WCDMA planning and

optimization

Beneyam Berehanu Haile

May 2018
Contents
 WCDMA network dimensioning
 WCDMA network planning
 WCDMA network optimization
Contents
 WCDMA network dimensioning
 WCDMA network planning
 WCDMA network optimization
Planning target and parameter definition
Planning targets are agreed between customer/operator and
planner
 Analyzing the quality-cost tradeoff
Service scenarios should be defined:
 Which kind of service is to be offered and where
Coverage target: geographical coverage, coverage thresholds,
coverage probability
 Typical coverage probability is 90–95 %
 Capacity target: subscriber map based on population map,
estimated traffic per user per service, available spectrum
 Accurate traffic forecasting is required
 A traffic forecast should be done by analyzing the offered busy
hour traffic per subscriber for different service bit rates

4
Coverage vs capacity
In WCDMA, coverage and capacity are interrelated
Dimensioning the coverage has to be planned for a service having
a load
 Used services and their load are input parameters for
dimensioning
 If the network load changes the coverage has to be planned for
a new load situation
WCDMA dimensioning is always a compromise between coverage
and capacity.
 By reducing the maximum load, the coverage can be extended.
 If more capacity is required the coverage area of an individual
cell shrinks, and this increases the number of required network
elements

5
WCDMA Radio Link Budget

6
Simplified RLB: An example
EIRP = Effective Isotropic Radiated Power,
contains transmitted power and antenna gain

BS Transmitter BS to MS
Transmitter Total transmission power 43 dBm (20 W)
characteristics Transmitter antenna gain 15 dBi
EIRP 58 dBm
Margins
Shadow fading margin 5 dB
Channel
characteristics Fast fading margin 6 dB
Penetration loss 10 dB
Total Margin 23 dB
Receiver MS Receiver (Max coverage)
characteristics Receiver sensitivity -100.7 dBm
System gain 158.7 dB
Number that is
used to estimate Allowed propagation loss 135.7 dB
the cell range
7
Simplified RLB: Terminology
 dBi = dB(isotropic). It is the forward gain of a certain antenna compared
to the ideal isotropic antenna which uniformly distributes energy to all
directions.
 dBm = dB(1 mW) is a measured power relative to 1 mW (e.g. 20W is
10*log(1000*20)= 43 dBm
 Effective isotropic radiated power is the amount of power that would
have to be emitted by an isotropic antenna (that evenly distributes
power in all directions and is a theoretical construct) to produce the
peak power density observed in the direction of maximum antenna
gain. EIRP can take into account the losses in transmission line and
connectors and includes the gain of the antenna.

8
Simplified RLB
 In link budget calculations we
– Define transmitter and receiver characteristics. These numbers are system (and
product) related.
– Define margins according to channel properties.
– As a result we calculate allowed propagation loss for the system. This is important
number because it is used in the dimensioning of the system.
 Average path loss models are used for system range estimation
– Once we know the allowed propagation loss and environment (+antenna heights
etc), then we can calculate range using a selected average path loss model.
 See Fundamentals of CNP slides for
– Okumura-Hata path loss model (most widely applied outdoor model)
– Shadow fading discussion: check how shadow fading margin is computed
– Multipath fading discussion

Link budget Allowed propagation loss

System range Path loss model

9
RLB through simple equations
 The Allowed Propagation Loss (APL) can be calculated as follows:
APL  EIRP  min PRX  M Total
 PTX  G  min PRX  M SF  M FF  M Penetration

min PRX   Receiver sensitivit y [dBm]

Here

PTX  Transmissi on power in BS [dBm]

G  BS antenna gain [dBi]
M SF  Shadow fading margin [dB]
M FF  Fast fading margin [dB]
M Penetration  Indoor penetratio n loss [dB]
Penetration loss simply depends on the expected building wall losses.

10
 Example
 Assume that according to RLB the allowed path loss for WCDMA DL speech
connection is 146dB. Then cell range in different environment types can be
estimated from the figure below. Note that CF=2100MHz and BS antenna height is
30 meters

146dB Outdoor user

Indoor penetration loss
126dB Indoor user

11
WCDMA Link budget, 12.2 kbps speech
12.2kbps voice, DL 12.2kbps voice, UL
Target load 0.75 0.5
Transmitter characteristics Total transmitter power 20 W 0.125 W
Transmitter power on TCH 0.348718 W 0.125 W
25.42474 dBm 20.9691 dBm
TX antenna gain 17.42531 dBi 0 dBi
TX cable loss 2 dB 0 dB
TX Body loss 0 dB 2 dB
Transmitter EIRP 40.85005 dBm 18.9691 dBm

Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi

and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processinggain
Spreading gain 24.97971 dB 24.97971 dB
Required Eb/No 7 dB 5 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -112.116 dBm -120.126 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 2 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 3 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB
Allowed propagation loss 12
146.4659 dB 149.0205 dB
Link budget, TX characteristics
12.2kbps voice, DL 12.2kbps voice, UL
Target load 0.75 0.5
Transmitter characteristics Total transmitter power 20 W 0.125 W
Transmitter power on TCH 0.348718 W 0.125 W
25.42474 dBm 20.9691 dBm
TX antenna gain 17.42531 dBi 0 dBi
TX cable loss 2 dB 0 dB
TX Body loss 0 dB 2 dB
Transmitter EIRP 40.85005 dBm 18.9691 dBm

Network load assumption for dimensioning (target loading)

13
Target load
 Target load%
 Urban macro DL: 50-60% (heavy traffic and interference)
 Urban micro DL: 70% (heavy traffic and interference, capacity important)
 Rural DL, UL: 30-40% (low traffic and interference, coverage important)
 UL in general: 50%
 Target load should not be higher than 75% (especially UL is hard to manage when
load is high, interference explodes).
 Too low initial target can result as coverage holes and capacity problems, if
the traffic proves to be higher than predicted.
 Too high initial target load can result in too dense (and expensive) network.
Dense network can also be hard to manage in terms of cell overlapping.
 Currently capacity need is more easily underestimated than overestimated.
 DL load usually bigger than UL load (traffic asymmetry).

