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Nov 18, 2015
*WCDMA Capacity Dimensioning
Foreword WCDMA is intrinsical Interference limited system
Coverage and capacity depend on the interference
WCDMA is a Soft Capacity system
Outline Radio Dimensioning Procedure
Radio Link Budget
Capacity Dimensioning
AppendixStochastic Knapsack: Blocking ProbabilityCampbells Dimensioning ProcessInterference Analysis
CapacityQualityCoverageDependence among Capacity, Coverage and QualityCapacity-Coverage-Quality
Capacity vs. Coverage
Cell Load Coverage Range Cell Load Subscribers
Capacity vs. Quality
BLER Capacity GoS Capacity
Coverage vs. Quality
BLER Coverage RangeCapacity-Coverage-Quality
Capacity-Coverage-QualityIndependence among Capacity, Coverage and Quality of GSM System
Capacity: Timeslots and Carriers available and Reuse Mode Coverage Range: transmission Power on Uplink/Downlink (Link Balance)Quality of Call: be ensured by network design to minimize interference
In GSM system, capacity, coverage and quality requirements can be met by independently analysis and designFrequency Planning is a crucial issue to GSM system
Dependency among Capacity, Coverage and Quality of WCDMA SystemWCDMA system is interference-limited. Capacity vs. CoverageIncrease intended system loading will offer more capacity while increasing intra-cell interference and thus reduce coverage range (Application: Cell breathing)Capacity vs. QualitySystem capacity can be achieved by relaxing quality requirement for some connections (Application: Reduce BLER target value by outer-loop power control)Coverage vs. QualityCoverage range can be expanded by relaxing quality requirement for some connections (Application: Slow down data speed by AMRC to accommodate large path loss)CapacityQualityCoverageInterferenceInterference is the dominant concern in capacity analysisCapacity-Coverage-Quality
Radio Dimensioning Procedure Network dimensioning is an iterative process Downlink analysis checks whether NodeB power is enough to cover the users
Outline Radio Dimensioning Procedure
Radio Link Budget
Capacity Dimensioning
AppendixStochastic Knapsack: Blocking ProbabilityCampbells Dimensioning ProcessInterference Analysis
Radio Link Budget: PurposeCalculate the Maximum Path Loss
EIRPSensitivity of ReceiverMinimum Required Signal Strength
Calculate the Cell Range
Propagation ModelMaximum Path LossAntenna HeightCarrier Frequency
BS Antenna GainRx&Tx Cable LossPropagation Loss Body Loss Penetration Loss
Radio Link Budget: SketchTRX
Radio Link Budget: Important ParametersEIRPSensitivity of Receiver Minimum Signal StrengthEdge Coverage ProbabilityPropagation ModelMarginGainLoss
Radio Link Budget: Margin, Gain, Loss
Margins
Interference MarginSlow Fading MarginFast Fading MarginGains
Antenna GainSHO GainLoss
Body LossCable Loss Penetration Loss
Outline Radio Dimensioning Procedure
Radio Link Budget
Capacity Dimensioning
AppendixStochastic Knapsack: Blocking ProbabilityCampbells Dimensioning ProcessInterference Analysis
Capacity Dimensioning: Purpose Estimate Supported Subscribers
Cell Resource Mixed Services Service Traffic Respective GoSEstimate Site Number
Site Number (Coverage) Site Number (Capacity)
Capacity Dimensioning: Difficulties Cell edge is continuously moving according to the traffic load
Mixed services: multiple data rates
Respective GoS Requirement
Capacity Dimensioning: main methods Campbells Theorem
Stochastic Knapsack
Fractional Load
Stochastic Knapsack: What is it ?What is Knapsack ?
What is in the Knapsack ?
Knapsack for Uplink = ?
Knapsack for Downlink = ?
Stochastic Knapsack: Where is it from ? a Multi Service Traffic Model
Used in ATM Multiplexer Dimensioning
Simulate the Respective GoS of the Supported Services
Stochastic Knapsack: Introduced into WCDMA Blocking Probabilities
Shared Resource
Simulate actual Traffic Behavior
Uplink Resource: Cell Load (why)
Downlink Resource: Power (why)
Modified to WCDMA Air Interface Dimensioning (why)
Stochastic Knapsack: Resource Shared Resource Shared
TimeConsumed Resource
Stochastic Knapsack: Example
Users States for 2 services Video Phone CallVoice Call Knapsack? What is the user state in the Knapsack? Which call will be blocked? Which call can access the Knapsack?
Stochastic Knapsack: Example
the user state if not calls arrive? the user state if a voice call access? the user state if a video phone call access?
VoiceVideo PhoneUsers States for 2 services
Stochastic Knapsack: Example
Two ServicesBlocking Prob. for Service 1VoiceVideo Phonethe 4 states will be blocked for voice service. Why?
