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UMTS Applied Radio Planning
Prepared By
M. Ahsan Raza
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a s an
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Course Objectives
Understand the key planning parameters of the UTRAN
Produce UMTS Link Budgets for various services
Understand Capacity dimensioning in UMTS
Appreciate the Coverage/Capacity relationship in UMTS
va ua e - o- oca on ssues
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1- The UMTS Air Interface
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UMTSThe UMTS Air Interface
Universal Mobile Telecommunication System
Also called 3G, along with other IMT-2000 technologies
The evolution from GSM-GPRS-EDGE
,
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The UMTS Air Interface
1.1- WCDMA, Processing Gain and Codes
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CDMA - Direct Sequence Spread Spectrum
The UMTS Air Interface
Frame Period (we may still need
frames/timeslots for signaling)
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SPREAD SPECTRUM
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CDMA Spreading
The UMTS Air Interface
Essentially Spreading involves changing the symbol rate on the air interface
P
Spreading DespreadingP
f
Channelf
Tx Bit Stream P
P
f P Rx Bit Stream
f Air Interface
Chip Streamf
codesCode Chip Stream Code Chip Stream
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Spreading and Despreading
The UMTS Air Interface
1
-1
Code Chip Stream
XSpreading
Air Interface
Chip Stream
Code Chip Stream
esprea ng
Rx Bit Stream
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Spreading and Despreading with code Y
The UMTS Air Interface
1
-1
Code Chip Stream
XSpreading
Air Interface
Chip Stream
Code Chip Stream Y
Rx Bit Stream
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Interference mitigation
The UMTS Air Interface
Rx Signal (= Tx Signal + Noise)
f
P
P
Tx SignalP
fP
Channel
f f
P
f
Spreading Code
The gain due to Despreading of the signal over wideband
Wideband Noise/Interference
noise is the Processing Gain
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Processing Gain
The UMTS Air Interface
If the Bit Rate is Rb, the Chip Rate is Rc, the energy per bit Eb and theenergy per chip Ec then
ccbRREE =
cRG = We say the Processing Gain Gp is equal to: bR
Commonly the processing gain is referred to as the Spreading Factor
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Visualising the Processing Gain
The UMTS Air Interface
W/Hz W/Hz W/Hz
Io
Before
Spreading
After
Spreading With Noise
f f f
W/Hz W/Hz dBW/HzEb
N Eb
Eb/NoAfter
Despreading
Post
Filtering
o
W/HzSignal
f f f
EbNo
Eb/Nob
No
Intra-cell NoiseInter-cell Noise
PostFiltering
Orthog > 0
f f
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PROCESSING GAIN
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Types of Codes
The UMTS Air Interface
Channelisation Codes
Are used to separate channelsfrom a single cell or terminal S2
Scrambling Codes
Are used to se arate cells andterminals from each other ratherthan purely channels
S1
C1 C2 C3
Different base stations will usethe same spreading codes withseparation being provided by the
codes. C1 C2 C3
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USE OF CODESThe UMTS Air Interface
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Channelisation Codes
The UMTS Air Interface
Channelisation codes are ortho onal and hence rovidechannel separation
Number of codes available is dependant on length of code
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Channelisation Code Generation
The UMTS Air Interface
Used to separate transmissions from a single source
(from UE in uplink, from Node B in downlink) Uplink code lengths: 4 to 256
Downlink code lengths: 4 to 512
Code lengths are 2N, derived using the OVSF scheme enera e sprea ng
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OVSF codes
The UMTS Air Interface
Orthogonal Variable Spreading Factor Codes can be defined bya code tree:
Cch,2,0 = (1,1)
ch,4,0 = , , ,
Cch,4,1 = (1,1,-1,-1)
Cch,1,0 = (1)
Cch,2,1 = (1,-1)
Cch,4,2 = (1,-1,1,-1)
SF = 1 SF = 2 SF = 4
Cch,4,3 = (1,-1,-1,1)
SF = Spreading Factor of code (maximum 512 for UMTS)
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OVSF codes: Example 1
The UMTS Air Interface
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OVSF codes: Example 2
The UMTS Air Interface
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Scrambling Codes
The UMTS Air Interface
The spread data symbols are then scrambled by multiplyingwith a complex scrambling sequence
Scrambling codes do not affect the chip rate
The scrambling code is specific for a cell and thus serves to
There are 512 Scrambling Codes in the DL which can be
allocated by Radio Planners
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MULTIPATH EFFECTSThe UMTS Air Interface
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MULTIPATH EFFECTS AND THE RAKE RECEIVER
The UMTS Air Interface
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Power Control and Near/Far Effect
The UMTS Air Interface
When a UE is near the NodeB it doesnt need much power toreach it
In the same manner, if a UE is far away it needs greater power to
-powered mobile could block a Cell
Power Control is also needed in the DL to provide far away userswith enough power and to keep power low for near-by UEs
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NEAR FAR EFFECTThe UMTS Air Interface
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Open Loop Power ControlThe UMTS Air Interface
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CLOSED LOOP POWER CONTROLThe UMTS Air Interface
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Soft and Softer Handover
The UMTS Air Interface
In UMTS it is possible to have a UE connected to more than 1NodeB. This is called Soft Handover
When in Soft Handover, the RNC can combine the best signals ,
two cells on the same site. A Softer Handover gain also occurs.
