BSC EDGE Dimension Ing

BSC EDGE Dimensioning

DN7032469Issue 3-0 en draft

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BSC3120Nokia GSM/EDGE BSS12 SystemDocumentation

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2 (57) # Nokia Corporation DN7032469Issue 3-0 en draft


Contents

Contents 3

Summary of changes 5

1 BSC EDGE dimensioning 7

2 Planning process 9

3 Key strategies for EDGE dimensioning 11

4 Prerequisites for BSC EDGE dimensioning 13

5 BSC capacity 155.1 EGPRS-related BSC elements 16

6 Dimensioning process 236.1 Dimensioning of network elements and interfaces 236.2 BSC EDGE dimensioning process 276.3 Inputs for BSC EDGE dimensioning 296.3.1 Network capability 306.3.2 Input from Abis and BTS dimensioning 336.4 PCU calculations for BSC EDGE dimensioning 346.5 Outputs of BSC EDGE dimensioning 356.6 Evaluation of the BSC dimensioning results 37

7 Example of BSS connectivity dimensioning 397.1 BSS connectivity dimensioning 397.2 Dimensioning inputs 407.3 Radio interface capacity 417.3.1 Configuration before (E)GPRS 417.3.2 (E)GPRS deployment scenarios 437.3.3 Available capacity 447.3.4 Required capacity 487.4 Connectivity capacity 487.4.1 Default GPRS capacity (CDEF) 487.4.2 EDAP 497.4.3 PCU 537.4.4 Gb link dimensioning 557.5 Results of BSS connectivity dimensioning 55

8 BSC traffic monitoring principles 57



Contents

Summary of changes

Changes between document issues are cumulative. Therefore, the latest documentissue contains all changes made to previous issues.

Changes made between issues 3-0 and 2-0

The document has been restructured for better usability and the focus is more onthe actual dimensioning process. The following changes have been made:

. Chapter EDGE dimensioning has been renamed as Planning process. Thedimensioning strategy information has been moved to chapter Keystrategies for EDGE dimensioning and an overview of the dimensioningsteps has been moved to chapter Dimensioning of network elements andinterface and the content has been updated.

. All steps in the dimensioning process are now under the main chapterDimensioning process.

. Chapter Prerequisites for BSC EDGE dimensioning has been added.

. Information related to the BSC capacity has been moved from chapter BSCEDGE dimensioning to chapter BSC capacity. In addition, information ondigital signal processor (DSP) has been removed because it is not directlyrelated to dimensioning.

. The contents of chapter Inputs for BSC EDGE dimensioning has beenupdated. Information on software related to dimensioning has been movedto the BTS EDGE Dimensioning document.

. Chapter BSC EDGE dimensioning process and calculations has been splitinto two separate chapters: BSC EDGE dimensioning process and PCUcalculations for BSC EDGE dimensioning, and the content has beenupdated. In addition, the calculation formula has been simplified.

. Chapter Outputs of BSC EDGE dimensioning has been updated andreorganised according to the used strategy.

. Chapter Examples of BSC EDGE dimensioning has been removed. Adimensioning example is now included in chapter Example of BSSconnectivity dimensioning.



Summary of changes

. Chapter Traffic monitoring principles has been moved to the EDGE andGPRS Key Performance Indicators document.

. Information on BSC3i 1000 and BSC3i 2000 has been added.

Changes made between issues 2-0 and 1-0

The general description of BSC has been moved to chapter Nokia Base StationController in Nokia Base Station Subsystem. Some PCU information has beenmoved to chapter Packet Control Unit (PCU) hardware in BSC in (E)GPRSSystem Feature Description.

The information that the outputs of BSC dimensioning are used as inputs for Gbdimensioning has been added to BSC EDGE dimensioning and Outputs of BSCEDGE dimensioning.

The inputs in Inputs for BSC EDGE dimensioning have been reorganised into thefollowing categories:

. Traffic and quality inputs

. Network capabilities

The calculations in Examples of BSC EDGE dimensioning have been modified.

BSC traffic monitoring principles has been added.

The radio timeslot terminology has been unified.



1 BSC EDGE dimensioning

The aim of these guidelines is to give basic dimensioning information for BSCequipment when there is both circuit-switched (CS) and EGPRS traffic in theradio network. The dimensioning guidelines are related to EGPRS traffic and,therefore, only BSC hardware or software elements that have an impact onEGPRS traffic have been analysed. Voice traffic volume is not considered in BSCdimensioning and, because of this, Ater and transcoder dimensioning is notincluded in these guidelines.

The EDGE dimensioning guidelines in the BSS system documentation set coverBTS, Abis, BSC, Gb, and SGSN dimensioning and some parts of pre-planning.

These guidelines are related to 3GPP Releases 4 and 5, Nokia software ReleaseBSS12, the BSC products BSCi, BSC2i, and BSC3i, and to other relevantequipment related to these BSC products.

BSC dimensioning results in specific outputs that are used as input in the nextdimensioning phase, Gb EDGE dimensioning.