14
 TX power
12.2kbps voice, DL 12.2kbps voice, UL
Target load 0.75 0.5
Transmitter characteristics Total transmitter power 20 W 0.125 W
Transmitter power on TCH 0.348718 W 0.125 W
25.42474 dBm 20.9691 dBm
TX antenna gain 17.42531 dBi 0 dBi
TX cable loss 2 dB 0 dB
TX Body loss 0 dB 2 dB
Transmitter EIRP 40.85005 dBm 18.9691 dBm

In calculation of TCH transmission power we have used the formula

(1  Control overhead )  Total TX power
PTX ,TCH 
Load target  Maximum number of users

In this case we have assumed that maximum number of speech users is 65. In
WCDMA maximum number of users of a certain service can be estimated
through load equations or using system level simulations.
Load equation discussion can be found after15 a while.
TX power in BS

 Examples of the control overheads

 The maximum number of users for a certain service can be computed

using DL load equations (omitted)
 It is important to notice that by decreasing the DL load target the Traffic
Channel power can be increased and cell coverage extended.

16
RX characteristics
Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi
and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processing gain 24.97971 dB 24.97971 dB
Required Eb/No 7 dB 5 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -112.116 dBm -120.126 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 2 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 3 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB

Receiver noise figure is usually between 5 to 9 dB and BS have better NF.

Precise value of this parameter is product specific.

Noise figure represent the loss of the signal

power in the receiver RF parts
17
RX characteristics
Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi
and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processing gain 24.97971 dB 24.97971 dB
Required Eb/No 7 dB 5 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -112.116 dBm -120.126 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 2 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 3 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB

Receiver noise density (per Hz) is a sum of receiver noise figure and thermal
noise density.
Receiver noise power is equal to receiver noise density x chip rate

18
RX characteristics
Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi
and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processing gain 24.97971 dB 24.97971 dB
Required Eb/No 7 dB 5 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -112.116 dBm -120.126 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 2 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 3 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB

Processing gain is the chip rate divided by user bit rate

19
RX characteristics
Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi
and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processing gain 24.97971 dB 24.97971 dB
Required Eb/No 7 dB 5 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -112.116 dBm -120.126 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 2 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 3 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB

Eb/No values can be obtained by link simulations. There are also

informative values given in 3GPP specifications. Eb/No values are usually
provided by the network vendor

20
Eb/No
 Ec/Io is defined before the signal de-spreading operation and Eb/No
after de-spreading.
– Ec/Io can be be determined for the signal ”in the air”
 So Eb/No depends on the service (bit rate, CS/PS, receiving end) &
vendor
 Ec/Io is service independent
 Typical Eb/No values
– 12.2 kbps speech (BLER <7*10^-3) [UL 4-5 dB, DL 7-8 dB]
– CS 64 kbps data (BER <10^-4) [UL 2-3 dB, DL 6-7 dB]
– PS Streaming 64 kbps (BER<10^-3) [UL 3-4 dB, DL 7-8 dB]
– PS data 64 kbps (BLER <7*10^-3) [UL 2-3 dB, DL 5-6 dB]
– PS data 384 kbps (BLER <7*10^-3) [UL 2-3 dB, DL 5-7 dB]

21
Interference margin
 Receiver background noise increases in proportion to the
number of users.
 This needs to be taken into account in the link budget with a
specific interference margin, which is directly related to the
loading.

22
RX characteristics
Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi
and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processing gain 24.97971 dB 24.97971 dB
Required Eb/No 7 dB 5 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -112.116 dBm -120.126 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 2 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 3 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB

Interference is a function of loading. The value can be obtained from

Interference margin  10  log 10 1  Target load 
equation

This value can be used also in DL. 50% load => 3dB margin, 75% load =>
6dB margin 23
UL Interference margin
Interference binds the
1,2
capacity and coverage
1

The more traffic is brought to 0,8

Cell range
the cell, more interference is 0,6
produced
0,4

0,2

In order to win the interference

0
the terminals have to increase 0 0,2 0,4 0,6 0,8 1
their TX-power Cell loading

When the interference grows

in the cell the most far away New users cannot Cell range
terminal from the NodeB access the cell
cannot win the interference from distance
decreases
even with the maximum TX-
power

24
RX characteristics
Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi
and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processing gain 24.97971 dB 24.97971 dB
Required Eb/No 7 dB 5 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -112.116 dBm -120.126 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 2 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 3 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB

The required signal power (also called as sensitivity) represents the

weakest signal that can be received by the receiving antenna.

25
RX characteristics
Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi
and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processing gain 24.97971 dB 24.97971 dB
Required Eb/No 7 dB 5 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -112.116 dBm -120.126 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 2 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 3 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB

Fast fading margin = power control headroom

26
PC headroom/Fast fading margin
 PC headroom ensures that the UL PC is able to compensate
deep fades at cell border.
 PC Headroom is a function of UE speed, and the headroom is
largest for relatively slowly moving UEs (<50km/h)
– Typical value is 3dB for urban area and 4dB elsewhere
– Depends on assumed SHO gain and Eb/No -values
– In an operational network, the required PC headroom can vary from 0 to over
8dB.
 PC headroom is usually not needed in the downlink, since all
mobile terminals are served simultaneously with comparatively
less power than the maximum output power of the node B.

27
RX characteristics
Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi
and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processing gain 24.97971 dB 24.97971 dB
Required Eb/No 7 dB 5 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -112.116 dBm -120.126 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 2 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 3 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB

In soft handover two signals are combined

28
Soft/Softer handover gain
 Softer/Soft Handover gain results from combining signals either in Node
B’s RAKE or in RNC. In Downlink signals are combined in UE’s RAKE
receiver.
 Uplink soft HO gain comes from RNC selection combining. Gain is not
achieved as concrete gain in radio interface, but as more stable power
control.
 In uplink softer HO maximum ratio combining is performed in Node B’s
RAKE => gain 1-3 dB
 In downlink Soft HO maximum ratio combining is performed in UE’s
RAKE => gain 1-2 dB (low complexity receiver used).