However, too many mobiles in Soft or Softer Handover couldimpose a significant Overhead on the system
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SOFT HANDOVER
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SOFTER HANDOVER
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RELOCATION DRIFT RNC
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HARD HANDOVER
Compressed Mode
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CELL BREATHING
Cell breathing refers to the effectiveexpansion and contraction of a given
number of mobile users within the cell.
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1.2- Ec/Io, Eb/No, NR and Loading
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Interference and Noise Densities
From the point of view of a UE, every other UEs powerappears as Interference
Io is the Interference Density
No is the Interference + Noise Density
In general, when you talk about chips, or Ec, you use Io.When you talk about bits, or Eb, you use No.
No considers Thermal Noise at the NodeB
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Ec/Io
Ec/Io is the Chip Energy we obtain in the presence of theInterference generated by all other users
Ec/Io of the Pilot Channel is used to:
Estimate (sound) the channel (multipath characteristics)
Decide which server is best server
a e an over ec s ons
Typical requirement -15 dB
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CPICH The Common Pilot Indication Channel (CPICH) is a common channel
broadcast from each and every cell within a WCDMA network. It carries noinformation and can be thought of as a beacon constantly transmitting theScrambling Code of the cell.
Defines cell boundaries and provides each UE with a lock signal todetermine the ownership cell.
Initial system acquisition and to aid the channel estimation for the dedicatedchannels
The CPICH is one of the downlink channels utilized by each sector or cell. If the mobile is unable to clearly receive one dominant CPICH, due tointerference or coverage problems, the result is likely to be dropped calls,
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CPICH
The soft handoff algorithms for WCDMA are based on measurementsmade by the UE on the Primary Scrambling Code of the Common Pilot
anne .
Signal strength comparisons between base stations can be used todetermine when to o into soft handover between two cells.
If the UE cant see the CPICH the UE cant see the cell.
CPICH
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CPICH
From the Node B perspective the
to keep the initial cell boundaries
fixed.
Ec/IoPCPICH=33dBm
From the UE perspective the Pilot is perceivedas the ratio between the received energy perchip to total interference or Ec/Io
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CPICH Power
Increasing or decreasing the relative power allocated to this channel maymodify the CPICH coverage.
s common o a oca e - o a ava a e power o e
Node B Power Distribution per Sector
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CPICH Quality
Initial 3G network optimisation will be performed purely fromCPICH measurements. Three key related measurements for 3G
Ec - The Received Signal Level of a particular CPICH (dBm)
Io - The Total Received Power (dBm)
Ec/Io - The CPICH Quality (The ratio of the above two values)
Introduction
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IntroductionTotal Received Power Io
In a WCDMA network the User Equipment (UE) may receive signals frommany cells whether in handover or not
Io (RSSI) = The total sum of all of these signals + any background noise(dBm)
Ec1 Ec2
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IntroductionReceived Power of a CPICH Ec
Using the properties of the WCDMA downlink scrambling codes the UE isable to extract the respective CPICH levels from the sites received.
Ec (RSCP) = The Received Power of a Particular CPICH (dBm)
E E
Th CPICH Q lit E /I
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The CPICH Quality Ec/Io
From the previous two measures we can calculate a signal quality for eachCPICH (Scrambling Code) received. The quality of the CPICH can bemeasured in terms of Ec/Io, which is a representation of the signal to noiseratio for spread spectrum signals.
Ec/Io = Ec -Io (dB)
Ec1=-95dBm Ec2=-90dBm
From the above three measurements we can calculate for each pilot the
Io=-80dBm
(Ec/Io)1 = -95 - -80 = -15dB
(Ec/Io)2 = -90 - -80 = -10dB
stronger.
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Eb/No
Eb/No is the Bit Energy we obtain after despreading in thepresence of the Noise generated by all other users and the
o se rom o e equ pmen
Typical requirement 1 to 10 dB
, , ,Mobile Speed, and Type of Receiver.