Terms and definitions

The following terms are used in these guidelines:

GPRS General Packet Radio Service (GPRS) provides packetdata radio access for GSM mobile stations. It upgradesGSM data services to allow an interface with local areanetworks (LANs), wide area networks (WANs), and theInternet.

EDGE Enhanced data rates for GSM evolution (EDGE) enhancesGSM networks with 3rd generation-type capabilities. Withthe new 8-PSK modulations, EDGE is capable of treblingthe current GSM radio interface data throughputs. EDGEboosts packet-switched (PS) services. Enhanced GPRS(EGPRS) offers up to 59.2 kbit/s on one radio timeslot(RTSL).

(E)GPRS Refers to both the GPRS and the EDGE technology.



BSC EDGE dimensioning

EDAP In EDGE, the Abis interface has a dynamic part calledEGPRS dynamic Abis pool (EDAP). It differs from theGSM (and GPRS) transmission networks, where the Abisinterface is static. The shared timeslots can be shared bythe TRXs belonging to the same BCF.

Master channel A 16 kbit/s channel used for the allocation of an EGPRSchannel out of the EDAP in the Nokia dynamic Abis. Nota part of the EDAP.

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

Related topics

. BTS EDGE Dimensioning

. Abis EDGE Dimensioning

. Gb EDGE Dimensioning

. SGSN EDGE Dimensioning



2 Planning process

Dimensioning is the part of network planning that produces a master planindicating the selected network architecture and the number of network nodes andcommunication links required during the roll-out of the network.

The following phases are included in the network planning process:

. dimensioning

. pre-planning

. detailed planning

. implementation

. optimisation

. modernisation

Network dimensioning is done by creating a traffic model of the network andselecting the equipment to support it. Dimensioning takes into account theavailable equipment specifications, business plans, site availability and type,quality of service (QoS) requirements, and charging cases.

The EDGE dimensioning guidelines in the BSS system documentation set coverBTS, Abis, BSC, Gb, and SGSN dimensioning and some parts of pre-planning.

These guidelines focus on dimensioning. Network optimisation is not included inthe guidelines.

The dimensioning guidelines consist of both hardware dimensioning andsoftware dimensioning. Hardware dimensioning defines how many traffic typeand traffic volume dependent hardware units are needed in the BTS, BSC, andSGSN to support the targeted traffic and service performance. Softwaredimensioning defines the key system settings associated with traffic dependentunits. You can modify the existing configuration once the amount of neededtraffic dependent hardware and the associated software settings have beendefined. If necessary, you can place an order for additional products and licences,based on the agreed standard configurations.



Planning process

Nokia has a wide range of services and training available to support all phases ofsystem planning, deployment, and optimisation. Contact your local Nokiarepresentative for details.



3 Key strategies for EDGE dimensioning

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

. available data capacity

. required data capacity

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

Available data capacity

Available data capacity strategy is used when you want to introduce EDGE to anexisting network. Dimensioning determines how much traffic is available throughthe current system. The dimensioning input is a pre-defined system configuration.The dimensioning output is the available traffic volume with a definedperformance level. Alternatively, you can calculate available capacities fordifferent alternative configurations.

Figure 1. Available data capacity

All current resources in a cell

Average voice trafficresource usage

Averageavailableresources

Input information:

Current network configuration

Current equipment’sEDGE capability

Current network’s voiceperformance

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

Planned EDGE data resourcesare used for voice trafficwhen needed


EDGE data



Key strategies for EDGE dimensioning

Required data capacity

Required data capacity strategy is used when you want to design a network thatsupports the defined amount of traffic and targeted performance level. Thedimensioning inputs are traffic volume, type, and performance requirements. Thedimensioning output is the needed amount of traffic dependent hardware and theassociated software configurations.

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



4 Prerequisites for BSC EDGEdimensioning

Input summary

The results of BTS EDGE dimensioning and Abis dimensioning are used as thekey input for BSC EDGE dimensioning. In addition, you need to check someinformation of the existing BSC configuration before starting the dimensioning.Table Input parameters for BSC EDGE dimensioning shows the required inputinformation.

Table 1. Input parameters for BSC EDGE dimensioning

Input Status/value Activity

BSC variant BSCx Verify (or upgrade)

Packet control unit(PCU) variant

PCUx Verify (or upgrade)

BTS object (cell) Number Verify

Segment Number Verify

Transceiver (TRX) Number Verify

Base control function(BCF)

Number Verify

EGPRS dynamic Abispool (EDAP)

Number (size) Abis dimensioning

Associated BTSs perEDAP

Number Abis dimensioning

Radio timeslots(RTLSs) in the BTSs

Number (size) Abis dimensioning

Output summary

The BSC EDGE dimensioning output is described in table Output of BSC EDGEdimensioning. An important part of the dimensioning process is the evaluation ofresults and iteration, if required. The output is used as the input for Gbdimensioning.



Prerequisites for BSC EDGE dimensioning

Table 2. Output of BSC EDGE dimensioning

Output Value

BSC Type

PCU Number

Gb interface Number/size



5 BSC capacity

The BSC needs enough capacity for the Abis and A interfaces and for the internalprocessing of CS and PS traffic because all CS (erlang) and PS (Mbit/s) trafficfrom the radio network goes through the BSC to the core network.

