Nokia Gprs Edge

Nokia Siemens Networks GSM/EDGE BSS, rel. RG20(BSS), operating documentation, issue 01

Plan and Dimension

BSC EDGE Dimensioning

DN7032469

Issue 6-0Approval Date 2010-08-25

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The information in this document is subject to change without notice and describes only the product defined in the introduction of this documentation. This documentation is intended for the use of Nokia Siemens Networks customers only for the purposes of the agreement under which the document is submitted, and no part of it may be used, reproduced, modified or transmitted in any form or means without the prior written permission of Nokia Siemens Networks. The documentation has been prepared to be used by professional and properly trained personnel, and the customer assumes full responsibility when using it. Nokia Siemens Networks welcomes customer comments as part of the process of continuous development and improvement of the documentation.

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Nokia Siemens Networks will correct errors in this documentation as soon as possible. IN NO EVENT WILL Nokia Siemens Networks BE LIABLE FOR ERRORS IN THIS DOCUMENTA-TION OR FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO SPECIAL, DIRECT, INDI-RECT, 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.

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Copyright © Nokia Siemens Networks 2010. All rights reserved

f Important Notice on Product Safety Elevated voltages are inevitably present at specific points in this electrical equipment. Some of the parts may also have elevated operating temperatures.

Non-observance of these conditions and the safety instructions can result in personal injury or in property damage.

Therefore, only trained and qualified personnel may install and maintain the system.

The system complies with the standard EN 60950 / IEC 60950. All equipment connected has to comply with the applicable safety standards.

The same text in German:

Wichtiger Hinweis zur Produktsicherheit

In elektrischen Anlagen stehen zwangsläufig bestimmte Teile der Geräte unter Span-nung. Einige Teile können auch eine hohe Betriebstemperatur aufweisen.

Eine Nichtbeachtung dieser Situation und der Warnungshinweise kann zu Körperverlet-zungen und Sachschäden führen.

Deshalb wird vorausgesetzt, dass nur geschultes und qualifiziertes Personal die Anlagen installiert und wartet.

Das System entspricht den Anforderungen der EN 60950 / IEC 60950. Angeschlossene Geräte müssen die zutreffenden Sicherheitsbestimmungen erfüllen.

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Table of ContentsThis document has 62 pages.

Summary of changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1 BSC EDGE dimensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

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

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

4 Prerequisites for BSC EDGE dimensioning . . . . . . . . . . . . . . . . . . . . . . 13

5 BSC capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145.1 EGPRS-related BSC elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

6 Dimensioning process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216.1 Dimensioning of network elements and interfaces . . . . . . . . . . . . . . . . 216.2 BSC EDGE dimensioning process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256.3 Inputs for BSC EDGE dimensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . 276.3.1 Network capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276.3.1.1 Dynamic Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276.3.1.2 Packet Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316.3.2 Input from Abis and BTS dimensioning . . . . . . . . . . . . . . . . . . . . . . . . . 326.4 PCU calculations for BSC EDGE dimensioning. . . . . . . . . . . . . . . . . . . 336.5 Outputs of BSC EDGE dimensioning. . . . . . . . . . . . . . . . . . . . . . . . . . . 366.6 Evaluation of the BSC dimensioning results . . . . . . . . . . . . . . . . . . . . . 37

7 Example of BSS connectivity dimensioning. . . . . . . . . . . . . . . . . . . . . . 387.1 BSS connectivity dimensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387.2 Dimensioning inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407.3 Radio interface capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427.3.1 Configuration before GPRS/EDGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427.3.2 GPRS/EDGE deployment scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . 437.3.3 Available capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437.3.4 Required capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467.4 Connectivity capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477.4.1 Default GPRS capacity (CDEF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477.4.2 EDAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477.4.3 PCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507.4.3.1 Dynamic Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507.4.3.2 Packet Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547.4.4 Gb link dimensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547.5 Results of BSS connectivity dimensioning. . . . . . . . . . . . . . . . . . . . . . . 577.6 Impact of Downlink Dual Carrier on BSS connectivity dimensioning . . . 58

8 BSC traffic monitoring principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

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List of FiguresFigure 1 Available data capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Figure 2 Required data capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Figure 3 PCUs and BCSUs in the BSC2i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Figure 4 Available data capacity process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Figure 5 Required data capacity process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Figure 6 BSC dimensioning flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Figure 7 Needed PCU cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Figure 8 BSC redimensioning process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Figure 9 EDGE dimensioning phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Figure 10 Site configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Figure 11 2+2+2 configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Figure 12 4+4+4 configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Figure 13 E1 setup for 2+2+2 and 4+4+4 configurations . . . . . . . . . . . . . . . . . . . . 42Figure 14 RLC/MAC data rate dependency on signal level and C/I . . . . . . . . . . . . 43Figure 15 Territories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Figure 16 TRXs grouped by function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Figure 17 TRXs grouped by cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Figure 18 PCU calculation formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51Figure 19 PCU calculations for BSS connectivity dimensioning . . . . . . . . . . . . . . . 52Figure 20 PCU calculation for Packet Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54Figure 21 Number of DAPs (~BTS sites) per PCU2-E (PCU Abis channels utilisation

rate of 90%) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59Figure 22 Number of DAPs (~BTS sites) per PCU2-E (PCU Abis channels utilisation

rate of 70%) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

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List of TablesTable 1 Input parameters for BSC EDGE dimensioning . . . . . . . . . . . . . . . . . . 13Table 2 Output of BSC EDGE dimensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Table 3 BSC comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Table 4 Maximum number of BCSUs per BSC and PCUs per BCSU . . . . . . . . 15Table 5 Abis configuration examples for PCU2-D . . . . . . . . . . . . . . . . . . . . . . . 17Table 6 Abis configuration examples for PCU2-E with Flexi BSC . . . . . . . . . . . 17Table 7 PCU2-D capacity with Packet Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Table 8 PCU2-E capacity with Packet Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Table 9 Gb interface connectivity for different PCU types . . . . . . . . . . . . . . . . . 18Table 10 Connectivity of the first generation PCU (PCU1) . . . . . . . . . . . . . . . . . 28Table 11 Connectivity of the second generation PCU (PCU2) . . . . . . . . . . . . . . 29Table 12 Connectivity of the PCU units in Packet Abis . . . . . . . . . . . . . . . . . . . . 31Table 13 CSD and CSU parameter setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Table 14 BTS multiplexing factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48Table 15 EDAP sizes with different configurations . . . . . . . . . . . . . . . . . . . . . . . 48Table 16 TRXs grouped by function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Table 17 TRXs grouped by cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Table 18 Different configurations and their Abis and RTSL load . . . . . . . . . . . . . 52Table 19 Possible PCU configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Table 20 Example of the k factor for the Gb link . . . . . . . . . . . . . . . . . . . . . . . . . 55Table 21 Dimensioning results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Table 22 Radio interface setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Table 23 PCU usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

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BSC EDGE Dimensioning Summary of changes

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Summary of changesChanges between document issues are cumulative. Therefore, the latest document issue contains all changes made to previous issues.

Changes made between issues 6-0 and 5-0Chapter BSC capacity:

• Information on Flexi BSC (RG20) and new Exchange Terminals has been added to the table BSC comparison.

• Tables with capacity of PCU2-D and PCU2-E in Packet Abis added to the section EGPRS-related BSC parameters.

• New topic GCTF in PCU has been created. • Information about Exchange Terminals for Packet Transport added to topic

Exchange Terminals, Flexi BSC configuration updated.

Chapter Dimensioning Process

• Information about Packet Abis has been added to sections Network Capability and PCU calculation for BSC EDGE dimensioning

Changes made between issues 5-0 and 4-1Chapter BSC capacity:

• Information on Flexi BSC has been added to table BSC comparison and all the topics under section EGPRS-related BSC elements.

• Information on the PCU2-E plug-in unit has been added to table BSC comparison and topics BSC signalling unit (BCSU), Packet control unit (PCU), and EDAPs in the PCU.

• Information on the ETIP1-A plug-in unit has been added to topic Exhange Terminal. The contents of the topic have also been revised.

• Information on BSS21226: Asymmetrical PCU HW Configuration has been added to topic BSC signalling unit (BCSU).

• Table Maximum number of BCSUs per BSC and PCUs per BCSU has been added to topic BSC signalling unit (BCSU).

• Table Abis configuration examples (PCU, PCU-S) has been replaced by tables Abis configuration examples for PCU2-D and Abis configuration examples for PCU2-E with Flexi BSC in topic Packet control unit (PCU).

Chapter Dimensioning of network elements and interfaces: A note on BSS21226: Asym-metrical PCU HW Configuration has been added to section Available data capacity strategy.

Chapter Inputs for BSC EDGE dimensioning:

• Information on Flexi BSC and the PCU2-E plug-in unit has been added to section Network capabilities.

• The contents of section Input from Abis and BTS dimensioning have been revised.

Chapter Example of BSS connectivity dimensioning:

• A note on BSS21226: Asymmetrical PCU HW Configuration has been added to section Connectivity capacity.

• A new section Impact of Downlink Dual Carrier on BSS connectivity dimensioning has been added.

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Summary of changes

Changes made between issues 4-1 and 4-0Information on the maximum EDAP size has been updated in BSC capacity.

Changes made between issues 4-0 and 3-1Information related to PBCCH and PCCCH has been removed.

Updated PCU connectivity information.

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BSC EDGE Dimensioning BSC EDGE dimensioning

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1 BSC EDGE dimensioningThe aim of these guidelines is to give basic dimensioning information for BSC equipment when there is both circuit-switched (CS) and EGPRS traffic in the radio network. The guidelines are related to EGPRS traffic and, therefore, only BSC hardware or software elements that have an impact on EGPRS traffic have been analysed. Voice traffic volume is not considered in BSC dimensioning and, because of this, Ater and transcoder dimensioning is not included in these guidelines.

The EDGE dimensioning guidelines in the GSM/EDGE operating documentation cover BTS, Abis, BSC, and Gb dimensioning and some parts of pre-planning.

These guidelines are related to 3GPP Release 7, the BSC products BSCi, BSC2i, BSC3i, and Flexi BSC, and to other relevant equipment related to these BSC products.

BSC dimensioning results in specific outputs that are used as input in the next dimen-sioning phase, Gb EDGE dimensioning.

Terms and definitionsThe following terms are used in these guidelines:

GPRS general packet radio service (GPRS) provides packet data radio access for GSM mobile stations. It upgrades GSM data services to allow an interface with local area networks (LANs), wide area networks (WANs), and the Internet.

EDGE Enhanced data rates for GSM evolution (EDGE) enhances GSM networks with 3rd generation-type capabilities. With the new 8-PSK modulations, EDGE is capable of trebling the current GSM radio inter-face data throughputs. EDGE boosts packet-switched (PS) services. Enhanced GPRS (EGPRS) offers up to 59.2 kbit/s on one radio timeslot (RTSL).

GPRS/EDGE Refers to both the GPRS and the EDGE technology.

EDAP In EDGE, the Abis interface has a dynamic part called EGPRS dynamic Abis pool (EDAP). It differs from the GSM transmission networks, where the Abis interface is static. The shared timeslots can be shared by the TRXs belonging to the same BCF.

Master channel A 16 kbit/s channel used for the allocation of an EGPRS channel out of the EDAP in Dynamic Abis. Not a part of the EDAP.

Slave channel A 16 kbit/s channel belonging to an EDAP used for the allocation of extra capacity required by an EGPRS call with a coding scheme that is different from CS-1 or MCS-1.

Related topics

• BTS EDGE Dimensioning • Abis EDGE Dimensioning • Gb EDGE Dimensioning

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Planning process

2 Planning processDimensioning 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. These guidelines 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 configura-tion 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 Siemens Networks 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 Nokia Siemens Networks representative.

