading code and the original information recovered.
F
F
F
FF
FF
F
F
f
f
f
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Day 1 Section 4 Multiple Access Schemes
Code Division Multiple Access (cont.)
Frequency
FA FB FC FD FE FG
Frequency
FEntire Operator Allocation
UserData
-f f
SpreadingCode
-f f
TX
SpreadingCode
-f f
RX
fUserData
-f f
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Day 1 Section 4 Multiple Access Schemes
Code Division Multiple Access (cont.) Advantages:
Simple BS design, need only one wideband TX and RX
Secure – in order to intercept the signal, an eavesdropper
needs to know not only the baseband encryption but alsothe ‘scrambling code’
Wide flexibility in matching user data rate to air interface
User data is spread over a wide range of RF frequencies,
which reduces vulnerability to frequency-dependentfading. Also allows possibility for use of ‘rake’ receiverto increase the recovered signal by channel matching
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Day 1 Section 4 Multiple Access Schemes
Code Division Multiple Access (cont.)Disadvantages:
Increased complexity relative to FDMA and TDMA
Requires contiguous block of frequencies at least as
large as the baseband spectrum of the spreading code
High-power wideband RF amplifiers tend to be inefficient
All base stations and all MSs interfere with each other,there is no possibility of setting aside special frequencies
or groups of frequencies to manage difficult sites
IPR issues – Qualcomm holds many key CDMA patents
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Day 1 Section 5 The GSM Air Interface
GSM, developed in 1980’s by Groupe Spéciale Mobile GSM has a hybrid TDMA-with-FDMA air interface, withorigins in UK military comms
Aim of GSM was originally to develop a Europe -wide
mobile communications system using 900 MHz spectrumthat had recently (1982) been harmonised for EU use.The system was designed to access the ISDN.
System developed in tandem with the Digital CellularSystem, which was an upbanded version of GSM for
1800 MHz frequencies.
Systems were referred to as GSM900 and DCS1800
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Day 1 Section 5 The GSM Air Interface
GSM channel structureFirst generation systems tended to have FM channelsspaced at 25kHz. 8 of these are combined for a single200 kHz GSM channel
Gaussian Minimum Shift Keying (GMSK) modulation used,channel width is 260 kHz with 200 kHz channel spacing
Frequency
25 kHz
Frequency
200 kHz
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Day 1 Section 5 The GSM Air Interface
GSM Timeslot Structure8 timeslots of 15/26ms are grouped into 60/13ms frames
Time
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7
15/26ms577µs
60/13ms4.615ms
Information57 bits
Information57 bits
TrainingSequence
26 bits
Signalling1 bit
T a i l 3 b i t s
T a i l 3 b i t s
GuardPeriod
8.25 bits
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Day 1 Section 5 The GSM Air Interface
GSM Physical and Logical ChannelsOne view is that a physical channel is a combination of frequency, start and stop time (i.e. timeslot) in the frame
In successive frames, a physical channel supports one ormore logical channels. For example, the TACH/F physical
channel ‘multiframe’ has 26 Traffic Channel (TCH) bursts,1 Slow Associated Channel (SACCH) burst and 1 idle burst
Time
Broad-
cast
TACH 1 TACH 2 TACH 3 TACH 4 TACH 5 TACH 6 TACH 7
T T T T T T T T T T T T T S T T T T T T T T T T T T T I
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Day 1 Section 5 The GSM Air Interface
GSM Broadcast and Common Control Channel At least one basic physical channel on the first GSMcarrier, the ‘C0’ carrier, must carry the Broadcast andCommon Control Channel
Extra BCCH+CCCH blocks are needed in cases of low,medium, high and very high signalling load
0 1 2 3 4 5 6 7 7 0
BCCH+
CCCHTCH TCH TCH TCH TCH TCH TCH
BCCH+CCCH TCH TCH TCH TCH
BCCH+CCCH
BCCH+CCCH
BCCH+CCCH
BCCH+CCCH TCH TCH TCH TCH TCH TCH
BCCH+CCCH
TCH TCH TCH TCH TCHBCCH+CCCH
BCCH+CCCH
BCCH+CCCH
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Day 1 Section 5 The GSM Air Interface
51 Frame Structure and Schedule for BCCH+CCCH
The Broadcast Control Channel, BCCH, transmits infor-mation about the cell
The Frequency Correction and Synchronisation ChannelsFCCH and SCH allow the MSs to find and lock to the cell
The Common Control Channel CCCH controls MS access
TCH FCCH SCH BCCH CCCH
time time/8
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Day 1 Section 5 The GSM Air Interface
Frame Structure and Schedule for TACH/F and /H
TACH/H, even timeslots
TACH/H, odd timeslots
time/8
time TACH/F
Traffic Burst Slow Associated Burst Idle
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Day 1 Section 5 The GSM Air Interface
Frame Structure and Schedule for TACH/8 (No.0 shown)
Traffic and Associated Channel/8, TACH/8 is also known
as Standalone Dedicated Control Channel, SDCCH
Normally used for call setup and Short Message Service
Traffic Burst Slow Associated Burst Idle
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Day 1 Section 5 The GSM Air Interface
