Nokia_BTS_EDGE_Dimensioning.pdf

8/10/2019 Nokia_BTS_EDGE_Dimensioning.pdf

http://slidepdf.com/reader/full/nokiabtsedgedimensioningpdf 1/37

GSM/EDGE BSS, Rel. RG40(GSM 15), OperatingDocumentation, Issue 01

BTS EDGE Dimensioning

DN7032593

Issue 6-1Approval Date 2011-03-15

Nokia Networks



The information in this document applies solely to the hardware/software product (“Product”) specified

herein, and only as specified herein.

This document is intended for use by Nokia Solutions and Networks' customers (“You”) only, and it may not

be used except for the purposes defined in the agreement between You and Nokia Solutions and Networks

(“Agreement”) under which this document is distributed. No part of this document may be used, copied,

reproduced, modified or transmitted in any form or means without the prior written permission of Nokia

Solutions and Networks. If you have not entered into an Agreement applicable to the Product, or if that

Agreement has expired or has been terminated, You may not use this document in any manner and You

are obliged to return it to Nokia Solutions and Networks and destroy or delete any copies thereof.

The document has been prepared to be used by professional and properly trained personnel, and You

assume full responsibility when using it. Nokia Solutions and Networks welcome Your comments as part of

the process of continuous development and improvement of the documentation.

This document and its contents are provided as a convenience to You. Any information or statements

concerning the suitability, capacity, fitness for purpose or performance of the Product are given solely on

an “as is” and “as available” basis in this document, and Nokia Solutions and Networks reserves the rightto change any such information and statements without notice. Nokia Solutions and Networks has made all

reasonable efforts to ensure that the content of this document is adequate and free of material errors and

omissions, and Nokia Solutions and Networks will correct errors that You identify in this document. But,

Nokia Solutions and Networks' total liability for any errors in the document is strictly limited to the correction

of such error(s). Nokia Solutions and Networks does not warrant that the use of the software in the Product

will be uninterrupted or error-free.

NO WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO

ANY WARRANTY OF AVAILABILITY, ACCURACY, RELIABILITY, TITLE, NON-INFRINGEMENT,

MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, IS MADE IN RELATION TO THE

CONTENT OF THIS DOCUMENT. IN NO EVENT WILL NOKIA SOLUTIONS AND NETWORKS BE

LIABLE FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO SPECIAL, DIRECT, INDIRECT,

INCIDENTAL OR CONSEQUENTIAL OR ANY LOSSES, SUCH AS BUT NOT LIMITED TO LOSS OF

PROFIT, REVENUE, BUSINESS INTERRUPTION, BUSINESS OPPORTUNITY OR DATA THAT MAY

ARISE FROM THE USE OF THIS DOCUMENT OR THE INFORMATION IN IT, EVEN IN THE CASE OFERRORS IN OR OMISSIONS FROM THIS DOCUMENT OR ITS CONTENT.

This document is Nokia Solutions and Networks’ proprietary and confidential information, which may not be

distributed or disclosed to any third parties without the prior written consent of Nokia Solutions and

Networks.

Nokia is a registered trademark of Nokia Corporation. Other product names mentioned in this document

may be trademarks of their respective owners, and they are mentioned for identification purposes only.

Copyright © 2014 Nokia Solutions and Networks. All rights reserved.

f Important Notice on Product Safety This product may present safety risks due to laser, electricity, heat, and other sources of danger.

Only trained and qualified personnel may install, operate, maintain or otherwise handle this

product and only after having carefully read the safety information applicable to this product.

The safety information is provided in the Safety Information section in the “Legal, Safety and

Environmental Information” part of this document or documentation set.

Nokia Solutions and Networks is continually striving to reduce the adverse environmental effects of its

products and services. We would like to encourage you as our customers and users to join us in working

towards a cleaner, safer environment. Please recycle product packaging and follow the recommendations

for power use and proper disposal of our products and their components.

If you should have questions regarding our Environmental Policy or any of the environmental services we

offer, please contact us at Nokia Solutions and Networks for any additional information.


2 DN7032593 Issue: 6-1



Table of Contents

This document has 37 pages

Summary of changes..................................................................... 6

1 BTS EDGE dimensioning...............................................................8

2 Planning process..........................................................................10

3 Key strategies for EDGE dimensioning on air interface............... 11

4 Prerequisites for BTS EDGE dimensioning..................................13

4.1 Input summary............................................................................. 13

4.2 Output summary...........................................................................14

5 Dimensioning process..................................................................16

5.1 Dimensioning of network elements and interfaces.......................16

5.2 Inputs for BTS EDGE dimensioning.............................................20

5.2.1 Deployment strategy.................................................................... 20

5.2.2 Network capabilities..................................................................... 21

5.2.3 Traffic and quality inputs.............................................................. 28

5.3 BTS EDGE dimensioning calculations......................................... 32

5.3.1 Available capacity strategy...........................................................32

5.3.2 Required capacity strategy...........................................................33

5.4 Outputs of BTS EDGE dimensioning........................................... 35

5.5 Key parameters in BTS EDGE dimensioning...............................36

6 BTS traffic monitoring principles...................................................37


Issue: 6-1 DN7032593 3



List of FiguresFigure 1 GPRS and Circuit Switched territories in a cell.................................... 9

Figure 2 Available data capacity....................................................................... 11Figure 3 Required data capacity.......................................................................12

Figure 4 Available data capacity process......................................................... 16

Figure 5 Required data capacity process......................................................... 18

Figure 6 An example of a baseband hopping configuration............................. 23

Figure 7 An example of a mixed configuration BB hopping group....................24

Figure 8 An example of a configuration that uses Multi BCF Control...............24

Figure 9 Baseband hopping in the GSM/EDGE configuration..........................25

Figure 10 GPRS territory.................................................................................... 28

Figure 11 BTS dimensioning process for the available capacity strategy.......... 33Figure 12 BTS dimensioning process for the required capacity strategy........... 35


4 DN7032593 Issue: 6-1



List of TablesTable 1 Input parameters for available data capacity dimensioning................13

Table 2 Input parameters for required data capacity dimensioning.................14Table 3 Output parameters of BTS EDGE dimensioning................................ 15

Table 4 Mean number of timeslots available for GPRS...................................21

Table 5 GSM/EDGE hardware compatibility................................................... 22

Table 6 The number of free timeslots for different configurations................... 27

Table 7 Input signal level (for a normal BTS) at reference performance (BLER< 10%) for GMSK modulated signals................................................. 29

Table 8 Input signal level (for a MS) at reference performance for 8-PSK(BLER < 10%) modulated signals.......................................................30

Table 9 Minimum C/I for BLER < 10% in interference-limited scenarios (900

MHz band).......................................................................................... 31Table 10 Parameters for territory management.................................................36


Issue: 6-1 DN7032593 5



Summary of changes

Changes between document issues are cumulative. Therefore, the latest document

issue contains all changes made to previous issues

Changes made between issues 6-1 and 6-0

• Information on required capacity calculations has been revised in section

Requiredcapacity strategy in chapter Dimensioning process.


• Information on used terms and definitions has been revised.

• Information on Flexi Multiradio BTS type has been added to chapter BTS EDGE

dimensioning and section Network capabilities in chapter Dimensioning process.

• Information on Extended Common Control Channel (CCCHE) has been added to

section Network capabilities in chapter Dimensioning process.

• Information on required capacity calculations has been revised in section Required

capacity strategy in chapter Dimensioning process.


Chapter Dimensioning of network elements and interfaces: A note on BSS21226:

Asymmetrical PCU HW Configuration has been added to section Available data capacity

strategy .

Chapter Inputs for BTS EDGE Dimensioning :

• Information on dual band network has been revised in section Deployment strategy .