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BSC EDGE Dimensioning Key strategies for EDGE dimensioning on air interface

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3 Key strategies for EDGE dimensioning on air interfaceThe 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 capacityAvailable 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 dimension-ing output is the available traffic volume with a defined performance level. Alternatively, you can calculate available capacities for different alternative configurations.

Figure 1 Available data capacity

Required data capacityRequired data capacity strategy is used when you want to design a network that supports the defined amount of traffic and targeted performance level. The dimension-ing inputs are traffic volume, type, and performance requirements. The dimensioning output is the needed amount of traffic dependent hardware and the associated software configurations.

All current resources in a cell

Average voice trafficresource usage

Averageavailableresources

Input information:

Current network configuration

Current equipment'sEDGE capability

Current network's voiceperformance

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

Planned EDGE data resourcesare used for voice trafficwhen needed


EDGE data

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Key strategies for EDGE dimensioning on air interface

Figure 2 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 orare 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

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BSC EDGE Dimensioning Prerequisites for BSC EDGE dimensioning

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4 Prerequisites for BSC EDGE dimensioningInput summaryThe results of BTS EDGE dimensioning and Abis dimensioning are used as the key input for BSC EDGE dimensioning. In addition, you need to check some information of the existing BSC configuration before starting the dimensioning. Table Input parameters for BSC EDGE dimensioning shows the required input information.

(*) Dynamic Abis inputs

(**) Input from Abis dimensioning for Packet Abis

Output summaryThe BSC EDGE dimensioning output is described in table Output of BSC EDGE dimen-sioning. An important part of the dimensioning process is the evaluation of results and iteration, if required. The output is used as the input for Gb EDGE dimensioning.

Input Status/value Activity

BSC variant BSCx Verify (or upgrade)

Packet control unit (PCU) variant

PCUx Verify (or upgrade)

BTS object (typically a cell) Number Verify

Segment (typically a cell of several BTS objects)

Number Verify

Transceiver (TRX) Number Verify

Base control function (BCF) Number Verify

EGPRS dynamic Abis pool (EDAP) (*)

Number (size) Abis dimensioning

Associated BTSs per EDAP (*)

Number Abis dimensioning

Radio timeslots (RTLSs) in the BTSs

Number (size) Abis dimensioning

Abis bandwidth (**) Number (size) Abis dimensioning

Table 1 Input parameters for BSC EDGE dimensioning

Output Value

BSC Type

PCU Number

Gb interface Number/size

Table 2 Output of BSC EDGE dimensioning

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BSC capacity

5 BSC capacityThe BSC needs enough capacity for the Abis and A interfaces and for the internal pro-cessing of CS and PS traffic because all CS (erlang) and PS (Mbit/s) traffic from the radio network goes through the BSC to the core network.

The capacity of different BSC hardware/software releases is usually compared by using the maximum values of TRXs or the number of Abis channels for GPRS/EDGE use to be connected or delivered through the BSC. The capacity of BSCi, BSC2i, BSC3i, and Flexi BSC is presented in table BSC comparison.

* The maximum number of 504 BCF objects is supported in BSC3i 660 with AS7-C and GSW1KB hardware.

** Only applies to PCU2-D

*** Only applies to PCU2-E

**** Active interfaces. Doubled for redundancy: 12 + 12 or 16 + 16.

***** Number of BCFs depends of the number of TRXs => if 4200 TRXs are used then 180 BCFs can be used to leave enough control channels for transmission and signalling (6000 instances for TRXSIG and OMUSIG can be handled in total)

Flexi BSC (RG20)

Flexi BSC (RG10)

BSC3i 2000

BSC3i 1000

BSC3i 660 BSC2i BSCi

Max. number of TRXs

4200(*****) 3000 2000 1000 660 512 512

Max. number of base control func-tions (BCFs)

3000(*****) 3000 2000 1000 504* 248 248

Max. number of BTS objects

3000 3000 2000 1000 660 512 512

Max. number of traffic channels (TCHs)

33600 24000 16000 8000 5280 4096 2048

Max. number of logical PCUs

30+5 60+10**

30+5***

100+10**

30+3***

50+10**

15+3***

24+4

6+1***

16+2 8+1

Max. number of BSC signalling units (BCSUs)

6+1 6+1 10+1 5+1 6+1 8+1 8+1

Max. number of E1/T1 interfaces

800 800 800 384 256 144 88

Max. number of STM-1/OC-3 interfaces****

16 16 16 16 - - -

Max. number of ETIP units

8 8 8 8

Max. number of ETP units (******)

10 10 10 4

Traffic (Erl) 25200 18000 11880 5940 3920 3040 3040

Table 3 BSC comparison

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BSC EDGE Dimensioning BSC capacity

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****** Active units: 6 for Packet Abis + 4 for AoIP in Flexi BSC/BSC3i 2000 and 2 for Packet Abis + 2 for AoIP in BSC3i 1000

Note that STM-1/OC-3 interfaces can also be used together with E1/T1 interfaces. This gives the highest connectivity figures. However, it is not possible to have all the 800 E1/T1 and 16 STM1-/OC-3 interfaces in use at the same time.

For more information on the BSC, see:

• Product Description of BSC2i and BSCi High Capacity Base Station Controller • Product Description of BSC3i High Capacity Base Station Controller • Product Description of Flexi BSC

5.1 EGPRS-related BSC elementsTo set up the dimensioning, a BSC audit needs to take place. The aim of the audit is to verify the existing configuration, that is, the BSC variant and the number of BCSUs and PCUs. The BSC variant and different elements define the connectivity to the BTS which, at the end, may affect the BTS configuration and the Gb configuration. From this point of view, the EDGE network dimensioning is an iterative process.

The following are the main EGPRS traffic related functional units of a BSC:

Bit group switch (GSWB)For information on the GSWB, see Base Station Controller in BSS Description and Bit Group Switch in Product Description of BSC3i High Capacity Base Station Controller.

BSC signalling unit (BCSU)Table Maximum number of BCSUs per BSC and PCUs per BCSU shows how many BCSU units as well as PCU units per BCSU the different BSC types can have at the most.

* Exception: If PCU2-E is used in BSC3i 1000/2000, the number of PCU2-Es per BCSU is three at the maximum.

** Exception: If PCU2-E is used in BSC3i 660, only one PCU2-E can be equipped per BCSU.

Figure PCUs and BCSUs in the BSC2i shows an example layout of BCSU cartridges and PCU cards in BSC2i, where two PCU cards are implemented in one BCSU.

BSC type BCSUs per BSC

PCUs per BCSU

Flexi BSC 6+1 5

BSC3i 2000 10+1 5*

BSC3i 1000 5+1 5*

BSC3i 660 6+1 2**

BSC2i 8+1 2

BSCi 8+1 1

Table 4 Maximum number of BCSUs per BSC and PCUs per BCSU

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Figure 3 PCUs and BCSUs in the BSC2i

Possible BSC configurations:

• One or two PCU1 units in every BCSU in BSC2i or BSC3i 660. • One PCU1 and one PCU2 unit in every BCSU in BSC2i or BSC3i 660. • One or two PCU2 units in every BCSU in BSC2i or BSC3i 660.

In BSCi, one PCU1 or PCU2 unit can be configured in every BCSU. • One to five PCU2 units in every BCSU in BSC3i 1000/2000 and Flexi BSC.

If you are using BSS21226: Asymmetrical PCU HW Configuration, you can equip each BCSU with a different number and type of PCU plug-in units according to the actual traffic needs you have. You can also mix different PCU HW variants in the same BCSU track or leave a BCSU track empty when a PCU is not needed. For more information, see Creating and connecting the PCU in Activating and Testing BSS90006: GPRS.

Packet control unit (PCU)For both Abis implementations - Dynamic Abis and Packet Abis - the PCU variant limits the maximum number of radio timeslots that can be connected to a PCU plug-in unit simultaneously. For more information on the capacity of different PCU variants, see tables Connectivity of the first generation PCU (PCU1) and Connectivity of the second generation PCU (PCU2) in Inputs for BSC EDGE dimensioning.

In case of Dynamic Abis the PCU variant also limits the maximum number of Abis chan-nels. Tables Abis configuration examples for PCU2-D and Abis configuration examples for PCU2-E with Flexi BSC give examples of GPRS/EGPRS radio timeslot (RTSL) con-figurations when EDAP channels are also used.

Two PCU HW inevery BCSU forhigh EDGE traffic

PSA20PSFP

SW

1C

SW

1C

CL

OC

MC

MU

MC

MU

OM

U

WD

DC

WD

DC

ET

5C

ET

5C

BC

SU

BC

SU

BC

SU

PSA20PSFP

ET

5C

ET

5C

BC

SU

BC

SU

BC

SU

ET

5C

ET

5C

CLA

C

ET

5C

BC

SU

BC

SU

BC

SU

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In Packet Abis concept of EDAP is removed thus PCU allocation algorithm is modified. Connectivity is maintained but definition of “connectivity” is modified as PCU resources

GPRS (16 kbit/s) channels

EGPRS (16 kbit/s) master channels

EDAP (16 kbit/s) slave channels

Total number of channels

Coding

256 - - 256 CS1&2

- 128 128 256 MCS-5

- 64 192 256 MCS-7

64 64 128 256 MCS-6

- 51 204 255 MCS-9

Table 5 Abis configuration examples for PCU2-D

GPRS (16 kbit/s) channels

EGPRS (16 kbit/s) master channels

EDAP (16 kbit/s) slave channels

Total number of channels

Coding

1024 - - 1024 CS1&2

- 512 512 1024 MCS-5

- 256 768 1024 MCS-7

256 256 512 1024 MCS-6

- 204 816 1024 MCS-9

Table 6 Abis configuration examples for PCU2-E with Flexi BSC

RTSL Coding

256 CS-1&2

128 MCS-5

85 MCS-6

64 MCS-7

51 MCS-9

Table 7 PCU2-D capacity with Packet Abis

RTSL Coding

1024 CS-1&2

512 MCS-5

340 MCS-6

256 MCS-7

204 MCS-9

Table 8 PCU2-E capacity with Packet Abis

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are only needed for RTSLs (and not for “Abis subchannels” to which no attention is thus paid). The PCU variant depends on your needs and the PCU usage percentage has to be decided. Nokia Siemens Networks recommends that you consider 70% utilisation in dimensioning calculation as an average. The actual utilisation in each PCU may vary from 60% to 80%.

Each logical PCU can be connected to the SGSN to provide EGPRS services in the cells controlled by the PCU. The Gb interface can be one of the following types:

• Gb over IP: One PCU can be connected to one SGSN. The IP interface for a PCU can be either IPv4 or IPv6 but not both.

• Gb over frame relay (FR): The PCM interfaces for the frame relay are routed by the GSWB in the BSC to the PCU.

A PCU can be connected to the SGSN either via Gb over FR or Gb over IP interface, but not simultaneously via both interfaces. Gb over IP can be used with PCU1 and PCU2 units.

Table Gb interface connectivity for different PCU types shows the PCU limitations (in software licences and transmission hardware) for the Gb interface towards the SGSN when Gb over FR is used. The table shows the physical PCU plug-in units. Note that there are two logical PCUs in PCU-B and PCU2-D and Packet Abis is supported only in PCU2-D and PCU2-E.

On Gb over IP, the bandwidth of the interface does not limit the throughput.

The maximum rate of one frame relay bearer channel is 31 x 64 kbit/s (ETSI) or 24 x 64 kbit/s (ANSI). Therefore, the maximum Gb throughput requires multiple bearer chan-nels. For example, in the ANSI environment, the Gb interface must be split between two physical ET ports to support the maximum capacity of 32 x 64 kbit/s.

