wcdma rnp radio network dimensioning principle-20050818-a-1.2

Document code Product name

Target readers Product version V100R001

Edited by Document version WCDMA RNP

WCDMA RNP Radio Network

Dimensioning PrinciplesFor internal use only

Prepared by URNP-SANA Date 2003-12-19

Reviewed by Date

Reviewed by Date

Granted by Date

Huawei Technologies Co., Ltd.

All rights reserved

WCDMA RNP Radio Network Dimensioning Principle For internal use only

Revision record

Date Revision version

Revision Description Author

2003-12-19 1.00 Initial issued Wu Zhong

2004-06-15 1.10 In Chapter 3 “Capacity Dimensioning Principle”, replacing the old algorithm with the new one, that is Kaufman Robert algorithm for CS services, and Nokia algorithm for PS services.

Wu Zhong

2005-08-18 1.20 Change CE number in the Table1 and revise according to review.

Qinyan

23-4-18 All rights reserved. of 50


Table of Contents

1Overview....................................................................................................................................................82Link Budget Principle.................................................................................................................................83Capacity Dimensioning Principle...............................................................................................................93.1Brief Introduction to Cell Capacity Dimensioning................................................................................93.2Dimensioning of Cell Uplink Capacity of Mixed Services..................................................................11

3.2.1 Calculating Single User Load of Each Service in Cell Uplink......................................123.2.2 Calculating Total Number of Users Supported by Cell.................................................133.2.3 Calculating Cell Load of Single PS Service...................................................................133.2.4 Calculating Cell Load for All PS Services......................................................................153.2.5 Calculating CS Service GoS............................................................................................15

3.3Dimensioning of Cell Downlink Capacity of Mixed Services.............................................................163.3.1 Calculating Single User Load of Each Service in Cell Downlink.................................163.3.2 Calculating Total Number of Users Supported by Cell.................................................173.3.3 Calculating the Cell Load of Single PS Service............................................................183.3.4 Calculating the Cell Load of All PS Services.................................................................183.3.5 Calculating GoS of CS Service........................................................................................18

3.4Balance between Cell Coverage and Cell Capacity.............................................................................194NodeB CE Dimensioning Principle..........................................................................................................204.1Brief Introduction to NodeB CE Dimensioning..................................................................................204.2NodeB CE Number Calculation..........................................................................................................21

5Iub Interface Flow Dimensioning Principle..............................................................................................245.1Brief Introduction to Iub Interface.......................................................................................................245.2Basic Ideas for Iub Interface Flow Dimensioning...............................................................................275.3Dimensioning of Iub Interface Transmission Flow.............................................................................27

5.3.1 Dimensioning of Iub User Plane Flow.............................................................................275.3.2 Iub Control Plane Flow Dimensioning.............................................................................375.3.3 Iub Maintenance Bandwidth.............................................................................................425.3.4 Dimensioning of Total Transmission Flow of Iub Interface..........................................425.3.5 Iub E1 Configuration..........................................................................................................43

6Pending Problems.....................................................................................................................................437Appendix..................................................................................................................................................447.1About Soft Blocking Probability.........................................................................................................44



List of Tables

Table 1 Corresponding relation between bearer rate and CE_Amplitude...................................................21Table 2 Rate of FP control frame..........................................................................................................31Table 3 Rate of FP common channel.....................................................................................................32Table 4 Rate of signaling of Iub interface control plane............................................................................41



List of Figures

Figure 1 Basic idea of coverage and capacity iteration dimensioning.........................................................20Figure 2 UTRAN structure diagram........................................................................................................24Figure 3 Iub interface protocol structure..................................................................................................26


WCDMA Radio Network Dimensioning Principle For internal use only

WCDMA RNP Radio Network Dimensioning Principle

Key word: WCDMA radio network dimensioning, capacity dimensioning, CE, Iub,

interface

Abstract: This document is a summary collection of the dimensioning principles such as

capacity dimensioning, NodeB CE number dimensioning and Iub interface

transmission flow dimensioning based on the relevant documents of these

dimensioning principles. It emphasizes on the explanation of the detailed

process and theory of the capacity dimensioning for the mixed services.

List of abbreviations:

Abbreviations Full spelling

AAL ATM Adaptation Layer

AMR Adaptive Multi Rate

ATM Asynchronous Transfer Mode

BLER Block Error Ratio

CCH Control Channel

CE Channel Element

CS Circuit Switched

DCH Dedicated CHannel

DL Downlink

EIRP Equivalent Isotropic Radiated Power

FP Frame Protocol

GoS Grade of Service

HT Hilly Terrain

NodeB

PS Packet Switched

RA Rural Area

RNP Radio Network Planning

SHO Soft HandOver

TCH Traffic Channel

TMA Tower Mounted Amplifier

TU Typical Urban

UE User Equipment

UL Uplink

UMTS Universal Mobile



Abbreviations Full spelling

Telecommunications

System

WCDMA Wideband Code Division Multiple

Access



1 Overview

WCDMA radio network dimensioning involves cell uplink/downlink link budget, cell

uplink/downlink capacity dimensioning, NodeB CE number dimensioning and NodeB Iub

interface transmission flow dimensioning, and so on. These dimensioning principles are

introduced in dedicated documents separately, but provided no convenience for viewing

and learning the WCDMA radio network dimensioning principles as a whole. For this, the

document summaries these principles, providing clear physical explanations on various

parts of the radio network dimensioning principles, and providing mathematical deduction

process as much as possible.

This document comprises the following chapters:

Chapter 1: Brief introduction to the objective and main contents of this document.

Chapter 2: Introduction to the link budget principle. (To keep the integrity of the radio

network dimensioning principles, this part is presented as a chapter providing the

reference documents only, without the specific link budget principle).

Chapter 3: The capacity dimensioning principles are given, including the uplink

capacity and downlink capacity dimensioning principles.

Chapter 4: The dimensioning principle and dimensioning process of the number of

NodeB CEs are explained.

Chapter 5: The dimensioning principle and dimensioning process of NodeB Iub

interface transmission flow are described in detail.

Chapter 6: The pending problems in the radio network dimensioning are proposed.

Chapter 7: Appendixes.

2 Link Budget Principle

With link budget, we can work out the cell coverage radius in different scenarios and

different services covered. For the link budget principle, refer to WCDMA RNP

Technology Research on Special Topics – High-Level Design Specifications for Link

budget Tool [1]. It is not further described here.



3 Capacity Dimensioning Principle

3.1 Brief Introduction to Cell Capacity Dimensioning

The WCDMA system can provide the users with diversified services, such as voice

service, CS data service, and PS services at various rates. For these mixed services, the

analysis of the cell capacity is very complicated, and there is no good solution method

yet.

Before the capacity dimensioning for mixed services, you need to determine the

solutions for the following problems:

(1) GoS for CS services and PS services

GoS of CS services: It is the requirement on the blocking probability of the CS

services. For example, the GoS of the AMR12.2k voice

service can be represented by a blocking probability of

2%; and that of the Videophone can be represented by a

blocking probability of 5%.

GoS of PS services: It is the requirement on the probability for the delay which

dues to queuing of the PS services. For example, for a

90% probability, the queuing delay should be less than 2s.

(2) CS Service: Mixed sevice capacity dimensioning method

The Kaufman Robert algorithm is used to meet different GoS requirements of

various CS services. In the uplink capacity dimensioning, the uplink load of CS

service is taken as shared resource at the cell level; while in the donwlink

capacity dimensioning, the downlink transmit power of CS service is taken as

the shared resource at the cell level.

