UMTS Capacity Estimation

Content:

UMTS Service mode
Common Capacity Design Methods
Uplink Capacity Estimation
Downlink Capacity Estimation
Estimation Examples

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UMTS Service mode

CS Domain Service Model

PS Domain Service Model

PS Domain Service Model

• Dormant status and Active status conversion
• Every session can contain several packet calls, different data services and different user types have different features
• Resource occupied by packet call varies alone with the burst transmission

   

PS Service Model - Example

Service Category

User Group Classification

• Classification principle
• Based on user consumption capability and consumption behavior
• Note: User groups are distinguished by service type, service rate, service quality and service intensity. 

Service Penetration

• Percentage of user distribution in different application environments are different
• Percentage of high-end, middle-end and lower-end users in different application environments are different
• Service model statistic characteristic relates to percentages mentioned above

Traffic Analysis for Single Subscriber

• CS Domain
• Mean busy hour Erl. Per user=mean busy hour calls*mean call duration/3600

Traffic Analysis for Single Subscriber

• PS Domain
• Node: penetration rate means the percentage of UEs which support this service in total UEs. 
• Busy hour throughput per user = BHSA* mean calls in a session *mean packets in a call*mean packet size*8/1000 
• Equivalent Erl = Busy hour throughput per user / (Bearer rate *3600)

Traffic Analysis for Single Subscriber

• The average traffic according to the Service Model in each transmission environment is :
• Average traffic for each subscriber = ∑ Ratio of subscriber group* Service penetration * average traffic of this group

Common Capacity Design Methods

UMTS Network Dimensioning Procedure

Capacity Estimation Procedure

• Hybrid service intensity analysis
• The UMTS system provides multiple services and the hybrid service intensity analysis makes the system capacity consumed by various services equivalent to that consumed by a single service. 
• Uplink capacity estimation
• Estimate the NodeB number that meets the service demand based on the hybrid service intensity analysis. 
• Downlink capacity estimation
• It is a verification process. The NodeB transmission power formula is used to calculate the channel number that can be provided by the current NodeB scale so as to verify whether this channel number can meet the capacity requirement, and if it cannot, stations need be added.

Common Capacity Design Methods

• Equivalent Erlangs method
• Post Erlang-B method
• Campbell method

Equivalent Erlangs Method

• Principle: Make a service equivalent to another service and calculate the total Erl.
• Example
• Service A: 1 channel for each connection and the total is 12 erl.
• Service B: 3 channels for each connection and the total is 6 erl.
• If 1 erl service B = 3 erl service A, altogether 30 erl service A shall be equivalent and 39 channels shall be required (under 2% blocking rate).
• If 3 erl service A = 1 erl service B, altogether 10 erl service B shall be equivalent and 17 service B channels shall be required (equal 17*3=51 service A channels under 2% blocking rate).

Equivalent Erlangs Method

Post Erlang-B Method

• Principle: Calculate the capacity required by each service respectively and add them.
• Example
• Service A: 1 channel for each connection and the total is 12 erl.
• Service B: 3 channels for each connection and the total is 6 erl.
• Service A requires 19 channels (under 2% blocking rate).
• Service B requires 12 service B channels (equal 12*3=36 service A channels, under 2% blocking rate).
• These two services require 19+36=55 channels

Post Erlang-B Method

• Suppose services A and B are the same kind, where, 
• Service A: 1 channel for each connection and the total is 12 erl.
• Service B: 1 channel for each connection and the total is 6 erl.
• Based on the Post Erlang-B method
• Service A requires 19 channels (under 2% blocking rate).
• Service B requires 12 channels (under 2% blocking rate).
• Altogether 19+12=31 channels are required. 
• Based on traditional Erlang-B method
• The total traffic of services A and B is 12+6=18 erl and altogether 26 channels are required under 2% blocking rate. 
• Required channel number estimated through the Post Erlang-B method is too large.

Post Erlang-B Method

Campbell Method

• Principle: Make multiple services equivalent to a virtual service and calculate the capacity on the basis of the virtual service.

Campbell Method

• Example
• Service A: 1 channel for each connection and the total is 12 erl.
• Service B: 3 channels for each connection and the total is 6 erl 
• Mean & variance

Capacity factor c

Virtual traffic

• 21 channels (virtual channels) are required to meet the virtual traffic under 2% blocking rate. 
• Under 2% blocking rate, channel number required by each service is shown as follows:

• Different channel numbers are required to meet the GOS requirements of diversified services. 
• Compared with the former two methods, the calculation result through the Campbell method is more reasonable.
• If the reference service is the voice service：

Uplink Capacity Estimation
Uplink Load Analysis

• Eb/No the receive signal in the NodeB must reach Eb/No required by the service demodulation.

Uplink Load Analysis

Uplink Capacity Estimation

• In the case of a single service, evaluate the channel quantity provided by every cell according to the load formula and further evaluate the total number of base stations satisfying the uplink capacity requirement.
• To budget composite traffic, based on the Campbell algorithm, make different services consumption on the system resource equivalent to the single service consumption on the system resource, and then evaluate the quantity of channels to be provided by every cell according to load formula, and further evaluate the number of base stations satisfying the composite traffic requirement.

R99/HSUPA mixed calculation 

• During the uplink capacity calculation ,decide how much uplink load will be designed in R99 and HSUPA
• By simulation, calculate how much PS throughput can be carried by HSUPA
• Calculate how much of the remaining PS service to be carried by R99

R99 Uplink Capacity Algorithm

Downlink Capacity Estimation
Downlink Load Analysis

• To correctly demodulate useful signals, the UE must overcome interference from the following three aspects

• By referring to the derivation means of uplink load factor, denote the downlink load factors as follows:

• Total downlink power allocation

• The downlink capacity is limited by transmission power of the base station

Downlink Load and Scale Analysis

• Estimate downlink capacity after analyzing the channel quantity required by uplink capacity, and observe whether the downlink can support the mobile station to work in the designated coverage area and its channel quantity reaches the channel quantity generated by the uplink
• Calculate the quantity of equivalent voice channels to be provided by every cell
• Calculate the quantity of equivalent voice channels availably provided by every cell 
• Compare the above two results

Estimation Examples

Assumed Conditions

• Channel environment: downtown area TU 3 km/h
• System design load: 50% 
• Voice service blocking rate: 2%
• Interference factor from the adjacent cell: 0.65 
• Area of the city zone: 40.8 square kilometers

Estimation Flow Chart

Uplink Coverage Estimation

Downlink Capacity Estimation

• Integrate uplink and downlink coverage budget and uplink capacity budget to determine that there are 84 base stations currently and authenticate whether downlink power meets the requirement.

End of Course