Structure of GSM Common Control Channel, CCCHOn the downlink, the CCCH is shared between the PagingChannel, PCH, and the Access Grant Channel, AGCH
MSs listen to a pre-determined paging channel. When an
incoming call arrives the MS transfers to the AGCHIn low traffic cells, the AGCH ‘steals’ idle PCH blocks. Inhigh traffic cells, between 2 and 7 blocks are reserved
TCH FCCH SCH BCCH AGCHPCH
time time/8
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Day 1 Section 5 The GSM Air Interface
Structure of GSM Common Control Channel, CCCH (cont.)For low traffic cells, four TACH/8 channels and theirSACCHs can be combined onto the BCCH+CCCH BPC
This configuration avoids having to set aside a BPC ona single TRX site for 8 x TACH/8, leaving seven BPCsfor traffic
time time/8
TCH FCCH SCH BCCH TACH/8PAGCH
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Day 1 Section 5 The GSM Air Interface
Structure of GSM Common Control Channel, CCCH (cont.)The uplink portion of the BCCH+CCCH BPC is used bythe Random Access Channel, RACH. MSs send ‘AccessBursts’ on the uplink RACH in response to pages and torequest channels for outgoing calls. For the normal
configuration, all uplink timeslots are used by the RACH
In the low traffic configuration, the uplink timeslotscorresponding to the 4 x TACH/8 channels are not used
time time/8RACH/H
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Day 1 Section 5 The GSM Air Interface
Allowed GSM Channel Combination TypesLow Traffic Cell, 1 TRX:BPC 0: FCCH, SCH, BCCH, PAGCH/3, RACH/H, 4xTACH/8BPC 1-7: TACH/F
Medium Traffic Cell, 4 TRXs:C0: FCCH, SCH, BCCH, PAGCH/F, RACH/F, 7xTACH/FC1-3: 23xTACH/F, one BPC of 8xTACH/8
High Traffic Cell, 16 TRXs:C0 BPC 0: FCCH, SCH, BCCH, PAGCH/F, RACH/F
C0 BPC 2,4,6: BCCH, PAGC/F, RACH/FC1-15: 120xTACH/F,
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Day 1 Section 6 The UMTS Radio Access Network
UTRAN ArchitectureWCDMA Characteristics
Intra and Inter-System Handover in UMTS
UTRAN Channel Structure
UMTS coverage planning issues
UTRAN Evolution
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Day 1 Section 6 The UMTS Radio Access Network
UTRAN Architecture
Iub Iub
Iub
Iub Iub
Iur
Core Network
Iu Iu
Serving RNC Drift RNC
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Day 1 Section 6 The UMTS Radio Access Network
WCDMAcharacteristics
Flexible multiplexing of userdata, from low bitrate voiceto very high bitrate packet
Built-in capability tohandle multiple serviceswith different QoS andbitrate requirements
Many operating modes
available to the plannerto give high spectralefficiency from macrocellto pico and even femtocell
Support for IP packet data
handling, both instantaneouslyand explicitly through introduc-tion of HSPA extension modes
Robust interferenceaveraging to permithigh spectral efficiency
Designed in support for futuretransmit diversity, interferencecancellation, smart antennasand other advances
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Day 1 Section 6 The UMTS Radio Access Network
Intra and Inter-System Handover in UMTS
F
F
F
FAF sector 1
F sector 2
F
FII
Intersite Soft Handover
IntersystemHandover
3G
3G
3G
2G
IntersiteHard
Handover
IntersectorSofter Handover
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Day 1 Section 6 The UMTS Radio Access Network
UTRAN Channel Structure
Voice
FixedData
2G CN2G
BTS
Logical Channel
PhysicalChannel MS
3G CN3G
RBS
VoiceMusic
streamingVideo
StreamingDownloads
wwwetc.
+control
Logical Channel(s)
UE
Channel code 1
Channel code 2
Channel code 3
More physical channels
Transportchannel = f (logical
channel,transportformat)
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Day 1 Section 6 The UMTS Radio Access Network
UTRAN Channel Structure (cont.)
Broadcast Control Channel (BCCH)Broadcast Control Channel (BCCH) Broadcast Channel (BCH)Broadcast Channel (BCH)
Forward Access Channel (FACH)Forward Access Channel (FACH)
Paging Control Channel (PCCH)Paging Control Channel (PCCH) Paging Channel (PCH)Paging Channel (PCH)
Common Control Channel (CCCH)Common Control Channel (CCCH)Random Access channel (RACH)Random Access channel (RACH)
Forward Access Channel (FACH)Forward Access Channel (FACH)
Common Traffic Channel (CTCH)Common Traffic Channel (CTCH) Forward Access Channel (FACH)Forward Access Channel (FACH)
Dedicated Traffic Channel (DTCH)Dedicated Traffic Channel (DTCH)
&&
Dedicated Control Channel (DCCH)Dedicated Control Channel (DCCH)
Forward Access Channel (FACH)Forward Access Channel (FACH)
Dedicated Channel (DCH)Dedicated Channel (DCH)Downlink Shared Channel (DSCH)Downlink Shared Channel (DSCH)
Random Access channel (RACH)Random Access channel (RACH)
Common Packet Channel (CPCH)Common Packet Channel (CPCH)
Logical Channel Transport Channel
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Day 1 Section 6 The UMTS Radio Access Network
UMTS Coverage Planning Issues
2G networks could be plannedsite by site due to theirseparation in frequency
Mutual interference cannot be avoided
in 3G networks, so sites have to beidentified and planned as groups withbenign coverage/interference. These
groups are known as ‘clusters’.