(3) PS service: Mixed service capacity dimensioning method

Before the RRM simulation result comes out1, the PS service dimensioning is

performed with ErlangC, which can embody the GoS requirement of the PS

services. Dimensioning the PS services respectively. Then, dimensoning uplink

1 The RRM simulation team will provide the simulation result with the GoS requirement of PS

services affecting the PS service throughput.2004-06-22 All rights reserved. of 50


capacity , and sum up the uplink load generated by each PS service as the cell

uplink load requirement of all the PS services; for donwlink capacity

dimensioning, sum up the downlink transmit powers of each PS service as the

downlink transmit power of all donwlink PS services.

(4) Consideration on soft handover proportion

Uplink capacity dimensioning: Wihtout considering the influence of soft

handover on the uplink traffic

The uplink MDC gain is calculated based on

0.3dB.

Downlink capacity dimensioning: Considering the influence of soft handover

on the downlink transmit power

The downlink MDC gain is calculated based

on 1.0dB.

Note:

(i) RNC: Generally speaking, we perform soft handover processing for all the services with the

bearer rate less than 384k. In the network dimensioning, we may give a high-level item for setting

whether to perform soft handover processing for the services with the bearer rate above 64k.

(ii) Algorithm group: There is no simulation on the corresponding relation between the services with

different bearer rates and the MDC gains. After discussion with the simuation engineers, the MDC gain

varies a little with the services at different bearer rates. In the network dimensioning, we can consider

the MDC gains are identical for all sevices.

(5) Activity factors of various services

AMR voice service: the activity factor is 0.67.

CS data service: the activity factor is 1.0.

PS data service: the activity factor is 0.9 as recommended.

Note:

Suppose the DCCC switch is turned on, the activity factor of PS services should be close to 1, and

it is recommended to be 0.9.

The following are the cell uplink dimensioning process and cell downlink capacity

dimensioning process:



Note:

The cell capacity discussed here is specially for dedicated channel, instead of common channel.

Generally, some low-rate services (for example, lower than 32kbps) can be borne by common channels.

The capacity of common channel is under research.

3.2 Dimensioning of Cell Uplink Capacity of Mixed Services

Before the cell uplink capacity dimensioning, here brief the calculation of the cell

uplink load first.

The documentation of WCDMA for UMTS [3] provides the uplink load calculation, as

shown below:

(3-1)

The Radio Network Planning and Optimization for UMTS [4] provides the result, as

shown below:

(3-2)

Note:

(i) In the above two formulae, refers to the neighboring cell interference factor, is the chip

rate, is the bit rate of service , spcifies the activity factor of the sevice , and indicates

users are connected simultaneously in the same cell.

(ii) In the formula (3-2), specifies the sectorization gain, and refers to the number of sectors

of the BS.

The main difference between the formula (3-1) and the formula (3-2): a) in

the formula (3-1) corresponds to the activity factor , while that in the formula (3-2)



corresponds to full rate, so they are consistent in principle; b) In the formula (3-2),

sectorization gain is considered.

In the currernt calculation, we use the formula (3-1). But the existing is

obtained by means of simulation with full rate (that means the activity factor is 1), we

should use the formula (3-2).

Hence, for the cell uplink capacity calculation presents below, we use the formula (3-

2) for description and explanation.

3.2.1 Calculating Single User Load of Each Service in Cell Uplink

The single user load should be calculated for the users with soft handover and the

users without soft handover respectively. As the service with soft handover has

MDC gain, the corresponding single user load will be smaller. With the formula (3-

2), we can work it out as follows:

(1) Service , without soft handover: uplink load of a single user

(1)

(2) Service , with soft handover: uplink load of a single user

(2)

(3) Service , all users: uplink load of a single user

(3)

Note:

(1) : 3.84MHz.

(2) : Bearer rate of service .

(3) : Activity factor of service .



(4) : Demodulation performance of the receiver of NodeB of service .

(5) : The MDC gain of uplink of service .

(6) SHO: Ratio of users performing uplink soft handover.

3.2.2 Calculating Total Number of Users Supported by Cell

Calculate the number of covered users by means of link budget as the total number

of users the cell uplink needs to support.

Note: The above is only for the case of single carrier. For the case of multi-carriers,

it is calculated as follows:

.

Note:

(1) Calculate the cell coverage radius based on link budget result, and then work out the cell

coverage area.

(2) Calculate the total number of users supported by the cell based on the density of traffic and cell

coverage area.

(3) In terms of capacity, the number of users to be supported is greater than or equal to the number

of covered users, so the number of covered users calculated by means of link budget can be an input

for capacity dimensioning. It is similar for the downlink.

(4) If the total number of covered users can’t meet the GoS requirement of CS or PS service, the

capacity will be limited; otherwise, the coverage is limited.

3.2.3 Calculating Cell Load of Single PS Service

(1) Calculate the total throughput (Kbps) of PS services:

(4)

(2) Calculate the traffic in the case of no neighbouring interference:



(5)

(3) Calculate the maximum channel number corresponding to the traffic with the

premise of meeting the GoS requirement:

For PS services, the probability that the delay is less than is

.

According to the ErlangC calculation formula, the relation between maximum

channel number and GoS is shown blow:

(6)

Note:

(1) m refers to the maximum channel number.

(2) specifies the average call duration.

(3) is the average length of session of PS services. It is an input parameter. From the view of

service model, the average length vary with different PS services. For www, the average length of uplink

session is 12000Bytes, and that of downlink is 60000Bytes.

(4) .

(4) Calculate the cell load of this PS service:



(7)

3.2.4 Calculating Cell Load for All PS Services

Sum up the cell load of each PS service to get the uplink cell load of all the PS

services.

(8)

3.2.5 Calculating CS Service GoS

(1) Calculate the total cell load allowed for CS services:

(9)

(2) Calculate the traffic of each CS service in the case of no neighboring cell

interference:

(10)

(3) Calculate the blocking probability of each CS service:

(11)

Note:

(1) : Blocking probability of service k.

(2) , and this relation is setup: .



Where, K refers to the total CS bearer service in the cell, indicates the cell traffic corresponding to

the CS service k, indicates the single user load corresponding to the CS service k, and refers to

the number of users simultaneously connected of the CS service k.

(3) refers to the maximum load allowed by the CS service of the cell uplink, .

(4) Please note that both cell load and single user load are less than 100%, we can not calculate

the blocking probability of each service with the formula (11). To use the formula (11) properly, it is

necessary to adjust the cell uplink load of CS service and the single user load of CS service based on a

specific ratio. It is recommended to enlarge the single user load and cell uplink load by 10000 times.

Suppose the cell uplink load of CS service is 30%, and the single user load of the voice service is

0.82%. In the actual calculation, we can set the cell load of the CS service to 3000, and the single user

load of the voice service to 82. Of course, in the actual calculation process, we can find a suitable

multiple for enlarging based on the precision of the calculation result and the calculation rate.

3.3 Dimensioning of Cell Downlink Capacity of Mixed Services

3.3.1 Calculating Single User Load of Each Service in Cell Downlink

(1) Service , wihtout soft handover: average transmit power of a single user

(12)

(2)Service , with soft handover: average transmit power of a single user

(13)

(3)Service , all users: average transmit power of a single user

(14)



Note:

(1) : 3.84MHz

(2) : Bearer rate of service , : Activity factor of service

(3) SHO: Ratio of users performing downlink soft handover

(4) : Performance of the transmit end of the NodeB of service

(5) : Downlink MDC gain of service

(6) : Total transmit power of the downlink service channel

(7) : Average non-orthogonality factor; : Neighboring cell interference factor

(8) : the floor noise of the receiving end of the UE, including thermal noise, Noise Figure and

background noise

(9) : Average coupling loss of cell downlink

Note:

.

3.3.2 Calculating Total Number of Users Supported by Cell

Calculate the number of covered users based on the link budget result, and take it as the

number of users that the cell downlink needs to support.

Note: The above is only for the case of single carrier. For the case of multi-carriers, it

is calcualted as follows:

.