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N i Ri
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Noise Rise
The effective noise floor of the receiver increases as thenumber of active mobile terminals increases.
This rise in the noise level appears in the link budget and
limits maximum path loss and coverage range.
Three Users
Two Users
Background NoiseOne User
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Eff t f N i hb i C ll
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Effect of Neighbouring Cells
.
Typical ratio of power from other cells to power from
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, , .
Th N i Ri E ti
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The Noise Rise Equation
jMjtotal LI
=
===
1
11
jbj
j
RE
L
+ =1
11
If we have M identical users:
Mj
j
jWN
ML
+
==
= 01 1jb RE
N
tota
WN
MP
==
0
1RiseNoise
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jb RE
N i Ri d L di F t
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Noise Rise and Loading Factor
Capacity is linked to Eb/No value
Maximum Path Loss tolerated is linked to maximum NR
o se se oa ng ac or
1 dB 20%
6 dB 75%10 dB 90%
( )UL= 1log10RiseNoise 10
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Loading Factor
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Loading Factor
ThroughputActual
RM :ratedatawithusersidenticalFor
CapacityPole
( )iNEW
b
+
=
1
FactorLoading
viEb + 1
RW=0
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UL Pole Capacity
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UL Pole Capacity
usersofnumberlargeFor
( )iEb +
1
CapacityPole
0
0.53Eb/No3840000W === i
( )( )kbps853
5.013
3840000CapacityPole =
+
50% of this would give a Noise Rise of 3 dB.
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50% of 853 kbps = 426 kbps
DL Pole CapacityThe UMTS Air Interface
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DL Pole Capacity
The Downlink benefits from orthogonality between channelisation codes.
WCa acitPole( )i
N
Eb +
10
is orthogonality factor and has a value between zero and 1.
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Active Set and Pilot Pollution
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Active Set and Pilot Pollution
The Cells with which the UE is communicating form the UEsActive Set
This Active Set is made typically of 3 cells/pilot signals
Any Pilot which is not a member of a UEs Active Set and
>- .Polluter
Pilot Pollution is a common WCDMA issue that needs to besorted immediately
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Summary of Key Concepts
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Summary of Key Concepts
Processing Gain
Ec/Io Eb/No
Noise Rise
Cell Loading Pole Capacity
Near/Far Effect
o an o er an over a n
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Summary of Key FormulasThe UMTS Air Interface
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Summary of Key Formulas
Eb/No
( ) pcb GIE
dBN
E
+=
Pole Capacity
W W
( )iNEb +
1
0
( )iNEb +
1
0
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2- The UMTS Link Budget
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UMTS Link Budget vs GSMs
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UMTS Link Budget vs. GSM s
Interference Margin for Noise Rise
Target Eb/no
Processing Gain (dBs) in UMTS
=
ower on ro marg n
Handover Gains
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Interference Margin
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Interference Margin
An admission control parameter. Same as Noise Rise Limit
Puts a limit to how man users can be taken in the UL
NR= 3dB, Load Factor=50%
NR=6dB, Load Factor=75%
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Target Eb/No
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Target Eb/No
UMTS Link Budgets are made for Bearers
A UMTS service ma use one or more Bearers with each
Bearer having a QoS Eb/No requirement
A typical Voice Bearer requires an Eb/No of 5dB
yp ca ps earer requ res an o o a ou
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Processing Gain
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Processing Gain
Depends on the bitrate of the Bearer
Hel s with the re uired Ec/Io at the receiver
. ,
For a 128 kbps data Bearer, Gp= 15dB
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Power Control (Fast Fading) Margin
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Power Control (Fast Fading) Margin
Its entered to allow for adequate Power Control to compensate
for Fast Fading
Its dependent on the Speed Profile of the Mobile
At higher speeds, its smaller as the network cannot effectively
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Handover Gains
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Handover Gains
If a UE is in Soft or Softer Handover, this will provide Diversity
Gains
These gains can help the Link Budget by helping in achieving
the Target Eb/No with less power
paths
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UL Link Budget
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UL Link Budget
Because UL power is lower than DL power coverage is
UL limited.
Initiall , most attention is aid to the UL bud et.
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-120 dBm Receiver Sensitivity
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120 dBm Receiver Sensitivity
Typical noise floor of cell receiver is -104 dBm.
Considering full rate voice (12.2 kbps) processing gain is 25 dB.
If tar et Eb/No is 5 dB and allowed Noise Rise is 4 dB then:
UE must be capable of delivering (-104-25+5+4)= -120 dBm for
a successful connection.
-120 dBm is effectively the receiver sensitivity for 12.2k voice.