• Information on GPRS and EGPRS support for different baseband unit and RF unit

combinations has been added to table GSM/EDGE hardware compatibility in section

Network capabilities.

• Information on the PCU2-E plug-in unit, BSS21161: SDCCH and PS Data Channels

on DFCA TRX, and BSS21228: Downlink Dual Carrier has been added into section

Network capabilities.

Chapter BTS EDGE dimensioning calculations:

• Figure BTS dimensioning process for the available capacity strategy has been

corrected in section Available capacity strategy .

• Information on the functioning of EGPRS in TRXs having half rate timeslots has beenrevised in section Required capacity strategy .


Added information about Nokia Flexi EDGE BTS.

Added software requirements for new application software: Extended Cell Range.


The document has been restructured for better usability and the focus is more on the

actual dimensioning process. The following changes have been made:

Summary of changes BTS EDGE Dimensioning

6 DN7032593 Issue: 6-1



• Chapter EDGE dimensioning has been renamed as Planning process. The

dimensioning strategy information has been moved to chapter Key strategies for

EDGE dimensioning and an overview of the dimensioning steps has been moved to

chapter Dimensioning of network elements and interface and the content has been

updated.

• All steps in the dimensioning process are now under the main chapter Dimensioning

process.

• Chapters Prerequisites of BTS EDGE dimensioning and Key parameters in BTS

EDGE dimensioning have been added.

• Information on Dual Transfer Mode, Extended Dynamic Allocation, High Multislot

Classes and available GPRS resources within the circuit-switched design have been

added to chapter Inputs for BTS EDGE dimensioning . In addition, GPRS territory and

BTS configuration information has been updated. Information on software the do not

affect dimensioning has been removed.

• Information that the outputs of BTS dimensioning are used in all other dimensioning

phases has been added to chapter Outputs of BTS dimensioning .• Chapter Examples of BTS EDGE dimensioning has been removed. A dimensioning

example is now included in the BSC EDGE Dimensioning document, in chapter

Example of BSS connectivity dimensioning .

• Chapter Traffic monitoring principles has been moved to the EDGE and GPRS Key

Performance Indicators document.

• Information on Enhanced Quality of Service (EQoS) has been removed because it is

not supported in BSS12.

BTS EDGE Dimensioning Summary of changes

Issue: 6-1 DN7032593 7



1 BTS EDGE dimensioning

The guidelines provide information on EDGE dimensioning with the Nokia BSS line base

stations (BTS) in an existing GSM network. These base stations are: Flexi Multiradio

Base Station, Flexi EDGE Base Station, UltraSite EDGE Base Station, and MetroSite

EDGE Base Station.

The focus is put on calculating the required number of hardware elements, i.e. the

number of transceivers (TRXs) to serve both voice and data services with a given quality

of service assuming that sufficient coverage is already provided to the network.

The EDGE dimensioning guidelines contained in the GSM/EDGE operating

documentation cover BTS, Abis, BSC and Gb dimensioning and some parts of pre-

planning. An example of the BSS connectivity dimensioning is included in the BSC

EDGE Dimensioning guidelines.

The outputs of the BTS dimensioning are used as inputs to the next dimensioningphases, i.e. Abis EDGE dimensioning, BSC EDGE dimensioning, and Gb EDGE

dimensioning.

Terms and definitions

BTS BTS equipment, including all the base station control

function (BCFs) of the same site.

Cell Logical cell at the BTS site, usually transmitting from the

antennas of a single sector.

GB Guaranteed bit rate refers to dedicated data capacity

(dedicated timeslots) or guaranteed throughput. It is not

defined per user, but per cell.

Non-GB Non-guaranteed bit rate refers to non-dedicated (default)

data capacity or non-guaranteed throughput. It is not

defined per user, but per cell.

Circuit-switchedterritory

The number of consecutive radio timeslots reserved for

circuit-switched (CS) GSM calls. It also includes radio

timeslots kept free by a BSC (the spare CS territory size

defined with a BSC configuration parameter). The use of

additional radio channels requires a territory upgrade and

a channel request from the CS territory.

Default GPRS territory Predefined set of radio timeslots that can be initially used

for both: GPRS and EGPRS transmissions. Default GPRS

channels are defined on a BTS-to-BTS basis according to

the operator-defined parameters. The PCU uses the

GPRS territory resources.The BSC can later broaden the

GPRS territory based on the actual need and according to

the requests of the PCU. Radio timeslots available within

Default GPRS territory forms common CS and PS

resources, however, CS services have priority over PS

services in channel allocation in that territory. In principle,

PS releases its resources as soon as they are needed for

BTS EDGE dimensioning BTS EDGE Dimensioning

8 DN7032593 Issue: 6-1



circuit switched traffic. In order to prevent release of the

resources a part of Default GPRS territory can be defined

as Dedicated GPRS territory. The radio timeslots available

within that territory are blocked for CS calls. The defaultGPRS territory is measured in percentage and specified

with the default GPRS capacity (CDEF) parameter.

Dedicated GPRSterritory

Part of Default GPRS territory that is dedicated to packet

switched transmissions only. The number of radio timeslots

belonging to Dedicated GPRS territory can be fewer than

or equal to the number of default GPRS channels. The

dedicated GPRS capacity is measured in percentage and

specified with the dedicated GPRS capacity (CDED)

parameter.

Additional GPRS

territory

The term refers to additional radio timeslots, the BSC

allocates for GPRS use according to the requests from thePCU apart from the timeslots of the default and dedicated

GPRS territory. The size of the additional GPRS territory

can be restricted by the user-modifiable max GPRS

capacity (CMAX) parameter. The guard time of the

GPRS territory upgrade specifies how often the PCU can

request new radio timeslots for GPRS use.

GPRS territory Default plus additional GPRS territories. This corresponds

to the timeslots available for the packet-switched (PS)

data. The size of the EGPRS territory is usually defined

during radio network planning. However, the capacity

limitations of a BSC often have an effect on the overallnumber of traffic channels (TCHs) in the GPRS territories

of the BSC area. The GPRS territory also includes

additional capacity timeslots, if allocated to PS use by the

BSC.

Figure 1 GPRS and Circuit Switched territories in a cell

Related topics

• Abis EDGE Dimensioning

• BSC EDGE Dimensioning

• Gb EDGE Dimensioning

BTS EDGE Dimensioning BTS EDGE dimensioning

Issue: 6-1 DN7032593 9



2 Planning process

Dimensioning is the part of network planning that produces a master plan indicating the

selected network architecture and the number of network nodes and communication

links required during the network roll-out.

The following phases are included in the network planning process:

• dimensioning

• pre-planning

• detailed planning

• implementation

• optimisation

The EDGE dimensioning guidelines in the GSM/EDGE BSS operating documentation set

cover BTS, Abis, BSC, and Gb dimensioning and some parts of pre-planning. Theseguidelines focus on dimensioning. Network optimisation is not included in the guidelines.

The dimensioning guidelines consist of both hardware dimensioning and software

dimensioning. Hardware dimensioning defines how many traffic type and traffic volume

dependent hardware units are needed in the BTS, BSC, and SGSN to support the

targeted traffic and service performance. Software dimensioning defines the key system

settings associated with traffic dependent units. You can modify the existing configuration

once the amount of needed traffic dependent hardware and the associated software

settings have been defined. If necessary, you can place an order for additional products

and licences, based on the agreed standard configurations.

Nokia has a wide range of services and training available to support all phases of system

planning, deployment, and optimisation. For more information, contact your local Nokiarepresentative.

