03 OWJ100102 WCDMA Radio Network Capacity Planning (With Comment) ISSUE 1
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Transcript of 03 OWJ100102 WCDMA Radio Network Capacity Planning (With Comment) ISSUE 1
www.huawei.com
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA RadioNetwork CapacityPlanning
Page2Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Foreword� WCDMA is a self-interference system
� WCDMA system capacity is closely related to coverage
� WCDMA network capacity has the “soft capacity” feature
� The capacity planning of the WCDMA network is performed
under certain traffic models
Page3Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Objectives� Upon completion of this course, you will be able to:
� Grasp the parameters of 3G traffic model
� Understand the factors that restrict the WCDMA networkcapacity
� Understand the methods and procedures of estimating multi-service capacity
� Understand the key technologies for enhancing networkcapacity
Page4Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents1. Traffic Model
2. Uplink capacity analysis
3. Downlink capacity analysis
4. Multi-service capacity estimation
5. Network estimation procedure
6. Capacity enhancement technologies
Page5Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents1. Traffic Model
1.1 Overview of traffic model
1.2 CS traffic model
1.3 PS traffic model
Page6Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Service Overview� The WCDMA system supports multiple services
� Variable-rate services (e.g. AMR voice)
� Combined services (e.g. CS & PS)
� High-speed data packet services (384k service)
� Asymmetrical services (e.g. stream service )
� Large-capacity and flexible service bearing
Page7Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
QoS Type
Data integrity should be maintained. Small delay
restriction, requiring correct transmission
Request-response mode, data integrity must be
maintained. High requirements on error tolerance,
low requirements on time delay tolerance
Typically unidirectional services, high requirements
on error tolerance, high requirements on data rate
It is necessary to maintain the time relationship
between the information entities in the stream.
Small time delay tolerance, requiring data rate
symmetry
Background
download of
Background
Web page
browse,
network gameInteractive
Non real-tim
e category
Streaming
multimediaStreaming
Voice service,
videophoneConversational
Real-tim
e category
Page8Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Objectives of Setting Up Traffic Model� In order to determine the system configuration, we need to
determine the capacity of the air interface first
� In the data service, different transmission model willgenerate different system capacities
� We need to set up an expected data transmission model ofthe customer so that we can plan the network properly
� In order to set up a right model, the operator should providesome statistic data as reference
Page9Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Traffic Model
� Traffic model is a means of researching the capacity
features of each service type and the QoS expected by the
users who are using the service from perspective of data
transmission
� In the data application, the user behaviour research mainly
forecasts the service types available from the 3G, the
number of users of each service type, frequency of using
the service, and the distribution of users in different regions
Page10Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
System Configuration
User behaviour
Service Pattern
Traffic ModelResults
The Contents of Traffic Model
Page11Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Typical Service Features Description� Typical service features include the following feature
parameters:
� User type (indoor ,outdoor, vehicle)
� User’s average moving speed
� Service Type
� Uplink and downlink service rates
� Spreading factor
� Time delay requirements of the service
� QoS requirements of the service
Page12Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents1. Traffic Model
1.1 Overview of traffic model
1.2 CS traffic model
1.3 PS traffic model
Page13Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
CS Traffic Model� Voice service is a typical CS services. Voice data arrival
conforms to the Poisson distribution. Its time interval
conforms to the exponent distribution
� Key parameters of the model
� Penetration rate
� BHCA Mean busy-hour call attempts
� Mean call duration (s)
� Activation factor
� Mean rate of service (kbps)
Page14Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
CS Traffic Model Parameters� Mean busy-hour traffic (Erlang) per user = BHCA * mean call