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Day 1 Section 6 The UMTS Radio Access Network
UTRAN EvolutionImproved throughput, RTT than existing legacy RAN
Seamless incorporation of future HSPA modes, LTE
IP network transport replaces ATM
Use of open specifications, i.e. IETF
Control and User planes allowed to scale independently,i.e. better flexibility and reliability
Better native handling of user data at intermediatenodes, e.g. MPLS, deep packet inspection etc
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Day 1 Section 6 The UMTS Radio Access Network
UTRAN Evolution (cont.)
ATM-based transport betweenRNC and NodeB
Centralised ‘Radio Network Controller’
Radio-specific User Data handlingin RNC for Radio Link Control,Medium Access Control
IP based transport network management at Layer 3
Centralised termination of Iu_controlinterface in RAN server for RANAP
Radio independent control interface
SHO support on Iur between mergedNodeBs
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
Review of 3G EvolutionGSM vs 3GSM
GSM Access and Core Network
Spreading and Modulation
Link Structures
High Data Rate Capabilities
Migration Scenarios
Packet Switched Networks
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
Review of 3G Evolution
MSC/ VLR
BSC
BTS BTS BTS BTS
Abis Abis
A
A
PSTN
C7
Signalling
ATM
Data
IP
FrameRelay
SGSN
Internet
Gb
Gb
2.5G2.5G
BSC
2.75G2.75GEDGE EDGE EDGE EDGE
MSCserver
RNC
NodeB NodeB NodeB NodeB
Iubis Iubis
Iu-CS
Iu-CS
PSTN
ATM
SGSN
Internet
Iu-PS
Iu-PS
RNC
ATM
Iubis
3G >3G >
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
GSM vs 3GSM
Voice:support for half
rate, AMR modesbeing retrofitted to BSS
Data capability up to ~400kb/s
via GPRS and E-GPRS
Some mobility, relocation
Spectral efficiency ~ 53 users/ 5MHz max.
Designed to access the ISDN
packet capability retro-fitted but neverfully exploited
Voice:native support
for half rate, AMR,DTX, DRX
Data capability up to 2Mb/s
(R99) and > 10MB/s (HSPA)
Enhanced radio resourcemanagement via 3G-SGSN
Spectral efficiency ~ 95 users/ 5MHz max.
Designed for advancedIP level access to
Internet
GSMGSM3GSM/ 3GSM/ UMTSUMTS
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
GSM Access and Core Network
Abis
A
A
PSTN
Internet
Gb
Gb
Abis
MSC Server/ Visitor Location Register
Gateway GPRSSupport Node
Serving GPRSSupport Node
PacketControl
Unit
Media Gateway
HomeLocationRegister
Base StationController
Base StationController
Fixedmapping
links
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
Spreading and Modulation
XWidebandModulator
CarrierGenerator
CodeGenerator
WidebandDemodulator
CarrierGenerator
De-spreading
CodeGenerator
Code Sync/ Tracking
Transmitter Receiver
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
Spreading and Modulation (cont.)
Multiplication of symbol andchip information ‘spreads’ the spectrum over anextent equal to the base-
band chip rate
The ratio between chipand symbol rate is the
‘processing gain’
Processing Gain Gp =Chip rate/ Symbol rate
Chip rateChip rateSymbol rateSymbol rate
2 x Symbol rate2 x Symbol rate
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
Spreading and Modulation (cont.)
0 1 0Symbol
De-Spread
Data
Chip
Local Code
ReceivedData
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
Link Structures
Downlink
Acknowledgement: LM Ericsson
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
Link Structure (cont.)
UplinkAcknowledgement:
LM Ericsson
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
High Data Rate Capabilities
High Speed Downlink Packet Access
Uses all spare power to transmit two new channel types
MSs share the High Speed Downlink Shared Channel
Control is via the High Speed Shared Control Channel
The link is maintained over A-DCHs between sites
HS-DSCH
HS-SCCH
A-DCH A-DCH
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
High Data Rate Capabilities (cont.)
Physical channels associated with HS-DSCH and HS-SCCHconsume whatever power is left after common anddedicated channel power has been allocated
HSDPA
Common channels (not power controlled)
Dedicated channels (power controlled)
T o t a
l a v a i l a b l e c e l l p o w e r
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
Migration Scenarios
All operators have re-engineered for 2.5G GSM-GPRS
The main hassle is not hardware but software issues
MSC MGW SGSN3G- 3G- 3G-
C7/FR
3G Antennasand feeder
Aggregated Transmission
2G BTS 3G RBS/ NodeB BSC
ATM
RNC
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
Migration Scenarios (cont.)
2G→3G: Straight swap of BSS for hybrid 2G/3G kit
2.5G→3G: GPRS capability can be upgraded, MSC, SGSN,MGW→3G-SGSN, 3G-MSC, 3G-MGW, add RNCs and Iur,2G BTS unlikely to be upgradable so replace with newand upgrade transmission to site
2.75G→3G: Probably only need software upgrade in MSC,SGSN, and MGW, add RNCs and Iur, EDGE BTSs likelysoftware or easily hardware upgradable to 3G. Power
at each site may need upgraded due to extra loadingfrom 3G RBS. Transmission to sites can probably copebut again may need upgraded
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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G
Packet Switched Networks
Serving GPRSSupport Node
Gateway GPRSSupport Node
IP Domain
RNC
BSC
IP Mobility Management,RRM, tracks MSs and UEs at
cell level, terminates PacketData Protocol, performsMSC-like functions in packetdomain
Very large ATM switch,interfaces IP domain,VPNs and Internet to theSGSN(s) and BSS/UTRAN
Packet DataProtocol
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Overview of Day 2
Basics of Radio Network Planning
Radio Network Pre-planning
Radio Network Parameter Planning
Antenna and Feeder Cable Design
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Day 2 Section 8 Basics of Radio Network Planning
Scope of RNP
Cell Shape
Elements in a Radio Network
Radio Network Planning Process
Radio Cell and Wave Propagation
Wave Propagation Effects and Parameters
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Day 2 Section 8 Basics of Radio Network Planning
Scope of RNP Define Service Area
Select Sites based onlocal clutter criteria
Simulate coverageand quality
Optimisation
Coverage/ quality criteria
met?