Planning process BTS EDGE Dimensioning

10 DN7032593 Issue: 6-1



3 Key strategies for EDGE dimensioning on air interface

The dimensioning of a network can be based on two different approaches:

• available data capacity

• required data capacity

The dimensioning strategy must be selected before the BTS dimensioning begins.

Available data capacity

Available data capacity strategy is used when you want to introduce EDGE to an existing

network. Dimensioning determines how much traffic is available through the current

system. The dimensioning input is a pre-defined system configuration. The dimensioning

output is the available traffic volume with a defined performance level. Alternatively, youcan calculate available capacities for different alternative configurations.

Figure 2 Available data capacity

All current resources in a cell

Average voice trafficresource usage

Averageavailableresources

Input information:

Current network configuration

Current equipment'sEDGE capability

Current network's voice

performance

Current network's radioconditions (C/N, C/I)

Planned EDGE data resourcesare used for voice trafficwhen needed


EDGE data

Required data capacity

Required data capacity strategy is used when you want to design a network that

supports the defined amount of traffic and targeted performance level. The dimensioninginputs are traffic volume, type, and performance requirements. The dimensioning output

is the needed amount of traffic dependent hardware and the associated software

configurations.

BTS EDGE Dimensioning Key strategies for EDGE dimensioning on air interface

Issue: 6-1 DN7032593 11



Figure 3 Required data capacity

Input information:

Current network configuration

Current equipment'sEDGE capability

Current network's voiceperformance

Current network's radioconditions (C/N, C/I)

Required EDGE capacity

Required EDGE performance

Planned EDGE dataresources may be fully or are at least partiallydedicated to data traffic.Dedicated resources are notused for voice traffic.

All current resources in a cell


Average availableresources


EDGE data

Shared Dedicated

Required EDGE Capacity

Key strategies for EDGE dimensioning on air interface BTS EDGE Dimensioning

12 DN7032593 Issue: 6-1



4 Prerequisites for BTS EDGE dimensioning

4.1 Input summary

The needed input information depends on the chosen dimensioning strategy. When the

EDGE implementation is based on the available capacity strategy, the dimensioning

process is more straightforward. In both cases EDGE dimensioning considers

combination of CS and PS traffic. Therefore, information on the CS traffic is the input for

the dimensioning. The input parameters for both strategies are presented in tables Input

parameters for available data capacity dimensioning and Input parameters for required

data capacity dimensioning .

Available capacity

The available radio interface capacity for data services can be estimated when the

existing BTS hardware and the current voice traffic load is considered. In such scenario

the PS dimensioning aims at estimating the achievable PS capacity taking into account

the average number of available timeslots for data traffic. By assuming a certain

throughput per timeslot and estimating the proportion of GPRS/EDGE users, a value for

the maximum average throughput per cell can be calculated. Voice blocking remains

unchanged, as long as timeslots are not dedicated for data and voice traffic does not

increase.

Table 1 Input parameters for available data capacity dimensioning

Input

Status/value

Activity

Hardware capability EDGE compatibili ty Verify (or upgrade)

Software capability EDGE compatibility Verify (or upgrade)

Voice traffic load Number of TSLs Measure

TRX

configuration

- Number of TRXs Verify

Signalling

channels

Number of TSLs Verify (or define)

Free TSLs (guard

TSLs)

Number of TSLs Define

GPRS territory

(dedicated,

default, and

additional)

Number of TSLs Define

Deployment - Single/multi-layer Define

Coverage C/N Simulate/measure

BTS EDGE Dimensioning Prerequisites for BTS EDGE dimensioning

Issue: 6-1 DN7032593 13



Table 1 Input parameters for available data capacity dimensioning (Cont.)

Input

Status/value

Activity

Interference C/I Simulate/measure

Throughput/TSL kbit/s Estimate

GPRS/EDGE % Estimate

Required capacity

In the required capacity strategy, a certain PS capacity must be offered by the network.

In this case the goal of the dimensioning is to find BTS configurations (number of TRXs

per cell) and the number of BTS sites in the network that are capable of serving requiredCS and PS traffic combination. Based on the number of users and data usage profile the

number of required radio resources per cell basis can be estimated.

Table 2 Input parameters for required data capacity dimensioning

Input

Status/value

Activity

Hardware capability EDGE compatibility Verify (or upgrade)

Software capability EDGE compatibility Verify (or upgrade

Voice traffic load Number of TSLs Measure

Data volume Per cell Estimate

Traffic mix Voice % Estimate

Data % Estimate

- Single/multi-layer Define

Deployment Coverage C/N Simulate/measure

Interference C/I Simulate/measure

Throughput/TSL kbit/s Estimate

GPRS/EDGE % Estimate

4.2 Output summary

The output of BTS EDGE dimensioning results in the BTS configuration and the

estimation of EDGE performance. The main output parameters are presented in tableOutput parameters of BTS EDGE dimensioning .

Prerequisites for BTS EDGE dimensioning BTS EDGE Dimensioning

14 DN7032593 Issue: 6-1



Table 3 Output parameters of BTS EDGE dimensioning

Output

Value

TRX

configuration

- Number of TRXs

Signalling channels Number of TSLs

Free TSLs (guard TSLs) Number of TSLs

GPRS territory (dedicated, default,

and additional)

Number of TSLs

Throughput/TSL kbit/s

Simulation results Coverage

BTS EDGE Dimensioning Prerequisites for BTS EDGE dimensioning

Issue: 6-1 DN7032593 15



5 Dimensioning process

5.1 Dimensioning of network elements and interfaces

The dimensioning of GSM EDGE network elements and interfaces is proposed to be

done as described in this section. Depending on the dimensioning strategy, you can use

either the available capacity strategy or the required capacity strategy. At first, the input

for BTS dimensioning has to be agreed. Once this has been done, the output of each

element or interface serves as the input for the next phase.

Available data capacity strategy

The dimensioning process of the available data strategy is illustrated in figure Available

data capacity process.

Figure 4 Available data capacity process

1. Estimate the average available data capacity andthroughput.

2. Use existing TRX hardware capacity.3.-6. Dimension the rest of the elements according to the

available capacity estimate done in step 1.

TSL

TRX

Cell

BTS

PCU

BSC

Basic unit

2G SGSNGb Abis

1

2

3 4 5 6

The available data capacity strategy consists of the following steps:

1. Definition of the input information

• Select the data deployment strategy.• Calculate the existing traffic load.

• Review the hardware/software capability.

• Define the BTS/transceiver (TRX) configuration.

• Simulate the coverage and interference performance (carrier-to-noise ratio (C/N),

carrier-to-interference ratio (C/I)).

2. BTS dimensioning

• Estimate throughput/radio timeslot (RTSL).

• Calculate the available capacity/number of RTSLs based on the circuit-switched

(CS) traffic needs.

• Verify the dimensioning outcome.

Dimensioning process BTS EDGE Dimensioning

16 DN7032593 Issue: 6-1



The dimensioning process results in throughput/RTSL, territory size/BTS,

guaranteed/not guaranteed throughput, RTSL configuration of TRXs, numbers of

TRXs per cell, and the simulation results.

3. Abis dimensioning• Use the output of BTS dimensioning as the input.

• In case of Dynamic Abis:

– Define the EGPRS dynamic Abis pool (EDAP) size. The dimensioning

process results in the size of each EDAP.

– Define the Circuit Switch Dynamic Abis Pool (CSDAP – in case when

Orthogonal Sub-channel or/and Orthogonal Sub-channel support for AMR FR

features are in use. The dimensioning process results in the size of each

CSDAP.

• In case of Packet Abis:

– Define the bandwidth required in backhaul to ensure enough space totransmit (within required delay and packet loss rate) all packets produced by

BTS.