duration /3600
� Mean busy hour throughput per user (kbit) (G) = BHCA * mean
call duration * activation factor * mean rate
� Mean busy hour throughput per user (bps) (H) = mean busy hour
throughput per user * 1000/3600
Page15Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents1. Traffic Model
1.1 Overview of traffic model
1.2 CS traffic model
1.3 PS traffic model
Page16Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
PS Traffic Model� The most frequently used model is the packet service
session process model described in ETSI UMTS30.03
Page17Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
PS Traffic Model
Data Burst Data Burst Data Burst
Packet Call
Session
Packet Call Packet CallDownloading Downloading
Active Dormant Dormant Active
Page18Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Traffic model
PS Traffic Model Parameters
Packet Call Num/Session
Packet Num/Packet Call
Packet Size (bytes)
BLER
Typical Bear Rate (kbps)
Reading Time (sec)
Page19Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Parameter Determining
� The basic parameters in the traffic model are determined in
the following ways:
� Obtain numerous basic parameter sample data from the
existing network
� Obtain the probability distribution of the parameters through
processing of the sample data
� Take the distribution most proximate to the standard probability
as the corresponding parameter distribution through
comparison with the standard distribution function
Page20Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
NBLER
BLERNBLERNBLERNBLERNN n *1
1**** 32
−=+++++ ΛΛ
PS Traffic Model Parameters
� Typical Bearer Rate (kbps):
� Bearer rate is variable in the actual transmission process
� BLER
� In the PS service, when calculating the data transmission time,
the retransmission caused by erroneous blocks should be
considered. Suppose the data volume of service source is N,
the air interface block error rate is BLER, the total required
data volume to be transmitted via the air interface is:
Page21Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
User behaviour
PS User Behaviour Parameters
User Distribution (High, Medium, Low
end)
BHSA
Penetration Rate
Page22Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
PS User Behaviour Parameters
� Penetration Rate
� The percentage of the users that activates this service to all the
users registered in the network.
� BHSA
� The times of single-user busy hour sessions of this service
� User Distribution (High, Medium, Low end)
� The users are divided into high-end, mid-end and low-end
users. Different operators and different application situations
will have different user distributions
Page23Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
PS Traffic Model Parameters� Session traffic volume(Byte): Average traffic of single session
of the service
� Data transmission time (s) : The time in a single session of servicefor purpose of transmitting data.
� Holding Time(s): Average duration of a single session of service
eTypicalRatfficVolumeSessionTra
BLERsissionTimeDataTransm 1000/8**
11)(
−=
)(Re*)1/(
sissionTimeDataTransmadingTimeSessionlNumPackketCaleHoldingTim
+−=
)/(*)/(*)( SessionNumPacketCallPacketCallPacketNumPacketSizefficVolumeSessionTra =
Page24Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
� Active factor:
� The weight of the time of service full-rate transmission among the
duration of a single session.
� Busy hour throughput per user (Kb):
� PS throughput equivalent Erlang formula (Erlang)
eHoldingTimissionTimeDataTransmorActiveFact =
1000/8**/ fficVolumeSessionTraBHSAuseroughputBusyHourTh =
PS Traffic Model Parameters
)3600
(_ ∑ ⋅⋅⋅⋅=
orActiveFactredRateTypicalBeanEviromentApplicatioderTypicalroughputUnBusyHourThgRatePenetratinUserOfDiffrentPercentageErlangData
Page25Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents1. Traffic Model
2. Uplink capacity analysis
3. Downlink capacity analysis
4. Multi-service capacity estimation
5. Network estimation procedure
6. Capacity enhancement technologies
Page26Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
NotherownTOT PIII ++=
Uplink Interference Analysis—UplinkInterference Composition
� :Interference from the users of this cell
� : Interference from users of adjacent cell
� :Noise floor of the receiver
ownIotherI
NP
Page27Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Basic Principles� In the WCDMA system, all the cells share the same frequency,
which is beneficial to improve the system capacity. However, co-
frequency multiplexing causes interference between users. This
multi-access interference restricts the capacity
� The radio system capacity is decided by uplink and downlink.