For a 128kbps service, the Rec. Sensitivity is around -110dBm
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Link Budget - voice
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Link Budget voice
Noise Floor -104 dBm
o se se m
Processing Gain 25 dB
Target Eb/No 5 dB
-
UE Tx Power +21 dBm
Maximum Link Loss 141 dB
Feeder loss 3 dB
Body loss 1 dB
Maximum ath loss 154 dB
Margins 24 dBTarget path loss 130 dB
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UL Link Budget - VT
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UL Link Budget VT
UMTS is introduced to offer higher level services such as video
.
VT will typically operate at 64 kbit/s.
Processing gain = 17.8 dB
If all other parameters remain the same, then the maximum
path loss will be 154 - 25 + 17.8 = 146.8 dB.
Different service:- different range.
Typically range for voice = 1.6 x range for VT
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UL Link Budget- 128 kbps
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Thermal Noise: -104 dBm, Noise Figure: 4 dB, Eb/No: 1.5 dB
Processing Gain: 15 dB (10 log[3840/128])
Receiver Sensitivity -113.5 dBm
Max Link Loss = 21 dBm - -113.5 dBm = 134.5
Antenna Gains: 20 dBi Feeder Loss: 3dB Body Loss: 0dB
Maximum Path Loss: 151.5 dB
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DL Link Budget- 128 kbps
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Allowable Path Loss: 151.5 dB
Receiver Sensitivity -113.5 dBm
Required Tx Power: 24 dBm per channel
Eb/No= 1.5 dB, which in linear is 10^(1.5/10)= 1.41
i = 0.5 1+i = 1.5
( )( )Mbps3
6.05.0141.1
1084.3CapacityPoleDL
3
=+
= x
For 50% loading capacity = 1.5Mbps or 11- 128kbps channels
=
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.
Conclusions
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Eb/No and capacity intimately linked.
Link budgets are affected by fast fading and interference margins.
Uplink and downlink affected differently by increased loading.
.
Asymmetric traffic requirements can be designed in.
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3- Coverage Planning
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Coverage ObjectivesCoverage Planning
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Achieve Minimum Pilot Coverage on Service Area
Minimum Coverage dependant on:
ALP
Loading
KPIs
RSCP (Ec)
RSS (Io)
Ec/Io Pilot Pollution (Scrambling Code overlapping)
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Factors affecting Coverage
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ALP is a function of:
Clutter Type
Shadow Fading Margin
erv ces:
The higher the bitrate the lower the coverage
Different Eb/No re uirements
Loading:
The higher the loading the lower the coverage
Loading factor tied to Noise Rise Limit
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Coverage Planning
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.
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Dimensioning Inputs
Coverage Planning
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SiteConfigurationService
GeographicDemographic
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Simple Coverage
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Link Budget based
i.e. simple numerical calculationCreate Link Budget
Firstly a link budget is created Calculate Range
Max PL
The maximum path loss is used to calculate thecell range using a propagation model
Calculate Site Area
Max Range
The cell range is used to calculate the site area Max Area
Site Numbers = (Total Area)/(Site Area)
Sites in a given Area
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Shadow Fading and Building Penetration
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Building Penetration
Mean and standard deviation per environmentP(connect)
50% 75%
Shadow Fading
Typically calculated using Jakes
( )
+=
berf
baerfFu 1exp1
2 2
( )0 = xa
= log10
e
nbWhere: ;
x0 -
P(connect)
0
2x0-= Fade Margin
= Standard Deviation of Model
=
Point Location Probability
x0 -5.6
Area Location Probability
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This assumes an isolated omni directional site
Environment Distribution
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prea s ee s on eawith topology or
morphology accurately,
distributed target areas
Interference and trafficcaptured by sites willvary
Margins for site Suburban Site Numbers?acquisition and overlap
are required Urban Area Site NumbersArea
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Coverage Planning
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.
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Pilot Power as an Indicator
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If pilot power is 33 dBm, the pilot
strength on the ground is an
indicator of link loss.
113 dB loss: -80 dBm pilot
120 dB loss: -87 dBm pilot
Popular indicator as drive test
measurements report on pilot
strength.
> -80 dBm
> -87 dBm
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Pilot Power as an Indicator -Coverage Planning
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Pilot powers not necessarily equal
deployment of MHA at selected sites
will alter target pilot values.
Even if MHAs are universally,
feeder loss.
Generally, MHAs have a different
effect on UL to DL, therefore DL
measurement not a reliable indicator of
> -80 dBm
> -87 dBm .
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Letting the tool do the work
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It is possible to define:
The UE: in articular Tx Power
The bearer: bit rate and Eb/No.