4. BSC dimensioning

• Use the output of BTS and Abis dimensioning as the input.

• Verify the amount of packet control units (PCUs).

• Verify the number of BSC signalling units (BCSU) and exchange terminals (ETs).

In case of Multicontroller BSC (mcBSC), verify the number of modules.

• Verify the Gb requirements for BSC dimensioning.

•

Define the BSC configuration.• Perform a use check.

The dimensioning process results in the number and type of BSCs, the number and

type of PCUs, and the number and size of Gb interfaces. Note that if you are using

BSS21226: Asymmetrical PCU HW Configuration, you do not have to install the

same number of PCUs in every BCSU.

5. Gb dimensioning

• Use the output of BTS and BSC dimensioning as the input.

• Calculate the amount of payload.

• Verify the number of network service elements (NSEs) and BCSUs.

• Estimate the need for redundant links.

• Evaluate the results.

The dimensioning process results in the number of timeslots, number of payloads,

number of network service virtual connections (NS-VCs), and number of frame relay

timeslots/data transfer capacity.

6. SGSN dimensioning

• Use the output of BTS and Gb dimensioning as the input.

• Define the maximum number of attached subscribers and packet data protocol

(PDP) contexts to be expected in the routing area (RA) served by the SGSN.

• Calculate the amount of total data payload (generated user traffic) during a busy

hour.

BTS EDGE Dimensioning Dimensioning process

Issue: 6-1 DN7032593 17



• Verify the needed basic units/SGSN according to the previously calculated

generated traffic and the expected subscribers served in the area.

• Check all other restrictions, especially the expected mobility profiles of the users

versus the dynamic capacity of the SGSN.The dimensioning process results in the number of packet processing units (PAPUs)

and signalling and mobility management units (SMMUs).

Required data capacity strategy

The dimensioning process of the required data strategy is illustrated in figure Required

data capacity process.

Figure 5 Required data capacity process

1. Calculate the required TSL count based on required data

capacity and throughput.

2. Calculate the required amount of TRX hardware.3.-6. Dimension the rest of the elements according to therequired capacity calculation done in step 1.

TSL

TRX

Cell

BTS

PCU

BSC

Basic unit

2G SGSNGb Abis

1

2

3 4 5 6

The required data capacity strategy consists of the following steps:

1. Definition of the input information

• Select the data deployment strategy.

• Determine the targeted traffic capacity.

• Estimate the traffic mix.

• Review the hardware/software capability.

• Define the BTS/TRX configuration.• Simulate the coverage and interference performance (C/N, C/I).

2. BTS dimensioning

• Calculate the required throughput.

• Estimate throughput/RTSL.

• Calculate the required number of RTSLs.

• Verify the dimensioning outcome.

The dimensioning process results in throughput/RTSL, territory size/BTS,

guaranteed/not guaranteed throughput, TSL configuration of TRXs, number of

TRXs/cell, and the simulation results.

3. Abis dimensioning


18 DN7032593 Issue: 6-1



• Use the output of BTS dimensioning as the input.

• In case of Dynamic Abis:

– Define the EGPRS dynamic Abis pool (EDAP) size. The dimensioning

process results in the size of each EDAP.

– Define the Circuit Switch Dynamic Abis Pool (CSDAP – in case when

Orthogonal Sub-channel or/and Orthogonal Sub-channel support for AMR FR

features are in use. The dimensioning process results in the size of each

CSDAP.

• In case of Packet Abis:

– Define the bandwidth required in backhaul to ensure enough space to

transmit (within required delay and packet loss rate) all packets produced by

BTS.

4. BSC dimensioning

• Use the output of BTS and Abis dimensioning as the input.

• Calculate the needed amount of PCUs.

• Calculate the number of BCSUs and ETs.

• Calculate the number and types of modules for mcBSC.

• Calculate the Gb requirements for BSC dimensioning.

• Define the BSC configuration.

• Perform a use check.

The dimensioning process results in the number and type of BSCs, the number and

type of PCUs, and the number and size of Gb interfaces.

5. Gb dimensioning

• Use the output of BTS and BSC dimensioning as the input.

• Calculate the amount of payload.

• Calculate the required number of NSEs and BCSUs.

• Estimate the need for redundant links.

• Evaluate the results.

The dimensioning process results in the number of timeslots, the number payloads,

the number of NS-VCs, and the number of frame relay timeslots/data transfer

capacity.

6. SGSN dimensioning

• Use the output of BTS and Gb dimensioning as the input.

• Define the required number of attached subscribers and PDP contexts to be

expected in the RA served by the SGSN.

• Calculate the amount of total data payload (generated user traffic) during a busy

hour.

• Calculate the needed basic units/SGSN according to the previously calculated

generated traffic and the expected subscribers served in the area.

• Check all other restrictions, especially the expected mobility profiles of the users

versus the dynamic capacity of the SGSN.

The dimensioning process results in the number of PAPUs and SMMUs.


Issue: 6-1 DN7032593 19



5.2 Inputs for BTS EDGE dimensioning

5.2.1 Deployment strategy

An operator may have more than one layer (frequency or logical) in use in the network.

The way data is deployed on different layers has an impact on the achieved throughput

per timeslot. This section discusses different deployment strategies in detail.

Single band network

An operator with a single frequency band and narrow bandwidth has a challenging task

for frequency planning. In such a case, even the broadcast control channel (BCCH)

frequencies can be relatively interfered, at least in macro cells.

If the operator has a fairly wide bandwidth in use, it is possible to divide the frequenciesfor BCCH and traffic channel (TCH) usage to ensure better quality on the BCCH

frequencies. Packet data can then be used on the BCCH transceivers (TRXs) to

guarantee as large a data coverage as possible.

Dual band network

A dual band network allows the operator to use two different frequency bands for both

voice and data services. Thus, more frequency channels are available, interference can

be reduced, and the quality perceived by the user improved.

Macro/micro cells

The location of the BTS antennas dictates the propagation environment. Macro cellshave antennas above the average height of the rooftops, whereas micro cells have

antennas clearly below rooftops, increasing the propagation loss significantly. In a dense

traffic environment, micro cells lower the total interference level in the network, because

the signals attenuate rapidly. This allows the operator to build a high-capacity network

even if the bandwidth is fairly narrow.

In a macro cell environment, signals propagate further, causing interference. When

building macro sites, it is important to use antenna tilting and avoid situations where

antennas point towards water areas or cause interference to remote areas (in other

areas where radio waves propagate easily). In addition, it is recommended to use

antennas with a narrow vertical beam width.

A useful way to lower the interference from macro cells is to use natural or man-madeobstacles to point antennas to. This attenuates the signal propagation towards a certain

direction.

Indoor/outdoor locations

Operators need to build coverage almost anywhere where customers require service.

This includes indoor locations, such as office buildings, shopping centres, airports, and

underground parking garages. In these areas, interference is not usually as big a

problem as in an outdoor environment. Walls, ceilings, and other materials in buildings or

other indoor locations absorb signal energy. This decreases interference. However, it

makes building indoor coverage more challenging, especially in large indoor areas.


20 DN7032593 Issue: 6-1



In indoor areas, interference tends to be very low regardless of the signal level. This

allows very high data rates for packet-switched (PS) services if the signal level is

adequate.

Throughput per timeslot estimates

If the network has already been launched with data (GPRS) services, the operator can

monitor the average throughput values on a cell level and estimate the average

throughput per timeslot (TSL). If the operator has not started with data services,

measuring the average coverage and interference levels in the network helps to estimate

the average data throughput values.

If the network has not been launched or if the measuring would take too much time and

resources, it is possible to use radio network planning tools to predict the average

coverage and interference levels and estimate the average throughput values for

EGPRS services.