Stochastic Knapsack: Example
Two ServicesBlocking Prob. for Service 2VoiceVideo Phonethe 7 states will be blocked for video phone service. Why?
Stochastic Knapsack: Questions What is the advantage?
What is the disadvantage?
Campbells Theorem
Virtual ServiceVideo Phone CallVoice Call
Campbells Theorem Multi services one Virtual Service Virtual Service Load Virtual Service Traffic How to Calculate? (Appendix)
One Service Calculation Erlang B Formula
Campbells Theorem What is the advantage?
What is the disadvantage?
Fractional Load Traffic for each service Traffic/BH/Sub Supported Subscribers Channels needed for each service GoS requirement Erlang B Fractional Load for each service single link load channels Cell Load for all services accumulate all the fractional load
Fractional LoadTimeConsumed Resource
Fractional Load What is the advantage?
What is the disadvantage?
Comparison of the Methods Stochastic Knapsack
Complicated
actual traffic behavior
resource shared
respective GoS for each service
only one GoS for all services can guarantee all the GoS requirements?
resource shared
easy to calculate
Fractional Load
Campbells Theorem
resource not shared
easy to calculate
Comparison of the Methods only one service the same result (why) Fractional Load pessimistic more NodeB sites Campbells Theorem uncertain optimistic e.g. 2% GoS for all services Stochastic Knapsack reasonable
Dimensioning Result:
Contents
Uplink capacity analysis
Downlink capacity analysis
Uplink capacity analysisSingle CS service Single PS serviceMixed services
Single CS serviceTo single CS service, the uplink total received power in BS can be calculated as:
meet Poisson arrival, and the mean value is:
Single CS service
ThenSo
Single CS service
The number of uplink channel supported by system with corresponding uplink loading is:
Single CS service
Defining: Then the soft-blocking formula based on interference of uplink is
Uplink capacity analysisSingle CS service Single PS serviceMixed services
Single PS service PS service model
Single PS service
Then the soft-blocking formula based on interference of uplink is
Single PS serviceBecause the blocking characteristic of PS service is determined by the acceptable delay, according to ErlangC formula, defining the channel number: the probability of call with delay can be calculated as:
So the probability with delay exceeding t(s) of any call is:
Single PS service
Mean delay is:
Mean throughput of Uplink is
Here:A is the supported total traffic, N is the channel number, H is the average duration per call of the service.
Uplink capacity analysisSingle CS service Single PS serviceMixed services
mixed service
First, we assume these following variables :the user number is X,the number of service type is M, the ration of other-cell to own-cell interference is f, is the cell loading.
mixed service
The traffic of specific service can be calculated as:The loading factor of one service per user can be calculated as:
mixed service
We convert all services to one virtual service and introduce two variables C1 and C2: And the loading factor of per virtual service is:
mixed service
Then the total traffic of virtual service that the cell can support is:here:traffic of voice service :traffic of the ith type data service :traffic of the virtual service
mixed service
According to the preconcerted cell loading , the number of virtual service channel N is:Based on ErlangB formulary:Then:Fromwe can get the number of users X.
mixed service
Then we can get the uplink data throughput rate per carry as following formulary:
Contents
Uplink capacity analysis
Downlink capacity analysis
Downlink capacity analysisSingle CS service Single PS serviceMixed services
Single CS service
The total received interference of a specific UE is:here,is non-orthogonal factor, ith UE from jth site. Assuming the ratio of the dedicated power for Then:So:is the total received power of
UEi to total power is:
Single CS service
Defining:the ratio of other-cell interference is f :then:The following equation must be satisfied: is the power of common channels
is the corresponding power of RRM congestion threshold.
Single CS service
Then: Defining channel number:Then we can get the downlink soft block traffic soft block Erlang,and the downlink throughput rate per carry is:From formula:
Downlink capacity analysisSingle CS service Single PS serviceMixed services
Single PS serviceThe method of downlink single PS service capacity analysis is similar with that of uplink:Defining channel number:and:
Single PS service
the probability of call with delay can be calculated by:So the probability with delay exceeding t(s) of any call is:
Single PS service
Mean delay is:
Mean throughput of Uplink is
Here: A is the supported total traffic, N is the channel number, H is the average duration per call of the service.
Downlink capacity analysisSingle CS service Single PS serviceMixed services
mixed service
First, we assume these following variables :the user number is X,the number of service type is M, is the non-orthogonal factor, the ration of other-cell to own-cell interference is f, is the downlink cell loading.
mixed service The traffic of specific service can be calculated as:The loading factor of one service per user can be calculated as:
mixed service
Defining:And the loading factor of per virtual service is:Then the total traffic of virtual service that the cell can support is:
mixed service According to the preconcerted cell loading , the number of virtual service channel N is:Based on ErlangB formulary:Then:Fromwe can get the number of users X.
mixed service
Then we can get the downlink data throughput rate per carry as following formulary:
According to the demand of traffic and terrain characteristic, distinguish the planning region into different areas, like as dense urban, urban, suburban, rural and so on.