Note:

The total number of users supported by the cell downlink is calculated in the similar method of

uplink capcity dimensioning.



3.3.3 Calculating the Cell Load of Single PS Service

(1) Calculate the traffic of a PS service:

(15)

(2) Calculate the maximum channel number corresponding to the traffic with the

premise of meeting the GoS requirement.

The calculation method is the same as that for uplink.

Based on the ErlangC calculation formula, the maximum channel number

with the GoS requirement of the PS service can be worked out:

(3) Calculate the downlink transmit power of this PS service:

(16)

3.3.4 Calculating the Cell Load of All PS Services

Sum up the downlink transmit power of each PS service to get the downlink transmit power

of all the PS services in the cell:

(17)

3.3.5 Calculating GoS of CS Service

(1) Calculate the traffic of each CS service in the case of soft handover:

(18)

(2) Calculte the transmit power of a signle user of each CS service of the cell

downlink:

It is worked out with the formula (14).

(3) Calculate the blocking probability of each CS service:



(19)

Please note that the downlink resource here refers to the downlink transmit power of CS

service. As the downlink transmit power of PS service has been worked out with the formula (18),

so we can get the maximum CS service transmit power by subtracting the PS service transmit

power from the total transmit power. Suppose the target load of the cell downlink is 75%, with

25% for common channels and 50% for traffic channel. If the maximum transmit power of the cell

downlink is 20W, the total transmit power of the traffic channels will be 10W. Suppose the

transmit power of PS service is 5W, the maximum transmit power of CS service will be 5W too.

Note:

(1) : Blocking probability of service k

(2) , and a relation is set up:: .

Where, K refers to the total number of CS service types in the cell. But being different from the above,

specifies the cell traffic corresponding to CS service k, specifies the average transmit power of a

single user corresponding to CS service k, and specifies the number of users connected with the CS

service simultaneously.

(3) specifies the maximum transmit power of CS service in the cell, refers to a certain transmit

power, and ;

(4) Similar to uplink dimensioning, it is necessary to present the transmit power of CS service of cell

downlink and the transmit power of a single user in integers. It is recommended to use mW as the

power unit. In the actual iteration dimensioning, you can select a suitable unit for optimal dimensioning

precision and dimensioning speed, for example, 5mW.



3.4 Balance between Cell Coverage and Cell Capacity

The cell coverage radius corresponding to the cell load can be worked out by means

of link budget, together with the density of traffic, the number of covered users can be

calculated. Then based on the number of users supported by the uplink cell and that

supported by the downlink cell worked out by means of uplink/dowlink capacity

dimensioning, compare the number of the covered users with the cell capacity. If the

coverage and capacity are not balanced, you can balance them by adjusting the cell load

(uplink load or downlink load), so as to complete the iteration dimensioning to get the cell

radius after coverage and capacity balancing. For a certain coverage area, the minimum

number of NodeBs required for coverage and the maximum number of users supported

by each sector can be worked out.[7].

The following figure shows the basic idea of coverage and capacity iteration

dimensioning.

Figure 1 Basic idea of coverage and capacity iteration dimensioning

4 NodeB CE Dimensioning Principle

4.1 Brief Introduction to NodeB CE Dimensioning

CE, channel element, corresponds to basic base band processing unit one by one.

For the existing NodeB version, the CE resource of NodeB is shared within the site.



Huawei recommends calculating the number of CEs based on Site.

In the calculation of the number of CEs, use the principle similar to that for NodeB

capacity dimensioning, namely, Campbell theorem, and then combine different bearers

into a virtual bearer to get the Erlangs of this virtual bearer, including uplink Erlang and

downlink Erlang. With this method, the number of NodeB CEs worked out will be neither

optimistic nor pessimistic. The documentations [2, 8] provide the comparison result.

With the ErlangB calculation formula based on a certain blocking probability, you can

work out the trunks required for the corresponding virtual bearer (for uplink and downlink

respectively). Based on the trunks required for virtual bearer together with the

CE_Amplitude under this virtual bearer, you can work out the number of CEs of uplink

and downlink of the NodeB site.

Of course, you can further calculate the number of uplink boards and downlink

boards to be configured in NodeB.

4.2 NodeB CE Number Calculation

1. Corresponding relation between bearer rate and CE_Amplitude

Different bearer rates may consume different numbers of CEs. The corresponding

relations between bearer rates and the equivalent CE numbers are shown in the

following table.

Table 1 Corresponding relation between bearer rate and CE_Amplitude

UL CE_Amplitude DL CE_Amplitude

AMR12.2k 1.00 AMR12.2k 1.00

CS64k 3.00 CS64k 2.00

PS64 3.00 PS64 2.00

PS144 5.00 PS144 4.00

PS384 10.00 PS384 8.00

Note:

The bearer rates and the corresponding CE_Amplitude in the table above, are provided by NodeB.

2. Calculation of NodeB CE number



(a) Calculate the traffic at each bearer rate within NodeB: (The suffix

represents different bearer rates)

For voice service and CS data, as the traffic of a single user in busy hours is

known, you can calculate the corresponding and

based on the number of users supported by NodeB,. For example,

= Traffic of a single user in busy hours × number of users supported by NodeB.

The traffic of the CS data service can be calculated in the same method.

For PS services, as the throughput of a single user in busy hours is known,

you can calculate the traffic of a single user of the corresponding PS service in

busy hours. Together with the number of users supported by NodeB, you can

calculate of the PS service with the method similar to that for

of CS service.

The following is the calculation fomula of the traffic for a single user of the PS

service in busy hours.

.

(b) Calculate the CE_Amplitude of the virtual service:

With the campbell theory, you can convert the mixed service (at different

bearer rates) to a certain virtual service, so as to calculate the CE_Amplitude of

this virtual service, as shown below:

.

(c) Calculate virtual traffic:



Obviously, the virtual traffic can be calculated as follows:

( _ )_ _

_ _

i ii

CE Amplitude ErlangVirtual CE Traffic

Virtual CE Amplitude

.

(d) Calculate the virtual trunks required:

In the view of soft handover ratio and GoS, you can use the ErlangB formula to

calculate the virtual trunks corresponding to the virtual traffic, as shown

below:

.

Where, represents the ratio of soft handover.

(e) Calculate the number of CEs required for NodeB:

The virtual trunks and the corresponding CE_Amplitude are worked out with

the above formula. Then you can calculate the number of CEs to be configured

for the NodeB. However, for virtual service, adding one trunk requires adding

CEs, as the following formula:

.

(f) Calculate the number of uplink boards and downlink boards to be configured:

,

.

Note:

(i) Currently, the uplink board can provide 128 CEs, and the downlink board can provide 384 CEs at

the maximum.



(ii) The NodeB CE number dimensioning is to calculate the number of uplink CEs and downlink CEs

respectively, or in one process. What’s difference is the Erlang corresponding to different bearer rates in

NodeB of the uplink and downlink may be different.

5 Iub Interface Flow Dimensioning Principle

5.1 Brief Introduction to Iub Interface

The UMTS system is composed of three parts: CN, UTRAN and UE. The interface

between CN and UTRAN is defined as Iu interface, and that between UTRAN and UE is

defined as Uu interface. UTRAN can comprise multiple radio network subsystems (RNS).

Each RNS can contain one RNC and one or more NodeBs.

The interface between RNC and NodeB is Iub interface. The following is the

structure diagram of UTRAN:

Figure 2 UTRAN structure diagram

In the 3GPP protocol, all the interfaces in UTRAN and the interface between UTRAN



and CN apply the Asynchronous Transfer Mode (ATM) as the transmission mechanism.

The Iub interface is open. The basic functions implemented by the Iub interface are

as follows:

(1) Iub transmission resource management

(2) NodeB operation and maintenance, including: Iub link management, cell

configuration management, radio network performance measurement,

common transmission channel management, radio resource management,

radio network configuration queue, and so on.