No
Yes
Management & Strategy
Site Acquisition &Civils Construction
Radio Planning
Radio Planning
No
Yes
All sites acquired?RNP occupies the
stratum betweenservice area
definition and radionetwork optimisation
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Day 2 Section 8 Basics of Radio Network Planning
Cell Shape
Due to signal propagation limitations,
real-world cell shapes are fardifferent from the idea RNP scenario
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Day 2 Section 8 Basics of Radio Network Planning
Elements in a Radio Network
2G MS
TerminalEquipment
SubscriberIdentityModule
GSM Air Interface
3G UE
TerminalEquipment
USIM
Uu Interface
Mobile
Equipment
3G Air Interface
Cu Interface
Radio, channel
funtionalities
User applications
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Day 2 Section 8 Basics of Radio Network Planning
Elements in a Radio Network (cont.)
RF Filter
WidebandPower
Amplifier
InputCombiner
TRX
PowerSupply
ApplicationManager
andSignal
Processor
Summingand
Multiplexing
ATMMultiplexer
andInterface
Unit
Transmission
Baseband Unit
BTS Manager
TRXs
Power Supply
Combiner& Filter
Generic 2G BTS Nokia UltraSite 3G RBS
Singlesectorshown
For a 3G RBS, the term NodeB describesthe collection of radio equipment for allsectors. These must be grouped together asa functional unit to permit softer handover
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Day 2 Section 8 Basics of Radio Network Planning
Channel Configuration in GSM
Rural Configuration:Single TRX Site, OmniAntennas, Low Capacity
Suburban Configuration:2-4 TRX per sector,Sector Antennas, Low-Medium Capacity
Urban Configuration:2-4 TRX per sector Site, SectorAntennas, Medium Capacity
Dense Urban Configuration:8-16 TRX per sector Site, SectorAntennas, High Capacity
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Town 1 Town 2
Town 3
Town 4
Day 2 Section 8 Basics of Radio Network Planning
Radio Network Planning Process
Two key steps – siteidenfication/selectionand coverage simulation
Define ‘search radii’, withinwhich option sites are to beidentified
Simulate area coverage andquality using ‘hot option’ sites
(not necessarily best radioquality)
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Day 2 Section 8 Basics of Radio Network Planning
Radio Cell and Wave Propagation
F(bi,x)
b1
b2 b3
bnFor each location, calculate:
CoverageBest Server
Mutual Interference ProbabilityAssignment Probability
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Day 2 Section 8 Basics of Radio Network Planning
Lfs[db] = 10*log(F0 /F1)
= 32.4+ 20*log(d/km)
+ 20*log(f/MHz)
Half wave dipole
f
2 f
Antenna
EffectiveAperture
Wave Propagation Effects and Parameters
In free space, electromagnetic wave loss depends onlyon frequency and distance between transmitter andreceiver
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Day 2 Section 8 Basics of Radio Network Planning
Wave Propagation Effects and Parameters (cont.)
The propagation of radio waves is more complex, and depends onconditions within the first ‘Fresnel Zone’. This is an ellipsoid ofrevolution defined by all points where the summed distance betweenbase antenna and MS exceeds free space by half a wavelength
Free space loss can be assumed only if the first Fresnel Zone is unobstructed.This is almost never true. Instead, especially close to the MS there areobstructions due to a) mountains, hills and other terrain profile features and b)
buildings trees and other features of the morphostructure.
Shadowing and reflections from obstructions in the first Fresnel Zone causelosses that cannot be computed analytically, the planner must choose anappropriate empirical pathloss model
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Day 2 Section 8 Basics of Radio Network Planning
Wave Propagation Effects and Parameters (cont.)
R e c
e i v e d P o w e r
Distance/Time
|| (rand[-1..1] + rand [-j..j]) ||
rand[-1..1]
rand[-j..j]
Incoming wavefrontfrom base station
Field Strength = Σ Ai cos (2πf+∆i)N
i=1
Rayleigh Fading
Many random, smallE-field contributionsfrom objects 30-40m
away from MS
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Day 2 Section 8 Basics of Radio Network Planning
Wave Propagation Effects and Parameters (cont.)
[0..Lossmax] [0..Lossmax] [0..Lossmax] [0..Lossmax]
A number of objectsintervene between
base station and MS
with random lossesbetween 0 and Lossmax
N u m b e r
o f s a m p l e s
Loss (dB)
LognormalDistribution
2
2
2
))(ln(
2
1),;( σ
µ
π σ σ µ
−−
=
x
e x
xF
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Day 2 Section 8 Basics of Radio Network Planning
Wave Propagation Effects and Parameters (cont.)