Available GPRS resources within the circuit-switched design

A system designed for circuit-switched (CS) traffic usually allows basic GPRS

throughput. Since the system has been designed for a sufficient margin to permit a low

blocking level, some of the extra instantaneous capacity can be used for packet data

transmission. As long as the packet traffic can be temporarily interrupted to

accommodate the peaks in circuit-switched traffic, there is no decrease in the CS

services.

Table Mean number of timeslots available for GPRS shows the mean number of

timeslots available for GPRS, for different numbers of TRXs per cell and for circuit-

switched blocking probabilities of 1% and 2%. The free timeslots between territories are

taken into account.

Table 4 Mean number of timeslots available for GPRS

Number of

TRXs (TCHs)

GSM traffic

(Erl) at 1%

blocking

GSM traffic

(Erl) at 2%

blocking

Mean free

TCHs for

GPRS at 1%

blocking

Mean free

TCHs for

GPRS at 2%

blocking

1 (7) 2.5 2.9 3.5 3.1

2 (14) 7.3 8.2 5.2 4.3

3 (22) 13.6 14.9 6.9 5.6

5.2.2 Network capabilities

Hardware capabilities

The Flexi Multiradio BTS can transmit and receive multicarrier signals of multiple radio

technologies concurrently. The radio frequency part of the BTS is supported by Flexi

Multiradio Module (RFM), which is optimized for 3 sector Macro BTS use (the module

consists of 3 independent pipes). Each pipe can carry up to 6 carriers/TRXs, hence the

total single RFM capacity is up to 18 carriers/TRXs (6+6+6). Further capacity extension

can be done by installing additional RFM. All the carriers/TRXs are GPRS as well as


Issue: 6-1 DN7032593 21



EGPRS capable.The Flexi EDGE BTS has 12 dual TRX modules, each of which can

carry 2 TRX objects. All the TRX objects in Flexi EDGE BTS are GPRS and EGPRS

capable.

In UltraSite EDGE BTS, the GSM/EDGE radio frequency (RF) unit (TSxB) alwaysrequires an EDGE-capable baseband unit (BB2E or BB2F) even if it operates in GSM

mode only.

EGPRS support requires an EDGE-capable baseband unit (BB2E or BB2F) and an

EDGE-capable RF unit (TSxB).

The EDGE-capable baseband unit (BB2E or BB2F) is backward compatible and also

supports the GSM RF unit, TSxA.

Table GSM/EDGE hardware compatibility shows the compatibility for the different BB2x

and TSxx combinations, as well as the GPRS and EGPRS support for the combinations.

Table 5 GSM/EDGE hardware compatibility

Unit

Compatibility

GPRS support

EGPRS support

BB2A + TSxA OK OK NOK

BB2A + TSxB NOK N/A N/A

BB2E + TSxA OK OK NOK

BB2E + TSxB OK OK OK

BB2F + TSxA OK OK NOK

BB2F + TSxB OK OK OK

BTS configurations

This section describes the different BTS configurations in detail and includes

recommendations for EGPRS.

1. Low configurations (one or two TRX per cell)

The options are limited for one TRX per cell. GPRS territory must be on the same

TRX as the BCCH. It is recommended to set the dedicated/default GPRS territory to

start from the last TSL 7 to maintain the data continuity. For two TRXs per cell, it ispossible to decide whether GPRS territory is set on the BCCH or TCH TRX. Setting

the GPRS territory on the BCCH TRX may ensure better carrier-to-interference ratio

(C/I) performance if the operator has a limited frequency band in use for the TCH

TRXs. It is recommended to introduce GPRS territory in the BCCH layer first and

then, when required (when there are no more TSLs available in the BCCH TRX), use

the hopping layer. If an EDGE TRX (TSxB) is used, the baseband unit must be BB2E

or BB2F.

2. High configurations (more than three TRXs per cell)

The same information applies as in the previous sections. If baseband (BB)

hopping is used in a cell (preferably at least three TRXs), there are a few

alternatives for the hardware configuration.


22 DN7032593 Issue: 6-1



• GSM hardware configuration: BB2A + TSxA

No limitations in baseband hopping: BB hopping can be used in the GSM mode. This

configuration supports GPRS only.

•

GSM hardware configuration with EDGE BB unit: BB2E or BB2F + TsxANo limitations in baseband hopping: BB hopping can be used in the GSM mode. This

configuration supports GPRS only.

• GSM/EDGE hardware configuration: BB2E or BB2F + TSxB

No limitations in baseband hopping. This configuration also supports BB hopping

when EGPRS is activated.

• Mixed GSM hardware with GSM/EDGE hardware configurations

In mixed configurations GSM and GSM/EDGE hardware are in the same

sector/layer. In mixed configurations, baseband hopping is supported in the GSM

mode only. In mixed configurations where baseband hopping is possible, only GPRS

is supported. However, in the "Mixed GSM hardware: GSM/EDGE hardware

configuration", also EGPRS is supported.

• Mixed GSM hardware: BB2A and BB2E or BB2F with TSxAUltraSite EDGE BTS SW CX3.3-1 or later software allows baseband hopping in

configurations where GSM RF units (TSxA) are controlled by any baseband unit.

This is not possible with BTS software releases prior to CX3.3-1. Figure An example

of a baseband hopping configuration illustrates a baseband hopping configuration

with four TSxAs controlled by one BB2A and one BB2E or BB2F.

Figure 6 An example of a baseband hopping configuration

TSxA f1

TSxA f2

TSxA f3

TSxA f4

TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7

BCCH*

BB2A

BB2Eor BB2F

Timeslot 0 of TRXs 2-4hop over MA (f2-f4)

All 7 timeslots hop over MA (f1-f4)

* BCCH timeslot does not hop

• Mixed GSM hardware: BB2A and BB2E with TSxA and TSxB

Baseband hopping between TSxA and TSxB is not possible in this configuration

without Multi BCF Control. The TSxB and TSxA units need to be configured in their

own hopping groups and have separate BTS objects for TSxA and TSxB units.

• Mixed GSM hardware: BB2A and BB2F with TSxA and TSxB

CX3.3-1 or later software and BB2F unit enable a mixed configuration BB hopping

groups to be formed within UltraSite EDGE BTS. Mixed configuration BB hopping

has the following constraints: a mixed configuration hopping group is restricted to

GMSK calls only and each new TSxB that is configured for mixed configuration BB

hopping requires a BB2F unit to control it. In this way, TSxB may be used to replace


Issue: 6-1 DN7032593 23



TSxA without loss of GMSK. Figure An example of a mixed configuration BB hopping

group illustrates a possible mixed configuration BB hopping group with two TSxAs

and two TSxBs, controlled by one BB2A and one BB2F.

Figure 7 An example of a mixed configuration BB hopping group

TSxA f1

TSxA f2

TSxB f3

TSxB f4


BCCH*

BB2F


All 7 timeslots hop over MA (f1-f4)

* BCCH timeslot does not hop

BB2A

• Mixed GSM hardware: GSM/EDGE hardware configuration

When EGPRS is enabled, the EDGE-capable TRXs have to be configured to

separate hopping groups from the GSM TRXs. In mixed GSM hardware with

GSM/EDGE hardware configurations, the EDGE TRXs can be configured to

separate hopping groups by using Multi BCF Control. For more information on Multi

BCF Control, see BSS10046: Multi BCF Control .Figure 8 An example of a configuration that uses Multi BCF Control

TSxA f1

TSxA f2

TSxB f3

TSxB f4


BCCH*

BB2E

or BB2F


All 7 timeslots hop over MA (f1, f2)* BCCH timeslot does not hop

BB2ABTS-1

BTS-1'

TRX-1

TRX-2

TRX-3

TRX-4

BTS-1':EDGE TRXs

BTS-1:NON-EDGE TRXs

Timeslot 0 of TRX2is using MA (f2)

All 7 timeslots hopover MA (f3, f4)

• GSM/EDGE hardware configuration

There are no limitations in baseband hopping in the GSM/EDGE configuration when

EGPRS is enabled.