The capacity of different BSC hardware/software releases is usually compared byusing 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, and BSC3i is presented in Table BSC comparison.

Table 3. BSC comparison

BSC3i2000

BSC3i1000

BSC3i 660 BSC2i BSCi

Max.number ofTRXs

2000 1000 660 512 512

Max.number ofbase controlfunctions(BCFs)

2000 1000 504* 248 248

Max.number ofBTS objects

2000 1000 660 512 512

Max.number oftrafficchannels(TCHs)

16000 8000 5280 4096 2048

Max.number ofPCUs(logical)

100+10** 50+10** 24+4 16+2 8+1



BSC capacity

Table 3. BSC comparison (cont.)

BSC3i2000

BSC3i1000

BSC3i 660 BSC2i BSCi

Max.number ofBSCsignallingunits(BCSUs)

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

Max.number ofE1(T1)s

800 384 256 144 88

Traffic (Erl) 11880 5940 3920 3040 3040

* The maximum number of 504 BCF objects is supported in BSC3i 660 withAS7-C and GSW1KB hardware.

** Only applies to PCU2.

For more information on the BSC, see the BSS Description document. Also seeProduct Description of Nokia BSC2i and BSCi High Capacity Base StationController and Product Description of Nokia BSC3i High Capacity Base StationController in BSC/TCSM documentation.

5.1 EGPRS-related BSC elements

To set up the dimensioning, a BSC audit needs to take place. The aim of the auditis to verify the existing configuration, that is, the BSC variant and the number ofBCSUs and PCUs. The BSC variant and different elements define theconnectivity to BTS which, at the end, may affect the BTS configuration and theGb configuration. From this point of view, the EDGE network dimensioning is aniterative process.

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



Bit group switch (GSWB)

For information on the GSWB, see chapter Base Station Controller in the BSSDescription document and chapter Bit Group Switch in Product Description ofNokia BSC3i High Capacity Base Station Controller in BSC/TCSMdocumentation.

BSC signalling unit (BCSU)

In the maximum configuration, BSCi and BSC2i contain eight active BCSUs andone redundant BCSU. In the maximum configuration, BSC3i 660 contains sixactive BCSUs and one redundant BCSU, whereas BSC3i 2000 contains 10 activeBCSUs and one redundant BCSU.

Each BCSU in BSCi can be equipped with zero or one PCU. Each BCSU inBSC2i or BSC3i 660 can be equipped with zero, one, or two PCU(s). Each BCSUin BSC3i 1000/2000 can be equipped with up to five PCU2s. For high EDGEtraffic, two PCUs are required for each BCSU.

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



BSC capacity

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.

Packet control unit (PCU)

The PCU card limits the maximum number of radio timeslots that can beconnected to a PCU card simultaneously.

Two PCU HW inevery BCSU forhigh EDGE traffic

PSA20PSFP

SW1C

SW1C

CLOC

MCMU

MCMU

OMU

WDDC

WDDC

ET5C

ET5C

BCSU

BCSU

BCSU

PSA20PSFP

ET5C

ET5C

BCSU

BCSU

BCSU

ET5C

ET5C

CLAC

ET5C

BCSU

BCSU

BCSU



Table 4. BTS and TRX capability of different PCU types

PCU type BSC type BTSs TRXs RTSLs Abischannels

PCU BSCi, BSC2i 64 128 128 ch 256

PCU-S BSCi, BSC2i 64 128 128 ch 256

PCU-T BSCi, BSC2i 64 128 256 ch 256

PCU-B BSC3i 2 x 64 2 x 128 2 x 256 ch 2 x 256

PCU2-U BSCi, BSC2i 128 256 256 ch 256

PCU2-D BSC3i 2 x 128 2 x 256 2 x 256 ch 2 x 256

The PCU card also limits the maximum number of Abis channels. Table Abisconfiguration examples (PCU, PCU-S) gives examples of GPRS/EGPRS radiotimeslot (RTSL) configurations when EDAP channels are also used.

Table 5. Abis configuration examples (PCU, PCU-S)

GPRS (16kbit/s)channels

EGPRS (16kbit/s) masterchannels

EDAP (16kbit/s) slavechannels

Totalnumber ofchannels

Coding

128 - - 128 CS1&2

- 128 128 256 MCS-5

- 64 192 256 MCS-7

64 64 128 256 MCS-6

- 51 204 255 MCS-9

The PCU variant depends on your needs and the PCU usage percentage has to bedecided. The percentage is usually 75-80%.

Table The capability of the Gb interface for different PCU types shows the PCUlimitations for the Gb interface towards the SGSN with Gb over frame relay andGb over IP.

Table 6. The capability of the Gb interface for different PCU types

PCU type BSC type Gb over frame relay Gb over IP

PCU BSCi, BSC2i 32 x 64 kbit/s 2 Mbit/s

PCU-S BSCi, BSC2i 32 x 64 kbit/s 2 Mbit/s



BSC capacity

Table 6. The capability of the Gb interface for different PCU types (cont.)