Lin-car ≈10 dB
Lindoor ≈3-15 dB
Lindoor ≈ 13-25 dB
The network operator may specify that thenetwork has to be engineered for operation
inside buildings and vehicles. This isaccounted for as an extra loss on top of that
computed from the pathloss model
Lindoor ≈ 17- ∞dB
Lindoor ≈7-18 dB
Flr 1-10- 2.7 dB/flr
Flr 11+- 0.3 dB/flr
gheight
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Day 2 Section 8 Basics of Radio Network Planning
Wave Propagation Effects and Parameters (cont.)
Incoming wavefront
The interior of a building is illuminatedby only a subset of primary andsecondary scatterers
The fading statisticsof the surroundingenvironment aresuperceded by anaverage set of
statistics derived forbuildings in the areaor country of interest.
σindoor ≈ 5dB
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Day 2 Section 8 Basics of Radio Network Planning
Wave Propagation Effects and Parameters (cont.)
For propagation over water, it is usual to remove an amountof pathloss corresponding to the ‘opening’ of the first
Fresnel Zone. The propagation loss is then roughly equal to
free space loss. The actual loss factor dependson the measured statistics for the area.
Lwater = -5 to -10 dB
D 2 S i 8 B i f R di N k Pl i
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Day 2 Section 8 Basics of Radio Network Planning
Wave Propagation Effects and Parameters (cont.)
Summer
Winter
In summer, loss in decidous forest isapprox 10dB, in winter approx 5dB
For evergreen forests,there is very little difference
between summer and winterloss (approx. 6 and 5 dB)
D 2 S ti 8 B i f R di N t k Pl i
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95% of signalsamples fall
within twostandarddeviations of
the mean value
2σ
Day 2 Section 8 Basics of Radio Network Planning
Wave Propagation Effects and Parameters (cont.)
Why are the fading statistics important?
Received Power (dBm)
Probability
ofReceived
Power
Computer toolscalculate averagereceived power
If we wish 95% probability of service, we must engineer everywhere for a mean power level 2 σ dBm greater than threshold
D 2 S ti 8 B i f R di N t k Pl i
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Day 2 Section 8 Basics of Radio Network Planning
Wave Propagation Effects and Parameters (cont.)
Received Power (dBm)
Interference Margin
S i g n a l S t r e n g t h Interference approximately
constant over service area of site
For normal frequency reuse ina GSM system, the background
noise level is raised by
approximately 2 dB due tosystem-wide cochannel
interference
Add an ‘interference margin tomove the entire received powerprobability distribution curve up
by the amount of theinterference introduced
D 2 S ti 8 B i f R di N t k Pl i
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Day 2 Section 8 Basics of Radio Network Planning
Wave Propagation Effects and Parameters (cont.)
Receiver sensitivity depends on required C/N ratio. Whenfrequencies are reused the the received carrier powermust be large enough to combat both noise and inter-ference, i.e. C/(N+I) must exceed the receiver threshold
In a normal GSM system, with frequency hopping,dynamic power control and DTC, an interference marginof 2dB is used.
Due to the mutual interference of 3G networks, a higher
interference margin of 3 dB is used. This varies withtraffic, and is called the ‘System Noise Rise’
D 2 S ti 9 R di N t k P Pl i
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Day 2 Section 9 Radio Network Pre-Planning
Capacity and Quality
Site Survey and Site Selection
Result of Site Survey Process
Frequency Hopping
Equipment Enhancements
Power Control
Handover
D 2 S ti 9 R di N t k P Pl i
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Day 2 Section 9 Radio Network Pre-Planning
Capacity and Quality
CapacityCapacityLow bandwidth,Low bandwidth,
bitratebitrate perperbasic physicalbasic physicalchannelchannel
QualityQualityHigh bandwidth,High bandwidth,
bitratebitrate perperbasic physicalbasic physical
channelchannel
The requirements of capacity and quality
conflict in the network design
Da 2 Section 9 Radio Net ork Pre Planning
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Day 2 Section 9 Radio Network Pre-Planning
Capacity and Quality (cont.)
Introduce HalfRate Codec
Legacy GSM Network, 7 cell repeat
Full rate codec, 13kb/s,high quality
Half rate codec, 5.6kb/s,medium/low quality
No change to frequencymanagement structure
No extra investment in
Base Station TRXs etc
MSs must support HR
Day 2 Section 9 Radio Network Pre Planning
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Day 2 Section 9 Radio Network Pre-Planning
Capacity and Quality (cont.)
0
5
10
15
20
25
F R
A M R 1
2 . 2
A M R 1
0 . 2
A M R 7
. 9 5
A M R 7
. 4
A M R 6
. 7
A M R 5
. 9
A M R 5
. 1 5
A M R 4
. 7 5
B i t R a t e ( k b / s )
Increasing robustness
Channel Coding
Source Coding
8 dB 2.8 dBFull Rate C/(N+I) for 1% FER
0
2
4
6
8
10
12
H R
A M R 7
. 9 5
A M R 7
. 4
A M R 6
. 7
A M R 5
. 9
A M R 5
. 1 5
A M R 4
. 7 5
B i t
R a t e ( k b / s )
Increasing robustness
18 dB 8.5 dB
Half Rate C/(N+I) for 1% FER
Day 2 Section 9 Radio Network Pre Planning
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Day 2 Section 9 Radio Network Pre-Planning
Capacity and Quality (cont.)