When planning the capacity, we must analyze from both uplink
and downlink perspectives
Page28Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Uplink Interference Analysis—UplinkInterference Composition
� Receiver noise floor PN
� K:Boltzmann constant, 1.38×
� T:Kelvin temperature, normal temperature: 290 K
� W:Signal bandwidth, WCDMA signal bandwidth3.84MHz
� 10lg(KTW) = -108dBm/3.84MHz
� NF = 3dB (typical value of macro cell BTS)
�
NFWTKPN += )**log(10
KJ /10 23−
MHzdBmNFWTKPN 84.3/105)**log(10 −=+=
Page29Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Uplink Interference Analysis—UplinkInterference CompositionUplink Interference Analysis—UplinkInterference Composition
� :Interference from users of this cell
� Interference that every user must overcome:
� is the receiving power of the user j , is active factor
� Under the ideal power control :
� Hence, :
� The interference from users of this cell is the sum of power of all the
users arriving at the receiver
( )jjjTOT
jj vR
WPI
PNoEb 1/ ⋅⋅
−=
∑=N
jown PI1
( ) jjj
TOTj
vRW
NoEb
IP 1/11 ⋅⋅+
=
jtotal PI −
jVjP
jP
ownI
Page30Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Uplink Interference Analysis—UplinkInterference Composition
� :Interference from users of adjacent cell
� The interference from users of adjacent cell is difficult to analyzetheoretically, because it is related to user distribution, cell layout,and antenna direction diagram.
� Adjacent cell interference factor :
� When the users are distributed evenly� For omni cell, the typical value of adjacent cell interference factor is
0.55
� For the 3-sector directional cell, the typical value of adjacent cellinterference factor is 0.65
own
other
IIi =
otherI
Page31Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Define
Then
Uplink Interference Analysis
( )( )
N
N
jjj
TOT
NotherownTOT
P
vRW
NoEb
Ii
PIII
+⋅⋅+
+=
++=
∑1 1
/11
1
( ) jjj
j
vRW
NoEb
L 1/11
1
⋅⋅+=
( ) N
N
jTOTTOT PLiII +⋅+⋅= ∑1
1
Page32Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
ObtainObtain( ) ∑⋅+−
⋅= N
j
NTOT
LiPI
111
1
Uplink Interference Analysis
� Suppose that:
� All the users are 12.2 kbps voiceusers, the demodulation thresholdEb/No = 5dB
� Voice activation factor vj = 0.67
� Adjacent cell� interference factor
� i = 0.55
Page33Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Uplink Interference Analysis—UplinkLoad Factor
� Define the uplink load factor
� When the load factor is 1, is infinite, and the corresponding
capacity is called “threshold capacity”.
� Under the above assumption, the threshold capacity is approx 96 users.
( ) ( )( )
∑∑⋅⋅+
⋅+=⋅+=N
jjj
N
jUL
vRW
EbvsNo
iLi11 111
111η
TOTI
Page34Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Uplink Interference Analysis—LoadFactor and Interference� According to the above mentioned relationship, the
noise will rise:( )
1
1 111 1
TOTN
N ULj
INoiseRiseP i L η
= = =−− + ∑
50% Load50% Load —— 3dB3dB60%60% LoadLoad —— 4dB4dB75%75% LoadLoad —— 6dB6dB
Page35Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Uplink Interference Analysis—Limitation of the Current Method� The above mentioned theoretic analysis uses the following
simplifying explicitly or implicitly:� No consideration of the influence of soft handover
� The users in the soft handover state generates the interference which isslightly less than that generated by ordinary users.
� No consideration of the influence of AMRC and hybrid service� AMRC reduces the voice service rate of some users, and makes them
generate less interference, and make the system support more users. (Butcall quality of such users will be deteriorated)
� Different services have different data rates and demodulation thresholds.So, we should use the previous methods for analysis, but it will complicatethe calculation process.
� Since the time-variable feature of the mobile transmission environment, thedemodulation threshold even for the same service is time-variable.