If you are using the PCU2-E plug-in unit in a Flexi BSC, it is possible to create FR NS-VCs with 16 bearer channels per PCU2-E. The maximum number of bearers for the other PCU types is four. Note that on PCU2-E, the bearers must fit on four internal PCM circuits of 32 x 64 kbit/s each. The absolute maximum throughput is achieved with a con-figuration of 8 x 16 x 64 kbit/s.

Note that the WAN band needed for Gb traffic is determined on the basis of the Gb traffic in the BSC site. The IP connection may be used by one or more BSC(s) on the same site.

EDAPs in the PCU

PCU type BSC type Gb over FR

PCU BSCi, BSC2i 32 x 64 kbit/s

PCU-S BSCi, BSC2i 32 x 64 kbit/s

PCU-T BSCi, BSC2i 32 x 64 kbit/s

PCU-B BSC3i 2 x 32 x 64 kbit/s

PCU2-U BSC2i 32 x 64 kbit/s

PCU2-D BSC3i, Flexi BSC 2 x 32 x 64 kbit/s

PCU2-E BSC3i 2 x 32 x 64 kbit/s

Flexi BSC 4 x 32 x 64 kbit/s

Table 9 Gb interface connectivity for different PCU types

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The optimal size of the EDAP is planned in Abis EDGE Dimensioning. The following PCU boundary conditions are taken into account:

• The maximum number of Abis channels (16 kbit/s) in the PCU2-E is 512 (in BSC3i) or 1024 (in Flexi BSC). In all the other PCU1 and PCU2 variants, the maximum is 256 channels.

• The EDAP size can be 1 to 29 TSLs (64 kbit/s) in a Flexi EDGE BTS. In UltraSite and MetroSite BTSs, the size can be 1 to 12 TSLs.

• The recommended number of EDAPs in the PCU1 variants is 1, 2, 4, or 8. With the PCU2, the recommendation is 1-8 in the PCU2-D/U and 1-30 in the PCU2-E. With the PCU1 variants and PCU2-D/U, the maximum number of EDAPs is 16, whereas with PCU2-E, it is 32 (in BSC3i) or 60 (in Flexi BSC).The rule for the recommended number of EDAPs guarantees the same amount of resources for each equally weighted EDAP within the PCU. Other configurations may be used to increase PCU connectivity. However, the PCU resources might be distributed unevenly between the EDAPs and, therefore, some of the cells might have slightly different performance compared to the others. To ensure that the most important cells get more resources than the less important ones, the weight of the EDAP can be tuned. The weight is the number of 16 kbit/s EDAP channels plus the total number of RTSLs on default territories associated to the EDAP. One way to increase/decrease the relative weight of an EDAP is to increase/decrease the default territory by one in the most/least important cell which is associated to the EDAP.

• The sum of EDAP sizes in the PCU2-E is 104 TSLs (in BSC3i) or 204 TSLs (in Flexi BSC). In all the other PCU1 and PCU2 variants, the sum is no more than 51 TSLs. However, if for some reason all 16 EDAPs are in use, the sum of the EDAP sizes is 48 TSLs at the maximum.

GCTF in PCU

In Packet Abis concept of EDAP is removed. The new parameter is required by resource allocation algorithm in PCU when Packet Abis is in use. For that purpose the GPRS capacity throughput factor (GCTF) is introduced to distinguish between cells where con-nectivity shall be guaranteed (GCTF set to low value) and those where high throughput is expected (GCTF set to high values). Such differentiation is necessary to optimize resource allocation at system start-up (and after re-configuration) as well as for optimum hunting of idle resources during territory upgrades. For legacy systems (i.e. with Dynamic Abis) a trade-off between connectivity cells and throughput cells is managed by allocation of EDAPs with different size (but in Packet Abis, due to removal of EDAP concept, a new indicator of cells’ „priorities” is needed)

For more information on the PCU, see Packet Control Unit (PCU) under Requirements for GPRS/EDGE in EDGE System Feature Description.

Exchange TerminalAll 2.048 Mbit/s (in the ETSI environment) or 1.544 Mbit/s (in the ANSI environment) interfaces for the MSC, SGSN, and BTSs are connected to the Exchange Terminals (ET). The ETs adapt the external PCM circuits to the GSWB. The BSC variants BSC3i 1000/2000 and Flexi BSC can also have SDH/Sonet exchange terminals (SET) for STM-1/OC-3 interfaces, and BSC3i 1000/2000 and Flexi BSC can have Ethernet exchange terminals (EET) for Gigabit Ethernet (PWE3) interfaces and also native IP transport is supported by BSC3i 1000/2000 and Flexi BSC with new ET plug-in unit type which is Exchange Terminal for Packet Transport called ETP.

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In BSC2i, a second PCU can be added to all configured BCSUs as a GPRS/EGPRS extension. The addition of a second PCU board implies the extension of the GSWB from 192 to 256 PCMs and an optional E1/T1 extension from 112 to 144 (72 ET2E/A units).

The ETs of BSC3i 660 are housed in ET4C-B cartridges. In the maximum configuration of BSC3i 660, one ET4C-B cartridge can contain up to 32 ET4 plug-in units. The total number of ET4 plug-in units in BSC3i 660 with GSW1KB is 64, and the total number of PCMs is 256.

The ETs of BSC3i 1000/2000 are housed in GT6C-A and/or GT4C-A cartridges. In the maximum configuration of BSC3i 1000, two GT4C-B cartridges can contain up to eight ET16 plug-in units and two GT6C-A cartridges up to four ET16 plug-in units. The total number of the ET16 plug-in units is 24, which gives the total of 384 PCMs. In the maximum configuration of BSC3i 2000, up to 50 ET16 plug-in units can be spread out in the GT6C-A and GT4C-A cartridges, giving the total of 800 PCMs.

The GT4C-A cartridge of BSC3i 1000/2000 can also contain a GTIC module for up to 16 ETS2 plug-in units. They can handle up to 16 x 63 E1s/16 x 84 T1s in maximum. Also up to 8 ETIP units can be installed in GTIC cartridge in BSC3i 1000/2000.

The ETs of a Flexi BSC are housed in SGC1C-A cartridges containing GTIC or ETC modules. The GTIC can be shared between ETS2 and/or ETIP1-A and/or ET16 and/or ETP plug-in units, whereas the ETC can contain only ET16 and/or ETP plug-in units.

When Flexi BSC in a new delivery (always 1 cabinet configuration) then:

• GTIC and ETC can be installed. • 1 GTIC offers 8 slots that can be shared between ETS2 and/or ETIP and/or ET16

and/or ETP. • 2 ETC offers in total 17 slots that can be used by ET16 and ETP. • Up to 50 ET16 can be installed in the configuration, in such case there are no slots

for other ET types • Up to 8+8 ETS2 can be installed • Max 16 SET can be active, each active SET handles equivalence of 63 E1 or 84 T1. • Up to 8+8 ETIP can be installed. • Each active ETIP handles up to 126 E1 or 168 T1 . Note that the ETIP capacity

depends on several parameters. For more information, see Ethernet based trans-port / CESoPSN in BSSTransmission Configuration.

• Up to 10 active ETP can be installed where 6 ETP for Packet Abis + 4 ETP-A for AoIP.

When Flexi BSC is an upgrade (1 or 2 cabinets in use) then:

• Basic cabinet:– GTIC only installed– GTIC can be either shared between ETS2 and ETIP and ETP or used by ET16

• Extension cabinet may be only in use in upgraded Flexi BSC when • Either more than 16 ET16 are desired (i.e. more than 256 E1/T1 lines) or some ET16

are desired in addition to ETS2/ETIP/ETP– In such case ETS2/ETIP/ETP are installed in the base cabinet and ET16 in the

extension one– In the extension cabinet also ETP plug-in units (those that does not fit in GTIC

due to lack of slots) can be installed • Mixture of ET16 with ETS2 and ETIP and ETP is allowed provided that 2 cabinets

are in use

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BSC EDGE Dimensioning Dimensioning process

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6 Dimensioning process

6.1 Dimensioning of network elements and interfacesThe 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 strategyThe dimensioning process of the available data strategy is illustrated in figure Available data capacity process.

Figure 4 Available data capacity process

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.The dimensioning process results in throughput/RTSL, territory size/BTS, guaran-teed/not guaranteed throughput, RTSL configuration of TRXs, numbers of TRXs per cell, and the simulation results.

3. Abis dimensioning

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 SGSNGbAbis

1

2

3 4 5 6

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• 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 feature is 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. • Verify the amount of packet control units (PCUs). • Verify the number of BSC signalling units (BCSU) and exchange terminals

(ETs). • 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. • Verify the needed basic units/SGSN according to the previously calculated gen-

erated 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 strategyThe dimensioning process of the required data strategy is illustrated in figure Required data capacity process.

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Figure 5 Required data capacity process

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, guaran-teed/not guaranteed throughput, TSL configuration of TRXs, number of TRXs/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 feature is 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.

1. Calculate the required TSL count based on required datacapacity and throughput.

2. Calculate the required amount of TRX hardware.3.-6. Dimension the rest of the elements according to the

required capacity calculation done in step 1.

TSL

TRX

Cell

BTS

PCU

BSC

Basic unit

2G SGSNGbAbis

1

2

3 4 5 6

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• Calculate the needed amount of PCUs. • Calculate the number of BCSUs and ETs. • 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 capac-ity.

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.

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6.2 BSC EDGE dimensioning processBSC dimensioning for EGPRS traffic is a straightforward process that starts from EDGE BTS and transmission dimensioning inputs, continues to the dimensioning of the PCU card, and then to the dimensioning of the Gb interface towards the SGSN (see figure BSC dimensioning flow). The number of required Abis and dynamic Abis channels (EGPRS dynamic Abis pool, EDAP), Exchange Terminal (ET) cards, packet control unit (PCU) cards, and Gb interface licences can be calculated from the voice, GPRS, and EGPRS traffic.

Figure 6 BSC dimensioning flow

Before BSC dimensioning work can be started, some decisions related to system, radio network, and BSC configurations have to be made. It is important to know whether the system is European (ETSI) or American (ANSI). In the ANSI standard, for example, transmission is slightly different from the ETSI specifications. Next, the exact BSC software release (the assumption in these guidelines is S15) and BSC product version (the assumption in these guidelines is BSCi, BSC2i, BSC3i, or Flexi BSC) have to be known to identify the maximum Abis, PCU, and Gb capacities for the dimensioning work. When the BSC software release and the BSC product types are known, also the ET, PCU, and Gb interfaces can be selected.

The BSC dimensioning work can be divided into the following steps:

1. Defining the BSC type, software, number of BSC signalling units (BCSUs) and ETs, and limitations.For more information, see Network capability.

2. Collecting inputs from EDGE BTS and transmission dimensioning.For more information, see Input from Abis and BTS dimensioning.

3. Calculating the required number of PCUs.For more information, see PCU calculations for BSC EDGE dimensioning.

EDGE BSC dimensioning

Traffic mix

Total numberof TCHs

Total numberof TRXs

Total numberof BTSs/BCFs

Check PCU typeand limitations

PCU usagepercentage

Total numberof EDAPs *

BH Gb throughputto be handled

PCU-EDAPassociation*

Calculate the neededamount of PCUs

BSC type andSW release

BSC usagepercentage

Total numberof BSCUs

Total number of ETs

Gb interface FR or IP

Gb capacity ETSIor ANSI

Gb usagepercentage

User data *Overhead(%)

Inputs from Gbplanning

(*) EDGE transmission network planning:the calculation of the EDAP size

Total number ofPCUs

Type of PCUs

Total number ofBCSUs

Total number ofGb interfaces

Triggers forredimensioning

Step 3:BSC

Step 4:Gb interface

Step 5:Outputs

Step 2:PCU

Step 1:Inputs from BTSEDGE dimensioning

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4. Calculating the required number of Gb links for SGSN traffic.Gb traffic now also includes Gb overhead. Gb interface dimensioning is described in Gb EDGE dimensioning. In these guidelines, the assumption is to use Gb over FR. The number of the Gb interfaces can be calculated, as can the number of the required ET cards, depending on the standard (ETSI/ANSI).Always use the same usage criteria for the Gb interface and ET card as for the other BSC elements. The Gb interface capacity should be in line with the EDAP size.