7 cell repeat, 2 TRXs per cell
Full rate codec, 13kb/s,high quality
4 cell repeat, 3-4 TRXs per cell
AMR codecs, 12.2 – 4.75kb/s, high - low quality
Introduce AMRCodec
HigherCell Interference
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Day 2 Section 9 Radio Network Pre-Planning
Site Survey and Selection
First Choice Sites
● Site survey
● Verification measurements
● Negotiations with owners
Preliminary NetworkDesign and Analysis
Site proposals Preliminary site selections
Detailed network designand analysis
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Day 2 Section 9 Radio Network Pre-Planning
Site Survey and Selection (cont.)
The site acquisition process is costly and time consuming
Need to consider:
Site Access and Availability
Installation conditions (antenna mounting and cabling,availability of equipment rooms, possibility of aircon, etc)
Available and adequate mains power supply
In urban areas:
Check antennas can be installed significantly above roof
No ‘clipping’ from nearby higher buildings and towers
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Day 2 Section 9 Radio Network Pre-Planning
Results of the Site Survey Process
Ideal coverage scenario
Site too low
Site too high
Coverage hole
Poorhandover
zone
Sitemissing
Multiple streetfurniture sites
Real-World coverage scenario
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Day 2 Section 9 Radio Network Pre-Planning
Frequency Hopping
Baseband hopping on F1-F4 combatsRayleigh fading for slow moving MSs
Resultant after de-interleaving and error correction
Resultant after hopping on F1-F4
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Day 2 Section 9 Radio Network Pre-Planning
Frequency Hopping (cont.)
Need high reliability decoding of the Broadcast and Pagingchannels, so no frequency hopping on the BCCH/C0carrier. High quality 7 site or medium quality 4 site repeat
F1 F2
F3
F4 F5
F6
F7 F8
F9
F10 F11
F12
F13 F14
F15
F16 F17
F18
F19 F20
F21
21 x 200kHz= 4.2MHz
F1 F2
F3
F4 F5
F6
F7 F8
F9
F10 F11
F12
12 x 200kHz= 2.4MHz
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Day 2 Section 9 Radio Network Pre-Planning
Frequency Hopping (cont.)
For the frequencies carrying only traffic channels, theseare gathered together in three groups in a 1 x 3 config-uration or as a global ensemble in a 1 x 1 configurationand RF/synthesiser frequency hopping employed
1x3 TCHrepeat
1x1 TCHrepeat
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Day 2 Section 9 Radio Network Pre-Planning
Frequency Hopping (cont.)
Power reduction toMS close to the sitereduces its C/(N+I) tothe minimumacceptable, but alsoensured that little
interference spillsover to MSs inadjacent cells in thesame timeslot
Synthesiserfrequency hoppingworks by trying to
average out theC/(I+N) for each
MS to the minimumpossible
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Day 2 Section 9 Radio Network Pre Planning
Equipment Enhancements
Two receive antennas are installed at thebase location to create RX diversity. With
sufficient antenna spacing, the fadingprocesses are uncorrelated between thetwo antennas. At the receiver, the two
received signals are combined bitwise.
Where space does not permit twohorizontally spaced antennas, a single
antenna with two separate cross-polarisedbrances may be used
For both configurations, GDIVERSITY ≈ 3.5dB in rural areas,and 4.5dB in suburban/urban areas
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Day 2 Section 9 Radio Network Pre Planning
Equipment Enhancements (cont.)
‘Cell splitting’, where a singleexisting omnidirectional antennais changed out for three or moresector antennas, is the simplestform of capacity enhancement.
When cells are split, thefrequency reuse pattern must berevised.
1
2
3
4
4
2
1
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Day 2 Section 9 Radio Network Pre Planning
Equipment Enhancements (cont.)
If a particularly high site has tobe accepted in the planning, thesignal coverage may be much
larger than intended
The solution is to add a downtiltkit to the top of the antenna,tilting it forward and reducing
the coverage area
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Day 2 Section 9 Radio Network Pre Planning
Equipment Enhancements (cont.)
Downtilting can also be used to limitthe amount of traffic handled by acell. The traffic is given by theintegral over the area where the siteis ‘best server’, i.e. the area where a
new call will be assigned to the site,multiplied by the ‘offered traffic’ map
High Traffic Lower Traffic
Town 1 Town 2
Town 3
Town 4
Traffic Erlangs/km²
0.01 0.1 1 10
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Day 2 Section 9 Radio Network Pre Planning
Equipment Enhancements (cont.)
The nature of the constructed network depends on ‘average antenna height’.
For a high coverage, medium capacity GSM900 network, the desired antennaheight is approximately 30m. For a high capacity GSM1800 or W-CDMA
network, average antenna height is 20m
In the case of siteswhich are lower than
the specifiedminimum, a stubmast may have to beconstructed to raise
the antennas tomimimum height
If a particularly highsite is acquired, theantennas must bedropped down thesite of the structure 20-30m
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Day 2 Section 9 Radio Network Pre Planning
Power Control
Frequency hopping,power control and DTX(DiscontinuousTransmission) areessential for goodquality with 1 x 3 or 1 x1 reuse on TCHfrequencies
MS distant, high power MS in middle of cell,medium power
User of MS talking,uplink active, downlink
inactive due to DTX
MS close to site, downlink power low
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Day 2 Section 9 Radio Network Pre Planning
Handover
Normal Handover Zone
During voice calls or data sessions, the MS tries to attach itself to the basesite with the lowest pathloss. This ensures that the minimum power necessaryto maintain the link is used. This process is called handover. The handoverprocess may fail for a number of reasons, and if so the MS ‘drags’ coverageinto adjacent cells
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Handover (cont.)