Page36Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Uplink Interference Analysis—Limitation of the Current Method
� Ideal power control assumption� The power control commands of the actual system have certain
error codes so that the power control process is not ideal, andreduces the system capacity
� Assume that the users are distributed evenly, and theadjacent cell interference is constant
� Considering the above factors, the system simulation is amore accurate method:
� Static simulation: Monte_Carlo method
� Dynamic simulation
Page37Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents1. Traffic Model
2. Uplink capacity analysis
3. Downlink capacity analysis
4. Multi-service capacity estimation
5. Network estimation procedure
6. Capacity enhancement technologies
Page38Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
NotherownTOT PIII ++=
Downlink Interference Analysis—Downlink Interference Composition
� : Interference from other downlink DCH of this cell
� : Interference from the downlink DCH of adjacent cell
� : Noise floor of the receiver
ownI
otherI
NP
Page39Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Downlink Interference Analysis—Downlink Interference Composition
� Receiver noise floor PN
�
� K Boltzmann constant, = 1.38*
� T Kelvin temperature, normal temperature 290 K
� W Signal bandwidth, WCDMA signal bandwidth 3.84MHz
� NF: Receiver noise figure
� 10lg(KTW) = -108dBm/3.84MHz
� NF = 7dB ( UE typical value )
NFWTKPN += )**log(10
KJ /10 23−
MHzdBmNFWTKPN 84.3/101)**log(10 −=+=
Page40Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Downlink Interference Analysis—Downlink Interference Composition� :Interference from other downlink DCH of this cell
� The downlink users are identified with the mutually orthogonal OVSF
codes. In the static propagation conditions without multi-path, no mutual
interference exists.
� In case of multi-path propagation, certain energy will be detected by the
RAKE receiver, and become interference signals. We define the
orthogonal factor α to describe this phenomenon.
� In the formula, PT is a total transmitting power of BTS, which includes the
dedicated channel transmitting power and the common channel transmitting
power
( ) ( )1 Town jj
j
PIPL
α= − ⋅
∑+=N
jCCHT PPP1
ownI
Page41Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Downlink Interference Analysis—Downlink Interference Composition
� : Interference from the downlink DCH of adjacent cell
� The transmitting signal of the adjacent cell BTS will causeinterference to the users in the current cell. Since thescrambling codes of users are different, such interference isnon-orthogonal
� Assume the service is distributed evenly, the transmittingpower of all BTSs will be equal. k,j In the system, there are Kadjacent cell BTSs, where path loss from the number k BTSto the user j is PLk,j. Hence we obtain:
( ) ∑⋅=K
jkTjother PLPI
1 ,
1
otherI
Page42Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Downlink Interference Analysis—Downlink Interference Composition
( ) N
K
jkT
j
Tj
NotherownTOT
PPL
PPLPPIII
+⋅+⋅−=
++=
∑1 ,
11 α
Suppose the power control is desired, we obtainSuppose the power control is desired, we obtain
( ) ( ) jjjTOT
j
j
j vRW
IPL
P
EbvsNo 1⋅⋅=
ThenThen
( ) ( ) jjTOTjj
jj PLIvWR
EbvsNoP ⋅⋅⋅⋅=
Page43Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
BecauseBecause ∑+=N
jCCHT PPP1
ThenThen
( ) ( )
( ) ( )
( ) ( )
⋅+⋅+⋅−⋅
⋅⋅+=
+⋅+⋅−⋅
⋅⋅⋅+=
⋅⋅⋅⋅+=
∑∑
∑∑
∑
jN
K
jk
jTTj
N
jj
jCCH
N
K
jkT
j
Tj
N
jjj
jCCH
N
jjTOTjj
jCCHT
PLPPLPL
PPvWR
EbvsNoP
PPL
PPLPPLv
WR
EbvsNoP
PLIvWR
EbvsNoPP
1 ,1
1 ,1
1
1
11
α
α
Downlink Interference Analysis—Downlink Interference Composition
Page44Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Resolve PT to obtainResolve PT to obtain
( )
( ) ( )∑
∑
⋅⋅⋅+−−
⋅⋅⋅⋅+
=N
jj
jjj
N
jjj
jNCCH
T
vWR
EbvsNoi
PLvWR
EbvsNoPPP
1
1
11 α
wherewhere iijj is the adjacent cell interference factor of the useris the adjacent cell interference factor of the user,,defined as:defined as:
∑=K
jk
jj PL
PLi
1 ,
Downlink Interference Analysis—Downlink Interference Composition
Page45Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Downlink Interference Analysis� According to the above analysis, we can define the downlink load factor:
� When the downlink load factor is 100%, the transmitting power of the BTS isinfinite, and the corresponding capacity is called “threshold capacity”.