5. Defining the BSC configuration and evaluating the results (redimensioning).

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6.3 Inputs for BSC EDGE dimensioningThe basic voice dimensioning of the BSC depends mainly on the number of base stations (BTSs) and transceivers (TRXs) connected to the BSC. For information on con-straints related to the BSC signalling unit (BCSU), see BSC signalling unit (BCSU).

EGPRS traffic (kbit/s) is a key element in Abis, packet control unit (PCU), and Gb dimen-sioning. Because of very different coding schemes and throughput rates, it is extremely relevant to know whether the traffic is GPRS or EDGE. Therefore, the main decision needed for BSC dimensioning is the number of timeslots used, on average, for EGPRS traffic during a busy hour and the deviation of traffic between the peak and minimum values (this also provides the difference between the peak and average values).

In these guidelines, it is assumed that the TRX and BTS limitations per a PCU card are based on the 75% rule, where 25% of the capacity is reserved for future extensions.

The same 75/25% rule is also used for the calculations of the maximum throughputs of the PCU cards and Abis and Gb/IP interfaces, but for budgetary dimensioning, it is rec-ommended to use 70/30% reservation. The actual usage of the CPU may vary from 50% to 80% in typical usage scenarios.

6.3.1 Network capability

6.3.1.1 Dynamic Abis

BSC configuration

• BSC variant (BSCi, BSC2i, BSC3i, Flexi BSC) • PCU variant (PCU, PCU-B, PCU-S, PCU-T, PCU2-D, PCU2-U, PCU2-E) • installed software (BSS11.5, BSS12, BSS13, S14) • Abis channels

• size and count of the EGPRS dynamic Abis pools (EDAPs) • total number of the radio timeslots (TSLs) in EGPRS territories in all TRXs under

the PCUs • total number of the BTS objects (sectors) with GENA = Y under the PCUs • total number of the SEGMENTs configured under the PCUs • total number of the TRXs with GTRX = T under the PCUs

PCU connectivityIn PCU dimensioning, you need to take into account the following restrictions listed in tables Connectivity of the first generation PCU (PCU1) and Connectivity of the second generation PCU (PCU2). In addition, note that that the maximum theoretical number of dynamic Abis pools in the BSC is:

• 256 in BSC2i (16 EDAPs in each PCU and 16 PCUs in each BSC2i) • 384 in BSC3i (16 EDAPs in each PCU and 24 logical PCUs in each BSC3i). From

BSS12 onwards, there can be 1600 dynamic Abis pools in BSC3i (16 EDAPs in 100 logical PCUs).

• 1800 in Flexi BSC (60 EDAPs in each PCU and 30 logical PCUs in each Flexi BSC)

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PCU variant Logical PCUs/board

BSC type Capability Connectiv-ity

PCU 1 BSCi, BSC2i

Max. BTSs 64

Max. TRXs 128

Max. SEGs 64

Max. radio TSLs

128

Max. Abis channels at 16 kbps

256

Max. Gb channels at 64 kbps

32

Max. EDAPs 16*

PCU-S 1 BSCi, BSC2i

Max. BTSs 64

Max. TRXs 128

Max. SEGs 64

Max. radio TSLs

128


256


32

Max. EDAPs 16*

PCU-T 1 BSCi, BSC2i

Max. BTSs 64

Max. TRXs 128

Max. SEGs 64

Max. radio TSLs

256


256


32

Max. EDAPs 16*

Table 10 Connectivity of the first generation PCU (PCU1)

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*The recommended number of EDAPs is 1, 2, 4, or 8.

PCU-B 2 BSC3i Max. BTSs 2 x 64

Max. TRXs 2 x 128

Max. SEGs 2 x 64

Max. radio TSLs

2 x 256


2 x 256


2 x 32

Max. EDAPs 16*



PCU2-U 1 BSCi, BSC2i

Max. BTSs 128

Max. TRXs 256

Max. SEGs 64

Max. radio TSLs

256


256


32

Max. EDAPs 16*

Table 11 Connectivity of the second generation PCU (PCU2)



Table 10 Connectivity of the first generation PCU (PCU1) (Cont.)

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*The recommended number of EDAPs is 1-8 in the PCU2-D/U and 1-30 in the PCU2-E.

PCU2-D 2 BSC3i, Flexi BSC

Max. BTSs 2 x 128

Max. TRXs 2 x 256

Max. SEGs 2 x 64

Max. radio TSLs

2 x 256


2 x 256


2 x 32

Max. EDAPs 16*

PCU2-E 1 BSC3i Max. BTSs 256

Max. TRXs 512

Max. SEGs 128

Max. radio TSLs

512


512


2 x 32

Max. EDAPs 32*

Flexi BSC Max. BTSs 384

Max. TRXs 1024

Max. SEGs 256

Max. radio TSLs

1024


1024


4 x 32

Max. EDAPs 60*



Table 11 Connectivity of the second generation PCU (PCU2) (Cont.)

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6.3.1.2 Packet Abis

BSC configuration

• BSC variant (BSC3i 1000/2000, Flexi BSC (RG10), Flexi BSC (RG20) ) • PCU variant (PCU2-D, PCU2-E) • Installed software (S15) • Total number of the radio timeslots (TSLs) in EGPRS territories in all TRXs underthe

PCUs • Total number of the BTS objects (sectors) with GENA = Y under the PCUs • Total number of the SEGMENTs configured under the PCUs • Total number of the TRXs with GTRX = T under the PCUs

PCU connectivityBecause Packet Abis requires PCU2-D or PCU2-E and EDAP concept is removed from the Abis only the following limits must be taken into account in PCU dimensioning.

PCU variant Logical PCUs/boards


PCU2-D 2 BSC3i, Flexi BSCi

Max. BTSs 2 * 128

Max. TRXs 2 * 256

Max. SEGs 2 * 64

Max. radio TSLs

2 * 256


2 * 32

PCU2-E 1 BSC3i Max. BTSs 256

Max. TRXs 512

Max. SEGs 128

Max. radio TSLs

512


2 * 32

PCU2-E 1 Flexi BSC Max. BTSs 384

Max. TRXs 1024

Max. SEGs 256

Max. radio TSLs

1024


4 * 32

Table 12 Connectivity of the PCU units in Packet Abis

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6.3.2 Input from Abis and BTS dimensioningThe total number and type of the required Exchange Terminal (ET) plug-in units per a BSC needs to be defined based on the realisation of the connectivity on the given inter-face (Abis, Ater, Gb and E1/T1, STM-1/OC-3, CESoPSN, IP) and the required capacity.

Input from Abis and BTS planning:

• number of BTS objects • number of segments • number of TRXs • number of EDAPs (*) • number of associated EDAPs per BTS (*) • size of the radio timeslots in the BTSs • Abis bandwidth (**)

Related topics

• BTS EDGE Dimensioning • Abis EDGE Dimensioning • Gb EDGE Dimensioning

(*): valid only for Dynamic Abis

(**): only in case of Packet Abis

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6.4 PCU calculations for BSC EDGE dimensioningIn the packet control unit (PCU) dimensioning phase, dimensioning inputs (or guide-lines) have to be given to meet the network evolution and quality targets.

First, only a certain maximum number of base stations (BTSs) and transceivers (TRXs) is connected to the PCU cards, and the minimum number of PCU cards can be calcu-lated.

Next, the capacity extension criteria of different EGPRS traffic related elements have to be defined for the future capacity increase resulting from network evolution. In the EDGE dimensioning guidelines, the dimensioning criterion is that a maximum 75% of the total capacity of each configuration can be used and 25% is reserved for future extensions. This usage has to be used for the Exchange Terminal (ET) and PCU cards and for Gb interface licences. Therefore, similar calculations have to be made for the ET cards and Gb interfaces.

It is recommended to leave some of the installed PCUs for future configuration upgrades and use the rest as efficiently as possible. This is achieved by dimensioning the PCUs using the formula in figure Needed PCU cards and the given design rules. Please note that this formula can be used to estimate number of PCU units only for the Dynamic Abis case. For Packet Abis formula must be changed and can be found in next section.

Figure 7 Needed PCU cards

The equation is used to check that the PCU capabilities are not exceeded. In the equa-tion:

• RTSLs is the total number of RTSL in the GPRS and EGPRS territories that are associated to a given logical PCU.

• Abischs is the total number of Abis channels associated both to the master channels and EDAP channels of a given logical PCU. RTSLs + 4 x sum size of all EDAPs in a 64k TSL.

• EDAPs is the total number of EDAPs associated to a given logical PCU.

L = roundup

radioTSLs

max. radio TLSs x U

max

Abischs

max.Abischs x U

EDAPs

max. EDAPs

BTSobjs

max. BTSobjs

SEGs

max. SEGs

max. BHGbThroughput x U

BHGbThroughput

TRXs

max. TRXs

,

,

,

,

,

,

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• BTSobjs is the total number of BTSobjects under SEGments with GENA = Y + other BTSobjects with GENA = Y associated to a given logical PCU.

• SEGs is the total number of SEGments with GENA = Y associated to a given logical PCU.

• TRXs is the total number of TRXs with GTRX = Y associated to a given logical PCU. • BHGbThroughput is the total BHGb capacity required for the PS traffic for a given

logical PCU as a number of 64k TSLs. • U is the chosen degree of the statically allocated PCU Abis resources. An average

of 70% is used for dimensioning calculations. Respectively, 100% - U is left for ter-ritory upgrades.

• L is the number of needed logical PCUs. The maximum object counts are shown in tables BTS and TRX capability of different PCU types and Abis configuration examples (PCU, PCU-S).

The different maximum values in the equation depend on the selected PCU variant. If the PCU variant is PCU-B or PCU2-D (includes two logical PCUs), the number of needed physical cards (N) is (regardless of the installed software version):

N = L/2

For all other PCU variants the number of needed physical cards (N) is:

N = L

PCU dimensioning for Packet AbisIn Packet Abis concept of EDAP is removed thus formula that has been used so far for PCU dimensioning must be appropriately changed. Please note that dimensioning of PCU for Dynamic Abis is exactly the same, and PCUs must be evaluated separately for Packet Abis and Dynamic Abis.

Introduction of new transport concept for Abis interface have direct impact on PCU and for this Abis realization dimensioning is much simpler than before. Following changes has been done:

• Utilization in radio timeslot criteria is recommended to set 50% not 70% like in Dynamic AbisFor RTSL Utilization = 50% which is recommended value (to leave enough capacity for territory upgrade and higher coding scheme/modulation),and PCU2-E which support up to 1024 RTSL, 512 RTSLs is available for cell. Number of cells that can be handled by one PCU is calculated based on the following formula:

With this number of RTSLs one PCU2-E unit can support e.g.:– 256 cells (and this is maximum number of cells that can be served by PCU2-E)

with CDEF=2, which in sum gives 512 RTSL. This “extra small” configuration, in terms of default territory can be used to provide connectivity to very high number of cells.

– 128 cells with default territory = 4, and this configuration is recommended Con-nectivity Cell configuration as it is placed between extra small and medium con-figuration.For both Connectivity Cells configurations recommended CMAX value is 16 (two TRXs) to leave more capacity for Throughput Cell. Please also note that all Con-

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nectivity Cells supports higher peak rates than before (Dynamic Abis) due to lack of EDAP (DSP bandwidth resources is Packet Abis are used for higher coding schemes and territory upgrades and PCU handles the requests in the order of coming)

– Up to 42 cells with CDEF equal to 12 RTSLs. This configuration is example of a Throughput Cell in which higher throughput rate is offered per cell. For this con-figuration recommended EGPRS TRXs is 4 or 5 per cell.