Cell receiver: noise floor noise
rise; feeder loss; MHA
characteristics.
Margins required.
This allows maximum path loss to
coverage ac eve
Voice coverage achievedeac ce o e e erm ne an
coverage to be calculated directly.
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Pilot Strength PlotCoverage Planning
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Assessing Interference with aCoverage Planning
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a c na yser - c o Pilot Ec/Io indicates pilot
power as a ratio of total
wideband power (including
the pilot itself).
Not terribly scientific but
t correspon s rect y to
measurement reported by
the UE in drive tests.
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Ec/Io PlotCoverage Planning
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Assessing Interference with a Static
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na yser - o
the pilot.
Effect of ortho onalit
on own-cell interference
is considered.
Pilot power not
considered as
interference.
Pilot SIR is always better
than Ec/Io.
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Coverage Planning
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.
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Limiting mutual interference
Coverage Planning
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Downtilt antennas.
side of buildings.
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Limiting mutual interference
Coverage Planning
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6Elec 0Mech
0
6
6
0Elec 6Mech
66Elec -6Mech
-6
00
6
0
12
0
Controlling the backlobe can produce a small
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but significant improvement in capacity.
Limiting mutual interference
Coverage Planning
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Key parameter: Frequency Re-use Efficiency (FRE).
FRE IntraN
=
(W)ceinterferencell-intratheisIntra
InterIntra
N
-Inter
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Mast Head Amplifiers (TMAs)
Coverage Planning
Used to lower the Noise Figure of the receiver
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Used to lower the Noise Figure of the receiver
Can offset feeder losses
MHA used to increase coverage range
Typ. 1.6 dB Noise Figure (NF).
Increase uplink capacity
Adds Insertion loss on DL (~ 1.3 dB)
AntAntBiasBias--TT
TMATMA
by passby pass
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Uplink Receive Space Diversity
Coverage Planning
Common to have two receive antennas per sector at the base station
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Common to have two receive antennas per sector at the base station.
~ ,
improvement.
-
m apart.Receive
antenna 2
Receiveantenna 1
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Uplink Receive Space Diversity
Coverage Planning
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This is not conventional space diversity.
Each antenna is connected to a separate finger of the Rake receiver.
This is possible due to the synchronisation and channel estimationer ve rom e o c anne .
Thus Eb/No is improved, rather than simply an effective power gain.
ery ow n v ua o w pro a y mean a very ow p o evewhich will lead to poor coherence and little gain - process becomes
self-defeating.
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Coverage Planning
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.
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Typical vendor valuesCoverage Planning
Pilot Power = 5-10% of Total Power (30-35 dBm)
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Pilot Power 5 10% of Total Power (30 35 dBm)
Control Channel Powers = 3-5 dB below Pilot (27-33 dBm)
CCPCHs
Other signalling Channels = 3-5 dB below Pilot (27-33 dBm)
, ,
Summary: Total Non-Traffic Channels = 20-25% of total power
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Some additional constraintsCoverage Planning
GSM existing coverage
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GSM existing coverage
GSM legacy sites
Antenna limitations: height, azimuths, etc.
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4- Capacity Planning
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Capacity ObjectivesCapacity Planning
Manage effectively predicted Load on Service Area
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g y p
Capacity dependant on:
Number of users
os t on o users re at ve to t e ce
Services demanded
UE Power Control
KPIs
Cell UL Load Factor
Cell DL Power
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Factors affecting Capacity
Capacity Planning
Number of Users: The more users the more noise
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Position of Users: The farther away, the more noise
Services demanded: The more high-bitrate users on the cell, theless overall number of users possible
UE Power Control: Imperfect power control will account for morenoise in the network
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Soft and Hard Capacity
Capacity Planning
Hard Capacity: Hard limit imposed by actual channel elements
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p y p y
Typ. 16 Kbps Channel elements. Also called Resources or
Cards
Soft Capacity: Variable, depending on Network loading
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UL Pole Capacity
Capacity Planning
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Capacity is typically limited on the UL
This is because, in the UL we dont have Orthogonality to help us
( )iEb +
1
CapacityPoleUL
0
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103
UL Pole Capacity Exercise- VoiceCapacity Planning
If we assume a service with Eb/No = 6dB and i = 0 8
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If we assume a service with Eb/No = 6dB and i= 0.8
Eb/No= 4 (linear) UL Pole Capacity= 533 kbps
If you consider 12.2 kbps Voice bearers:
533/12.2 = 43.7 Voice Trunks
Adding a typ. Voice activity factor (+overhead) of 58%
New number of voice trunks is 533/(12.2x0.58) = 75.3
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UL Pole Capacity Exercise- VoiceCapacity Planning
A typical UMTS Cell can handle about 40E of Voice services
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With 75.3E being 100% capacity, 40E = 53% Loading
Noise Rise= -10log (1-0.53) = 3.2dB
,
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UL Pole Capacity Exercise- VTCapacity Planning
If we assume a service with Eb/No = 3dB and i = 0 8
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If we assume a service with Eb/No = 3dB and i= 0.8
Eb/No= 2 (linear) UL Pole Capacity= 1066 kbps
If you consider 64 kbps VT bearers with 100% activity factors:
1066/64 = 16.6 Voice Trunks
Comparing bitrates: 64kbps/7.1kbps = 9 (7.1= 12.2x0.58)
Comparing trunks: 75.3/16.6 = 4.5
Difference is due to different Eb/Nos 3dB (VT) vs 6dB (voice)
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Capacity Planning
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4.1 Multi-Services Capacity andapac y mens on ng
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Multi-Service CapacityCapacity Planning
Eb/No Activity Factors
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Voice= [email protected]
VT= 3.8dB@64kbps
58%
100% .