(3) System information management

(4) Common channel traffic management, including access control, power

management, data transmission, and so on.

(5) Dedicated channel traffic management, including radio link management, radio

link monitoring, channel allocation/cancellation, power management,

measurement report, dedicated transmission channel management, data

transmission, and so on.

(6) Common channel traffic management, including channel allocation/cancellation,

power management, transmission channel management, data transmission,

and so on.

(7) Timing and synchronization management, including: transmission channel

synchronization (frame synchronization), NodeB-RNC node synchronization,

NodeB-NodeB node synchronization.

The protocol structure of Iub interface is as follows[9]:



Figure 3 Iub interface protocol structure

From the view of horizontal plane of the above figure, the protocol structure

comprises radio network layer and transmission network layer; from the view of vertical

plane, the protocol structure comprises control plane and user plane.

An Iub interface is connected with one RNC and one NodeB. The transmission

information in the Iub interface can be divided into three types:

(1) Radio application relevant signaling: The Iub interface allows the negotiation

between RNC and NodeB for the relevant radio resource. The information for

broadcast channel control and the information transmitted on the broadcast

channel are this type of signaling. In addition, the operation maintenance

signaling between NodeB and RNC belong to this type of signaling.

(2) Iub dedicated channel data stream

(3) Iub common channel data stream

The dimensioning of the transmission flow of the Iub interface involves not only the

service data transmission flow of the expected users on the Iub interface, but also the



factors like signaling flow. Based on the related documentations[10] and Huawei’s relevant

document[11], the transmission bandwidth required for the Iub interface and the relevant

transmission configurations as well can be calculated.

5.2 Basic Ideas for Iub Interface Flow Dimensioning

The main purpose of the Iub interface transmission flow is to provide reference for

interface configuration in the engineering procedure, as well as the interface

configuration in other occasions.

The following factors need to be considered for the dimensioning of data

transmission flow of the Iub Interface:

(1) FP data frame utilization

(2) AAL2 utilization ratio

(3) NBAP flow

(4) AAL5 utilization ratio

(5) ATM cell utilization ratio

(6) E1 utilization ratio

(7) ALCAP flow

(8) FP payload flow

(9) FP control frame flow

(10) Operation maintenance signaling flow

We can view from the protocol structure of Iub interface from Figure 3 that the

transmission flow of the Iub interface is the sum of three parts of flows, that is, Iub user

plane flow + Iub control plane flow + Iub maintenance bandwidth. Therefore, the following

are the dimensioning procedures for Iub user plane flow and Iub control plane flow

respectively.

5.3 Dimensioning of Iub Interface Transmission Flow

5.3.1 Dimensioning of Iub User Plane Flow

1. Flow features with considering FP/AAL2 encapsulation overhead

For the frame format, refer to TS25.427. As the overhead of the uplink FP frame is



greater than that of the downlink FP, the flow should be calculated based on the uplink

FP overhead.

The data encapsulated by FP is then encapsulated by AAL2. During AAL2

encapsulation, 3 bytes of overhead (CID/LI/UUI/HEC) is added to the header of each

micro cell. The payload of each micro cell is 44 bytes, and the excessive ones will be

segmented for encapsulation.

The calculation formula for the data rate after FP/AAL2 encapsulation is as follows:

(Header CRC/FT+CFN+TFI+TB+QE+CRCI+spare+CRC+AAL2 HEAD)×8/TTI .

Note:

According to the protocol, the spare of data frame is 0 to 2 bytes, the spare of control frame is 0 to

32 types. The RNC supports filling in, but not during transmitting (that means it is not for downlink).

In the following flow calculation, it is specified that the uplink data frame uses a 2-byte spare, and

the control frame uses a 0-byte spare, for calculating the maximum flow in theory, and the one in the

actual application can be analogized according to NodeB.

The following are the data rates of the AMR full rate service after FP/AAL2

encapsulation (The ARM takes the coding unit of 20ms, that is, 50 frames/s, and full rate

means the channel activity factor is 1)

12.2kbps: (1+1+3+11+13+8+1+1+2+2+3)×8/0.02=18.4kbps

10.2kbps: (1+1+3+9+13+5+1+1+2+2+3)×8/0.02=16.4kbps

7.95kbps: (1+1+3+10+11+1+1+2+2+3)×8/0.02=14kbps

7.4kbps: (1+1+2+8+11+1+1+2+2+3)×8/0.02 =12.8kbps

6.7kbps: (1+1+2+8+10+1+1+2+2+3)×8/0.02=12.4kbps

5.9kbps: (1+1+2+7+8+1+1+2+2+3)×8/0.02=11.2kbps

5.15kbps: (1+1+2+7+7+1+1+2+2+3)×8/0.02=10.8kbps

4.75kbps: (1+1+2+6+7+1+1+2+2+3)×8/0.02=10.4kbps

The data rate of CS data service after FP/AAL2 encapsulation (full rate):

32kbps: (1+1+1+1×80+1+1+2+2+3×3)×8/0.02=39.2kbps (TTI=20ms)

64kbps: (1+1+1+2×80+1+1+2+2+3×4)×8/0.02=72.4kbps (TTI=20ms)

14.4kbps: (1+1+1+1×72+1+1+2+2+3×2)×8/0.04=17.4kbps (TTI= 40ms)

28.8kbps: (1+1+1+2×72+1+1+2+2+3×4)×8/0.04=33kbps (TTI= 40ms)



57.6kbps: (1+1+1+4×72+1+1+2+2+3×7)×8/0.04=63.6kbps (TTI= 40ms)

The data rate of PS data service after FP/AAL2 encapsulation (full rate):

8kbps: 1+1+1+1×42+1+1+2+2+3×2)×8/0.04=11.4kbps (TTI=40ms)

16kbps: (1+1+1+1×42+1+1+2+2+3×2)×8/0.02=22.8kbps (TTI=20ms)

32kbps: (1+1+1+2×42+1+1+2+2+3×3)×8/0.02=40.8kbps (TTI=20ms)

64kbps: (1+1+1+4×42+1+1+2+2+3×5)×8/0.02=76.8kbps (TTI=20ms)

128kbps: (1+1+1+8×42+1+1+2+2+3×8)×8/0.02=147.6kbps (TTI=20ms)

144kbps: (1+1+1+9×42+1+1+2+2+3×9)×8/0.02=165.6kbps (TTI=20ms)

256kbps: (1+1+1+8×42+1+1+2+2+3×8)×8/0.01=295.2kbps (TTI=10ms)

384kbps: (1+1+1+12×42+1+1+2+2+3×12)×8/0.01=439.2kbps (TTI=10ms)

3.4kbps channel associated signaling overhead (full rate):

(1+1+1+1×19+1+1+2+2+3)×8/0.04=6.2kbps (TTI=40ms)

2. FP control frame overhead

(a) TIMING ADJUSTMENT: 5byte, Spare Extension: 0--32byte

When a time window appears, NodeB sends the time adjusting frame,

supposed once per 100TTI (TTI=20ms) for each DCH bearer, the flow will be

16 bps.

The time adjusting frame seldom occurs in the actual environment.

(b) DL SYNCHRONIZATION: 3byte. Spare Extension: 0--32byte

Transport channel synchronization is used for the synchronization of the initial

setup stage, and for the troubleshooting for the bottom layer AAL2 as well.

The flow of synchronization for the initial stage can be omitted (as service data

transmission has not started yet), and that of the synchronization for

troubleshooting is related to the detection cycle.

For example, if the detection is performed once per 5s, the flow will be 9.6

bps.