PCU type BSC type Gb over frame relay Gb over IP

PCU-T BSCi, BSC2i 32 x 64 kbit/s 2 Mbit/s

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

PCU2-U BSCi, BSC2i 32 x 64 kbit/s 2 + 2 Mbit/s

PCU2-D BSC3i 2 x 32 x 64 kbit/s 2 + 2 Mbit/s

Note

The maximum rate of one frame relay bearer channel is 31 x 64k (ETSI) or 24x 64k (ANSI). If there is more than one bearer in a logical PCU, theirmaximum summary rate is 32 x 64k. In the ANSI environment, the Gbinterface must be split between two physical ET ports to support the maximumPCU capacity for Gb over FR.

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

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

. Gb over frame relay: The PCM interfaces for the frame relay are routed bythe GSWB in the BSC to the PCU.

A PCU can be connected to the SGSN either via Gb over frame relay or Gb overIP interface but not simultaneously via both interfaces. Gb over IP can be usedwith PCU1 and PCU2 units.

EDAPs in the PCU

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

. A maximum of 256 channels (16 kbit/s) in the PCU.

. The maximum EDAP size is 12 TSLs (64 kbit/s).



. It is recommended to use 1, 2, 4, or 8 EDAPs per PCU.

This rule guarantees the same amount of resources for each equallyweighted EDAP within the PCU. Other configurations may be used toincrease PCU connectivity. However, the PCU resources might bedistributed unevenly between the EDAPs and, therefore, some of the cellsmight have slightly different performance compared to the others. Toensure that the most important cells get more resources than the lessimportant ones, the weight of the EDAP can be tuned. The weight is thenumber of 16 kbit/s EDAP channels plus the total number of RTSLs ondefault territories associated to the EDAP. One way to increase/decreasethe relative weight of an EDAP is to increase/decrease the default territoryby one in the most/least important cell which is associated to the EDAP.

. The sum of EDAP sizes in the PCU is no more than 51 TSLs. However, iffor some reason all 16 EDAPs are in use, the sum of the EDAP sizes is 48TSLs at maximum.

For more information on the PCU, see Packet Control Unit (PCU) in BSC in (E)GPRS System Feature Description.

Exchange Terminal

All 2.048 Mbit/s (in the ETSI environment) or 1.544 Mbit/s (in the ANSIenvironment) interfaces for the MSC, SGSN, and BTSs are connected to theExchange Terminals (ET). The ETs adapt the external PCM circuits to theGSWB.

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 ofthe GSWB from 192 to 256 PCMs and an optional E1/T1 extension from 112 to144 (72 ET2E/A units).

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

The ETs of the BSC3i 1000/2000 are housed in GT6C-A and/or GT4C-Acartridges. One GT4C-B cartridge can contain up to eight ET plug-in units andone GT6C-A cartridge can contain up to four ET plug-in units.



BSC capacity

6 Dimensioning process

6.1 Dimensioning of network elements and interfaces

The dimensioning of GSM EDGE network elements and interfaces is proposed tobe done as described in this section. Depending on the dimensioning strategy, youcan use either the available capacity strategy or the required capacity strategy. Atfirst, the input for BTS dimensioning has to be agreed. Once this has been done,the output of each element or interface serves as the input for the next phase.

Available data capacity strategy

The dimensioning process of the available data strategy is illustrated in figureAvailable data capacity process.

Figure 4. Available data capacity process

1. Estimate the average available data capacity andthroughput.

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

available capacity estimate done in step 1.

TSL

TRX

Cell

BTS

PCU

BSC

Basic unit

2G SGSNGbAbis

1

2

3 4 5 6



Dimensioning 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/timeslot (TSL).. Calculate the available capacity/number of TSLs based on the

circuit-switched (CS) traffic needs.. Verify the dimensioning outcome.

The dimensioning process results in throughput/TSL, territory size/BTS,guaranteed/not guaranteed throughput, TSL configuration of TRXs,amount of TRXs per cell, and the simulation results.

3. Abis dimensioning. Use the output of BTS dimensioning as the input.. Define the EGPRS dynamic Abis pool (EDAP) size.

The dimensioning process results in the size of each EDAP.

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, thenumber 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.. 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 ofpayloads, number of network service virtual connections (NS-VCs), andnumber 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 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 previouslycalculated generated traffic and the expected subscribers served inthe area.

. Check all other restrictions, especially the expected mobility profilesof the users versus the dynamic capacity of the SGSN.

The dimensioning process results in the number of packet processing units(PAPUs) and signalling and mobility management units (SMMUs).

Required data capacity strategy

The dimensioning process of the required data strategy is illustrated in figureRequired data capacity process.

Figure 5. Required data capacity process

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




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/TSL.. Calculate the required number of TSLs.. Verify the dimensioning outcome.

The dimensioning process results in throughput/TSL, territory size/BTS,guaranteed/not guaranteed throughput, TSL configuration of TRXs,amount of TRX/cell, and the simulation results.

3. Abis dimensioning. Use the output of BTS dimensioning as the input.. Define the EDAP size.

The dimensioning process results in the size each EDAP.