Because EDAP concept is removed in Packet Abis and Abis channels are not in use for this Abis implementation these 2 criteria’s must be also removed from the formula. It means that for Packet Abis following formula must be used.

Utilization for Gb throughput is recommended to set 70% to leave safety margin in case of peak in several BTSs in the same time.

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6.5 Outputs of BSC EDGE dimensioningBSC dimensioning results in specific outputs. These outputs are used as input in the next dimensioning phase, Gb EDGE dimensioning.

Available capacity strategyBSC dimensioning outputs:

• number and type of BSCsNote that if EDGE is deployed into an existing network, the number and type of BSCs is an input.

• number of BSC signalling units (BCSUs) • number and type of packet control units (PCUs) • number of Gb interfaces

Required capacity strategyBSC dimensioning outputs:

• total number and type of BSCs • total number and type of PCUs • total number of BCSUs • total number of Gb interfaces

Triggers for redimensioning:

• too many BTSs per BSC • too many PCUs per BSC • too many radio timeslots/Abis channel per PCU • too many EGPRS dynamic Abis pools (EDAPs) per PCU • too much Gb traffic per PCU

To do in redimensioning:

• Optimise the number of BTSs for each BSC. • Re-estimate traffic to avoid over dimensioning. • Optimise the EDAP size. • Optimise the size of the radio timeslots.

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6.6 Evaluation of the BSC dimensioning resultsThe dimensioning process is often very iterative. If the number of required BSCs is too high, for example, new BTS dimensioning is required: coverage and traffic estimations need to be re-evaluated. A higher BSC usage level may help. Also a new transmission plan, including the optimisation of the number and size of the EGPRS dynamic Abis pools (EDAPs) in Dynamic Abis, has an impact on the number of packet control units (PCUs).

First, only a certain maximum number of base stations and transceivers (TRXs) is con-nected to the PCU cards, and the minimum amount of PCU cards can be calculated. Next, based on the traffic demand coming from the radio network, the final number of required PCU cards is calculated. The average traffic demand is used because we need to take into account the maximum use of the PCU card that future extension needs and peak traffic cause.

The BSC and PCU can be selected according to the dimensioning results, keeping in mind the different possible configurations. For example, because of N+1 redundancy principles one PCU1 or PCU2 plug-in unit is required for each BSC signalling unit (BCSU), the number of activated PCUs is selected according to the dimensioning results. It is important to apply the 75% usage criterion to a fully equipped BSC, for example, BSC2i with 8+1 BCSU and 16+2 PCU units. If, according to the calculations, a full BSC configuration is not needed, a higher usage level can be used. Network growth can be achieved by adding extra hardware when needed.

Figure BSC redimensioning process illustrates what triggers redimensioning and what needs to be done during redimensioning.

Figure 8 BSC redimensioning process

BSC dimensioning

Triggers for redimensioning:-Too many BTSs per BSC-Too many PCUs per BSC-Too much Gb traffic per PCU-New BTS/TRX

To do in redimensioning:-Optimise the number of BTSsunder BSC

-Re-estimate traffic to avoidover dimensioning

-Optimise the EDAP size-Optimise the number ofthe radio timeslots

BSC configurations:-Total number and type of BSCs-Total number and type of PCUs-Total number of BCSUs-Total number of Gb interfaces

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Example of BSS connectivity dimensioning

7 Example of BSS connectivity dimensioning

7.1 BSS connectivity dimensioningThe EDGE dimensioning guidelines include an example of BSS connectivity dimension-ing. The example shows one calculation method for dimensioning the following:

• default GPRS capacity (CDEF)The value of the default GPRS capacity parameter is calculated in chapter Radio interface capacity.

• dynamic Abis pool (DAP) sizeThe size of the EGPRS dynamic Abis pool (EDAP) is calculated in chapter Connec-tivity capacity.

• number of packet control units (PCUs)The number of PCUs is calculated in chapter Connectivity capacity.

• Gb link sizeThe size of the Gb link is calculated in chapter Connectivity capacity.

In addition, a Downlink Dual Carrier (DLDC)-specific BSS connectivity dimensioning example is included in chapter Impact of Downlink Dual Carrier on BSS connectivity dimensioning.

The dimensioning is not based on a detailed network audit with all the configuration, parameter, and software information (such as the BSC types, number of available PCUs, and location area (LA) / routing area (RA) borders). Instead, the dimensioning is based on data about the number of base control functions (BCFs), BTSs, and transceiv-ers (TRXs) with traffic volume assumption of existing circuit-switched (CS) traffic and requirements on packet-switched (PS) data rate (if there is any). Note that SEGMENT is not used in this example.

The BSS connectivity dimensioning example uses PCU1 (except for the DLDC-specific example, which uses PCU2). However, the dimensioning principle applies to both PCU1 and PCU2, and to any variant as far as the variant specific data is used.

The example assumes that radio frequency (RF) dimensioning has already been done and, therefore, the bit rate per radio timeslot has already been defined, as shown in figure EDGE dimensioning phases.

Figure 9 EDGE dimensioning phases

The outcome of the dimensioning is the size of the following:

• dedicated GPRS capacity (CDED) • default GPRS capacity (CDEF) • EDAP • Gb link resources • the number of PCUs needed to handle the resources

RFBit rateper RTSL

Connectivity

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BSC EDGE Dimensioning Example of BSS connectivity dimensioning

Id:0900d805807c2038

When the BSC variant is known, the number of physical PCU plug-in units can be defined. This example is limited to the number of logical PCUs.

In this example, first CDEF and CDED are defined. Then, the EDAP size is calculated, based on CDEF, and the Gb link size is calculated, based on the EDAP size.

This example illustrates two different scenarios for PCU dimensioning:

1. pure dimensioning without mapping the EDAPs to the PCUThis scenario is simple and clear and requires less calculations. In this scenario, a PCU usage (U) percentage of 70 is used. A higher usage value may decrease the accuracy of the dimensioning.

2. partial planning to ensure that the PCU can handle the configurationThis scenario requires more calculations but gives more accurate results. In this scenario, the PCU usage may vary from 60 to 80%, depending on the configuration.

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7.2 Dimensioning inputsThe aim of the dimensioning is to calculate the default GPRS capacity (CDEF), EGPRS dynamic Abis pool (EDAP) size in Dynamic Abis case, number of packet control units (PCUs), and the size of the Gb link because EDGE/GPRS is implemented on top of existing CS voice.

The following inputs are used in the calculation example:

• one BSC with 40 base control functions (BCFs) • three BTSs per BCF • site configurations

• 2+2+2, 25 BCFs: "surrounding area" (light blue in figure Site configurations) – Configuration 1

• 4+4+4, 15 BCFs: "central area" (deep blue in figure Site configurations) – Con-figuration 2

Figure 10 Site configurations • BCF voice traffic

• 2+2+2 site has traffic of 8 Erl per BTS on average • 4+4+4 site has traffic of 18 Erl per BTS on average • blocking criteria is 2%

• data traffic • streaming user support requirement per BTS ~ 50 kbit/s • average data throughput per BTS (by operator):

"central area": 200 kbit/s"surrounding area": 100 kbit/s

• other considerations • average mobile station (MS) multislot support in the network: 4 timeslots (TSLs) • all BTSs and TRXs are EDGE capable • frame relay planned as the Gb implementation

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To simplify the BSS connectivity dimensioning example, it is assumed that all BTSs within the site/BCF have a similar traffic profile. In addition, it is assumed that the data traffic need for the 4+4+4 configuration is higher than for the 2+2+2 configuration. In reality this might not be the case, and some 2+2+2 configurations could have higher data traffic and need for higher data capacity than 4+4+4 configurations.

Note that it is assumed that the given data amount per BTS does not need to be sup-ported simultaneously in all BTSs. This information is used for EDAP and Gb link dimen-sioning.

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7.3 Radio interface capacity

7.3.1 Configuration before GPRS/EDGEFigures 2+2+2 configuration and 4+4+4 configuration show the TRX configurations used in the BSS connectivity dimensioning example.

Figure 11 2+2+2 configuration

Figure 12 4+4+4 configuration

In the 2+2+2 configuration, two radio timeslots (RTSLs) are reserved for uncombined signalling (broadcast control channel (BCCH) and stand-alone dedicated control channel (SDCCH)), while the rest of the RTSLs are full rate RTSLs (no dual rate (DR) / half rate (HR) implemented).

In the 4+4+4 configuration, there are three RTSLs that are used for signalling (one BCCH and two SDCCHs), while the rest of the RTSLs are full rate RTSLs (no DR/HR implemented).

Regardless of the configuration, each base control function (BCF) has its own E1 for transmission.

Figure 13 E1 setup for 2+2+2 and 4+4+4 configurations

TSL0 TSL1 TSL2 TSL3 TSL4 TSL5 TSL6 TSL7

BCCH MBCCH SDCCH TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F

TCH TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F

TSL0 TSL1 TSL2 TSL3 TSL4 TSL5 TSL6 TSL7

BCCH MBCCH SDCCH TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F


TCH SDCCH TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F


0 0

1 TCH0 TCH1 TCH2 TCH3 1 TCH0 TCH1 TCH2 TCH3









1 0 TCH4 TCH5 TCH6 TCH7 1 0 TCH4 TCH5 TCH6 TCH7



1 3 TRXSIG1 TRXSIG2 1 3 TCH0 TCH1 TCH2 TCH3



1 6 BCFSI G 1 6 TCH4 TCH5 TCH6 TCH7

1 7 1 7 TCH0 TCH1 TCH2 TCH3



20 20 TCH4 TCH5 TCH6 TCH7





25 25

26 26

27 27 TRXSIG1 TRXSIG2 TRXSIG3 TRXSIG4

28 28 TRXSIG5 TRXSIG6 TRXSIG7 TRXSIG8

29 29 TRXSIG9 TRXSIG1 0 TRXSIG1 1 TRXSIG1 2

30 30 BCFSIG

31 31Q1 m anagement Q1 management

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7.3.2 GPRS/EDGE deployment scenariosAll the TRXs are GPRS and EGPRS capable, so the following parameter setup is used:

• TRX: GTRX = Y • BTS: GENA = Y, EGENA = Y, CMAX = 100%

The TSL data rate depends on the signal level and interference. The capacity limitations are not taken into account in this example. Figure RLC/MAC data rate dependency on signal level and C/I shows the dependency for two timeslots.

Figure 14 RLC/MAC data rate dependency on signal level and C/I

In the BSS connectivity dimensioning example, the following average EGPRS radio link control (RLC) / medium access control (MAC) TSL data rate is used: 35 kbit/s (BCCH layer).

Typically the best carrier-to-interference ratio (C/I) TRX is preferred for maximum throughput. Depending on the frequency plan, this can be either a BCCH or TCH TRX. In the BSS connectivity dimensioning example, the BCCH TRX is preferred.

7.3.3 Available capacityBefore the calculations, the size of the free RTSL must be defined. Figure Territories shows how two TRXs are divided into territories.

RLC/MAC d ata rate (FTP d own load on 2 TSLs)

0

20

40

60

80

100

120

-65 -70 -75 -80 -85 -90 -95 -100 -105

Sign al l eve l (dBm)

kbp

s

No Interference

C/I 25 dB

C/I 20 dB

C/I 15 dB

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Figure 15 Territories

Free RTSLs between the circuit-switched (CS) and packet-switched (PS) territory are required to serve the immediate incoming CS calls without blocking.

• CS downgrade: If there are less RTSLs free in the CS territory than required, a PS territory downgrade is triggered.