� As different from the theoretic calculation of uplink capacity, and inthe downlink capacity formula are variable related to user position. Namely,the downlink capacity is related to the spatial distribution of the users, andcan only be determined through system simulation.
( ) ( )∑
⋅⋅⋅+−=
N
jj
jjjDL vWR
EbvsNoi1
1 αη
ja ji
Page46Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Downlink Interference Analysis—Simulation Result
Page47Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Downlink Interference Analysis—Simulation Result Analysis
� When the transmitting power of the BTS is 43dBm (20W), the
supported maximum number of users is approx 114.
� In order to ensure system stability, we do not allow the mean
transmitting power of the BTS to be more than 80% of the
maximum transmitting power, namely, 42dBm. This way, the
supported number of users is 111.
Page48Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents1. Traffic Model
2. Uplink capacity analysis
3. Downlink capacity analysis
4. Multi-service capacity estimation
5. Network estimation procedure
6. Capacity enhancement technologies
Page49Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents4. Multi-service capacity estimation
4.1 Network capacity restriction factors
4.2 Typical capacity design methods
Page50Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Capacity Restriction Factors� The WCDMA network capacity restriction factors in the
radio network part include the following:
� Uplink interference
� Downlink power
� Downlink channel code resources (OVSF)
� Channel element (CE)
� Iub interface transmission resources
Page51Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Downlink Transmit Power� The downlink transmit power has two parts:
one part is used for common channel, andthe other part for dedicated (traffic) channel.
� The transmit power is allocated by the cellto each user varies with servicedemodulation threshold, propagation pathloss and the interference received by theuser
� The downlink transmit power of the cell isshared by all the users in the cell
� We generally use the simulation method toanalyze the downlink interference.
∑+=N
jCCHT PPP1
Page52Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Downlink Channel Code Resources� The WCDMA network use the codes
whose SF is 4~512. The smaller theSF is, the higher the supported datarate will be.
� In the code tree, the allocable codesshould meet the following conditions:
� No codes on the path from thiscode to the root node of code treeare allocated
� No codes in the sub-tree whoseroot node is this code are allocated
� Try to reserve the code wordswhose SF is small, so as toimprove the utilization efficiency
1
1 -1
1 1
1 1 1 1
1 1 -1 -1
1 -1 1 -1
1 -1 -1 1
C1,0
C2,0
C2,1
C4,0
C4,1
C4,2
C4,3
SF = 1 SF = 2 SF = 4
1
1 -1
1 1
1 1 1 1
1 1 -1 -1
1 -1 1 -1
1 -1 -1 1
C1,0
C2,0
C2,1
C4,0
C4,1
C4,2
C4,3
SF = 1 SF = 2 SF = 4
Page53Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Downlink Channel Code ResourcesFollowing is an example of code resources allocationFollowing is an example of code resources allocation
SF 4 8 16 32 64 128 256 512┏┏● C(256, 0) : PCPICH 2
┏ 0 ┫
┃ ┗┏● C(256, 1) : PCCPCH 3┏ 0 ┫
┃ ┃ ┏┏● C(256, 2) : AICH 6┃ ┗ 1 ┫
┃ ┗┏● C(256, 3) : PICH 10┏ 0 ┫
┃ ┗┏● C(64, 1): SCCPCH 8┏ 0 ┫
┃ ┃ ┏┏● C(64, 2): SCCPCH 9┃ ┗ 1 ┫
┃ ┗┏┗3┏ 0 ┫
┃ ┗┏┗1┏ 0 ┫
┃ ┗┏┗1┃
┗┏┗1
┏┏┗2┃
┗┏┗3
Page54Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Channel Element (CE)� The Channel element the quantitative data that measures the
resources logically occupied for service processing
� The resource occupied by the service processing is mainly related
to the spreading factor of this service. The smaller the SF is, the
greater the data traffic will be, and more resources will be occupied
� The SF of typical services are:
� AMR12.2kbps SF=128
� CS64kbps SF=32
� PS64kbps SF=32
� PS144kbps SF=16
� PS384kbps SF=8
Page55Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Channel element (CE)� If we define the resources required for processing AMR 12.2kbps
services as a channel processing unit, the number of channel
processing units occupied by other services is:
� AMR12.2kbps 1
� CS64kbps 4
� CS144kbps 8
� CS384kbps 16
� PS64kbps 4
� PS144kbps 8
� PS384kbps 16
Page56Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Iub Interface Capacity� The contents transmitted on the
Iub interface include:
� The user data encapsulated in