4. BSC dimensioning. Use the output of BTS and Abis dimensioning as the input.. Calculate the needed amount of PCUs.. Calculate the number of BCSUs and ETs.. Calculate the Gb requirements for BSC dimensioning.. Define the BSC configuration.. Perform a use check.

The dimensioning process results in the number and type of BSCs, thenumber 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 numberpayloads, the number of NS-VCs, and the number of frame relay timeslots/data transfer capacity.



6. SGSN dimensioning. Use the output of BTS and Gb dimensioning as the input.. Define the required number of 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 inthe area.

. Check all other restrictions, especially the expected mobility profilesof the users versus the dynamic capacity of the SGSN.

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

6.2 BSC EDGE dimensioning process

BSC dimensioning for EGPRS traffic is a straightforward process that starts fromEDGE BTS and transmission dimensioning inputs, continues to the dimensioningof the PCU card, and then to the dimensioning of the Gb interface towards theSGSN (see figure BSC dimensioning flow). The number of required Abis anddynamic Abis channels (EGPRS dynamic Abis pool, EDAP), Exchange Terminal(ET) cards, packet control unit (PCU) cards, and Gb interface licences can becalculated 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 knowwhether the system is European (ETSI) or American (ANSI). In the ANSIstandard, for example, transmission is slightly different from the ETSIspecifications. Next, the exact BSS software release (the assumption in theseguidelines is BSS12) and BSC product version (the assumption in theseguidelines is BSCi, BSC2i, or BSC3i) have to be known to identify the maximumAbis, PCU, and Gb capacities for the dimensioning work. When the BSSsoftware release and the BSC product types are known, also the ET, PCU, and Gbinterfaces 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 in chapter Inputs for BSCEDGE dimensioning.

2. Collecting inputs from EDGE BTS and transmission 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 andBSS SW 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



For more information, see Input from Abis and BTS dimensioning inchapter Inputs for BSC EDGE dimensioning.

3. Calculating the required number of PCUs.

For more information, see chapter PCU calculations for BSC EDGEdimensioning.

4. Calculating the required number of Gb links for SGSN traffic.

Gb traffic now also includes Gb overhead. Gb interface dimensioning isdescribed in the Gb EDGE Dimensioning document.

In these guidelines, the assumption is to use Gb over FR. The number ofthe Gb interface can be calculated, as can the number of required ET cards,depending on the standard (ETSI/ANSI).

Always use the same usage criteria for the Gb interface and ET card as forthe other BSC elements. The Gb interface capacity should be in line withthe EDAP size.

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

6.3 Inputs for BSC EDGE dimensioning

The basic voice dimensioning of the BSC depends mainly on the number of basestations (BTSs) and transceivers (TRXs) connected to the BSC. For informationon constraints related to the BSC signalling unit (BCSU), see BSC signalling unit(BCSU) in chapter BSC capacity.

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

In these guidelines, it is assumed that the TRX and BTS limitations per PCU cardare based on the 75% rule, where 25% of the capacity is reserved for futureextensions.

The same 75/25% rule is also used for the calculations of the maximumthroughputs of the PCU cards and Abis and Gb/IP interfaces.




6.3.1 Network capability

BSC configuration

. BSC variant (BSCi, BSC2i, BSC3i)

. PCU variant (PCU, PCU-B, PCU-S, PCU-T, PCU2-D, PCU2-U)

. installed software (BSS11, BSS11.5, BSS12)

. 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 of the packet common control channels (PCCCHs) / packet

broadcast control channels (PBCCHs) in all TRXs under the PCU1s

. total number of the BTS objects (sectors) with GENA = Yunder the PCUs

. total number of the SEGMENTs configured under the PCUs

. total number of the TRXs with GTRX = T under the PCUs

PCU connectivity

In PCU1 dimensioning, the following restrictions need to be taken into account:

. The maximum amount of EDAPs connected to a PCU is 16. Therecommendation is one, two, four, or eight EDAPs under one PCU.

. The maximum theoretical number of dynamic Abis pools in the BSC is256 in BSC2i (16 EDAPs in each PCU and 16 PCUs in each BSC2i), and384 in BSC3i (16 EDAPs in each PCU and 24 logical PCUs in eachBSC3i). From BSS12 onwards there can be 1600 dynamic Abis pools inBSC3i (16 EDAPs in 100 logical PCUs).



Table 7. Connectivity of the first generation PCU (PCU1)

PCUvariant

LogicalPCUs/board

BSC type Capability BSS10.5ED andBSS11

BSS11.5andBSS12

PCU 1 BSCi,BSC2i

Max. BTSs 64 64

Max. TRXs 128 128

Max. SEGs 64 64

Max. radioTSLs

256 128

Max. Abischannels at16 kbps

256 256

Max. Gbchannels at64 kbps

32 32

PCU-S 1 BSCi,BSC2i

Max. BTSs 64 64

Max. TRXs 128 128

Max. SEGs 64 64

Max. radioTSLs

256 128


256 256


32 32

PCU-T 1 BSCi,BSC2i

Max. BTSs 64 64

Max. TRXs 128 128

Max. SEGs 64 64

Max. radioTSLs

256 256


256 256


32 32




Table 7. Connectivity of the first generation PCU (PCU1) (cont.)