(c) UL SYNCHRONIZATION: 5byte, Spare Extension: 0--32byte

The transport channel synchronization is used for the synchronization of the

initial setup stage, and for the troubleshooting for the bottom layer AAL2 as

well. The flow of synchronization for the initial stage can be omitted (as service



data transmission has not started yet), and that of the synchronization for

troubleshooting is related to the detection cycle.

For example, if the detection is performed once per 5s, the flow will be 64 bps.

(d) OUTER LOOP POWER CONTROL: 3byte, Spare Extension: 0--32byte

The SIR used for updating outer loop power control. Suppose it is once per

400ms, the load flow will be 120 bps.

(e) DL NODE SYNCHRONIZATION: 5byte, Spare Extension: 0--32byte

Node synchronization is used for Iub delay estimation. It does not attach to call

service, thus can be omitted.

(f) UL NODE SYNCHRONIZATION: 11byte, Spare Extension: 0--32byte

Node synchronization is used for Iub delay estimation. It does not attach to call

service, thus can be omitted.

(g) DSCH TFCI SIGNALLING [FDD]: 5byte, Spare Extension: 0--32byte, once

per10ms

At present, the system does not support DSCH, so the flow of DSCH TFCI

SIGNALLING is not considered for the moment.

(h) RADIO INTERFACE PARAMETER UPDATE [FDD]: 6byte, Spare Extension: 0--

32byte

Radio parameter update will be initiated after the handover is completed and

RLS is added. It can be omitted.

Note:

The typical structure of control frame is: (Frame CRC+FT)+Control Frame Type+Control

Information+Spare Extension. Where Frame CRC+FT is 1byte, and Control Frame Type is 1byte.

In the above calculation, the uplink control frame uses a 32-byte spare, for calcualting the maximum

flow in theory. It can be analogized according to the realization of the NodeB in the actual application.

Spare filling is not performed for the downlink RNC.

The following table lists the data rates corresponding to various FP control frames.

Table 2 Rate of FP control frame

Message name Rate (bps)

TIMING ADJUSTMENT 160

DL SYNCHRONIZATION 9.6



UL SYNCHRONIZATION 64

OUTER LOOP POWER CONTROL 120

DL NODE SYNCHRONIZATION It is used for Iub delay estimation, and it does not attach to call service, thus can be omitted.

UL NODE SYNCHRONIZATION It is used for Iub delay estimation, and it does not attach to call service, thus can be omitted.

DSCH TFCI SIGNALLING[FDD] The system does not support DSCH, so it is not considered for the moment.

RADIO INTERFACE PARAMETERUPDATE[FDD]

Radio parameter update will be initiated after the handover is completed and RLS is added, so it can be omitted.

From the above analysis, the flow of control frame is much lower than that of service

data frame, so it can be omitted.

3. Common channel

Common channel is set up in the cell setup stage with the default channel

configurations for general cases.

The default configurations of various channels are as follows:

(a) RACH

TBSize=168 or 360bit, TTI=10ms, the maximum traffic is calculated based on

360 bits.

Header CRC/TF+CFN+TFI+PropagationDelay+TB+CRCI+spare+CRC+AAL2

header

The flow after FP/AAL2 encapsulation is:

(1+1+1+1+360 / 8+1+2+2+3×2)×8 / 0.01 = 48kbps.

Each cell can be configured with one to two RACH channels.

(b) FACH

(i) FACH signaling

TBSize=168, TBNum=2, TTI=10ms

Header CRC/TF+CFN+TFI+TransmitPowerLevel+TB+spare+CRC+AAL2

header


(1+1+1+1+168×2 / 8+2+3×2)×8 / 0.01 = 43.2kbps.

(ii) FACH data




Header CRC/TF+CFN+TFI+Transmit power level+TB+spare+CRC+AAL2

header


(1+1+1+1+360 / 8+2+3×2)×8 / 0.01 = 45.6kbps.

Each cell can be configured with one to four FACH channels. In case there is

only one FACH channel, the signaling and data are multiplexed, in the

configuration mode for signaling FACH.

(c) PCH


Header CRC/TF+CFN/PI+TFI+PI-bitmap+TB+spare+CRC+AAL2 header

The length of PI-bitmap is related to the configuration of common channel.

Corresponding to the configurations of 18, 36, 72 and 144 segments of the PI,

it is 3, 5, 9 and 18 bytes in length.

The current common channel uses configuration of the PI with 18 segments.

The traffic after FP/AAL2 encapsulation is:

(1+2+1+3+30+2+3)×8 / 0.01 = 33.6kbps.

Each cell supports one PCH channel.

The following table lists the rates of various FP common channels:

Table 3 Rate of FP common channel

Common

channel name

Rate (kbps) Ramark

RACH 48 Each cell can be configured with one to two RACHs channels.In Huawei’s product, each cell is configured with one RACH channels.

FACH Signaling rate: 43.2Data rate: 45.6

Each cell can be configured with one to four FACHs channels.In case of there is only one FACH, the signaling and data will be multiplexed, in the configuration mode of signaling FACH.In Huawei’s product, each cell is configured with two FACHs, one of which for signaling transmission and the other for data transmission.



PCH 33.6 Each cell supports one PCH.

4. AAL2 sub-multiplexing

The AAL2 multiplexing can improve the ATM transmission efficiency, but the

additional overhead caused by sub-multiplexing must be considered. When configuring

the flow of Iub interface, it is recommended to add 10% of AAL2 multiplexing overhead to

it.

In the case of AAL2 multiplexing, each ATM cell has 1 byte of overhead (STF

domain). In addition, the header of each ATM cell has 5 bytes of overhead.

Note:

At present, the TIMER_CU of the AAL2 micro code is set to 500us, that is, a single cell may be in

the 500us additional delay brought by sub-multiplexing, namely the maximum PAD filling rate of AAL2.

The data of a single application are transmitted equably (for example, AMR TTI=20ms), but the

transmission between multiple upper-layer applications are not dispersed equally. That is to say, the

flow peak value may occur in a period of time due to the concurrent transmission of multiple

applications; and may be idle for a period of time. This is the case of uneven peak/off-peak. As the

buffer of the AAL2 micro cell is restricted, if the buffer is full when the transmission failure due to burst

flow, the QoS will be surely lowered, thus affecting the performance of the equipment. Therefore, the

ATM flow must be able to adapt to this application requirement.

Take the 12.2kbps AMR voice for example, the length of each micro cell is 46 bytes. If the

TIMER_CU of only one micro cell expires, the PAD of one byte is added. If the single TIMER_CUs of

two micro cells expire, the PAD of two bytes is added behind the second one. If the TIMER_CUs of

three micro cells expire, the former two cells are transmitted, and the third one will be transmitted in the

next time of expiration. Similarly, one AAL2 PACH can bear 248 CIDs, which is updated once per 20ms.

The maximum PAD added is 248 bytes (it is an extreme), and the minimum PAD added is 13 bytes (it is

transmitted at each TIMER_CU). The corresponding maximum sub-multiplexing overhead is 99.2kpbs,

with 2% of multiplexing overhead increased. Take the 10.2kbps AMR voice for example, the extreme

multiplexing overhead is 7.8%.

By means of analysis on other service types, you can get the application with the lower rate, whose

extreme multiplexing overhead is the larger.



5. Activity rate of 3.4K channel associated signaling channel

The RRC signaling exchanged for each call and the length are shown as follows:

Where, the red ones are for uplink and the blue ones are for downlink.[3].

RB Release 96

RB Release Complete 80

RB Setup 208

RB Setup Complete 83

RRC Connection Release 8

RRC Connection Release Complete 6

RRC Connection Request 91

RRC Connection Setup 159

RRC Connection Setup Complete 45

Initial Direct Transfer 40

Uplink Direct Transfer 60

Downlink direct Transfer 60

UE Capability Enquiry 46 RNC ==> UE

UE Capability Information 80 UE ==> RNC

UE Capability Information confirm 46 RNC ==> UE

Measurement Control 50

Measurement Report 68 (Event triggering

measurement report)

Active Set Update 54 (Soft handover signaling)

Active Set Update Complete 78 (Soft handover signaling)

The algorithm of switch setting can be used for the measurement on Uu interface.