24 DN7032593 Issue: 6-1





Dual Transfer Mode (DTM) means a simultaneous voice and data connection that

can be supported in cells that include a GPRS territory. A DTM temporary block flow

(TBF) is established in EGPRS mode if the mobile station (MS) is EGPRS capable

and if the DTM call is allocated from an EGPRS-capable PS territory. If not, the DTM

TBF is established in GPRS mode.

For more information, see BSS20088: Dual Transfer Mode.

• Extended Dynamic Allocation and High Multislot Classes

Extended Dynamic Allocation (EDA) and High Multislot Classes (HMC) enable a

combined downlink and uplink timeslot sum of 6. The new maximum allocations are

5+1 or 4+2. With EDA support, 3+3 and 2+4 are also possible. EGPRS must be

available and active in the network for EDA and HMC to work. Certain DTM channel

configurations can be supported only if the Gs interface is also supported.

With paging coordination the MS can make or receive voice calls even when it is in

packet transfer mode. This is enabled by Network Operating Mode I (NOM I) that

requires the optional Gs interface between the MSC and the SGSN.

For more information, see BSS20089: Extended Dynamic Allocation and BSS20084:

High Multislot Classes.

• SDCCH and PS Data Channels on DFCA TRX

SDCCH and PS Data Channels on DFCA TRX enables DFCA TRXs to support

GPRS/EDGE and carry SDCCH channels. With this feature, a separate layer for data

traffic is no longer required in DFCA BTSs if BCCH resources are not sufficient for

data traffic. This results in more efficient use of the available radio resources and

increases PS capacity without the need for an additional, regular TRX installation.

For more information, see BSS21161: SDCCH and PS Data Channels on DFCA

TRX .

• Downlink Dual Carrier

Downlink Dual Carrier (DLDC) offers a possibility to enhance the data rates of DLDC-

capable MSS by increasing the number of radio timeslots that can be allocated for the downlink (DL) TBFs of such mobiles. This is achieved by assigning the resources

of an EGPRS DL TBF on two TRXs. One of these channels can be, for example, in a

BCCH carrier and the other in a TCH with frequency hopping. The MS receives both

radio frequency channels, and thus, DL throughput can be doubled. An uplink TBF,

on the other hand, is assigned on one TRX only. Downlink Dual Carrier doubles DL

peak throughput up to 592 kbps. However, the final throughput gain depends highly

on the network load.

For more information on DLDC, see BSS21228: Downlink Dual Carrier .

For information on the impact of DLDC on BSS connectivity dimensioning, see

Impact of Downlink Dual Carrier on BSS connectivity dimensioning in BSC EDGE

Dimensioning .

Free timeslot (guard timeslot)

The guard TSLs are used to cope with voice pre-emption. There are timeslots between

the CS and the PS territory. They are used temporarily by voice while a downgrade in the

PS territory is being performed to allocate a new voice call.

Preliminary values for the number of free timeslots in the CS territory are given in table

The number of free timeslots for different configurations. The mean number of free

timeslots in the CS territory is also given. The assumption is that there are, on average,

an equal number of upgrades and downgrades.


26 DN7032593 Issue: 6-1

http://localhost/var/www/apps/conversion/tmp/scratch_2/DN7032469-0900d80580a4727e.pdf

http://localhost/var/www/apps/conversion/tmp/scratch_2/DN7032469-0900d80580a4727e.pdf



Table 6 The number of free timeslots for different configurations

TRXs

Free TSLs(after a CS

downgrade)

Free TSLs (after a CS upgrade)

Mean free TSLsin the CS

territory

1 1 1 1

2 1 2 1.5

3 1 2 1.5

4 2 3 2.5

5 2 4 3

6 2 4 3

Signalling channels

Common BCCH

The usage of a common BCCH has an effect only on dual band sectors where the cell

signalling channels of the other band are not needed, leaving more timeslots for voice

and data.

GSM and EGPRS sharing a common control channel ( CCCH )

The Common Control Channel (CCCH) is composed of four logical channels: PagingChannel (PCH), Access Grant Channel (AGCH), and Notification Channel (NCH) in DL

and Random Access Channel (RACH) in UL. Common control channels transmit

information for CS as well as for PS operation. In case of PS operation PCH is used to

page an MS, RACH is used to access the cell and AGCH to establish connection prior to

packet transfer.

There are two ways in which the CCCH can be multiplexed onto a physical radio timeslot

(RTSL). With non-combined BCCH, RTSL 0 of the BCCH carrier is configured to carry

the BCCH, FCCH, SCH and nine CCCH blocks. With combined BCCH, RTSL 0 of the

BCCH carrier is configured to carry the BCCH, FCCH, SCH, three CCCH blocks and four

SDCCH channels with their associated SACCH. In the UL all CCCH blocks are used for

RACH channel, while in the DL they are dynamically shared between PCH and AGCHchannel. However, certain number of CCCH blocks can be reserved for AGCH channels

only.

In order to enhance the capacity of CCCH channel that might be a bottleneck, especially

in case of increased packet switched traffic with many TBFs being established),

extended CCCH channels (CCCHE) can be created. CCCHE channel contains 1 BCCH

block and 9 uncombined CCCH blocks per single RTSL that is reserved for CCCHE

usage. CCCHE channel can be configured only in case of uncombined BCCH

configuration and up to 3 RTSLs can be reserved for CCCHE purposes. This means that

it is possible to configure in a cell up to 4 RTSLs with 9 CCCH blocks each.


Issue: 6-1 DN7032593 27



Dedicated, default, and additional GPRS territories

It is possible to define, per cell, dedicated timeslots exclusively for GPRS. Only GPRS

can use these TSLs that can cause additional blocking for voice services. By using

dedicated timeslots, the operator can ensure a minimum throughput for PS services.Circuit-switched (CS) traffic has priority outside the dedicated territory. Within the default

GPRS territory, timeslots are allocated for GPRS when the CS load permits this. A

dedicated territory is a subset of the default territory.

When the default GPRS capacity is allocated for GPRS, and the GPRS load increases,

the PS radio resource management (RRM) can request additional TSLs. Based on the

CS load, the CS RRM controls the allocation of additional TCHs. The territories consist

of consecutive timeslots which is important for multislot operation. The maximum GPRS

territory is defined by the parameter max GPRS capacity.

The default territory size should be carefully considered. If the territory is large, multislot

MSS are well supported. This, however, leads to frequent territory downgrades by the

CS RRM, after which upgrade and intra-cell handover may be triggered. The network(including the PCU and the Abis interface) must also be capable of supporting large

territories. If the territory is small, multislot MSS cannot be fully used. In addition, the

number of territory upgrades grows, leading to intra-cell handovers.

A typical rule used in determining the default territory is:

CDEF = max(MS capability, GPRS traffic in cell)

Figure GPRS territory illustrates the concept of the GPRS territory.

Figure 10 GPRS territory

5.2.3 Traffic and quality inputs

This section presents the minimum requirements for carrier-to-noise ratio ( C/N,

coverage) and C/I (interference) for different coding schemes and describes the theory

behind calculating (or estimating) the throughput per a TSL. The TSL throughput

calculation is important because the required number of timeslots for data is totally

dependent on the throughput of a single timeslot. Experiences from different networks

show that the average throughput per timeslot for EDGE is about 30-36 kbps.