29
RX characteristics
Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi
and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processing gain 24.97971 dB 24.97971 dB
Required Eb/No 7 dB 5 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -112.116 dBm -120.126 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 2 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 3 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB

Shadow fading margin depends on the propagation environment, see

next slide

30
Shadow fading margin (SFM)
 SFM is needed because the buildings and other obstacles between the UE
and Node B are causing changes in the received signal level at the receiver
 SFM is taken into account in the WCDMA link budget to assure a minimum
signal level with the wanted probability
 According to measurements in live UMTS network, it has been noticed that
the practical SFM and standard deviation values are nearly the same for
WCDMA and GSM Shadow fading
margin
Network area/
Standard deviation
Parameter Area Area
probabil probabil
ity 90% ity 95%
Some values that are
used based on Dense urban / 8,5 dB 6 dB 9,5 dB
measurements Urban
Sub-urban 7,2 dB 4,7 dB 7,6 dB

Rural 6,5 dB 3,9 dB 6,6 dB

31
Cell range
Allowed propagation loss 146.4659 dB 149.0205 dB

Range (Okumura-Hata path loss model) Unit

Carrier frequency 2100 MHz
BS antenna height 25 m
MS antenna height 1.5 m
Parameter A 46.3
Parameter B 33.9
Parameter C 44.9
MS antenna gain function (large city) -0.00092
Path loss exponent 3.574349
Path loss constant 137.3351 dB
Downlink range 1.800742 km
Uplink range 2.12287 km
Cell range 1.800742 km

It seems that WCDMA and GSM 1800 admit pretty same speech coverage
(recall that GSM 1800 range is round 1.58 km). Actually if we would have
used the same parameters as for GSM 1800 then cell range would have
been 1.58 km also for WCDMA. Yet, WCDMA link budget contains much
more parameters => more potential error sources in dimensioning.

32
Link budget, 384kbps data
384kbps data, DL 384kbps data, UL
Target load 0.75 0.5
Transmitter characteristics Total transmitter power 20 W 0.25 W
Transmitter power on TCH 5.666667 W 0.25 W
37.53328 dBm 23.9794 dBm
TX antenna gain 17.42531 dBi 0 dBi
TX cable loss 2 dB 0 dB
TX Body loss 0 dB 0 dB
Transmitter EIRP 52.95858 dBm 23.9794 dBm

Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi

and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processing gain 10 dB 10 dB
Required Eb/No 7 dB 3 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -97.1361 dBm -107.146 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 0 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 4 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB
Allowed propagation loss 143.5947 dB 140.0511 dB

33
TX power
384kbps data, DL 384kbps data, UL
Target load 0.75 0.5
Transmitter characteristics Total transmitter power 20 W 0.25 W
Transmitter power on TCH 5.666667 W 0.25 W
37.53328 dBm 23.9794 dBm
TX antenna gain 17.42531 dBi 0 dBi
TX cable loss 2 dB 0 dB
TX Body loss 0 dB 0 dB
Transmitter EIRP 52.95858 dBm 23.9794 dBm

Data terminal may have

higher TX power
Recall the calculation of TCH transmission power

(1  Control overhead )  Total TX power

PTX ,TCH 
Load target  Maximum number of users
Now maximum number of users is only 4 => BS TX power on TCH is high

34
Receiver characteristics
Receiver characteristics RX antenna gain 0 dBi 17.42531 dBi
and margins Thermal noise density -174 dBm/Hz -174 dBm/Hz
Receiver noise figure 8 dB 5 dB
Receiver noise density -166 dB -169 dB
Receiver noise power -100.157 dBm -103.157 dBm
Processing gain 10 dB 10 dB
Required Eb/No 7 dB 3 dB
Interference margin 6.0206 dB 3.0103 dB
Required signal power -97.1361 dBm -107.146 dBm
RX Cable loss 0 dB 2 dB
RX Body loss 0 dB 0 dB
Diversity gain 0 dB 3 dB
Fast fading margin 0 dB 4 dB
Soft handover gain 1 dB 2 dB
Coverage probability (cell edge) 0.9 0.9
Shadow fading std deviation 6 dB 6 dB
Shadow Fading Margin 7.5 dB 7.5 dB
Indoor penetration loss 0 dB 0 dB

Processing gain is smaller due to higher data rate

Eb/No in UL is also slightly smaller.

35
Cell range
Allowed propagation loss 143.5947 dB 140.0511 dB

Range (Okumura-Hata path loss model) Unit

Carrier frequency 2100 MHz
BS antenna height 25 m
MS antenna height 1.5 m
Parameter A 46.3
Parameter B 33.9
Parameter C 44.9
MS antenna gain function (large city) -0.00092
Path loss exponent 3.574349
Path loss constant 137.3351 dB
Downlink range 1.496663 km
Uplink range 1.191201 km
Cell range 1.191201 km

Now system is clearly uplink limited (it was downlink limited for speech). Yet this
is only problem for symmetric services. Usually 384kbps is used for web
browsing which is putting more pressure on DL. If cell dimensioning is done for
speech then DL 384kbps coverage may not be a serious problem but capacity
becomes soon a bottleneck since system may support only few 384kbps users.

36
Task

In previous link budgets indoor penetration loss were

0dB. If we assume 20dB penetration loss (usual value),
what will be the inter-site distance for the 12.2kbps
speech and 384kbps data services assuming a 3 sector
sites?

37
Contents
 WCDMA network dimensioning
 WCDMA network planning
 WCDMA network optimization
WCDMA coverage planning
 The objective is to find optimal locations for base stations to build continuous
coverage according to the coverage criteria
 In coverage limited network, BS location is critical
 Propagation model is selected considering WCDMA technology and customized
with model tuning measurements before the coverage planning phase
 Considering parameters such as frequency, macro/micro cell environment,
BTS antenna height
 Accuracy of the map and the model affects accuracy of the coverage
predication
 First step: create a preliminary plan based
on the calculated number of base stations
from the dimensioning phase
 Second step: start to find actual base
station locations
 Next step: to generate updated plan with
the actual BS locations

39
Methods to improve coverage
 Finding optimal BS locations is an important but complicated task as it is a function of
various practical factors (coverage criteria, site acquisition, backhaul limitations, …)
 As a result careful iterative recalculation is required with various combinations of
parameters until agreed enhanced plan is attained
 Important factors during the coverage planning phase are accuracy of the link budget
parameters, BS coordinates and other coverage planning parameters
 Verification is recommended
 Same numbers are used from the planning through to the actual BTS
 Different result plots (e.g. composite plot, dominance plot) from network planning tools
help us to identify coverage challenges (holes and overlapping)
 Appropriate location updates and parameter fine-tunings are undertaken to address the
coverage challenges