The measurement modules involved include AMRC, DCCC, HO and LCS. Different

report modes are used for different measurement items. Event report, periodical report

and the period of periodical report are configurable at the background. There are six

periodical measurement reports and 6 event reports at the maximum. As LCS is used for

location only, it is not considered.

Each UE uses one type of service only, and use only two HO periodical



measurement items (mutually exclusive) and one AMRC or DCCC measurement item,

use only four HO event measurement items and one AMRC or DCCC event

measurement item. Suppose the period of periodical report is 1s, the event report is

transmitted once per 30s, the soft handover overhead is 30%, and there are 3 branches

(it is necessary to transmit the activity set update message for twice), the call duration is

60s, and the connecting time is 10s, you can get that the time from conversation to data

transmission is 50s.

The calculation formula is: (Total byte number×8bit / 60s)/ 3400bit/s).

Downlink: ((96+208+8+60+46+46+50×8+54×30%×2)×8/60)/3400 =3.5%;

Uplink: ((80+83+6+45+40+60+80+68×50×3+68×5×2+78×30%×2)×8/60)/ 3400 =

44%.

Because most RRC flows use the RCL confirmation mode, the activity rate of

3.4kbps channel associated signaling is 50%.

6. User plane flow of Iub interface

User plane flow=Common channel flow + Voice service flow + Data service flow +

Channel associated signaling flow

User plane flow (downlink)

=(FACH (Signaling) × The number of FACHs (Signaling)+ FACH (data)× The

number of FACHs (data) + PCH× the number of PCHs+ 12.2AMR rate × The

number of voice users × Voice activity factor + PS rate × The number of data

users × Data activity factor + Channel associated signaling flow× The number

of users × Signaling activity factor) × AAL2 sub-multiplexing × ATM

multiplexing

= (43.2×NFACH signaling + 45.6×NFACH data + 33.6×NPCH +18.4×Nvoice×VADV +

Vdata×Ndata×VADD+ 6.2×VADS×(Nvoice+Ndata))×1.1×53 / 47

User plane flow (uplink)

=(RACH × The number of RACH + 12.2AMR rate ×The number of voice users

× Voice activity factor + PS rate ×The number of data users × Data activity

factor +Channel associated signaling flow × The number of users ×



Signaling activity factor) × AAL2 sub-multiplexing × ATM multiplexing

= ( 48×NRACH + 18.4 × Nvoice× VADV + Vdata×Ndata × VADD + 6.2 × VADS ×

(Nvoice+Ndata)) × 1.1 × 53 / 47

Minimum number of AAL2 Paths = .

Note:

(i) The flow unit above is kbps.

(ii) NRACH, NFACH signaling, NFACH data and NPCH are the numbers of various types of common channels

supported by the whole NodeB.

(iii) Nvoice and Ndata are the number of voice users and the number of data users of the whole NodeB.

(iv) Vdata is the rate after FP/AAL2 encapsulation, which is contained when the data service is used.

(v) The common channel needs to bear the UE common procedures and the low-rate PS service,

so it has a high multiplexing efficiency, with the channel activity factor being 1. Generally, for voice

service, data service and channel associated signaling, it is used discontinuously, so it is necessary to

consider the activity factor. The activity factor of voice VADV ranges from 0.5 to 1. As the usage

character of the data service is unknown, it is recommended to set its acticity factor VADD to 1 for

guaranteeing its QoS, and set the activity factor VADS of signaling to 0.5.

(vi) If the common procedures of UE (such as attach, detach and short message) are implemented

with dedicated channel, it is necessary to add the requirement on the flow of these procedures. The

additioal flow = The number of Iub service users (considering the convergence ratio) × The number of

sevices in busy hour/3600 × Common procedure duration × 6.2 × VADS × 1.1 × 53/47.

(vii) If the tranamission equipment has plentiful resources, in terms of engineering, 25 percent of

headroom will be added for supporting burst service.

(viii) For the user plane of Iub interface, CBR and RT-VBR are used for PVC in most cases. In the

configuration, if CBR is used, it is required that its PCR be greater than or equal to the flow calculated

above; if RT-VBR is used, it is required that its SCR be greater than or equal to the above value. In

addition, the PCR is 120% of the SCR.

5.3.2 Iub Control Plane Flow Dimensioning

1. Control Plane composition



The Iub control plane is composed of one NCP link, one to n CCP links and one

ALCAP link. The NCP link is for transmitting the message related to the common

procedures, such as audit, cell setup/deletion/re-configuration, common channel

setup/deletion/re-configuration, common measurement and radio link setup. The

CCP links bears the messages related to dedicated procedures, such as RL

addition/deletion/re-configuration, RL recovery failure and dedicated

measurement. The ALCAP link is for transmitting the AAL2 connection message

at the Iub interface. The NCP/CCP/ALCAP link is over SAAL directly. Four bytes

of protocol head overhead are added for the SAAL (SSCOP). In addition, for the

SSCOP, one to three bytes should be filled in so as to align the PDU 4 bytes.

2. Overhead of AAL5

The control plane adopts AAL5 encapsulation, and the relation between SDU and

PDU of AAL5 is as follows:

If (SDU mod 48) > 40, then PDU = (SDU – SDU mod 48))+96.

Or, PDU = (SDU – (SDU mod 48)) + 48.

3. The signaling exchanged for one call of a single service.

The red ones are for uplink and the blue ones are for downlink. The column in the

middle specifies the actual length, and the last column specifies the length of the

message after AAL5 encapsulation.

RL_SET_REQ 122 => 144 <NCP>

RL_SET_RESPONSE 74 => 96 <NCP>

RL_RESTORE_INDICATION 27 => 48 <CCP>

RL_RECONFIG_PREP 299 => 336 <CCP>

RL_RECONFIG_READY 62 => 96 <CCP>

RL_RECONFIG_COMMIT 21 => 48 <CCP>

DEDI_MEASUREMENT_INIT 53 => 96 <CCP>

DEDI_MEASUREMENT_RESPONSE 19 => 48 <CCP>

DEDI_MEASUREMENT_REPORT 36 => 48 (TCP, AMRC/DCCC/DPB)

DEDI_MEASUREMENT_REPORT 36 => 48 (SIR, OLPC)

DEDI_MEASUREMENT_TERMINATE 16 => 48 <CCP>



RL_DELETE 34 => 48 <CCP>

RL_DELETE _RESPONSE 17 => 48 <CCP>

Four ALCAP signaling:

ERQ 76 => 96 <ALCAP>

ECF 13 => 48 <ALCAP>

RLSD 12 => 48 <ALCAP>

RLC 6 => 48 <ALCAP>

Common measurement:

COMM_MEASUREMENT_INIT45 => 96 (RTWP)<NCP>

COMM_MEASUREMENT_INIT45 => 96 (TCP) <NCP>

COMM_MEASUREMENT_RESPONSE 19 => 48 <NCP>

COMM_MEASUREMENT_REPORT 29 => 48 (RTWP) <NCP>

COMM_MEASUREMENT_REPORT 28 => 48 (TCP) <NCP>

Calculating with the consideration of IMSI attach, IMSI detach, location update, SMS

overhead: four times/user/h, based on the convergence ratio of 40, with the ratio of

processing frequency to call frequency is (40×4/3600): (1/60), that is 2.67. (Refer to the

MOT traffic model).

Generally, these procedures are implemented on common channels, without

considering this part of overhead. Huawei’s product is set with a switch. That is, the

transmission for the engineering can be performed on both dedicated channels and

common channels. Therefore, the following provides the analysis for both cases

respectively.