28 DN7032593 Issue: 6-1



Minimum requirements for coverage

In a PS network, the quality of service perceived by the user is typically measured by the

data throughput and the effective delay of the transmitted data. Detailed network

planning of the radio interface should ensure that the required coverage, capacity, anduser throughput is available for the system launch.

The coverage planning aspects of GPRS implementation include the provision of

sufficient C/N ratios across the coverage area to allow successful data transmission, on

both uplink and downlink. Each coding scheme defined for GPRS is suited to a particular

range of C/N (or Eb/No) for a given block error rate (BLER). Generally, the higher the

level of error protection, the lower required C/N.

Due to the differing C/N requirements of the coding schemes, their relative coverage

areas are different. In addition to the existing GSM voice service, it is useful to compare

the relative predicted coverage areas of the coding scheme.

In a mobile network, cells have to overlap to ensure mobility. This results in a better overall coverage than in a case of an isolated cell. In urban areas, cells tend to be much

closer to each other. In this case, the interference caused by reused frequencies is

usually the limiting factor, not the coverage.

For example, in a dense urban environment where indoor coverage has to be good,

handovers may take place at very high RX level values. In this case, it is possible that

even the highest coding schemes can be used almost everywhere within that cell if the

interference level is low.

Tables Input signal level (for a normal BTS) at reference performance (BLER < 10%) for

GMSK modulated signals and Input signal level (for an MS) at reference performance for

8-PSK (BLER < 10%) modulated signals give reference values for the minimum signal

level for different coding schemes. That is, the received signal level (without interference)has to be at a certain level to achieve the maximum throughput per TSL. For example,

for an MS receiving with the coding scheme MCS-6 (8-PSK modulated signal), the signal

level has to be at least -91 dBm without any interference (in the typical urban 50 km/h

propagation model without frequency hopping) to achieve the maximum throughput of

29.6 kbps per TSL. Below this signal level, a lower coding scheme has to be used. The

tables are from 3GPP specifications.

Table 7 Input signal level (for a normal BTS) at reference performance (BLER <10%) for GMSK modulated signals.

Type of

channel

Propagation conditions

Static TU50

(no

FH)

TU50

(ideal

FH)

RA250

(no FH)

HT100

(no FH)

PDTCH/CS-1 dBm -104 (x) -104 -104 (x) -104 (x) -103

PDTCH/CS-2 dBm -104 (x) -100 -101 -101 -99

PDTCH/CS-3 dBm -104 (x) -98 -99 -98 -96

PDTCH/CS-4 dBm -101 -90 -90 * *


Issue: 6-1 DN7032593 29



* PDTCH for MCS-x cannot meet the reference performance for some propagation

conditions.

Table 8 Input signal level (for a MS) at reference performance for 8-PSK (BLER <10%) modulated signals.

Type of

channel


Static TU50

(no

FH)

TU50

(ideal

FH)

RA250

(no FH)

HT100

(no FH)

PDTCH/MCS

-5

dBm -98 -93 -94 -93 -92

PDTCH/MCS

-6

dBm -96 -91 -91.5 -88 -89

PDTCH/MCS

-7

dBm -93 -84 -84 * -83**

PDTCH/MCS

-8

dBm -90.5 -83** -83** * *

PDTCH/MCS

-9

dBm -86 78.5** 78.5** * *

* PDTCH for MCS-x cannot meet the reference performance for some propagation

conditions

** Performance is specified at 30% BLER.

Minimum requirements for interference

The minimum BTS and MS performance in interference-limited scenarios have been

included in the 3GPP specifications. The minimum performance is specified as the

minimum carrier-to-interference (C/I) required to achieve 10% BLER for different channel

conditions.

In addition to the fact that the signal level has to be at a minimum level for certain

throughput, it also has to exceed the minimum required C/I value for that particular

coding scheme. For example, an MS receiving with coding scheme MCS-6 (minimum

signal level -91 dBm) can use the maximum throughput per TSL if the current

interference level is 18 dB below the current signal level. The values in the table are

minimum required values. The real throughput achieved is affected by the MS and BTS

properties. The current interference situation in a mobile network depends on the

deployment strategy.


30 DN7032593 Issue: 6-1



Table 9 Minimum C/I for BLER < 10% in interference-limited scenarios (900 MHzband).

Type of

channel


TU3

(no

FH)

TU3

(ideal

FH)

TU50

(no

FH)

TU50

(ideal

FH)

RA250

(no FH)

PDTCH/CS-1 13 9 10 9 9

PDTCH/CS-2 15 13 14 13 13

PDTCH/CS-3 16 15 16 15 16

PDTCH/CS-4 19 23 23 23 Perform

ance not

met

PDTCH/MCS

-1

13 9 9 9 9

PDTCH/MCS

-2

15 13 13 13 13

PDTCH/MCS

-3

16 15 16 16 16

PDTCH/MCS

-4

21 23 27 27 Perform

ance not

met

PDTCH/MCS

-5

18 14.5 15.5 14.5 16

PDTCH/MCS

-6

20 17 18 17.5 21

PDTCH/MCS

-7

23.5 23.5 24 24.5 26.5

(30%BLER)

PDTCH/MCS

-8

28.5 29 30 30 Perform

ance not

met

PDTCH/MCS

-9

30 32 33 35 Perform

ance not

met


Issue: 6-1 DN7032593 31





• Multiply the number of data TSLs by the average throughput per TSL.

– Calculate the average throughput on different cell layers.

4. Check the result.

• If the data throughput is too low, consider introducing half rate or dual rate for

voice to increase the number of TSLs for data.

Figure BTS dimensioning process for the available capacity strategy presents the

process of dimensioning data traffic on top of voice traffic.

Figure 11 BTS dimensioning process for the available capacity strategy

STEP 1: Calculate theavailable data TSLs

STEP 2: Calculate theachieved TSL

throughput

STEP 3: Calculate theachieved average

throughput

STEP 4: Check theresult

1.1 Calculate/measurethe current voice traffic(based on measurementsor configuration)

1.2 Make a note of thesignalling channels andfree timeslots

1.3 Calculate theavailable timeslots for data traffic

The available TSL for datais: 8 X TRX - signallingchannels - free TSLs -voice erlangs

2.1 Consider the coverageand interference situation(deployment strategy)

2.2 Estimate the GPRS/EGPRS division

2.3 Estimate the averagethroughput for GPRS andEDGE

2.4 Calculate the averagethroughput per TSL

3.1 Multiply the data TSLsby the average throughputper TSL (calculate theaverage throughput ondifferent cell layers)

4.1 If the datathroughput is too lowconsider introducing half/dual rate for voice toincrease the number of TSLs for data

5.3.2 Required capacity strategy

The operator may want to estimate the needed capacity based on assumptions on the

number of data users in the network and on the average user traffic during busy hour. In

this case the goal of the dimensioning is to find BTS configurations (number of TRXs per

cell) and the number of BTS sites in the network that are capable of serving required CS

and PS traffic mix.

Traffic mix

Voice

The amount of radio resources that are required to serve given voice traffic in a cell

needs to be estimated using ErlangB formula. For that purpose, the traffic volume that is

offered in busy hour and the acceptable blocking probability has to be known. Apart from

that, the percentage of the traffic that is going to be served using Dual Full Rate (DFR),

Half Rate (HR), or Dual Half Rate (DHR) mode has to be identified.

Two DFR or HR connections can be served by single radio timeslot (RTSL). Thus, in

case of the mixture of Full Rate (FR) and DFR or HR modes, the number of occupied

radio timeslots is significantly reduced comparing to 100% FR mode. DHR helps to


Issue: 6-1 DN7032593 33



utilize available radio resources even more efficiently than Dual Full Rate or Half Rate

mode. The feature enables to assign two calls on the same HR traffic channel what

means that up to four connections may be served by one radio timeslot.