Key methods for enhancing coverage

1. Optimize the link budget parameters (e.g. antenna height, antenna gain, BS
power, …)
2. Use supplementary hardware (e.g. Booster and mast head amplifier)
 A booster amplifies the BTS transmission
 A mast head amplifier strengthens the BTS reception
3. Antenna tilting and azimuth
 Electrical and mechanical
40
WCDMA capacity planning
 Capacity planning in WCDMA networks is much more complicated than in
GSM/EGPRS
 In uplink, capacity planning would need to calculate the interference and
the cell capacity
 The amount of uplink interference has a great impact on the cell
capacity and radius
 In downlink, the capacity is determined by the power transmitted by the
BS, locations of UE and interference.
 In the WCDMA system, the traffic can be asymmetric in the uplink and
downlink directions and thus the load can also be different in either
direction.
 The DL load is, however, higher than the UL load

41
Uplink load equation

42
Uplink wideband power
120 degree sector
 Illustration: 3 sectors = 3
antennas
cells in each site.
 Blue cell = ‘other’ cells,
green cell = ‘own’ cell
 All users are separated by
scrambling codes
 Signals from different users
are uncorrelated
 Path loss and antenna gain
attenuates signals from
‘other’ cells

43
Uplink load equation (1)

 Important measure that is used in system level

investigations is the noise rise (denoted by NR) that is
defined as a ratio between total received wideband
power and AWGN noise power
I total
(3) NR  Definition of uplink noise rise
PN
our goal is to deduce a formula (load equation) that
provides a connection between noise rise and link level
parameters.

44
Uplink load equation (2)
 Consider a single link and denote by Eb/No the received
energy per user bit divided by the noise spectral density. We
have

Eb / N 0  Processing gain  
Signal power
Total received power excluding own signal power

Hence, the minimum requirement for Eb/No is defined by

the processing gain + power that is needed to overcome the
interference from other users.
 Eb/No is an important variable since it actually maps the
link level performance to the system level performance.

45
Uplink load equation (3)

Let us formulate Eb/No mathematically. For a user j

there holds
Pj
(4) Eb / N 0  j 
W

 j R j I total  Pj
where

W  System chip rate

Pj  Signal power of user j
 j  Activity factor of user j
R j  Bit rate of user j
I total  Total received wideband power  thermal noise in base station

46
Uplink load equation (4)

The load generated by jth user is

Pj
(5) j 
I total
After combining (4) and (5) we find that
1
j 
1  W ( j R j  Eb / N 0  j )
(6)

This is uplink load generated by a single user

47
Uplink load equation (5)

 The load generated by N users in the ‘own’ cell is

obtained by summing over (6)
Uplink load equation in isolated cell

N N
1
(7) own   j  
j 1 j 1 1  W ( j R j  Eb / N 0  j )

Note: If there are e.g. 2 services used in the cell, then

load equation is of the form

N1 N2
own  
1  W ( 1R1  E b / N 0 1 ) 1  W ( 2 R2  E b / N 0 2 )

48
Uplink load equation (6)
 Formula (7) gives only the ‘own cell’ load which is
generated by users that are connected to the considered
(own) cell. In order to take into account also the load
coming from other cells we introduce other-to-own cell
interference factor
Other cell interference I other
(8)  
Own cell interference I own
 In practise other-to-own cell factor may greatly vary in
different parts of the network. Now we can write the
uplink load equation for non-isolated cell,
Uplink load equation for non-isolated cell
(9)   (1   )own
49
Uplink noise rise (1)
It is common to discuss on noise rise instead
of load. Let us deduce the connection
between noise rise and load. The total
received wideband power admit the form
N
(10) I total  (1   ) Pj  PN    I total  PN
j 1

where last term is the AWGN noise power

and we have used equations (2) and (5).

50
Uplink noise rise (2)

 After combining the definition of noise rise (3) and (10)

we obtain the formula

I total 1
(11) NR   Noise rise in terms of load
PN 1 

Noise rise is usually given in decibels. Thus

(12) NRdB  10 log(1   )

51
Uplink noise rise (3)
Noise rise of 3 dB is related to 50% load. This is
usually limit value when deployment is
coverage limited
Noise rise of 6 dB is related to 75% load. This
value is usual upper limit when deployment is
capacity limited.
Load and admission control is monitoring and
controlling the noise rise in different cells

52
Load equation: Parameters
 Suitable value of Eb/No can be obtained from link simulations,
measurements or from 3GPP performance requirements.
 Eb/No varies between services and its requirements are
coming from the predefined receiver block error rate that is
tolerated in order to meet the service QoS.
 Eb/No contains impact of soft handover and power control
– Example values for multipath channel:
– 12.2 kbps voice, Eb/No = 4.5 dB (3 km/h), Eb/No = 5.5 (120 km/h)
– 128 kbps data, Eb/No = 1.5 dB (3 km/h), Eb/No = 2.5 (120 km/h)
– 384 kbps data, Eb/No = 2.0 dB (3 km/h), Eb/No = 3.0 (120 km/h)

53
Load equation: Parameters
 System chip rate W:
– 3.84 Mcps for WCDMA (5 MHz bandwidth)
 Activity factor :
– Value 0.67 for speech (uplink recommendation)
– Value 1.0 for data
 Bit rate R:
– Depends on the service, usually up to 400-500 kbps
 Other-to-own cell interference :
– Depends on the antenna configuration and network topology
• Omni-directional antennas  = 0.55
• Three-sector cells  = 0.65
•  may greatly vary due to load variations in adjacent cells

54
Uplink load equations: Example (1)
Example. Plot uplink noise rise curves (in
decibels) for
– 12.2 kbps voice service (all users in the cell use the
same service)
– 128 kbps data services (all users in the cell use the
same service)
Give X-axis of the plot as a function of number
of users. All sites in the network admit three
sectors (cells) and user mobility is 3 km/h in the
first and 120 km/h in the second case.