(i) NCP

The radio link setup message and common measure message are major

messages. The procedures for cell management are initial procedures, which can

be omitted during flow calculation. In common measurement, two 200-ms

periodical measurements are started for each cell. Suppose the whole NodeB

support N users concurrently, and each user makes each call in 60s.

The following dedicated channels are used for the IMSI attach and other

procedures:



Downlink:

144×N/60×53/48×8×3.67

=(78×N)bps

Uplink:

((48+48)×M×1000/200+96×N/60×3.67)×53/48×8

=(4240×M+52×N)bps.

The following common channels are used for the IMSI attach and other

procedures:

Downlink:

144×N/60×53/48×8

=(22×N)bps

Uplink:

(96×M×1000/200+96×N/60)×53/48×8

=(4240×M +15×N)bps

Where, M is the number of cells supported by NodeB, and N=Nvoice+Ndata.

(ii) CCP

When the algorithm switch is turned on, the AMRC starts a periodical

measurement with the period of 4.8s, for every RL; the DCCC also starts a

periodical measurement with the period of 640ms, and starts a periodical

measurement with the period of 700ms for each RL in the case of soft

handover. Suppose the soft handover ratio is 30%, and two measurements are

started for each voice and data user and one is started for the attach type

service, the flow is calculated as follows:


procedures:

Downlink:

((336+48+(96+48)×2+48)+(96+48+48)×2.67)×N/60×53/48×8

=(182×N)bps

Uplink:

((48+96+48×2+48+(48+48+48))×2.67)×Nvoice/60+48×N



voice×(1/4.8+1/0.7×30%)+(48+96+48×2+48+(48+48+48)×2.67)×Ndata/60+48

×Ndata ×(1/0.64+1/0.7×30%))×53/48×8

=(370×Nvoice+968×Ndata)bps


procedures:

Downlink:

(336+48+(96+48)×2+48)×N/60×53/48×8

=(106×N)bps

Uplink:

((48+96+48×2+48)×Nvoice/60+48×N voice×(1/4.8+1/0.7×30%)

+(48+96+48×2+48)×Ndata/60+48×Ndata×(1/0.64+1/0.7×30%))×53/48×8

=(314×Nvoice+891×Ndata)bps

Where, N=Nvoice+Ndata. It is mainly required for measurement.

(iii) ALCAP

Suppose NodeB supports N users simultaneously, and each user makes

each call in 60s.


procedures:

Downlink:

((96+48)×2+(96+48)×2.67)×N/60×53/48×8

=(99×N)bps

Uplink:

((48+48)×2+(48+48)×2.67)×N/60×53/48×8

=(66×N)bps


procedures:

Downlink:

((96+48)×2)×N / 60×53 / 48×8

=(43×N)bps

Uplink:

((48+48)×2)×N / 60×53 / 48×8



=(29×N)bps

The following table lists the rates of various types of signaling of the Iub interface:

Table 4 Rate of signaling of Iub interface control plane

Name Uplink rate (bps) Downlink rate (bps) Remarks

NCP 4240×M+52×N 78×N Dedicated channels used for the IMSI attach and other procedures

4240×M +15×N 22×N Common channels used for the IMSI attach and other procedures

CCP 370×Nvoice+968×Ndata 182×N Dedicated channels used for the IMSI attach and other procedures

314×Nvoice+891×Ndata 106×N Common channels used for the IMSI attach and other procedures

ALCAP 66×N 99×N Dedicated channels used for the IMSI attach and other procedures

29×N 43×N Common channels used for the IMSI attach and other procedures

Note:

(i) N=Nvoice+Ndata,, and M is the number of cells supported by NodeB.

(ii) To consider the SAAL overhead and link utilization, it is necessary to add 10% of flow headroom

based on the flow mentioned above.

(iii) As the product supports the two modes of using dedicated channels and common channels for

IMSI attach and other procedures, the larger value of flow in the dimensioning will be used for the

signaling dimensioning. That is to calculate the signaling flow of the Iub interface in the mode of using

dedicated channels for IMSI attach and other procedures.

(iv) The AAL5 overhead has been considered in the signaling rate mentioned above.

5.3.3 Iub Maintenance Bandwidth

The operation and maintenance bandwidth of NodeB is set according to the



configuration.

The typical value of the operation and maintenance bandwidth of NodeB is 640kbps.

5.3.4 Dimensioning of Total Transmission Flow of Iub Interface

Based on the analysis and calculation of the user plane flow and control plane flow of

the Iub interface, together with the Iub interface maintenance bandwidth, the total

transmission flow of the Iub interface can be worked out as follows, considering the

soft handover headroom:

The total transmission flow of the Iub interface = (Iub user plane flow + Iub control

plane flow) × (1+ Soft handover headroom) + NodeB

operation and maintenance bandwidth.

Note:

(i) Sub-multiplexing headroom and burst redundancy are considered in the Iub user plane and

control plane.

(ii) Soft handover headroom should be added to the user plane flow and control plane flow.

5.3.5 Iub E1 Configuration

The utilization of the E1 link can be calculated in two modes, both of which are

supported by Huawei.

(1) UNI mode, the E1 utilization rate is: 1920kbps /2048kbps=93.75%.

(2) IMA mode, in the case of frame length being 32, the E1 utilization rate is:

1859kbps /2048kbps=90.77%;

in the case of frame length being 64, the E1 utilization rate is:

1889kbps /2048kbps=92.24%;


1904kbps /2048kbps=92.97%;


1911.5kbps /2048kbps=93.33%.

Therefore, based on the Iub transmission flow considering the E1 utilization, the



number of E1s to be configured can be worked out as follows:

The number of E1s to be configured is

.

6 Pending Problems

The above chapters present the WCDMA radio network dimensioning principles. But

our research on the radio network dimensioning is not so deep in many aspects so far,

and some pending problems are to be solved. At present, the purpose of capacity

dimensioning is to calculate the number of users that the cell uplink and downlink can

support under a certain cell load, and then compare the capacity dimensioning result with

the link budget. Is this dimensioning mode the only one for judging whether the coverage

and capacity are balanced? Can the dimensioning and comparison be performed

according to the throughput allowed by the PS service (such dimensioning is reasonable

and in accord with the ErlangC)? For example, based on the number of users covered by

the cell worked out by means of link budget, together with the traffic of a single user in

busy hours of CS service and that of PS service, we can calculate the throughput of the

PS services under a certain cell load with the premise of allowing concurrent CS user

connection. Similarly, by means of capacity dimensioning, we can work out the

throughput of the PS services allowed to access when the coverage requirement is met,

and then compare the PS service throughput calculated in these two cases, so as to

judge whether the coverage and capacity can be balanced.

7 Appendix

7.1 About Soft Blocking Probability

(1) Features of WCDMA data service

For WCDMA data service, the data rate is high, and the number of users

communicating simultaneously that can be borne is small. That is, the number of



channels is small. However, the channels of WCDMA are different from those of GSM,

which are hard channels. If the number of users is greater than the number of channels,

the excessive users will surely encounter blocking. The blocking probability can be

calculated with the Erlang formula. While the channels of WCDMA is soft channels, and

the number of channels varies with the interference. If the blocking probability of hard

channels is still used, with a threshold being set, and the Erlang value of the data service

being calculated with the Erlang formula, it will make big error. For example:

Create a WCDMA single service data model, with the activity factor being 0.1 and

the maximum channel capacity being 3.9, and then calculate the Erlang traffic when the

blocking probability is 0.02. If the hard threshold is adopted, the maximum channel

number is 3, the traffic will be 10Erlang_B(3, 0.02), that is 6; if the maximum channel

number is 4, the traffic will be 10Erlang_B(4, 0.02), that is 11. That is, when the channel

capacity is changed to 4 from 3.9, the traffic changes a lot, which is not practical at all.