Distance
R e c e i v e d P o
w e r
Site 1
Site 2
hysteresis
In the handover zone, shadowfading results in alternatingdominance of two base sites.
To reduce the number ofhandovers that would result, a
‘hysteresis’ level is set, which site2’s received power level mustexceed in order to initiatehandover.
High hysteresis reduces thenumber of handovers, but
increases the risk of coveragedragging. A good compromisevalue is 3 dB
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Signalling
Radio Resource and Mobility Management
Basics of Radio Network Optimisation
Network Performance Monitoring
Network Performance Assessment
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Signalling
An GSM MS exchanges call setup and control messageswith BTS, BSC and MSC. In the same way a 3G UEexchanges similar messages with the RBS, RNC and 3G-MSC. These messages can be captured at the radio and
network interfaces and used as valuable diagnostic aids
BTS BSC MSC2G MS
RBS RNC 3G-MSC3G UE
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Radio Resource and Mobility Management
Location Area 1
Location Area 2
Location Area 3
For paging purposes, sites are groupedinto ‘Location Areas’. As the 2G MS or
3G UE moves around, it sends LocationUpdate messages to the MobilityManagement function of the network
LocationUpdate
Location Update
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Radio Resource and Mobility Management (cont.)
RNCUE detectsmismatchbetween storedand receivedLocation Areas
Home LocationRegister
Visitor LocationRegister
3G-MSC
RBS
RBS
Location Update Request
Radio Resources ReservedChannel Setup
Channel Setup complete
Location Update RequestAuthentication
Information ReqAuthentication Request
Authentication ResponseSubscriber
Information Req
Location Update SuccessfulRadio Resource Release
Release
Signalling
shown for 3Gcase, 2Gsimilar
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Radio Resource and Mobility Management (cont.)
BA list
For 2G GSM the BTS sends a Base-station Allocation (BA) list to the MS.The MS uses the BA list as a
neighbour list and measures all thefrequencies, sending the strongest sixback to the BSC in a ‘measurementreport’, as potential handover targets.
Measurement Report
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Radio Resource and Mobility Management (cont.)
In both idle and dedicated mode, the MS receives aBasestation Allocation (BA) List from the network
This is a list of frequencies and Base Station IdentificationCodes (BSICs) for neighbouring 2G scrambling codes for
3G base stations
In idle mode, the BA list is used by the MS for cellreselection
In 2G dedicated mode the MS sends a list of the strongest
six received ARFCNs+BSICs to the Radio ResourceManagement function in the network to permit handover
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Radio Resource and Mobility Management (cont.)
MeasurementControl
In 3G, the UE receives Measurement Controlmessages from the Radio Resource Managementfunction in the RNC, containing the scrambling codes(SCs) of neighbouring base sites. The UE replies withMeasurement Report messages for all decoded SCs,and also requests the RNC to add, drop or modify theserving scrambling codes in Soft Handover.
Add SHO Add SHO
MeasurementReport
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Radio Resource and Mobility Management (cont.)
In 3G dedicated mode, the UE receives a list ofneighbouring Scrambling Codes (SCs) via a MeasurementControl message from the RNC
The Measurement Control message modifies a register in
the UE containing SCs the RNC is targeting for handover
The UE replies with a Measurement Report message,containing all the validly decoded SCs
The UE requests the RNC to add SCs its Active Set, when
these would otherwise cause unacceptable interference.When their power level recedes, they can be removed
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Basics of Radio Network Optimisation
Iubis
RNC
Iur
Iu
3G-MSC
Nethawk
L 3
Analysis of the‘Layer 3’ Mobility
and RadioResource
Managementmessages
between UE andRNC is the
majority of RNO
Occasionally, higher layer messages on the Iu, Iur andIubis need to be analysed to solve difficult problems
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Basics of Radio Network Optimisation
Identify Site Clusters
Test Drive
Site Cluster
Analyse L3 andother signalling data
Identify problem sectors/sites
Change Antennas,Downtilts, pans,
RAN parameters
PrelaunchPrelaunchOptimisation Optimisation
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Network Performance Monitoring
Gather Key Performance IndicatorsAnalyse and Report
Plan coverage / capacity / service /no. of sites enhancement
Implementation, logistics, fieldengineering, site construction and
preparation
Provision and upload radio networkparameter plan, dimension data
warehousing and storage
Engineering drivers:
performanceoptimisation andtroubleshooting
Business drivers:NW expansion andchange in offeredQoS
Schedule
Project setup
Progress
reports fromsiteimplemenation
Readyparameters,routing tablesetc
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Network Performance Assessment
MS
PAIR_INTERFACE
BTS
PBTS
BSC
PBSC
MSC
PMSC
TransportNetwork
PTRANSPORT_NETWORK
In the 2G case, with only voice and simple data as services,the end-to-end performance is a simple function of the
performance of each network element
Poverall = f ( PAIR_INTERFACE + PBTS + PBSC + PMSC + PTRANSPORT_NETWORK )
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Network Performance Assessment (cont.)
UE
RBS
RNC 3G-MSC
TransportNetwork
AMR12.2
AMR10.2
AMR7.95
AMR7.4
AMR6.7
AMR5.9
AMR5.15
AMR4.75
FR
HR
Voice
Video, Streaming, www, downloads etcSF8
SF16
SF32
SF64
SF128
HSDPA
It is impractical to optimise 3G at theindividual service level
3G Multiservice Environment
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Network Performance Assessment (cont.)