55
Uplink load equations: Example (2)

 Solution. We use equations

N N
1 N
own   j   
j 1 j 1 1  W ( j R j  E j ) 1  W (  R  E )

  (1   )own NRdB  10 log(1   )

,

Required parameters are

W  3.84 Mcps,   0.67, Rvoice  12.2 kbps, Rdata  128 kbps,
Eb / N 0 voice (3km / h)  4.5dB, Eb / N 0 data (3km / h)  1.5dB,
Eb / N 0 voice (120km / h)  5.5dB,
Eb / N 0 data (120km / h)  2.5dB,   0.65
56
Uplink load equations: Example (3)
Requested noise rise plot
6

4
Noise rise [dB]

0
0 10 20 30 40 50 60 70 80
Number of users

12.2 kbps voice service (solid curve) and 128 kbps data service (dashed
curve). Lower curves: 3km/h mobility, upper curves: 120 km/h mobility

57
Uplink load equations: Example (4)
 Observations:
 With 3 dB noise rise system can support in uplink
• Round 50 (40) voice users when user mobility is 3 km/h (120 km/h)
• Round 6 (5) data users when user mobility is 3 km/h (120 km/h)
 With 6 dB noise rise system can support in uplink
• Round 75 (60) voice users when user mobility is 3 km/h (120 km/h)
• Round 10 (8) data users when user mobility is 3 km/h (120 km/h)

• Note: these are example values that heavily

depend on the applied parameters

58
Downlink load equation

59
 Downlink load equation (1)
 We start the derivation of the downlink load equation
from the so-called pole equation.
 The baseline assumption is that fast power control is
applied. Then UEs are able to obtain exactly the
minimum required Eb/No.
 The link quality equation for the user j in cell m attain the
form
Received interference power
from ‘other’ node B’s
W  Pj
(13) Eb / N 0  
1
 , j  1,2,..., N own
j
R j  Lm, j N cells
(1   j ) P / Lm, j  P/ L
n 1, n  m
n, j  PN
Processing gain AWGN noise power

Received interference power

Power for user j 60
from ‘own’ node B
Downlink load equation (2)

Parameters in link quality equation are

W  System chip rate
Pj  Required signal power of user j in base station tr ansmission
P  Base station tr ansmission power
Lm , j  Path loss between considered base station (index m) and UE
R j  Bit rate of user j
Ln , j  Path loss between nth base station and UE
N cells  Number of cells

61
Downlink load equation (3)
 In equation (13) first term is the processing gain multiplied
by signal power after path loss.
W Pj

R j Lm , j
 The denominator of the second term defines the
interference and AWGN noise.
– First interference term contains the impact of imperfect code
orthogonality (due to multi-path fading) which is multiplied by
‘own’ base station power after path loss.
(1   j ) P / Lm, j
– The second interference term contains interference coming
N cells
from other cells.
P/ L
n 1, n  m
n, j

62
Note: It is assumed that all base stations apply the same
transmission power P
On orthogonality factor
 In operational network,  is continuously changing
  is estimated by base station based on UL multipath
propagation. According to experience,  for typical WCDMA
environments is
• 0,5 – 0,6 in macro cells
• 0,8 – 0,9 in micro cells (smaller cells, less multipath)
 Too optimistic  can lead to coverage problems
 Too modest  can lead to inefficient utilisation of DL
performance

63
 Base station transmission power (1)

 Let us solve the power that is needed for user j from

equation (13). We obtain
Eb / N 0  j  R j  N cells

(14) Pj    P  (1   j )  P  Lm, j / Ln , j  PN Lm , j ,
 j  1,2,..., N own
W  n 1, n  m 

We note that in downlink other-to-own cell interference

is different for different users. We have

N cells
P  Lm, j N cells
Lm, j
(15) j  
n 1,n m P  Ln, j
 
n1,n m Ln, j

64
Downlink other-to-own cell interference

 Illustration: 3 sectors = 3 cells

in each site.
 Blue cells = ‘other’ cells, green
cell = ‘own’ cell
 Other-to-own cell interference
depends on the user location
 Cells are separated by
scrambling codes
 Shadowing related to different
base stations is correlated to
some extent
 Path loss attenuates base
station signals from ‘other’
cells

65
 Base station transmission power (2)

 Next we sum up powers of different users and take into

account the activity factor. Then we obtain the formula
Eb / N 0  j R j j Eb / N 0  j R j j
 (1   j )   j   PN 
N own N own
(16) P  P Lm, j
j 1 W j 1 W
From (16) we solve the required total base station
transmission power
N own Eb / N 0  j R j j
PN  Lm, j
j 1 W Required base station
(17) P  N own 
Eb / N 0  j R j j transmission power in
1   (1   j )   j  downlink
j 1 W
66
Downlink load equation (4)

 In (17) we denote the downlink load by

Eb / N 0  j R j j
 (1   j )   j 
N own

Downlink load
(18) equation
j 1 W

and the downlink noise rise by

1
NR  NRdB  10 log(1   )
1 

67
 Base station transmission power (3)
 In decibels the required base station transmission power
is of the form (see eq. (17))
 N own Eb / N 0  j R j j  Required base station
(19) PdB  ( PN ) dB  10 log   Lm , j   NRdB transmission power in
 j 1 W  decibels

 The factors that impact to the required transmission

power in base station
– AWGN noise (first term)
– Transmission power that is needed to serve own cell users
(second term)
– Transmission power that is needed to overcome the
interference (third term). Interference contains contribution
from own cell (imperfect code orthogonality) and from other
cells.

68
Base station transmission power (4)
 In downlink it is important to estimate the required base
station power.
 Link budget gives the maximum transmission power which
is determined by the cell edge users
 However, planning should be based on the average
transmission power. This follows from the fact that users are
spread all over the cell and wideband transmission is a sum
over all signals. Hence, it contains signals to users on cell
edge as well as signals to users near the base station.
 The difference between maximum and average path loss is
typically 6 dB.

69
Downlink load equation (5)
 The average load in the cell is given by
N own Eb / N 0  j R j j Downlink average
(20)   E     (1   )    load equation
j 1 W

  is the mean orthogonality factor.

– In ITU Vehicular A channel  is round 0.5
– In ITU Pedestrian A channel  is round 0.9
  is the mean other-to-own cell interference factor
– In macro-cell deployment with omnidirectional antennas  is round
0.55
– In macro-cell deployment with 3-sector sites is round 0.65 

70
SIR/activity values for downlink
 Example values for Eb/No in downlink multi-path
channel:
– 12.2 kbps voice, Eb/No = 6.7 dB (3 km/h), Eb/No = 6.4
(120 km/h)
– 128 kbps data, Eb/No = 5.3 dB (3 km/h), Eb/No = 5.0
(120 km/h)
– 384 kbps data, Eb/No = 5.2 dB (3 km/h), Eb/No = 4.9
(120 km/h)
 Recommended activity factor in downlink:
– Value 0.58 for speech
– Value 1.0 for data.