• CS upgrade: A PS territory upgrade can be triggered if at least the required amount of RTSLs are free.

Free TSLs for upgrade and downgrade can be controlled with BSC parameters (see table CSD and CSU parameter setup).

The default value for parameter free TSL for CS downgrade (CSD) is 95%. The default value for parameter free TSL for CS upgrade (CSU) is 4.

In the calculations for 2+2+2 and 4+4+4 configurations, the following free TSL values are used:

TRX 1

TS

TS

= Dedicated GPRS capacity

TS

= Signal l ing

TS = Free TSL for CS

TS = Default GPRS capacity

GENA

CMAX

TS

TS

TSTS

TS

Territory border

TRX 2

TRX 1 BCCH TS TS TS TS TS TSSDCCH

TS TS TS TSTS TS TSTS

TS

TS

TSTS

TS TS

TS

TS

= CS territory

= GPRS/EDGE territory/additional capacityTS

TS

GTRX

GTRX

EGENA

BCCH

TSL number after CS downgrade

TRX number 1 2 3 4 5

Free TSLs for CS down-grade (%) (CSD)

70 0 0 0 1 1

95 1 1 1 2 2

99 1 1 2 2 2

TSL number after CS upgrade

TRX number 1 2 3 4 5

Free TSLs for CS upgrade (sec.) (CSD)

1 0 1 1 1 2

4 1 2 2 3 4

7 1 2 3 4 5

10 2 3 4 5 6

Table 13 CSD and CSU parameter setup

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• mean free RTSLs for two TRXs: (1+2)/2 → 1.5 • mean free RTSLs for four TRXs: (3+2)/2 → 2.5

Calculations for the 2+2+2 configurationBTS capacity calculations

• 2 TRXs, 16 RTSLs • 2 RTSLs for signalling • 14 RTSLs for CS traffic

• CS busy hour (BH) traffic: 8 Erl per BTS (all BTSs have the same amount of BH traffic)

• erlang B table: 1.7% CS blocking during BH • mean free RTSLs = 1.5 • average RTSLs available for PS traffic during CS BH:

amount_of_TRXs x 8 - signalling_RTSLs - CS_BH_traffic-free_RTSLs = 2 x 8 - 2 - 8 - 1.5 = 4.5 RTSLs

• average PS traffic during CS BH:4.5 x 35 kbit/s = 157.5 kbit/s (> 100 kbit/s)

This means that we are well above the average data throughput per BTS (required by the operator), which is 100 kbps for the "surrounding area."

Default territory calculations

• mobile station (MS) multislot capability (4 RTSLs) • data throughput: 100 kbit/s • radio interface: 35 kbit/RTSL

→ RTSLs to support 100 kbit/s → 100/35 = 2.9 TSLs ~ 3 RTSLs

Default territory size:

max(MS_multislot, traffic) = max(4, 3) = 4 RTSLs

Calculations for the 4+4+4 configurationBTS capacity calculations

• 4 TRXs, 32 RTSLs • 3 RTSLs for signalling • 29 RTSLs for CS traffic

• CS BH traffic: 18 Erl per BTS (all BTSs have the same amount of BH traffic) • erlang B table: 0.4% CS blocking during BH • mean free RTSLs = 2.5 • average RTLSs available for PS traffic during CS BH:

amount_of_TRXs x 8 - signalling_RTSLs - CS_BH_traffic-free_RTSLs = 4 x 8 - 3 - 18 - 2.5 = 8.5 RTSLs

• average PS traffic during CS BH:8.5 x 35 kbit/s = 297.5 kbit/s (> 200 kbit/s)

This means that we are well above the average data throughput per BTS (required by the operator), which is 200 kbps for the "central area."

Default territory calculations

• MS multislot capability (4 RTSLs) • data throughput: 200 kbit/s

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• radio interface: 35 kbit/RTSL→ RTSLs to support 200 kbit/s → 200/35 = 5.7 TSLs ~ 6 RTSLs

Default territory size:

max(MS_multislot, traffic) = max(4, 6) = 6 RTSLs

7.3.4 Required capacityThe required capacity is the required streaming user support per BTS (one streaming user). Streaming requires 50 kbit/s (required by the customer).

→ (50kbit/s) / (35 kbit/s / RTSL) = 2 RTSLs need to be dedicated (CDED) per BTS to support streaming

Calculations for the 2+2+2 configuration

• available RTSLs for CS traffic per BTS • 14 - 2 (CDED) = 12 RTSLs

• traffic per BTS = 8 Erl • erlang B (8 Erl, 12 TSLs) = 5.1% CS blocking • 5.1% > 2% - NOK

• needed channels for 2% CS blocking • erlang B (8 Erl, 2%) = 14 channels • either two more RTSLs (dual rate / half rate) are needed or a new TRX

In this case, the capacity increase is achieved with dual rate RTSLs.

Calculations for the 4+4+4 configuration

• available RTSLs for CS traffic per BTS • 29 - 2 (CDED) = 27 RTSLs

• traffic per BTS = 18 Erl • erlang B (18 Erl, 27 TSLs) = 1.1% CS blocking • 1.1% < 2% - OK

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7.4 Connectivity capacity

7.4.1 Default GPRS capacity (CDEF)The results of the default territory size calculations determine the value of the default GPRS capacity (CDEF) parameter.

Calculations for the 2+2+2 configurationCDEF is specified with the following formula: max(MS_multislot, traffic).

max(4, 2.9) => 4

The value of the default GPRS capacity (CDEF) parameter is set to 4 radio timeslots (RTSLs).

Calculations for the 4+4+4 configurationCDEF is specified with the following formula: max(MS_multislot, traffic).

max(4, 5.7) => 6

The value of the default GPRS capacity (CDEF) parameter is set to 6 RTSLs.

7.4.2 EDAP

General EDAP considerationsIn EGPRS dynamic Abis pool (EDAP) dimensioning, it is assumed that CDEF is dimen-sioned based on the traffic needs. In some cases, it is more cost-effective to use smaller CDEF values in the system than is needed on average. In such cases, the measured average territory size is used instead of the actual CDEF when the EDAP size is calcu-lated.

The following calculations are used when considering the size of the EDAP:

• min_EDAP_1 = MS_multislot_capability (= 4 TSLs)This ensures that the EDAP is large enough to support at least one mobile station (MS) that uses the MCS-9 coding scheme in a BTS. (This is needed if the MS mul-tislot capability is not taken into account in the default territory calculations.)

• min_EDAP_2 = max_default_territory_size_of_one_BTSThis ensures that the EDAP is large enough to support the MCS-9 traffic of all radio timeslots in an EGPRS territory.

• min_EDAP_3 = k x average (default_territory_size1, default_territory_size2, default_territory_size3)This is used to adjust the EDAP size, based on the number of territories associated to the EDAP and their size.

You can calculate the size of the EDAP using the input from above in the following formula:

EDAP_size = max(min_EDAP_1, min_EDAP_2, min_EDAP_3)

The BTS multiplexing factor (k) depends on the number of BTSs which are associated to the EDAP. The purpose of this factor is to ensure that the EDAP can handle simulta-neous traffic from all BTSs associated to it with an acceptable amount of resource sharing. The BTS multiplexing factor (k) can be estimated, for example, with the follow-ing formula:

k = 2/(1+1/x)

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where x = the number of BTSs in one EDAP (see table BTS multiplexing factor for an example).

In this example, the calculated EDAP size candidates are shown in table EDAP sizes with different configurations. The final decision on the EDAP size for Configuration 2 is made later, based on the selected Abis allocation strategy. One of the options requires two EDAPs. In the table, the size of the EDAPs is calculated for both options.

The EDAP size for Configuration 1 (2+2+2) is

EDAP_size = max(min_EDAP_1, min_EDAP_2, min_EDAP_3) = max(4, 4, 1.5 x aver-age(4,4,4)) = 6 TSLs (64 kbps each)

The EDAP size for Configuration 2 (4+4+4) with a single EDAP is

EDAP_size = max(min_EDAP_1, min_EDAP_2, min_EDAP_3) = max(4, 6, 1.5 x aver-age(6,6,6)) = 9 TSLs (64 kbps each)

If two EDAPs are used instead of one, the required sizes are:

EDAP1_size = max(4, 6, 1.3 x average(6,6)) = 8 TSLs (64 kbps each)

EDAP2_size = max(4, 6, 1.0 x average(6)) = 6 TSLs (64 kbps each)

Abis timeslot allocationThere are two options for Abis TSL allocation:

• TRXs are grouped by function so that all EDGE TRXs and EDAP are allocated to one E1/T1 frame. The non-EDGE resources are mapped to another E1/T1 frame. This example uses the ETSI environment.In this option, one EDAP is enough to serve all cells (BTS objects). The timeslots reserved for the EDAP are shown in blue in figure TRXs grouped by function. Cell A is shown in grey.

Number of BTSs k

1 1.0

2 1.3

3 1.5

Table 14 BTS multiplexing factor

Number of BTSs k Configuration 1 (2+2+2)

Configuration 2 (4+4+4)

1 1.0 4.0 6.0

2 1.3 5.3 8.0

3 1.5 6.0 9.0

Table 15 EDAP sizes with different configurations

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Figure 16 TRXs grouped by function • TRXs are grouped by cell so that two cells are allocated to one E1/T1 frame. The

third cell is allocated to the second E1/T1 frame. In this case, the EDAP is created for both groups. This example uses the ETSI environment.The timeslots reserved for the EDAP are shown in blue in figure TRXs grouped by cells. Cell A is shown in grey.

Figure 17 TRXs grouped by cells

TRXSIG1 TRXSIG2 TRXSIG3 TRXSIG4


TRXSIG9 TRXSIG1 0 TRXSIG1 1 TRXSIG1 2

0 0













1 3 1 3

1 4 1 4

1 5 1 5

1 6 1 6

1 7 1 7

1 8 1 8

1 9 1 9

20 20

21 21

22 22

23 23

24 24

25 25

26 26

27 27

28 28

29 29

30 BCFSIG 30

31 31Q1 management Q1 management



TRXSIG9 TRXSIG1 0 TRXSIG1 1 TRXSIG1 2

0 0









9 TCH0 TCH1 TCH2 TCH3 9

1 0 TCH4 TCH5 TCH6 TCH7 1 0







1 7 1 7

1 8 1 8

1 9 1 9

20 20

21 21

22 22

23 23

24 24

25 25

26 26

27 27

28 28

29 29

30 BCFSIG 30

31 31Q1 m anagement Q1 management

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Both options have their advantages and disadvantages. These are shown in tables TRXs grouped by function and TRXs grouped by cells. In table TRXs grouped by func-tion, the first E1 = 2+2+2 and the EDAP; the second E1 = 2+2+2 non-EDGE. In table TRXs grouped by cells, the first E1 = 4+4 and EDAP1; the second E1 = 4 and EDAP2.

In Configuration 1 (2+2+2), the EDAP fits into the existing E1 frame. In Configuration 2 (4+4+4), additional transmission capacity is required.

7.4.3 PCU

7.4.3.1 Dynamic AbisThe purpose is to calculate the optimal number of packet control units (PCUs) to serve the network. The calculation is based on table Connectivity of the first generation PCU (PCU1) in chapter Inputs for BSC EDGE dimensioning.

PCU dimensioning scenario 1 (pure dimensioning)In this scenario, the PCU usage for dimensioning is 70%. This allows an usage range from 60 to 80% in the planning phase (30% connectivity is available for territory upgrades).

In this scenario, the number of BTSs and TRXs can reach the maximum value (as spec-ified in table Connectivity of the first generation PCU (PCU1)).

The formula in figure PCU calculation formula is used to calculate the required number of logical PCUs.

Advantages Disadvantages

The maximum trunking gain of the EDAP can be achieved because less of total Abis capacity is required (number of TSLs for the EDAP = 9).