dB vs Linear Bitrate Ratios relative to voice
5.6dB= 3.6 (1x) 7.1 kbps
. .
2.8dB= 1.9
(18x) 128 kbps
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Campbells SpreadsheetCapacity Planning
CS CS PS PS PS
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Bearers (kbps) 12.2 64 64 128 384
PS Capture Data (Mbytes/hour) Not Applicable Not Applicable 0 0 0
Activi ty factor 58.0% 100.0% 0.0% 0.0% 0.0%
Average rate (kbps) 7.1 64.0 0.0 0.0 0.0
Eb/No 6 3 2 1.2 1.8
Eb/No ratio 3.98 2.00 1.58 1.32 1.51
Relative Ratio 1 0.50 0.40 0.33 0.38
Equivalent data rate (voice) 212.28 192 0.00 0.00 0.00
Factor for i 0.8
Reference Pole Capacity (kbps) 536
Loading of Cell 75.4%
UL Noise Rise Loadin 6.10
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Traffic ExerciseCapacity Planning
Manchester pop. = 2.2 Million
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Manchester pop. 2.2 Million
o e pene ra on = . on
For an operator with 25% market share = 440K Subs
With an avg voice traffic of 35mE per users = 15,400 Erlangs
Considering 30E per cell = 513 Cells or 171 Sites
This with 52% loading and 2% GOS
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Simple Capacity Dimensioning
Capacity Planning
Capacity calculation based Calculate CarrierCapacity
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Capacity
Calculate maximum capacityper carrier
Calculate SectorOffered Traffic
Calculate maximum offeredtraffic per sector
Calculate Maximum
Calculate site area based ontraffic density
Calculate Number of
Calculate the maximum number
Sites in a Given
Area
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Other Dimensioning Factors
Capacity Planning
GSM/UMTS Interaction
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Dont assume that UMTS carries all of the traffic
Microcells
Offer capacity relief to macrocells
This allows macrocells to be larger, potentially with a lower loading
Repeaters
Node-B
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2G analysis
Capacity Planning
Coverage thresholds can be set for various services and
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Coverage thresholds can be set for various services and
coverage examined in a similar manner to that for GSM
systems
ra c cap ure y ce s or ra c can e
interpreted as cell loading for UMTS systems.
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Capacity Planning
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4.2 Analysis of DL Capacity
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DL Pole CapacityCapacity Planning
WC itP lDL
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Ca acitPoleDL
( )i
N
Eb +
1
0
If i=0.6 and Eb/No is 6 dB; pole capacity is 960kbps.
At 50% loading UL capacity is 480 kbps (39 voice).
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Further Analysis of the Downlink
Capacity Planning
Minimum Rx power (25 dB processing gain, 3 dB Noise
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gure = - + + - = - m
If maximum Tx power is 21 dBm, then 141 dB link loss can
be tolerated. Can DL support this?
provide enough power to support it on the DL
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Capacity Planning
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.
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Traffic Density
Capacity Planning
Traffic Density is forecast in terms of a density in terms of Erlangs persquare kilometre.
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.
Knowing the clutter categories in the required service areas allows traffic
to be simulated.
Traffic Density Weightings
Clutter Category 1: 10
1
2
u er a egory :Clutter Category 3: 30
Clutter Category 4: 10
3
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Density versus Numbers
Capacity Planning
It is important to realise that the weightings are in terms of terminaldensities.
Sometimes the clutter category with the highest weighting occupies a small
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Sometimes the clutter category with the highest weighting occupies a smallpercentage of the area.