the AAL2 format (common
channel and dedicated channel)
� Signaling data encapsulated in
the AAL5 format
� BTS operation & maintenance
data
Page57Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Iub Interface Capacity� Factors to be considered when estimating the interface
capacity:
� Frame coding efficiency. Through segmentation and
encapsulation of the application data at each layer, the data
quantity at the bottom layer will be increased to different
extents compared with the application data at the upper
layers
� Traffic. More users will generate more data traffic
� Maintenance efficiency. Certain bandwidth is required in the
background maintenance for BTS data transmission
Page58Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents4. Multi-service capacity estimation
4.1 Network capacity restriction factors
4.2 Typical capacity design methods
Page59Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Erlang-B Formula (I)
� Erlang-B formula is used forestimating the peak traffic thatmeets certain call loss rate whenthe average traffic (Erlang) is given
� Erlang-B formula is only used for
� Circuit switched services
� Single service
� The WCDMA system provides CSand PS domain multi-services
Page60Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Erlang-B Formula (II)� The prerequisite of the Erlang-B is the requests of
resources take on a Poisson distribution, namely, itsvariance is equal to its mean value
� If, when a service establishes a link, the service requiresthe resources which are more than the unit resources, theresource request is no longer equal to its mean value, andthe Erlang-B formula is not applicable in this case
� Comparison of multi-service capacity estimation methods :
� Post Erlang-B
� Equivalent Erlangs
� Campbell’s Theorem
Page61Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Post Erlang-B 一
� By summing up the capacities
required for different services,
we obtain the capacities
required for the combined
services
� No consideration of the
resource efficiency of different
services
Page62Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Post Erlang-B (II)
� Consider that two services share resources
� Service 1: 1 unit resource/connection.12 Erlang
� Service 2: 3 unit resources/connection.6 Erlang
� Calculate capacity required for each service
� Service 1: 12 Erlangs require 19 connections (19 unit
resources), meeting the 2% blocking rate
� Service 2: 6 Erlangs require 12 connections (equivalent to the
36 unit resources of service 1), meeting the 2% blocking rate
� Total 55 unit resources
Page63Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Post Erlang-B overestimatesthe capacity requirements!
Post Erlang-B (III)� Consider that two services use the same resources
� Service 1: 1 unit resource/connection.12 Erlang� Service 2: 1 unit resource/connection.6 Erlang
� Calculate capacity required for each service� Service 1: 12 Erlangs require 19 connections, meeting the 2%
blocking rate� Service 2: 6 Erlangs require 12 connections, meeting the 2%
blocking rate� Total 31 unit resources
� However, the reasonable results should be: 18 Erlangsrequire 26 connections for meeting the 2% blocking rate
Page64Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Equivalent Erlangs (I)� By converting the bandwidth
from one service to another
service, combine different
services and then calculate the
required capacity
� Selecting different services as
the measurement benchmark
will lead to different capacity
requirements
Page65Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Equivalent Erlangs (II)� Consider that two services share resources
� Service 1: 1 unit resource/connection.12 Erlang
� Service 2: 3 unit resources/connection.6 Erlang
� If using service 1 as measurement benchmark, the two servicesare equivalent to 30 Erlangs in total� 30 Erlangs require 39 connections (39 unit resources), meeting the 2%
blocking rate
� If using service 2 as measurement benchmark, the two servicesare equivalent to 10 Erlangs in total� 10 Erlangs require 17 connections (equivalent to 51 unit resources of service
1), meeting the 2% blocking rate
The predication resultsare not unique!
Page66Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
ia
Campbell’s Theorem (I)� The Campbell theorem sets up a combined distribution
� Here:
� is service amplitude, namely, the channel resourcesrequired for a single link of the service.