71
Base station transmission power (5)
 In planning the following mean total transmission power in
base station is to be used
N own Eb / N 0  j R j j
N rf W  L  
j 1 W
(21) PBS  N own Eb / N 0  j R j j
1   (1   )   
j 1 W

Here N rf is the noise spectral density of the receiver front

end. There holds (in linear scale)
(22) N rf  k  T  NF
23
Where k  1.381  10 J/K is Boltzmann constant, T is
temperature in Kelvin and NF is receiver noise figure that
is usually between 5 to 9 dB.
72
Example
Plot maximum allowed path loss as a function
of number of users for 12.2 kbps voice service
and for 64 kbps data service when
– BS transmission power is 40W
– BS transmission power is 10W
All sites in the network admit three sectors
(cells), users mean mobility is 3 km/h, average
orthogonality factor is 0.5, average mobile noise
figure is 7dB.

73
 Example
 Solution. We solve mean path loss from equation
N own 
Eb / N 0  j R j j
N rf W  L  
j 1 W N rf  L  N own  Eb / N 0   R 
PBS  N own 

Eb / N 0  j R j j N own  Eb / N 0   R 
1   (1   )    1  (1   )   
j 1 W W

and compute its numeric value for different number of users by

substituting parameters
– N rf = -174+7dB,  = 0.5,  = 0.65,  = 0.58, W = 3.84 Mcps,
– R = 12.2 kbps, R = 64 kbps, Eb/No = 6.7 dB (voice), Eb/No = 5.3
dB (data),
– PBS = 0.85*40W, PBS = 0.85*10W (15% of BS power is spend on
control channels)
Finally, we add 6 dB margin to achieved mean path loss. The
resulting values are plotted in the figure of the following slide
74
Example
12.2 kbps voice
 Observations:
 Number of downlink data 170

users can be increased only 165

slightly by increasing the

Maximum allowed path loss [dB]

base station transmission 160

power 155

 Number of voice users can

be significantly increased 150

by increasing the base 145

station transmission power

140
0 10 20 30 40 50 60 70
Number of users

64 kbps data

75
Important planning aspects

76
Planning – antenna height
 Since WCDMA performance is
interference limited the cell
dominance areas should be kept
as controlled as possible
 If the antenna is located ”too
high” (no proper tilting) then
– The cell gathers more traffic and
external interference and thus the
”effective” capacity is decreased
– Produced interference decreases
the capacity of the surrounding
network
– Also surrounding network’s service
propability is negatively effected

N own Eb / N 0  j R j j
  E     (1   )   
j 1 W
77
Planning – antenna height
 If WCDMA base station antenna is placed over the
rooftop then antenna tilting is needed.

78
Planning – antenna azimuth
 Natural obstacles and buildings should be used to create good dominance
areas for WCDMA cells
 This improves the SHO performance and decreases interference

 Example of a UMTS cell, that is

naturally bordered (wall effect)
by buildings

79
Planning – antenna height
 When re-using the GSM sites, analysis should be made whether the UMTS antennas
should be positioned lower
 This analysis is done with simulations and visiting the site locations in practise
Part of network with re-used few High UMTS antenna positions
+40meter GSM antenna heights lowered to 25-35m

Dominance areas become

clear, so less interference
is introduced and HO
performance is better.

 Capacity is increased
and performance enhanced!

80
Planning – antenna tilt
 In addition to antenna height, downtilting is very important physical means for
interference minimizing in WCDMA
 Basic rule for antenna tilt is that the height of the antenna should be selected
with respect to the wanted amount of cell range
 If the cell range with respect to available antennas and their tilting with a
feasible amount of tx-power becomes too large to suit the network plan, then
the antenna must be lowered
 According to the experience, the analysis should start with the optimum tilting
and not by reducing the tx-powers of the cell, which can be optimised after
the tiltings are done

Horizontal plane

81
Planning – antenna tilt
 It is important to plan the tilting angle according to the antenna
characteristics
 Good choice is to tilt antenna such that is the first zero of the
antenna radiation pattern is pointed to horizontal direction
K742 234 radiation

45,0

40,0

35,0
0 elect tilt [deg]

30,0 1 elect tilt [deg]

2 elect tilt [deg]
attenuation

25,0 3 elect tilt [deg]

4 elect tilt [deg]
20,0 5 elect tilt [deg]
6 elect tilt [deg]
15,0 7 elect tilt [deg]
8 elect tilt [deg]
10,0

5,0

0,0
30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 -2 -4 -6 -8 -10 -12 -14 -16 -18 -20
m ech tilt 82
Planning – antenna tilt
 In previous slide the horizontal radiation power of the antenna is
set to minimum in order to receive minimum amount of direct
interference from the surrounding cells.
 Typically WCDMA macro-cell antenna has the first vertical lobe
radiation pattern zero around 7-8deg away from the maximum
point (depends on the antenna design), which still allows a
reasonable cell size
 The attenuation of the first zero is usually over 20dB compared to
the main lobe.
 Usually it is of no use to apply larger tilt than the one that points
the first zero to horizon since interference from the antenna
increases with larger tilt.
– This rule of thumb is not necessarily valid in urban (dense) deployments

83
Planning – antenna tilt
Mechanical or electrical tilting?
 If there is both electrical and mechanical tilting available, a combination of
these two can be combined properly case by case
 Mechanical tilt
– widens the antenna lobe horizontally, which can be used in some cases
– does not attenuate the radiation sideways
 Electrical tilt
– attenuates the radiation also on sideways
 By selecting a combination of these two the first zero of the antenna can be
set to horizontal level and the needed amount of power achieved on
sideways horizontally if there is a need for it
 When high building is used as a site the antennas can be wall-mounted, so
that the needed level of attenuation to the wanted directions are easier to
achieve.

84
Planning – antenna tilt

85
Transmission powers
 Default transmission powers are determined by the equipment vendors.
 In initial phase of the planning
– Transmission powers of TCHs and CCHs needs to be set
 In DL the power tuning between TCHs and CCHs has effect on network
performance
– More power to CCHs → better channel estimation, which improves the Eb/No
performance and thus improves coverage
– More power to TCHs → better capacity
– Rule of thumb: 15-20% of DL total power is used for CCHs
 Most important control channel is the primary common pilot channel (P-
CPICH)

86
Transmission powers
 Primary CPICH (P-CPICH) is transmitted continuously with
constant power (spreading factor 256, no power control) so it
is in fact a significant source of interference.
– If received P-CPICH is not included in the UE active set, all
the power received is interference (this is called as pilot
pollution)
 The physical cell range is defined by P-CPICH transmission
power
– The same coverage must be guaranteed for other common
channels as well
 The major effects when the pilot power is adjusted
– The handover behaviour of the network can be changed
– Load can be divided between cells to certain extent
– Ability to divide the base station power between cell coverage
and capacity.