3
Area Weightings
Clutter Category 1: 28
Weighting of Actual Traffic
per Category1
24
Clutter Category 3: 28
Clutter Category 4: 28
.
Clutter Category 2: 36.4
Clutter Category 3: 38.2
Clutter Category 4: 12.7
Notice that the actual traffic volume per category differs from the traffic
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ens ty. ra c ens ty s t e parameter entere n t e s mu at on too .
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.
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Coverage vs. CapacityCapacity Planning
Coverage vs. Capac ity
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165.00
170.00
ss
(dB)
150.00
155.00
160.00
umP
athlo Uplink
Dow nlink
145.00
100 200 300 400 500 600 700 800Maxi
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Link Loss vs. CapacityCapacity Planning
1200
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1200
800
1000
(k
bit/s)
200
400
Capacit
120 130 140 150 160
Link Loss (dB)
+37 dBm +40 dBm +43 dBm +46 dBm
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Orthogonality vs. CapacityCapacity Planning
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800
1000
1200
kbi
t/s)
200
400
600
apacity(
0
0 0.2 0.4 0.6 0.8 1
r ogona y
BTS Power: 37 dBm 40 dBm 43 dBm 46 dBm
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Out of Cell Interf. vs. CapacityCapacity Planning
1400
)
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)
600
800
1000
ity
(kbit/s
0
200
400
Capa
0 0.4 0.8 1.2 1.6 2
Out of Cell Inter ference
BTS Power: 37 dBm 40 dBm 43 dBm 46 dBm
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Capacity Planning SummaryCapacity Planning
Capacity dependant on: Number of users
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Position of users relative to the cell
Services demanded
Multi le Services Traffic characteristic of UMTS
Pole Capacity, UL Cell Loading and DL Cell Power
Erlangs vs. Number of Terminals
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- - -
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Co-location main IssuesGSM Co-location
Have to live with existing GSM sites
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Have to live with existing antenna heights/azimuths
GSM Interference: GSM1800, GSM1900, etc
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Interference Issues
GSM Co-location
Interference can occur:
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between carriers
between operators
between systems
Co-location of GSM and UMTS sites raises
.
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3rd Generation Spectrum Allocations
GSM Co-location
ITU
WARC-92
1885 1980 20102025 2110 2170 2200
MSS MSS
IMT-2000
Land Mobile
IMT-2000IMT-2000
Land Mobile
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Europe1920 1980 20102025 2110 2170 2200UMTS
Paired UL
UMTS
Paired DL
UMTS
SAT
UMTS
SAT
UMTS
Unpaired
UMTS
Unpaired
1900
DECTGSM 1800
1880
Japan2110
2110 21701920 1980
IMT-2000
Land Mobile UL
IMT-2000
IMT-2000
Land Mobile DL
IMT-2000
USA1850 1910 1930 1990 2110 2200
Land Mobile UL Land Mobile DL
PCS
UL
PCS
DLReserved
1800 20501900 1950 20001850 2100 2150 2200
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Intersystem Interference Issues
GSM Co-location
Wideband Noise - unwanted emissions from modulation process andnon-linearity of transmitter
S i E i i H i P i i I d l i d
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Spurious Emissions - Harmonic, Parasitic, Inter-modulation products
Blocking - Transmitter carriers from another system
Inter-modulation Products - Spurious emission, specifications considerthis in particular
c ve: non- near es o ac ve componen s - can e ere ou yCell Equipment
Passive: non-linearities of passive components - cannot be filtered
Other EMC problems - feeders, antennas, transceivers and receivers
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Isolation Requirements
GSM Co-location
GSM 900 GSM 1800 UMTSReceiving band
(UL)
890 915 MHz 1710 1785 MHz 1920 1980 MHz
Transmitting band 935 960 MHz 1805 1880 MHz 2110 2170 MHz
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Transmitting band
(DL)
935 960 MHz 1805 1880 MHz 2110 2170 MHz
For exampleFor example -- To prevent UMTS BTS blocking: with transmit power = 43 dBmTo prevent UMTS BTS blocking: with transmit power = 43 dBm
ax eve o nter er ng s gna or oc ng =ax eve o nter er ng s gna or oc ng = -- m nm n
Isolation required = 58 dBIsolation required = 58 dB
1805 MHz1805 MHz 1880 MHz1880 MHz
1920 MHz1920 MHz 1980 MHz1980 MHz1710 MHz1710 MHz 1785 MHz1785 MHz
2110 MHz2110 MHz 2170 MHz2170 MHz
GSM 1800 TxGSM 1800 Tx UMTS RxUMTS RxGSM 1800 RxGSM 1800 Rx UMTS RxUMTS Rx
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Typical Isolation Requirements
GSM Co-location
Isolation Requirements
Specification
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SpecificationRequirements
GSM900/GSM1
800 toUMTS Rx
UMTS Tx toGSM 900
Rx
UMTS Tx toGSM 1800
Rx
UMTS Txto UMTS
Rx
Blockingisolation
58 dB 40 dB 48 dB 63 dB
emissions/inter-modulation
products
39 dB 34 dB 34 dB 39 dB
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Achieving Isolation Requirements
GSM Co-location
Isolation can be provided in a variety ofGSMGSM
.