� is the mean value, v is the variance.
cfficOfferedTra α=
caCCapacity ii )( −=
∑∑
×
×==
ii
ii
aErlangs
aErlangsvc
2
α
α
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Campbell’s Theorem (II)� Consider that two services share resources
� Service 1: 1 unit resource/connection.12 Erlang
� Service 2: 3 unit resources/connection.6 Erlang
� The system mean value is
� The system variance is
� The capacity factor c is 1
3063121 =×+×=×=∑ iaErlangsα
2.23066 === α
vc
6636112 222 =×+×=×= ∑ iaErlangsv
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Campbell’s Theorem (III)� Combined traffic is:
� The number of connections for meeting the blocking rate of 2% is 21
� For the target services that meet the same GoS, the capacityrequired is (calculated on the basis of the unit resource of service 1)� Goal is service 1: C1 = (2.2×21) +1 =47
� Goal is service 2: C2 = (2.2×21) +3 =49
For different services, the same GoS requires different capacities.For the given capacity, the GoS of different services will differ slightly.
63.132.2
30 ===c
fficOfferedTra α
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The comparison of the differentcapacity method� Post Erlang-B
� Service 1 (1 unit resource/connection, 12Erl) and service 2 (3 unit
resources / connection, 6Erl), requiring 55 unit resources in total
� Equivalent Erlangs
� Calculated according to benchmark of service 1 (1 unit
resource/connection, 12Erl), a total of 39 unit resources are required
� Calculated according to benchmark of service 2 (3 unit
resources/connection, 6Erl), a total of 51 unit resources are required
� Campbell’s Theorem
� In the same conditions, 47~49 unit resources are required in total.
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Summary of This Chapter� This chapter deals with the three methods of estimating the
multi-service capacity
� The detailed process of using the Campbell theorem to
calculate the capacity is described
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Contents1. Traffic Model
2. Uplink capacity analysis
3. Downlink capacity analysis
4. Multi-service capacity estimation
5. Network estimation procedure
6. Capacity enhancement technologies
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Network estimation procedure
Cellradius
User density
Service message
Compareover
Yes
No
Assumption of cellload and carriernumber
Cellarea
Number of user percell
Balance between capacitydimensionand coverage dimension ?
Uplink capacity dimension ,downlink capacitydimension
Adjustment of cellload and carriernumber
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Contents1. Traffic Model
2. Uplink capacity analysis
3. Downlink capacity analysis
4. Multi-service capacity estimation
5. Network estimation procedure
6. Capacity enhancement technologies
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Transmission Diversity -TxDiv� Txdiv has two types in
WCDMA system:
� Open loop TxDiv
� Closed loop TxDiv
� TxDiv could improve downlink
capacity
� Need additional amplifier
� Need equipment support
� Don’t need additional antenna
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Transmission Diversity -TxDiv
� Gain of TxDiv
� The gain is obtained due to additional amplifier
� Pure gain is obtained due to TxDiv technology
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Transmission Diversity -TxDiv� Gain of TxDiv
� The gain is obtained due toadditional amplifier
� Pure gain is obtained due toTxDiv technology
� TxDiv should reduce downlinkpower
� TxDiv should reducerequirement of Eb/N0
� Usually ,closed loop TxDivwould obtain more gain thanopen loop TxDiv
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Transmission Diversity -TxDiv� Transmission diversity can enhance the downlink capacity
and coverage
� Conclusion of capacity enhancement of transmission
diversity
� STTD mode: Capacity increase of 17 ~ 24%
� TxAA(1) mode: Capacity increase of 16 ~ 23%
� TxAA(2) mode: Capacity increase of 31 ~ 37%
Page78Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Sectorization� In the dense urban areas and the normal urban areas with high
traffic, increasing sectors of the BTS is a method of improving the
capacity
� 6-sectors BTS generally use the antenna whose horizontal lobe is
33º
� The capacity of a 6-sector BTS is 1.67 times that of a 3-sector
BTS
� The capacity of a 3-sector BTS is 2.77 times that of a omni- BTS
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