87
Transmission powers
 P-CPICH takes typically 5-20% of the node B maximum
transmission power
 Clear dominance areas for cells should be ensured with
consistent P-CPICH power planning
– CPICH powers should be planned first, then other SHO
parameters
– Goal is to limit cell overlapping so that the P-CPICH power in the
cells outside active set is at least 10dB below the best cell in the
active set
 Large differencies in P-CPICH powers of neighbouring cells
should be avoided

88
Transmission powers
 Indicators for P-CPICH power level in practice
– Other-to-own cell interference (recall load equation discussion)
– Frequency of active set update messages
– Dropped calls and throughput
 With low amount of P-CPICH power, the interference
produced goes down, but also the robustness of the network
is effected negatively.
 Higher amount of P-CPICH power increase signaling and SHO
areas as well as produced interference, but the network
operation is more robust.

89
Transmission powers
Typical DL power recommendations
 Also other control channels
beside CPICH need power (for Channel Allocated power
example BCH) to enable correct
functioning of the system Max power of the Node B 43 dBm

 All the other common control

channels are powered in relation CPICH Max power – 10dB
to the P-CPICH
 The goal of allocating power to PCH Max power – 11 …13 dB

the common channels is to find a

minimum power level needed for SCH Max power – 11 … 12 dB
each channel to secure the
network operation and to provide FACH Max power – 12 – 13 dB
the same cell coverage area as
with CPICH, but not to waste any BCH Max power – 11 … 13 dB
capacity left for the traffic
channels.

90
Recall: Some control channels
 PCH: Paging channel initiates the communication from network side
 SCH: Synchronization channel
 FACH: Forward access channel carries control information to terminals
that are known to be located in the given cell. Is used to answer to the
UL RACH message.
 BCH: Broadcast channel carries network specific information to the
given cell (random access slots for UL, antenna configuration etc)
 PICH: Paging indicator channel is used to provide sleep mode operation
for UE
 AICH: Acquisition indicator channel is used to indicate the reception of
RACH
 CCPCH: Primary and secondary common control physical channels (P-
CCPCH and S-CCPCH) are physical channels that carry BCH, FACH and
PCH.

91
Example: Transmission powers
Channel Allocated Power out of Power out of
power the total the maximum  P-CCPCH transmitted with activity
common Node B
channel transmission
factor 0,9
powers power (20W)

P-SCH 0,331 W
 S-CCPCH transmitted with activity
factor 0,25

S-SCH 0,224 W  SCHs transmitted with activity factor 0,1

PICH 0,1 W
 AICH, PICH and CPICH are transmitted
continuously
AICH 0,126 W

 The BCH is transmitted on the P-

P-CCPCH 0,245 W CCPCH and the FACH and PCH on
the S-CCPCH.
S-CCPCH 1,165 W
 the BCH is transmitted on the P-
CPICH 1W 31 % 5% CCPCH continuously except during the
256 first chips, when the P-SCH and S-
SCH are transmitted we can assume 0,1
All common Ch 3,191 W 100% 16 %
activity factor for the SCHs and 0,9 for
the P-CCPCH.

92
Transmission powers/DCH’s
 Dedicated channel (DCH) is a transport channel that is mapped to dedicated
physical data channel (DPDCH) and dedicated physical control channel
(DPCCH)
 The initial power for DPDCH is important because of reliable service set-up
 The initial DCH power is determined by RRM via
– Spreading Factor
– Measured Ec/Io on P-CPICH
– Transmitted power on P-CPICH
– Service requirements
 Network planning usually needs to plan at least the ”initial DL SIR target” &
”default CPICH power”
 In Uplink the network planning can set initial PC settings, such as ”UL SIR
target”, which will effect the power of the first connection

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Transmission powers
 The minimum and maximum transmitted code powers can be set per cell
(interference & coverage control)
– It is rather important not to set this maximum power too high. Too high setting of the
maximum power will lead to instability in the downlink transmitted carrier power
behavior and might effect the quality of the common channels in a cell.
 During the operation, powers allocated per DCH connection can be set
according to vendor specific algorithm
– This is important to the service probability and allows improving of high bitrate
services if so decided

Planning only for P-CPICH power in terms

of achievable service coverage is not enough,
needed DCH power in relation to P-CPICH
needs to be set as well.

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Transmission powers
 Antenna and transmission power design lead to certain achievable
Ec/Io over the network, which in turn depict a certain service level

DCH Ec/Io determines the service coverage!

EC Eb / N 0  R RSCP
 
I O W  (1   ) RSSI
RSCP = Received signal code power = received power on one code after
despreading. Measured in terminal.
RSSI = Received signal strength indicator = received wideband power on
the whole bandwidth. Measured in terminal.

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Pilot pollution
 Pilot pollution is faced on a certain area when there is no clearly
dominant P-CPICHs over the others.
 The pilot pollution creates an abnormally high level of
interference, which is likely to result in the performance
problems
– Increased interference level
– Poor service quality, decreased throughput or increased delay
– Decreased service access
– Frequent changes in Active Set and potential risk for unnecessary
handovers.
– High non-controllable load

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Pilot pollution
 Pilot pollution can be (at least partly) avoided by planning
the CPICH powers and SHO parameters so that throughout
the network there is only 2-3 CPICHs available for the UE’s,
strong enough to be included in the Active Set.
 All CPICH outside Active Set should be clearly weaker
 Antenna design, height and tilt are selected carefully

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Neighbour cell relations
 The Monitored Set is also called as a Neighbour List. This list can be
defined in network planning and it can be later changed in network
optimization.
 The list of neighbours play an important role since WCDMA is interference
limited. Insufficient planning of neighbour relations will lead to
unnecessary high interference
– E.g. if suitable SHO candinate is not in the monitored set and thus it is not
selected to active set then it’s turning to a ”pilot polluter”
– On the other hand, unnecessary neighbours increase signalling and effects the
SHO selection negatively
 Accurate neighbour relations planning is much more important than in
GSM
– In GSM it is possible to ”hide” cell planning mistakes by frequency planning, in
CDMA the such inaccuracies will effect the system capacity
– The effort saved in frequency planning is spent in more detailed cell planning