RBSRNC
3G-MSC Event Counters
RRC Releases, RAB Setup, DroppedCalls, SF16 Admission Control, etc etc
The performance of the network is
‘abstracted’ from the physical servicesby collecting and processing event
counters from RBS, RNC and 3G-MSC
Key Performance
Indicators (KPIs)
Call Setup Rate
Call Completion Rate
PDP Context Activation Rate
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Network Performance Assessment (cont.)
Town 1 Town 2
Town 3
Town 4
Operator needs ability to visualisecoverage
Internal counters for 2G can be e.g.commanded power level, received incall power levels
Internal counters for 3G iscommanded power level, percentageof calls in SHO, softer HO, handeddown to 2G etc
External counters for 2G and 3G are
scanner received power levelmeasurements and for 3G, differencebetween this and RSSI (i.e. Ec/Io)
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Network Performance Assessment (cont.)
Capacity only assessed wherecoverage exists
Most important counters onthe Uu (air) interface, as
capacity can be planned on Iuan Iubis
Capacitycan be assessed at
either network orcell (hotspot) level
RBS
RNC
3G-MSC
RBS
RBS
Uu blocking rate, Admission Control
Iubis blocking, configurationetc
Iubis blocking, configurationetc
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Network Performance Assessment (cont.)
Quality of Service (QoS) can be set either on the cell ornetwork level
QoS QoS
Blocked calls - hardware
‘Soft’ blocking - interference
Call setup failures
Dropped calls
Call quality target missedR99 data retransmissions
HSDPA MAC-d data retransmissions
Hard Handover Failures
Downlink overload
Uplink overload
Excess delay and RTT
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Network Performance Assessment (cont.)
Key Performance Indicators
Cost Function 1
Cost Function 2
Cost Function n S t a r t i n g P a r a
m e t e r S e t
RadioNetwork
SubsystemSimulator
ChangedParameterValues
We attempt to simplify the optimisation process as a set of‘cost’ functions that trade off sometimes conflicting parameters
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Basics of Antennas
Antenna Gain
Directional Diagram
Polarisation
Antenna Diversity
Antenna New Technology
Shaped Beam Technology
Intelligent Antennas
Downtilt Planning
Downtilt Design
Antenna Selection
Current Antenna Use Problems
Urban Base Site Antennas
Rural Base Site Antennas
Highway Base Site Antennas
Combining and Distribution Unit
Combiner Principles
Outdoor Antenna FeederSystem
Tower Mounted Amplifiers
Feeder Cables
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Basics of Antennas
Current
Voltage
Minimum Radiation
Maximum Radiation
An antenna matches the impedanceof the feeder cable, usually 50Ω tofree-space impedance of ~ 73Ω. An
electric field propagates away fromthe antenna parallel to the elementsand a magnetic field perpendicular
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Antenna Gain When n dipole elements are fed by signals
in phase, the overall effect at a point in thefar field is that the electric field is multipliedby n and the power received by n².
The antenna ‘gain’ is definedrelative to the 2.2 dB ‘cardioid’ gainof an individual element, or relative
to a fictitious ‘isotropic’ radiator,where all of the power is distributed
evenly over 4π solid angle
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Directional Diagram
From above, the lines of equalelectric field strength, or ‘radiat-ion pattern’ form a near perfect
circle in the horizontal plane
If a long reflector is added close tothe colinear, the radiation pattern is
biased away from the reflector,creating gain in the horizontal plane
Dipole elements are stacked end on end to form a colinear antenna
RF
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Polarisation
Cellular antennas areusually vertically polarised,parallel to the verticalcolinear radiating structuresthey contain
When antenna diversitycannot be used, anantenna with two slantsenses of polarisation andseparate receive branches
may be used to obtain ‘polarisation diversity’
E
H
TX/RX
EH
45°
TX/RXTX/RX
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Antenna Diversity
d+
=
By combining the signal fromtwo horizontally spacedantennas, deep fades in theRayleigh fading processescan be evened out.Combining can either be on asignal level basis or ‘bestdecoded bit’ at the receiver
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Antenna New Technology
GSM and other 2G technologies not originally designed for ‘advanced’ antenna technologies
3G systems have built-in functionality to assist the lastestgeneration smart antennas
Antenna technology used either to extend coverage rangein rural areas or to give immunity to interference insuburban/urban areas
Interference reduction in 3G leads directly to capacity
gains, but space division multiple access (SDMA) may infuture be used to multiply base site capacity
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Shaped Beam Technology
RX
RX
RX
RX D i g i t a l S i g n a l P r o c e s s i n g
Beam 2
Beam 3
Beam 4
Beam 1
Range
Receiving range ofindividual sector antenna
UE falls within extendedrange of shaped beam 2
Plan view of shaped beamantenna, four elements
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Intelligent Antennas
RX
RX
RX
RX D i g i t a l S i g n a l P
r o c e s s i n gUE1
UE2
UEn
Intelligent beamformer createsdeep nulls to remove the two
interferers, while preserving gainin the direction of the wanted UE
Interferer 1
Interferer 2
Wanted UEtransmitsreference
information to aidthe beamformer
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Downtilt Planning
The vertical radiationpattern of the antenna
may result insignificant overshootand thus interference
in urban areas
By vertically downtiltingthe antenna the
interference zone iscurtailed. Downtilts
between 6°and 10°areused in urb