This is because the channel capacity is small for high-rate data service. When the

channel capacity is changed to 4 from 3, it is a large change. But the channel capacity is

large for voice service. For example, when the capacity is changed to 51 from 50, it is a

small change. So the hard channel blocking probability is not suitable for the calculation

of the WCDMA data flow.

(2) New traffic calculation method

We still use the above example.

When the number of users communicating simultaneously is 3, and the channel

capacity is 3.9, so 0.9 more users can access the system. If the method for hard channel

is used, no more new users can access. However, with the features of CDMA, we can

adopt the probability statistics method for analysis. If the system load is light, it can

accept more new users; if it is heavy, it will accept less new users. Therefore, when the

channel has headroom of 0.9, the new user accepting rate will be taken as 0.9, and the

rejection rate will be 0.1. By far, we can create a new queuing model to get the blocking

probability. In this case, the blocking probability can not be represented by the Erlang

formula, but should be calculated by means of mathematical derivation. The following



shows the derivation process:

Suppose the system is a Lost Call Cleared (LCC) system, which does not provide

queuing function for the call requests. When a user requests for service, the user can

access the system within the preset minimum call setup time if a channel is available. If

all the channels are occupied, the call will be blocked, and the user can not access the

system. The blocked user returns to an infinite user group at once, and can attempt to

access the system any time thereafter.

Suppose Pi specifies the probability of i users in the system, specifies the arrival

rate of the users, u refers to the user drop-out rate. Then suppose the system capacity is

c, which is not an integer. Round up c to get the maximum channel numberN c .

According to the detailed derivation process mentioned in Appendix A.1.1 of Reference

[12], we can get:

PN N/N! P0 (7-1)

When the number of users in the system isN, which is the maximum number of

users supported by the system, the blocking probability can be calculated with the Erlang

formula,

PB PrPrblocked /uN/N!

k0

N

( /uk/k!). As the maximum capacity of the system c

doesn’t reached when the number of users in the system isN, set a c N (where a is

a decimal fraction, and0 a 1), a more users can access the system. In terms of

ratio, the probability of new user permission is a. Therefore, when the number of users



reachesN, new users with the probability of a can access the system and new users with

the probability 1 a will be rejected. This is shown as the following state transition

formula:

PN1 PN a N1u (7-2)

The above formula indicates the new user permission probability is a when the

number of users in the system is N, so that the number of users in the system is N 1.

Based on the probability sum of 1, we can get that P0 ,P1PN1 .

k0

N1

Pk 1. Then

substitute the formulae (7-1) and (7-2) into it as follows:

P0 1

k0

N

u k/k!a

N1/N1!

,

PN N/N!

k0

N

u k/k!a

N1/N1! and

PN1 a

N1/N1!

k0

N

u k/k!a

N1/N1!

.

When the system has N users inside, the new user rejection probability is 1 a.

When the system has N 1 users inside, which is the maximum capacity of the system,

no more users can access the system, so the system blocking probability can be worked

out as follows:



PB PN1 1 a PN a. u N1/N1!1 a

u N/N!

k0

N

/uk/k!a u N1/N1!

　　　

.

The activity factor is not considered in the formula above. Suppose the activity factor

is v, the blocking probability of the system is.

PB a. vu N1/N1!1 a v

u N/N!

m0

N

v/um/m!a vu N1/N1!

　　　

(7-3)

If the traffic and the activity v are specified, PB can be worked out based on the

formula above.

If PB is specified, and the outgoing traffic is vu , you can not get the result with the

above formula, but with the following conversion formula:

PB

（1 aPBa1 au v N1

v

N1/N1!

k0

N1

vu k/k!

　　　

(7-4)

The right of the formula (7-4) is the Erlang formula for calculation convenient. The

following is an example of calculating the traffic with the formula (7-4).

(3) Application example

Suppose the capacity of a system is c3.1. Round it up to get N3, and then

a c N0.1. The Activity factor v0.1, and specify that PB＝0.02, and then

calculate the traffic, as shown below:

First calculate the approximate range v/u:

v/uErlang_B0.02, 3 0.6022



The left of the formula (7-4) is 0.02

0.9 0.020.10.9 4 1/0.6022 0.0033.

Then the actual traffic is:

/u 1/v Erlang_B0.0033, 46.192.

This is close to the actual situation, because when the capacity is 3, the traffic will be

6.022; when the capacity is 3.1, the traffic will be 6.192. The increase is small, which is in

accord with the actual situation.

Then suppose the channel capacity is 3.9, the left of the formula (7-4) is

0.020.10.020.90.141/0.6022 0.013, then the actual traffic is

/u 1/v Erlang_B0.013, 4 9.5.

When the channel capacity is 4, the traffic is 11. So the traffic when the channel

capacity is 3.9 is very close to the traffic when the channel capacity is 4. It is in accord

with the actual situation.

Suppose the channel capacity is 3.5, the left of the formula is

0.020.5 0.020.50.5 4 1/0.6022 0.005, then the actual traffic is

/u1/v Erlang_B0.005, 4 7. The traffic is between 6 and 11, which is in

accord with the actual situation.

Based on these, we can get the following conclusion:

Using the new traffic calculation method solves the problem of traffic mutation

caused by round-up. With the original method, for example, when the channel capacity is

3.99, the traffic can be calculated with the number of channels of 3. When the channel

capacity is 4, the traffic is calculated with the number of channels of 4. The channel

capacity is changed to 4 from 3.99, the traffic mutation occurs. With the new traffic

calculation method, the traffic varies continuously with the channel capacity, without

mutation.



The new traffic calculation method adopts the probability statistics method. The

lighter the load, the higher the user access probability, and vice versa. For example, if the

channel capacity is 3.9, and three channels are in use, a big headroom is available, so

the access probability of the system is big, which is 0.9; if the channel capacity is 3.1,

and three channels are in use, the headroom is small, so the access probability of the

system is small, which is 0.1. This is in accord with the actual situation.

To calculate the blocking probability based on traffic, you can use the formula (7-3).

To calculate the traffic based on blocking probability, you can use the formula (7-4). In

the formula (7-4), you can estimate the traffic first to get the value on the left of the

formula, and then calculate the actual traffic according to the Erlang formula.



List of references:

[1] Wang Mingmin, WCDMA RNP Technology Research on Special Topics -- High-Level

Design Specifications for Link budget Tool, internal document, 2002-08

[2] AirCom International Limited 2001, UMTS Applied Planning for Experienced

Engineers

[3] Harri Holma and Antti Toskala,WCDMA for UMTS, JOHN WILEY & Sons, LTD., 2000

[4] Jaana Laiho, Achim Wacker, Tomas Novosad, Radio Network Planning and

Optimization for UMTS, JOHN WILEY & Sons, LTD., 2002

[5] Wang Mingmin, WCDMA RNP Technology Research on Special Topics – Calculation

of Downlink Interference Headroom in Link Budget, internal document, 2002-05.

[6] Miao Jiashu, WCDMA RNP Radio Network Dimensioning Guide, internal document,

2002-09

[7] Wu Zhong, WCDMA RNP Low-level Design Specifications for Radio Network

Dimensioning, internal document, 2003-11

[8] Wu Zhong, WCDMA RNP CE Dimensioning Guide, internal document, 2003-07

[9] 3GPP TS 25.427 V3.10.0 (2002-12)

[10] Clint Smith, Daniel Collins, 3G WIRELESS NETWORKS, McGraw-Hill

[11] Win Shengyi, WCDMA RNC Transport Network Layer Traffic Configuration Scheme,

2003-12

[12]Theodore S. Rappaport Radio Communication Principles and Applications, Electronic

Industry Publishing Company, 1999.


wcdma rnp radio network dimensioning principle-20050818-a-1.2

Documents