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UMTSUMTS
.
B filterin out the interferin si nal.FilterFilter
GSMGSM
By using diplexers and triplexers withUMTSUMTS
GSMGSM
s are ee er an mu an an ennas.DiplexerDiplexer
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-
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Small, isolated cell
Practical Examples
Traffic is spread across a small area with low path loss to the
base station The cell is heavily loaded
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base station. The cell is heavily loaded.
associated with path loss.
Noise Rise will be the only radio-
related cause of failure.
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Small, isolated cell
Practical Examples
Capacity improvements can be achieved by:
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Increasing Noise Rise limit.
Reducing target Eb/No on the
A Mast Head Amplifier will not be
of much use as uplink Eb/No is
not a significant cause of failures.
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Large, isolated cell
Practical Examples
As loading increases, meeting Eb/No targets will be a problem.
Heavy loading will result in Cell Breathing.
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Heavy loading will result in Cell Breathing.
sers a a grea s ance rom e
base station will not be able to
make a connection.
Gaps will appear in network
.
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Sectored Sites
Practical Examples
Capacity will be affected by overlap of cell coverage areas.
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Cell overlap can be controlled by
pointing of antennas.
Combining mechanical and
electrical tilt can control backloberadiation.
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Pilot Pollution
Practical Examples
A mobile can be too well served.
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It may be impossible to decode a
.
Ec/Io and Eb/No failure due to co-
channel interference.
radiation patterns is vital.
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Soft Handover
Practical Examples
Soft handover regions must be controlled to ensure that
capacity is maximised.
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p y
.
Pilot owers can be scaled.
Effect on handover region can be
monitored.
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Dimensioning and Simulating a Network
Practical Examples
We are able to approximately dimension a network with a simple
s readsheet.
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This is a simplified network not considering the effects of mapping dataand uneven traffic distribution.
However, it is possible to simulate such a simplified network so that aclear understanding of the working of the simulator can be established.
The network can then be modified to incorporate practical features such
as terrain features and traffic distribution.
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.
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The Network and Height Profile
Practical Examples
3dB NR limit
20m antennas
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,
diversity
500 Terminalsspread on
Urban and
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Voice- Reason for Failure
Practical Examples
Polygon area
OK as far as
Voice Service
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Some NR Limitreac e a ures
(aqua pixels)
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VT- Reason for Failure
Practical Examples
Polygon area
shows UL Eb/No
failures
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NR Limitreac e a ures
(aqua pixels)
Changingazimuths on site
to the right of
polygon is not an
option due to
existing traffic
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res r c ons
VT- NR Limit increased to 6dB
Practical Examples
NR limit
parameter
chan ed from 3
dB to 6 dB on all
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cells
NR Limit
reached problem
UL Eb/No
problem still
there
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Pilot Coverage for Polygon
Practical Examples
Looking for the
causes of the
failure, a Pilot
Coverage plot is
d
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done
It can be seen
that Pilot level in
very low (around-105 dB)
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Height Profile for Polygon
Practical Examples
Looking for the
causes poor
covera e, a
Height Profile is
f d
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performed
that there is a
significant
obstruction
preventing agood UL
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Height increased to 40m
Practical Examples
Trying to fix the
UL Eb/No failure,
antenna hei ht is
increased from
20m to 40m
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20m to 40m
This decreases
the pathloss,
,
original problemis not solved
No interference
problems are
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crea e e er
Adding MHA and RX Diversity
Practical Examples
Another option is
to add an MHA
and RX Diversit
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These additionsprove e
solution for most
of the problem
polygon
Height is still
40m, due to
obstructions and
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poor s e oca on
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Summary of Key Concepts
Final Summary
Processing Gain
Ec/Io
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Eb/No
Noise Rise
Cell Loading
Pole Capacity Near/Far Effect
o an o er an over a n
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Summary of Key FormulasFinal Summary
Eb/No
( ) cb GE
dBE
+=
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( ) pGI
dB
N
+=
Pole Capacity
W W
( )iN
Eb +
1
0
( )iN
Eb +
1
0
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