PCUvariant

LogicalPCUs/board

BSC type Capability BSS10.5ED andBSS11

BSS11.5andBSS12

PCU-B 2 BSC3i Max. BTSs 2 x 64 2 x 64

Max. TRXs 2 x 128 2 x 128

Max. SEGs 2 x 64 2 x 64

Max. radioTSLs

2 x 256 2 x 256


2 x 256 2 x 256


2 x 32 2 x 32

Table 8. Connectivity of the second generation PCU (PCU2)

PCUvariant

LogicalPCUs/board

BSCtype

Capability BSS10.5ED andBSS11

BSS11.5andBSS12

PCU2-U 1 BSCi,BSC2i

Max. BTSs n/a 128

Max. TRXs n/a 256

Max. SEGs n/a 64

Max. radioTSLs

n/a 256


n/a 256


n/a 32



Table 8. Connectivity of the second generation PCU (PCU2) (cont.)

PCUvariant

LogicalPCUs/board

BSCtype

Capability BSS10.5ED andBSS11

BSS11.5andBSS12

PCU2-D 2 BSC3i Max. BTSs n/a 2 x 128

Max. TRXs n/a 2 x 256

Max. SEGs n/a 2 x 64

Max. radioTSLs

n/a 2 x 256


n/a 2 x 256


n/a 2 x 32

6.3.2 Input from Abis and BTS dimensioning

The total number of required Exchange Terminal (ET) plug-in units per BSC isnot taken into account in this BSC dimensioning because there is no Abisdimensioning. The total number of Abis and Gb (FR) links may not break the E1(T1) connectivity limit of the BSC.

Abis and dynamic Abis planning are described in the Abis EDGE Dimensioningdocument.

Inputs 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




6.4 PCU calculations for BSC EDGE dimensioning

In the packet control unit (PCU) dimensioning phase, dimensioning inputs (orguidelines) 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 amount of PCU cardscan be calculated.

Next, the capacity extension criteria of different EGPRS traffic related elementshave to be defined for the future capacity increase resulting from networkevolution. In the EDGE dimensioning guidelines, the dimensioning criterion isthat a maximum 75% of the total capacity of each configuration can be used and25% is reserved for future extensions. This usage has to be used for the ExchangeTerminal (ET) and PCU cards and for Gb interface licences. Therefore, similarcalculations have to be made for the ET cards and Gb interfaces.

It is recommended to leave some of the installed PCUs for future configurationupgrades and use the rest as efficiently as possible. This is achieved bydimensioning the PCUs using the formula in figure Needed PCU cards and thegiven design rules.

Figure 7. Needed PCU cards

L = roundup

TSLs

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

,

,

,

,

,

,



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

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

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

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

. 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 agiven logical PCU.

. TRXs is the total number of TRXs with GTRX = Y associated to a givenlogical PCU.

. BHGbThroughput is the total BHGb capacity required for the PS traffic fora given logical PCU as a number of 64k TSLs.

. U is the capacity reservation for territory upgrades. It is typically 75%.

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

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

N = L/2

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

N = L

6.5 Outputs of BSC EDGE dimensioning

BSC dimensioning results in specific outputs. These outputs are used as input inthe next dimensioning phase, Gb EDGE dimensioning.




Available capacity strategy

BSC dimensioning outputs:

. number and type of BSCs

Note that if EDGE is deployed into an existing network, the number andtype 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 strategy

BSC 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.



6.6 Evaluation of the BSC dimensioning results

The dimensioning process is often very iterative. If the number of required BSCsis too high, for example, new BTS dimensioning is required: coverage and trafficestimations need to be re-evaluated. A higher BSC usage level may help. Also anew transmission plan, including the optimisation of the number and size of theEGPRS dynamic Abis pools (EDAPs), has an impact on the number of packetcontrol units (PCUs) and digital signal processor (DSP) capacity.

First, only a certain maximum number of base stations and transceivers (TRXs) isconnected to the PCU cards, and the minimum amount of PCU cards can becalculated. Next, based on the traffic demand coming from the radio network, thefinal number of required PCU cards is calculated. The average traffic demand isused because we need to take into account the maximum use of the PCU card thatfuture extension needs and peak traffic cause.

The BSC and PCU can be selected according to the dimensioning results, keepingin mind the different possible configurations. For example, because of N+1redundancy principles one PCU1 or PCU2 plug-in unit is required for each BSCsignalling unit (BCSU), the number of activated PCUs is selected according tothe dimensioning results. It is important to apply the 75% usage criterion to afully 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 higherusage level can be used. Network growth can be achieved by adding extrahardware when needed.

Figure BSC redimensioning process illustrates what triggers redimensioning andwhat 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 size of the radiotimeslots

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



7 Example of BSS connectivitydimensioning

7.1 BSS connectivity dimensioning

The EDGE dimensioning guidelines include an example of BSS connectivitydimensioning. The example shows one calculation method for dimensioning thefollowing:

. default GPRS capacity (CDEF)

The value of the default GPRS capacity parameter is calculated inchapter Radio interface capacity.