DFR and DHR mode can be enabled in Flexi EDGE, Flexi Multiradio BTS, and inUltraSite BTS equipped with EDGE Ultra Site TRXs. The EDGE Ultra Site TRX supports

both EGPRS and OSC, however, the TRX does not support the concurrent use of

EGPRS and OSC. EGPRS and OSC also cannot operate together in Flexi EDGE BTS in

case it is equipped with Flexi EDGE EXxA (Epsilon) DTRXs. EGPRS cannot be used on

a TRX if all the timeslots of the TRX are configured as half rate. However, it can be used

if the TRX also has dual rate timeslots besides half rate timeslots.

Data

Data volume per cell can be calculated (or estimated) as the total data volume per cell,

or it can be based on subscriber information. The simplest way is to estimate the total

data volume going through a cell during a busy hour, based on the available average

throughput for EGPRS-enabled timeslots.

Calculating traffic using subscriber information is more complicated. First, the total

number of subscribers (or the data user penetration value) must be known. Then, the

user data amount per busy hour must be estimated as a total value or based on

assumptions of data usage (for example, Internet, FTP, and e-mail).

A significant factor in the dimensioning of the radio interface is the coding scheme. The

coding scheme has a significant role when the total throughput on cell basis is

calculated. For GPRS, the slowest coding scheme (CS-1) has a user bit rate of 9.05

kbps; the fastest (CS-4) has a user bit rate of 21.4 kbps. For EGPRS, the respective

values are 8.8 kbps for MCS-1 and 59.2 kbps for MCS-9.

Calculations1. Calculate the required throughput.

• Calculate the payload per cell during busy hour.

– the number of data users or data user penetration

– data user profile(s)

• Transfer payload to throughput (kbps).

• Make a note of whether the throughput has to be guaranteed or not (GB or non-

GB).

2. Estimate the average data throughput per timeslot, based on assumptions of the

applied deployment strategy.

• frequency band

• indoor/outdoor

• GPRS/EGPRS division

• Estimate the achieved throughput/TSL of the different layers.

3. Calculate the needed TSLs/TRXs and the final throughput.

• Calculate the needed data TSLs.

• Make a note of the needed voice TSLs at the required blocking rate.

– GB/non-GB


34 DN7032593 Issue: 6-1



• Calculate the needed signalling channels.

– stand-alone dedicated control channel (SDCCH) configuration

• Make a note of the free TSLs.• Calculate the number of required TRXs.

• Calculate the achieved throughput with the required configuration.

4. Check the result.

• OK

• over-dimensioned

– Introduce half rate/dual rate.

– Lower throughput requirements:

Check if there is enough bandwidth (C/I requirements can be met) for the

number of TRXs.

– OK

– If not OK, take the necessary actions.

Figure BTS dimensioning process for the required capacity strategy presents the

process of dimensioning data traffic for the required capacity strategy.

Figure 12 BTS dimensioning process for the required capacity strategy

STEP 1: Calculate therequired throughput

STEP 2: Estimate theachieved TSLthroughput

STEP 3: Calculate theneeded TSL/TRX andfinal throughput

STEP 4: Check theresult

1.1 Calculate the payloadper cell during a busyhour - the number of datausers or data user penetration

- data user profile(s)

1.2 Transfer payload tothe required throughput

1.3 Define whether GB or non-GB is used

2.1 Make a note of thecoverage and interfacesituation- deployment strategy

2.2 Estimate the GPRS/EGPRS division

2.3 Estimate the averagethroughput for GPRS andEDGE

2.4 Calculate the averagethroughput per TSL

3.1 Calculate the neededdata TSL

3.2 Make a note of theneeded voice TSLs at acertain blocking rate- GB/non-GB

3.3 Calculate the neededsignalling channels

3.4 Make a note of thefree TSLs

3.5 Calculate the requiredTRXs

3.6 Calculate the achievedthroughput with therequired configuration

4.1 Check whether theBTS is over dimensioned- introduce half rate/ dualrate

- lower the throughputrequirements

4.2 Check that the C/Irequirements are met

5.4 Outputs of BTS EDGE dimensioning

The outputs of dimensioning BTS are used as inputs in the next dimensioning phases.

The BTS output information includes the following:

• throughput/timeslot (TSL)


Issue: 6-1 DN7032593 35



• data TSL/transceiver (TRX)

• TSL configuration of TRXs

• number of TRXs/cell

• simulation results

The key output of BTS dimensioning is the number of TRX units.

5.5 Key parameters in BTS EDGE dimensioning

The key parameters that need to be taken into consideration in BTS EDGE dimensioning

and planning are listed in table Parameters for territory management .

Table 10 Parameters for territory management

Parameter

Value

Level

EGPRS enabled Y/N BTS

GPRS enabled TRX Y/N TRX

dedicated GPRS capacity % BTS

default GPRS capacity % BTS

prefer BCCH frequency GPRS Y/N BTS

GPRS territory update guard

time

sec BSC

max GPRS capacity % BTS

free TSL for CS upgrade sec BSC

free TSL for CS downgrade % BSC


36 DN7032593 Issue: 6-1



6 BTS traffic monitoring principles

BTS dimensioning focuses on defining the number of required timeslots and,

consequently, the number of transceiver (TRX) units. The packet data traffic channel

(PDTCH) congestion key performance indicators (KPIs) Downlink multislot allocation

blocking , Downlink multislot soft blocking , and Downlink TBFs per timeslot are very

useful in BTS traffic monitoring and detecting the potential need to optimise the

configuration. For more information on the KPIs, see Congestion KPIs in EDGE, GPRS,

and GSM Voice Key Performance Indicators.

If the operator has not dedicated any capacity for EGPRS, voice blocking is not affected

by data traffic, because voice always has priority over data in such a case.

If dedicated data capacity is used, voice blocking caused by data traffic may occur.

When dedicated data capacity is used, increased voice blocking is fairly easy to notice

compared to a situation where dedicated data capacity is not used. If voice blocking

increases (without increased voice traffic) after a dedicated EGPRS territory is

introduced, it is obvious that the dedicated data capacity causes the voice blocking. This

should trigger a capacity expansion or a review of the number of dedicated data

timeslots in the cells that suffer from blocking. Alternatively, if the voice capacity usage is

very low, the data territory can be increased (if necessary) or the TRX count lowered.

If the dimensioned data capacity is too low, both the data usage and the territory upgrade

rejection ratio can be very high. In this case, the dedicated data capacity should be

increased. If the dimensioned data capacity is too high, the data usage and territory

upgrade ratio are very low. In this case, the dedicated data capacity can be lowered.

If the statistics show that according to the Downlink multislot allocation blocking KPI

there is blocking, but there are no upgrade requests yet, the reason may be that the

territory is smaller than defined in the default settings (circuit-switched (CS) use). The

packet control unit (PCU) will not make an upgrade request. This is because the CS side

returns the default channels back to the packet-switched (PS) territory as soon as the CS

load allows this. This means that territory upgrade rejections may not happen even if

there is a lack of resources.

BTS EDGE Dimensioning BTS traffic monitoring principles

http://localhost/var/www/apps/conversion/tmp/scratch_2/DN7032527-0900d80580a3f9ec.pdf

http://localhost/var/www/apps/conversion/tmp/scratch_2/DN7032527-0900d80580a3f9ec.pdf

Date post:	02-Jun-2018
Category:	Documents
Upload:	jesus-lopez
View:	213 times
Download:	0 times

Nokia_BTS_EDGE_Dimensioning.pdf

Documents