Special care is needed to maintain and upgrade the configuration to keep with the original split.

A smaller number of EDAPs saves PCU resources and Abis capacity.

The number of EDGE TRXs which can be connected to the EDAP is smaller. This leads to a smaller maximum theoretical ter-ritory size.

Table 16 TRXs grouped by function

Advantages Disadvantages

Straightforward to maintain and upgrade. The trunking gain of the EDAPs is smaller, and more total Abis capacity is required (number of TSLs for the EDAP = 8 + 6 = 14).

All TRXs can be connected into the EDAP, and the maximum territory size does not depend on the Abis configuration.

A larger number of EDAPs consumes more PCU resources.

Table 17 TRXs grouped by cells

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Figure 18 PCU calculation formula

In this example, the following figures are used in the calculations:

• RTSLs = 25 sites of 2+2+2 and 15 sites of 4+4+4 → 25 x 12 RTSLs + 15 x 18 RTSLs = 570 RTSLs

• Abischs = 25 x (12 channels for RTSLs in the default territories + 6 x 4 channels in the EDAP) + 15 x (18 channels for RTSLs in the default territories + 9 x 4 channels for the EDAP) = 1710 channels

• BTSobjs = 25 x 3 + 15 x 3 = 120 BTSs • SEGs is not used • TRXs = 25 x 6 + 15 x 6 (TRXs with GTRX = Y) = 240 TRXs • BHGbThroughput = 6 Mbit/s

In this example, it is estimated that the BSC level Gb busy hour traffic volume is no more than 20% of the cells in the 2+2+2 configuration and 25% of the cells in the 4+4+4 configuration. The protocol overhead peak and safety margin make together 60% of the approximately one Mbit/s size Gb links in the frame relay case: (20% x 100 kbit/s x 25 sites x 3 cells per site + 25% x 200 kbit/s x 15 sites x 3 cells per site) x (1 + 60%) = 6 Mbit/s.

• U = 70%

Figure PCU calculations for BSS connectivity dimensioning illustrates how the PCU cal-culation formula is used in the calculations.

L = roundup

radioTSLs

max. radio TLSs x U

max

Abischs

max.Abischs x U

EDAPs

max. EDAPs

BTSobjs

max. BTSobjs

SEGs

max. SEGs

max. BHGbThroughput x U

BHGbThroughput

TRXs

max. TRXs

,

,

,

,

,

,

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Figure 19 PCU calculations for BSS connectivity dimensioning

The number of required logical PCUs is 10. The given variant has one logical PCU in the PCU plug-in unit and, therefore, the needed number of active PCU plug-in units is also 10. The actual hardware to be installed depends on the number of BSC signalling units (BCSUs). The full BSC2i configuration has 8 + 1 BCSUs. Each of those needs to have an identical configuration, meaning that two PCUs in each BCSU is needed (18 PCUs).

The result of PCU dimensioning scenario 1 is that 10 active PCUs (18 PCU plug-in units in BSC2i) are needed.

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.

PCU dimensioning scenario 2 (partial planning)In this scenario, the recommended number of EDAPs per PCU (PCU1) is 1, 2, 4, or 8. With PCU2, the recommendation is 1-8 EDAPs per PCU.

The number of Abis channels in each EDAP and associated default RTSLs is calculated for each BTS site configuration.

Table Different configurations and their Abis and RTSL load shows the Abis and RTSL load of different configurations.

EDAP splitting strategy

N/A TRX grouped by cells TRX grouped by function

Configurations Configuration 1 Configuration 2 (cells A and B)

Configuration 2 (cell C)

Configuration 2 (cells A, B, and C)

EDAP size 6 8 6 9

Table 18 Different configurations and their Abis and RTSL load

= 1.9

570

128 x 0.7

max

1710

256 x 0.7

40

16

120

64

0

64

31 x 64 x 0.7

6000

240

128

,

,

,

,

,

,

= 2.5

= 9.6

= 6.4

= 1.9

= 4.3

L2 = roundup = 10

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From table Different configurations and their Abis and RTSL load, Configuration 2 with TRXs grouped by function is used in this example.

Table Possible PCU configurations lists the possible PCU combinations with base control function (BCF) combinations. Configuration 1 has 36 subTSLs and Configuration 2 has 54 subTSLs in the Abis interface.

In PCU configurations A, B, G, and I, the PCU usage is too far from the 75% goal. In PCU configurations C, E, F, and H, the PCU usage is reasonably close to the target value.

In this example, PCU configurations C and H are used. However, also other configura-tions could be used.

With the selected PCU configurations (C and H), we can calculate the needed number of PCUs:

• five PCUs with configuration C • four PCUs with configuration H

(5 x (Configuration 1 + 3 x Configuration 2) + 4 x (5 x Configuration 1) = 15 x Configura-tion 2 + 25 x Configuration 1

Number of RTSLs in the territory

4 6 6 6

Number of BTSs (territories) per EDAP

3 2 1 3

Number of EDAP subTSLs

24 32 24 36

Number of Abis channels for RTSLs

12 12 6 18

Number of Abis subTSLs

36 44 30 54

PCU configuration A B C D E F G H I

Number of BCFs with Configuration 1

0 0 1 3 2 4 3 5 4

Number of BCFs with Configuration 2

4 3 3 2 2 1 1 0 0

Total PCU Abis load (TSLs)

216 162 198 216 180 198 162 180 144

Total PCU load (%) 84 63 77 84 70 77 63 70 56

Table 19 Possible PCU configurations

EDAP splitting strategy

N/A TRX grouped by cells TRX grouped by function

Configurations Configuration 1 Configuration 2 (cells A and B)

Configuration 2 (cell C)

Configuration 2 (cells A, B, and C)

Table 18 Different configurations and their Abis and RTSL load (Cont.)

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In this more accurate scenario, the number of PCUs is slightly lower than in the basic dimensioning scenario. Note that the actual EDAP-to-PCU mapping also uses the adja-cency information of sites. When this information is available, the actual EDAP-to-PCU mapping might be different. This might affect the number of needed PCUs.

The result of PCU dimensioning scenario 2 is that nine active PCUs (18 PCU plug-in units in BSC2i) are needed.

Note that the PCU calculation formula is used to verify the PCU need against other resources, such as the number of TRXs.

7.4.3.2 Packet AbisFor Packet Abis the following figures from PCU calculation in Dynamic Abis are used:

• RTSLs = 570 RTSLs • BTSobjs = 120 BTSs • SEGs is not used • TRXs = 240 TRXs • BHGbThroughput = 6 Mbit/s

In calculation PCU2-E is used.

Figure PCU calculation for Packet Abis illustrate how formula is used in the calculation

Figure 20 PCU calculation for Packet Abis

7.4.4 Gb link dimensioningThe outcome of the Gb link dimensioning is the size of the Gb links. This might affect SGSN dimensioning and needs to be taken into account when SGSN dimensioning is performed. (SGSN dimensioning is not included in this example.)

Gb link dimensioning can be based on either of the following methods:

• the average EDAP sizes • the exact EDAP-to-PCU mapping (if available)

This example illustrates both methods.

Gb link dimensioning based on the average EDAP sizesIn this method, the maximum of all the EDAP sizes and the average of all EDAP sizes are used. The accuracy of this method is usually enough for dimensioning purposes. The following calculations are used:

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• min_Gb_1 = 1.25 x max_EDAP_sizemin_Gb_1 = 1.25 x max(6,9) TSLs = 11.25 TSLsThis ensures that the Gb link is able to handle the short term peak traffic of any single EDAP.

• min_Gb_2 = k x average(EDAP_size_1 to EDAP_size_n)k based on the average number of EDAPs per PCU ( = 40 EDAPs / 10 PCUs = 4 ) is 1.9min_Gb_2 = 1.9 x (25 x 6 TSLs + 15 x 9 TSLs) / 40 = 1.9 x 7.1 TSLs = 13.5 TSLsThis ensures that the average traffic from several EDAPs can be handled also when one of the EDAPs is in its peak traffic.

The k factor is selected based on the estimate of short term traffic distribution. If no specific information about the distribution is available, it is recommended to use the default values for k. The average number of EDAPs per PCU is used.

The maximum is selected to be the average Gb link size:

Gb_link_size = max(min_Gb_1, min_Gb_2)

Gb_link_size = max(11.25, 13.5) = 14 TSLs

The final Gb link size might need to be adjusted to fit to the available E1/T1 links. When estimating whether to decrease or increase the Gb link size because of E1/T1 capacity, availability of the traffic distribution needs to be considered. If it is unlikely to have high traffic simultaneously over a short period of time in several EDAPs, lower k values may be considered.

In this example, the options to achieve good E1 usage are either a 10 to 11 TSLs link or a 15 to 16 TSLs link. Optimally, one E1 line carries either links with the sizes of 10, 10 and 11, or 15 and 16.

In this example, the link size of 15 and 16 TSLs is selected.

Gb link dimensioning based on the exact EDAP-to-PCU mappingIn this method, the principle of the calculation is exactly the same as in the method based on the average EDAP sizes. However, the maximum and average calculations

Number of EDAPs

k

Short term traffic distribution

Close to unequal Default Close to equal

30% 50% 70%

1 1.0 1.0 1.0

2 1.3 1.5 1.7

3 1.4 1.8 2.2

4 1.4 1.9 2.5

5 1.4 1.9 2.8

6 1.4 2.0 2.9

7 1.4 2.0 3.1

8 1.4 2.0 3.1

Table 20 Example of the k factor for the Gb link

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are done per PCU. The accuracy of this method is slightly better than in the method based on the average EDAP sizes.

The dimensioning accuracy may be further increased by using more accurate estimates of short term traffic distribution among cells to define the appropriate k factor.

Inputs from PCU planning:

• five PCUs with configuration C, maximum EDAP size = 9 • four PCUs with configuration H, maximum EDAP size = 6

Minimum Gb link sizes for PCU configuration C:

• min_Gb_1 = 1.25 x max_EDAP_sizemin_Gb_1 = 1.25 x 9 TSLs = 11.25 TSLs

• min_Gb_2 = k x average(EDAP_size_1 to EDAP_size_n)k = four EDAPs per PCU (see tables Possible PCU configurations and Example of the k factor for the Gb link)k = 1.9 min_Gb_2 = 1.9 x (6 + 3 x 9) / 4 = 1.9 x 8.25 TSLs = 15.7 TSLs

• Gb_link_size = max(min_Gb_1, min_Gb_2)Gb_link_size = max(11.25, 15.7 ) TSLs = 15.7 TSLsThe practical sizes would be 15 and 16 TSLs.

Minimum Gb link sizes for PCU configuration H:

• min_Gb_1 = 1.25 x max_EDAP_sizemin_Gb_1 = 1.25 x 6 TSLs = 7.5 TSLs

• min_Gb_2 = k x average(EDAP_size_1 to EDAP_size_n)k = five EDAPs per PCU (see tables Possible PCU configurations and Example of the k factor for the Gb link) k = 1.9min_Gb_2 = 1.9 x (5 x 6) / 5 = 1.9 x 6 TSLs = 11.4 TSLs

• Gb_link_size = max(7.5, 11.4 ) TSLs = 11.4 TSLsThe practical sizes would be 10 and 11 TSLs.

The maximum size of a single Gb link is defined by the E1/T1 frame, which is 31/24 TSLs.

When Gb links are combined into E1s, a maximum of 31 TSLs can be used. In this example, there are five PCUs with a 15 TSL link and four PCUs with a 10 TSL link.

• two E1s to carry two 15 TSL links each (four big ones) • one E1 to carry 15 TSL links and one 10 TSL link (one big one and one small one) • one E1 to carry three 10 TSL links

A total of four E1 lines are needed to support the required Gb links.