. dynamic Abis pool (DAP) size

The size of the EGPRS dynamic Abis pool (EDAP) is calculated in chapterConnectivity capacity.

. number of packet control units (PCUs)

The number of PCUs is calculated in chapter Connectivity capacity.

. Gb link size

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

The dimensioning is not based on a detailed network audit with all theconfiguration, 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 controlfunctions (BCFs), BTSs, and transceivers (TRXs) with traffic volume assumptionof existing circuit-switched (CS) traffic and requirements on packet-switched(PS) data rate (if there is any).

The BSS connectivity dimensioning example uses all PCU1 variants. PCU2 isnot taken into account in the calculations.



Example of BSS connectivity dimensioning

7.2 Dimensioning inputs

The aim of the dimensioning is to calculate the default GPRS capacity (CDEF),EGPRS dynamic Abis pool (EDAP) size, number of packet control units (PCUs),and the size of the Gb link because EDGE/GPRS is implemented on top ofexisting 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) – Configuration 2

Figure 9. 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

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

Note that it is assumed that the given data amount per BTS does not need to besupported simultaneously in all BTSs. This information is used for EDAP and Gblink dimensioning.

7.3 Radio interface capacity

7.3.1 Configuration before (E)GPRS

Figures 2+2+2 configuration and 4+4+4 configuration show the TRXconfigurations used in the BSS connectivity dimensioning example.

Figure 10. 2+2+2 configuration

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




Figure 11. 4+4+4 configuration

In the 2+2+2 configuration, two radio timeslots (RTSLs) are reserved foruncombined signalling (broadcast control channel (BCCH) and stand-alonededicated control channel (SDCCH)), while the rest of the RTSLs are full rateRTSLs (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 E1for transmission.

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




Figure 12. E1 setup for 2+2+2 and 4+4+4 configurations

7.3.2 (E)GPRS deployment scenarios

All the TRXs are GPRS and EGPRS capable, so the following parameter setup isused:

. TRX: GTRX = Y

. BTS: GENA = Y, EGENA = Y, CMAX = 100%

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

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 BCFSIG 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 management Q1 management




Figure 13. RLC/MAC data rate dependency on signal level and C/I

In the BSS connectivity dimensioning example, the following average EGPRSradio 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 formaximum throughput. Depending on the frequency plan, this can be either aBCCH or TCH TRX. In the BSS connectivity dimensioning example, the BCCHTRX is preferred.

7.3.3 Available capacity

Before the calculations, the size of the free RTSL must be defined. FigureTerritories shows how two TRXs are divided into territories.

RLC/MAC data rate (FTP down 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)

kbps

No Interference

C/I 25 dB

C/I 20 dB

C/I 15 dB



Figure 14. Territories

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

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

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

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

Table 9. CSD and CSU parameter setup

TSL number after CS downgrade

TRX number 1 2 3 4 5

Free TSLs for CSdowngrade (%) (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 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

= (E)GPRS territory/additional capacityTS

TS

GTRX

GTRX

EGENA

BCCH




Table 9. CSD and CSU parameter setup (cont.)

TRX number 1 2 3 4 5

Free TSLs for CSupgrade (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

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 TSLvalues are used:

. 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 configuration

BTS 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 amountof BH traffic)

. erlang B table: 1.7% CS blocking during BH

. mean free RTSLs = 1.5

. average RTLSs 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 (requiredby 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


BTS 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 BHtraffic)

. 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 (requiredby the operator), which is 200 kbps for the "central area."

Default territory calculations

. MS multislot capability (4 RTSLs)

. data throughput: 200 kbit/s

. 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 capacity

The required capacity is the required streaming user support per BTS (onestreaming user). Streaming requires 50 kbit/s (required by the customer).

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


. 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.


. 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

7.4 Connectivity capacity

7.4.1 Default GPRS capacity (CDEF)

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




CDEF 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 radiotimeslots (RTSLs).


CDEF 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 considerations

The following must be taken into consideration when considering the size of theEGPRS dynamic Abis pool (EDAP):

. Whether support for MCS-9 at least with one mobile station (MS) in oneBTS of the base control function (BCF) is required. (This is needed if theMS multislot capability is not taken into account in the default territorycalculations.)

min_EDAP_1 = MS_multislot_capability (= 4 TSLs)

. Whether support for MCS-9 in all GPRS territory timeslots of the BTSs isrequired.

min_EDAP_2 = max_default_territory_size_of_one_BTS

. If the EDAP has more than one BTS attached to it, the BTS multiplexingfactor can be taken into account if it is estimated that the EDAP peak loadexceeds one BTSs territory size.

You can calculate the minimum EDAP size from the input with the followingformula:

min_EDAP_size = max(min_EDAP_1, min_EDAP_2)

You can calculate the EDAP size with the following formula:




EDAP_size = k x min_EDAP_size

Table BTS multiplexing factor shows the value for k for a different number ofBTSs.