Different propagation models for areas.
Different user numbers and traffic models for each area.
The demands of QOS and GOS for each service and area.The carry demand for each area, one, two or more carriers.
Capacity dimension input
According to the above inputs of capacity dimension, we can get the number of site and site configuration based on capacity demands.
Comparing the dimension result of capacity with that of coverage, the limited result is proposed .
Capacity dimension
Rough Dimensioning Result a Rough Dimensioning Result
a flat and homogenous landscape Digital database (Heights, Clutters, Vectors)
Further Simulation
homogeneous interference
the propagation model simple propagation laws
the actual traffic behavior
regular hexagon pattern
traffic growth expectation
uniform traffic demand
Simulation Tool Enterprise, etc
Outline Radio Dimensioning Procedure
Radio Link Budget
Capacity Dimensioning
Appendix: Stochastic Knapsack: Blocking ProbabilityCampbells Dimensioning ProcessInterference Analysis
Stochastic Knapsack: Blocking Probability
State Probability:: the traffic of service k: the connecting users of service k
Stochastic Knapsack: Blocking Probability
Blocking Probabilities:: the blocking probability for service k: the blocked state for service kBk
Campbells TheoremVirtual LoadVirtual Traffic: the load of a single user for service j: busy hour traffic of a single user for service j
Campbells TheoremVirtual service channelsTotal Traffic: using Erlang B Formula
Campbells TheoremSupported Subscribers in the cell
Interference Analysis Uplink Interference Analysis
Downlink Interference Analysis
Uplink Interference AnalysisIown interference caused by users of own cellIotherinterference caused by users of other cellsPN equivalent noise input of the receiver
Noise power of receiver: PN
PN = 10lg(KTW) NF
K: Boltzmann Constant= 1.3810-23 J/KT: temperature in degrees KelvinW: Bandwidth of signal3.84MHz for WCDMANF: Noise figure of receiverAnd 10lg(KTW) = -108dBm/3.84MHz NF = 3dB (typical value for Marco-cell) PN = 10lg(KTW) + NF = -105dBm/3.84MHzUplink Interference Analysis
Iown : Own-cell interference
Interference should be overcome by each user: ITOT - PjPj : desired signal power from user j received by NodeBWith perfect power control:
Pj can be estimated by
Own-cell interference: totally received power from all users of own cell:Uplink Interference Analysis
Iother : Other-cell interference
Difficult to analyze theoretically, and depends on user distribution, cell position, antenna patterns and so on
Definition of i, the ratio of other-cell to own-cell interferenceUplink Interference Analysis
Define:The total interference can be estimated:Uplink Interference Analysis
Then: Defining uplink load factor:
ITOT reaches infinity while load factor equals 1Uplink Interference Analysis
Noise Figure defined as follows:
50% load 3dB60% load 4dB75% load 6dBUplink Interference Analysis
Interference AnalysisUplink Interference Analysis
Downlink Interference Analysis
Iown: Interference from BS of own cellIother: Interference form BSs of other cellsPN: Equivalent noise input of the receiverDownlink Interference Analysis
Iown : Own-cell interference
Individual channel distinguished by orthogonal OVSF code. The orthogonality between channels can be achieved in static propagation environment without multipath. Then there is no interference over each other in downlink.In multipath environment, not all paths of signal transmitted for a channel can be applied by RAKE and some energy adds to interference. It can be modeled by the introduction of orthogonal factor :
in the formula above, PT is the total power transmitted by BS, including power of common channels and dedicated channels
Downlink Interference Analysis
Iother : Other-cell interference
Signals transmitted by BSs of other cells can cause interference over the target cell. Due to different scrambling codes, these signals are not orthogonal with those of the target cell.
Assuming uniformly distributed service and equal powers transmitted by all BSs, if there are K of other cells and the path loss from Kth BS to user j is PLk,j, then:Downlink Interference Analysis
With perfect power control, there isThe required transmission power of DCH for user j isDownlink Interference Analysis
SinceTotal transmission power can be estimated as follows:Downlink Interference Analysis
PT can be resolved as follows: ij is the ratio of other-cell to own-cell interference for user j. and it is defined as follows:Downlink Interference Analysis
Downlink load factor
defined in common as the ratio of total transmission power to maximal transmission power of the BS.
The ratio of PCCH to PMAX is about 20%.
Downlink Interference Analysis