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7.5 Results of BSS connectivity dimensioningTable Dimensioning results shows the results of the BSS connectivity dimensioning example.

Table Radio interface setup shows the radio interface setup of the BSS connectivity dimensioning example.

Table PCU usage shows the Abis timeslot usage of the PCUs.

Basic dimensioning EDAP-to-PCU mapping

DR RTSLs 150 150

PCUs 10 9

Total E1s for Abis (in half E1 fragments)

25 x 1 E1 + 15 x 1.5 = 47.5

E1s required by EGPRS (in half E1 fragments)

0.5 x 15

E1 for Gb 10/2 = 5 4

Table 21 Dimensioning results

Configuration CDED CDEF EDAP


2 4 6


2 6 9

Table 22 Radio interface setup

Number of PCUs

PCU configura-tions

Usage of Abis TSLs

Gb link size per PCU configuration

5 C 77% 15 or 16

4 H 70% 10 or 11

Table 23 PCU usage

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7.6 Impact of Downlink Dual Carrier on BSS connectivity dimensioningThis section illustrates the impact that introducing BSS21228: Downlink Dual Carrier (DLDC) into the network has on BSS connectivity dimensioning.

Note that introducing DLDC into the network requires the following:

• The licence covering DLDC has been turned to ON (with enough network capacity). • EGPRS is enabled in the cell. • The BTS is served by PCU2-D or PCU2-E.

In addition, you need to ensure that:

• the BTS has two normal-area TRXs which are EGPRS capable and belong to the same EGPRS dynamic Abis pool (EDAP).

• the default GPRS capacity is configured in such a way that the GPRS territory is split onto two TRXs.

This means that the minimum configuration for DLDC is "x" TSLs on the first EGPRS-capable TRX (depending on the channel configuration, that is, how many TSLs are reserved for signalling) and 1 TSL on the second EGPRS-capable TRX.

However, to fully benefit from the highest DC MS multislot capabilities (5+5 TSLs in DL), the PS territory must comprise at least 5 TSLs on each TRX and BSS20084: High Mul-tislot Classes must also be activated. This, in turn, requires an extension of the default GPRS territory size on the radio interface. The extension of the GPRS territory needs to be aligned with the Abis, PCU, and Gb interface dimensioning results calculated when DLDC is not ON, using the calculation methods introduced in BSS connectivity dimen-sioning.

Note that the appropriate approach depends on the PCU2 HW variant you have in use.

PCU2-D and DLDCThe following example shows how to analyse the impact of DLDC on BSS connectivity dimensioning when PCU2-D is in use.

First, let us assume a network with 100 BTS sites and the following BTS site configura-tion (type A):

• Each site with a configuration of 2+2+2 EGPRS-capable TRXs (non-EGPRS-capable TRXs are also possible, but they are not mentioned, as they do not affect the calculations)

• default GPRS capacity (CDEF) = 4 RTSLs (in each cell) • EDAP = 6 TSLs • MS multislot capability = 5 RTSLs

Next, let us take into account a typical BTS site configuration that allows you to fully exploit DLDC (type B):

• 2+2+2 EGPRS-capable TRXs • CDEF = 13 RTSLs (in each cell) • EDAP = 10 TSLs • MS multislot capability = 10 RTSLs

With homogenous network layout, one PCU2-D unit can handle up to 5 BTS sites of type A or 2 sites of type B (using the calculation methods introduced in BSS connectivity dimensioning and the PCU utilisation rate of 70%).

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When it is assumed that, for example, 20% of the sites type A migrate to DLDC, it can be estimated how many additional PCU2-D units are required in the network. After the migration, there are 80 BTS sites without DLDC (type A) and 20 BTS sites with DLDC enabled (type B). Thus, before introducing DLDC, you would need 100 / 5 = 20 PCU2-D units, while after introducing DLDC, you would need 80 / 5 + 20 / 2 = 26 PCU2-D units.

The extension of the EDAP size and PCU2 count is reflected in the size of the Gb links. Before introducing DLDC, you need the minimum Gb link size of 1.25 x 6 = 8 TSLs, while after introducing DLDC, you need to extend the minimum Gb link size to 1.25 x 10 = 13 TSLs. Note that the impact of short traffic distribution should be included in the calcula-tion. For more information, see table Example of the k factor for the Gb link.

The maximum user RLC/MAC peak throughput that PCU2-D supports is ~ 450 kbit/s, while PCU2-E supports up to 592 kbit/s. Therefore, to maximise the user peak through-put, you are advised to allocate as many DLDC sites to PCU2-E as possible.

PCU2-E and DLDCThe following example shows how to analyse the impact of DLDC on BSS connectivity dimensioning when PCU2-E is in use.

The tables in figures Number of DAPs (~BTS sites) per PCU2-E (PCU Abis channels utilisation rate of 90%) and Number of DAPs (~BTS sites) per PCU2-E (PCU Abis channels utilisation rate of 70%) show the maximum number of BTS sites with a given configuration (expressed in terms of the total default territory RTSLs associated to the EDAP, that is, CDEFsum and DAP size) that can be handled by a single PCU2-E unit with the PCU utilisation rates of 90% and 70%.

Besides individual sites, the tables are also applicable to site groups. In that case, the DAP and CDEFsum represent the sum of the individual DAP and CDEFsum values of the sites in the given group. The grey area in the tables is not applicable to an individual site, but denotes site groups only. N/A denotes a combination not applicable with the given PCU2-E utilisation rate.

Figure 21 Number of DAPs (~BTS sites) per PCU2-E (PCU Abis channels utilisation rate of 90%)

DAP[TSL]

CDEFsum 4 6 8 10 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66

3 54 48 42 42 36 30 30 24 24 18 18 18 18 18 12 12 12 12 12 12 12 12 64 42 42 36 30 30 24 24 24 18 18 18 18 12 12 12 12 12 12 12 12 12 6 65 36 30 30 30 24 24 24 18 18 18 18 12 12 12 12 12 12 12 12 12 6 6 66 30 30 24 24 24 18 18 18 18 18 12 12 12 12 12 12 12 12 6 6 6 6 67 24 24 24 24 18 18 18 18 12 12 12 12 12 12 12 12 12 6 6 6 6 6 68 24 24 18 18 18 18 18 12 12 12 12 12 12 12 12 12 6 6 6 6 6 6 69 18 18 18 18 18 18 12 12 12 12 12 12 12 12 6 6 6 6 6 6 6 6 6

10 18 18 18 18 12 12 12 12 12 12 12 12 12 6 6 6 6 6 6 6 6 6 612 12 12 12 12 12 12 12 12 12 12 6 6 6 6 6 6 6 6 6 6 6 6 614 12 12 12 12 12 12 12 12 6 6 6 6 6 6 6 6 6 6 6 6 6 6 616 12 12 12 12 12 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 618 12 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 620 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 622 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 624 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 N/A N/A N/A

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Figure 22 Number of DAPs (~BTS sites) per PCU2-E (PCU Abis channels utilisation rate of 70%)

The tables are relevant both with and without DLDC. Thus, when the number of BTS sites per PCU2-E unit is known, the remaining calculation steps can be conducted sim-ilarly to those shown in the example for PCU2-D in PCU2-D and DLDC.

In the example for PCU2-D, there are 80 sites (type A) having a three-sector EGPRS site configuration with DAP = 6 TSLs and CDEF = 4 RTSLs in each cell (CDEF sum 12 RTSLs) and 20 sites (type B) with DAP = 10 TSLs and CDEF = 13 RTSLs each (CDEF sum 39 RTSLs). Based on the 90% table in figure Number of DAPs (~BTS sites) per PCU2-E (PCU Abis channels utilisation rate of 90%), up to 24 sites of type A or 6 sites of type B can be allocated to one PCU2-E unit. The number of PCU2-E units required is 80 / 24 = 3.3 for type A and 20 / 6 = 3.3 for type B. With this simple method, the total number of PCU2-E units would thus be 7 (round up: 3.3 + 3.3).

The tables are based on homogeneous network layout and may not give accurate results when applied to inhomogenous sites. To obtain more accurate dimensioning results, the tables may be applied for site combinations instead of individual sites.

The method of combining sites before applying the tables

You can create possible site combinations by summing up the DAP and CDEFsum values. The first option is to apply one site of type A and one of type B. In this case, the table is read from DAP = 16 and CDEFsum = 51. Another option that you can consider is to combine two sites of type A with one site type B. The table is read from DAP = 22 and CDEFsum = 63. Based on the 90% table, one PCU2-E unit is able to handle 6 of either of these combinations.

First, the number of PCU2-E units required for the site type B is calculated. As there is only one site type B in the site combinations exemplified above, the number of PCU2-E units can be calculated by dividing the total number of site types B by the number of combinations one PCU2-E unit is able to handle. Thus, 20 / 6 = 3.3 PCU2-E units for 20 sites of type B. These PCU2-E units also take care of the 40 sites of type A.

The number of PCU2-E units for the rest of the site types A can also be calculated by applying the remaining number of the site types A; 40 / 24 = 1.7. The total number of PCU2-E units would thus be 5 (round up: 3.3 + 1.7).

To be on the safe side, these subresults need to be rounded up before summing up, especially in this case where the 90% table is used and there is no margin left. The rec-ommended number of PCU2-E units would then be 6 (round up: 3.3 + 1.7).

To sum up, in this case, the method of combining sites before applying the tables gives 6 PCU2-E units, while the simple method gives 7 PCU2-E units.

4 6 8 10 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 663 42 36 36 30 30 24 24 18 18 18 12 12 12 12 12 12 12 6 6 6 6 6 64 36 30 30 24 24 18 18 18 18 12 12 12 12 12 12 6 6 6 6 6 6 6 65 30 24 24 24 18 18 18 12 12 12 12 12 12 12 6 6 6 6 6 6 6 6 66 24 24 18 18 18 18 12 12 12 12 12 12 12 6 6 6 6 6 6 6 6 6 67 18 18 18 18 18 12 12 12 12 12 12 6 6 6 6 6 6 6 6 6 6 6 68 18 18 18 12 12 12 12 12 12 12 6 6 6 6 6 6 6 6 6 6 6 6 69 18 12 12 12 12 12 12 12 12 6 6 6 6 6 6 6 6 6 6 6 6 6 6

10 12 12 12 12 12 12 12 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 612 12 12 12 12 12 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 614 12 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 N/A16 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 N/A N/A N/A N/A18 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 N/A N/A N/A N/A N/A N/A20 6 6 6 6 6 6 6 6 6 6 6 6 6 6 N/A N/A N/A N/A N/A N/A N/A N/A N/A22 6 6 6 6 6 6 6 6 6 6 6 N/A N/A N//A N/A N/A N/A N/A N/A N/A N/A N/A N/A24 6 6 6 6 6 6 6 6 6 N/A N/A N/A N/A NA N/A N/A N/A N/A N/A N/A N/A N/A N/A

DAP[TSL]

CDEFsum

DN7032469Issue 6-0

61


Id:0900d8058059149d

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62 DN7032469Issue 6-0


Id:0900d805805914a2

BSC traffic monitoring principles

8 BSC traffic monitoring principlesWhen the BSC dimensioning has been done accurately, traffic flow is at an optimal level, that is, as high as possible. You can use counters related to the radio interface to monitor the use and congestion level of the BSC. It is also useful to monitor the perfor-mance of all hardware units of the BSC. Good tools for this are EDGE key performance indicators (KPIs) and overload alarms related to the hardware units. For more informa-tion on EDGE KPIs, see EDGE, GPRS, and GSM Voice Key Performance Indicators.

To check whether dimensioning has been successful, you need to compare real traffic against the traffic estimations done during the dimensioning. If there is a serious discrep-ancy, you have to re-plan the network.

Date post:	31-Dec-2015
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