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Neighbour cell relations
 The parameters to control the neighbor relations and the algorithms how
system evaluates neighbors for cell lists depend on vendor
– minimum P-CPICH RSCP or Ec/Io
– Ec/Io margin
– maximum number of neighbors
 A neighboring set (or monitored set) is defined for each cell
– Utilize planning tools automatized functions and check with drive tests
– Optimize according to P-CPICH coverage and SHO parameters
 UE monitors the neighboring set that may contain
– Intra-frequency monitored list: Cells on the same WCDMA carrier (Soft HO)
– Inter-frequency neighbor list: Cells on another WCDMA carrier (hard HO)
– Inter-system neighbor list: For each neighboring PLMN
 Missing neighbor can be detected during drive tests
– If the best cell shown in the 3G scanner does not enter to the active set then there is a
missing neighbor
– Include the missing cell to neighbor list if it’s wanted to the active set or change cell plan

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 SHO planning
 Soft/Softer HO planning and correct operation is one
of the most important means of planning WCDMA
networks
 The importance is high because of the high bit rate
(pathloss sensitive) and RT (delay sensitive) RABs
 SHO is measured in terms of probability:
The percentage of all connections that
are in SHO state
 The probability is effected by
network planning and parameter
settings

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SHO planning
Probability for soft HO should be set to 30-50% and for softer HO to 5-
15%, depending on the area
Too high SHO% results in excess overlapping between cells → other-cell
interference increases → capacity decreases
Too high SHO% also leads to poorly utilised network capacity
(unnecessary links)
With too low SHO% the full potential of network is not utilised and
transmission powers cannot be minimized → trouble with interference
SHO performance is planned with a planning tool and optimised by
measurements in live network.
In early stage SHO % can be planned high, since the traffic density is smaller.
With increasing traffic coverage decreases and SHO areas become smaller.
SHO % can be tuned with related parameters and dominance areas

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WCDMA code and frequency planning
 WCDMA code and frequency planning are seen as a simple task from a network
planning point of view
 The system takes care of most of the code allocation
 Main task for network planning is the allocation of scrambling codes for the
downlink
 There are 512 set of scrambling codes available
 The code reuse for downlink is 512
 Simple planning but usage of planning system is recommended to avoid
errors
 Frequency planning has minor importance compared with GSM
 At most the UMTS operators have two or three carriers thus there is not much to
plan
 Yet, there are a few key decisions to make:
 which carrier(s) is used for macro cells?
 Which carrier(s) is used for micro cells?
 Any carrier(s) is reserved for indoor solutions?
 When making the decisions the interference aspects should be considered.

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Parameter planning
 Common channel power setting parameters need to be planned for optimal
related operations.
 Home-PLMNSeachPeriodTime parameter used to set the frequency with
which the mobile searches its home PLMN in the automatic selection mode.
 In the manual mode, the UE gives the user an option to select from a list
of found PLMNs where the signal level is considered good enough (RSCP,
or received signal code power> −95 dBm)
 Cell search related parameters: transmit power parameters for
synchronization channels and timing offset to make sure that synchronization
channels are transmitted at different times in each cell of the same site
 Cell re-selection: measurement criteria and frequency parameters including
Sintrasearch, Sintersearch, SsearchRAT, TmeasureFDD, TmeasureGSM
parameters
 Handover, power control, admission control and other RRM related
parameters

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Contents
 WCDMA network dimensioning
 WCDMA network planning
 WCDMA network optimization
Optimization overview
 Once planned network is rolled out, optimization takes place to maximize
benefits while minimizing capital and operational costs
 Note that operators are worried about their network quality perceived by
end user as their competitiveness highly based on it and of course pricing
 Therefore, operators need to continuously monitor quality of their networks
and perform appropriate actions to maintain and improve user quality of
experience
 Optimization engineers make deep analysis on data collected from
monitoring systems to identify required optimization tasks such as
 Site re-engineering,
 Parameter tuning,
 Frequency plan review
 Optimization is a continuous process
WCDMA optimization approach
 Cluster based optimization
 Network is divided into geographical areas called clusters, each consisting of 10
to 20 sites, based on different methods such as geographical proximity and
interference coming in to the cluster from neighboring areas should be
minimized
 Each cluster is optimized to ensure QoS in that area
 Cluster preparation consists of activities that can be done without drive test data:
 Defining clusters
 Planning the drive route
 Radio parameter audit
 Site configuration check
 Neighbor list verification
 Fault management check
 Cell availability check
 Prior to any drive tests a cluster should have the majority of its sites integrated be
operational and available.

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Example important indicators

traffic drop calls

traffic deviation handovers per call
traffic mix handovers per cell
soft handover inter-system
percentage handovers
average TX power Throughput
average RX power BER, BLER, FER
QoS monitoring and spotting problems
 Analyzing statistics is a top-down process.
 High level (network or RNC level) performance indicators are monitored to find
out if there is a problem in the network
 High level performance problems, anomalies and regular patterns of
performance variation are triggers that indicate a need for further investigation
 Typical granularity of high level performance data is one day and the monitored
period lasts for two months.
 Examples of high level performance indicators are: cell availability, call setup
success rate, drop call rate
 After identifying a problem in high level performance indicators in order to find
out what is causing the problem, low level performance indicators need to be
analyzed based on large numbers of statistical counters
 It can be started from cell-level KPI calculation or counter based problem
identification leading to problematic cell
 Analyzing the geographical proximity of cells having problems might indicate
something wrong with a whole cluster of cells, e.g. the HW/SW problem related to
the transmission network, etc.

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QoS monitoring and spotting problem
Ready-made
queries if well-
Problematic known problem
network Problem
element Diagnosis Detail counter
identified analysis to
classify the
problem

The field measurements analysis is usually started after looking at (statistical)

performance data (counters) to evaluate how much the analyzed area had
problems from end user perspective.

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Details on counters and drive test
parameters
NMS/OMS/OSS and drive and test product specific

Example counters: RAB active failures

Example drive and test parameters: RSCP, Ec/Io

TASK: Identify and examine some counters and drive and test
parameters for WCDMA NMS and drive and test products available
on the market, say those applied by Ethio Telecom

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WCDMA optimization

Based on identified network problems seen using indicators,

appropriate optimization tasks including those approaches
applied during planning phase need to be applied so that the
network continuously deliver quality services for subscribers!

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