Table 10. BTS multiplexing factor

Number of BTSs k

1 1.0

2 1.3

3 1.5

The EDAP size with different configurations can be calculated by using theinformation in table EDAP sizes with different configurations.

Table 11. EDAP sizes with different configurations

Number ofBTSs

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

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

min_EDAP_size = max(min_EDAP_1, min_EDAP_2) = max(4, 6) = 6 TSLs (64kbps)

The EDAP size for Configuration 2 (4+4+4) is

min_EDAP_size = max(min_EDAP_1, min_EDAP_2) = max(4, 9) = 9 TSLs (64kbps)

Abis timeslot allocation

There are two options for Abis TSL allocation:



. TRXs are grouped by function so that all EDGE TRXs and EDAP areallocated to one E1. The non-EDGE resources are mapped to another E1frame. One EDAP is enough to serve all cells (BTS objects).

Figure TRXs grouped by function illustrates grouping based on thefunction. Cell A is shown in grey.

Figure 15. TRXs grouped by function

. TRXs are grouped by cell so that two cells are allocated to one E1. Thethird cell is allocated to the second E1. In this case, and EDAP is createdfor both groups.

Figure TRXs grouped by cells illustrates grouping based on the cells. CellA is shown in grey.

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





Figure 16. TRXs grouped by cells

Both options have their advantages and disadvantages. These are shown in tablesTRXs grouped by function and TRXs grouped by cells.

Table 12. TRXs grouped by function

Advantages Disadvantages

The maximum trunking gain of the EDAPcan be achieved because less of totalAbis capacity is required (number of TSLsfor EDAP = 9).

Special care is needed to maintain andupgrade the configuration to keep with theoriginal split.

A smaller number of EDAPs saves PCUresources and Abis capacity.

The number of EDGE TRXs which can beconnected to the EDAP is smaller. Thisleads to a smaller maximum theoreticalterritory size.



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




Table 13. TRXs grouped by cells

Advantages Disadvantages

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

All TRXs can be connected into theEDAP, and the maximum territory sizedoes not depend on the Abisconfiguration.

A larger number of EDAPs consumesmore PCU resources.

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

7.4.3 PCU

The target is to calculate the optimal number of packet control units (PCUs) toserve the network. The calculation is based on table Connectivity of the firstgeneration PCU (PCU1) in chapter Inputs for BSC EDGE dimensioning.

The following are taken into account in this example:

. PCU usage is recommended to be around 75% for Abis timeslots (TSLs).(25% connectivity is available for territory upgrades.)

. The number of BTSs and TRXs can reach the maximum value (asspecified in table Connectivity of the first generation PCU (PCU1)).

. The recommended number of EGPRS dynamic Abis pools (EDAPs) perPCU1 is 1, 2, 4, or 8. With PCU2, the recommendation is a maximum of 8EDAPs per PCU. However, this example uses only PCU1.

. The optimal number of EDAPs and associated default radio timeslots(RTSLs) is calculated for each PCU configuration.. For example, up to 5 EDAPs of size 6 TSLs, serving three cells each

with a default territory size of 4 RTSLs, can be allocated to the PCUwithout exceeding 75% (see table Different configurations and theirAbis and RTSL load).

. To meet the 1, 2, 4, and 8 recommendation, the number of EDAPswould be 4.




Table 14. Different configurations and their Abis and RTSL load

EDAP splittingstrategy

N/A TRX grouped by cells TRX groupedby function

Configurations Configuration1

Configuration2 (cells A andB)

Configuration2 (cell C)

Configuration2 (cells A, B,and C)

EDAP size 6 6 8 9

Number of RTSLsin the territory

4 6 6 6

Number of BTSs(territories) perEDAP

3 1 2 3

Number of EDAPsubTSLs

24 24 32 36

Number of RTSLs 12 6 12 18

Number of AbissubTSLs

36 30 44 54

From table Different configurations and their Abis and RTSL load, Configuration2 with TRXs grouped by function is used in this example.

Table Possible PCU configurations lists the possible PCU combinations.Configuration 1 has 36 subTSLs and Configuration 2 has 54 subTSLs in the Abisinterface.

PCUconfiguration

A B C D E F G H I

Number of BCFswith Configuration 1

0 0 1 3 2 4 3 5 4

Number of BCFswith 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

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 tothe target value.

In this example, PCU configurations C and H are used. However, also otherconfigurations could be used.



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

. 5 PCUs with configuration C

. 4 PCUs with configuration H

(5 x (Configuration 1 + 3 x Configuration 2) + 4 x (5 x Configuration 1) = 15 xConfiguration 2 + 25 x Configuration 1

7.4.4 Gb link dimensioning

TBD

7.5 Results of BSS connectivity dimensioning

Table Dimensioning results shows the results of the BSS connectivitydimensioning example.

Table 15. Dimensioning results

Dual rate RTLSs 150

PCUs 9

E1s for Abis 15

E1s for Gb 3

Table Radio interface setup shows the radio interface setup of the BSSconnectivity dimensioning example.

Table 16. Radio interface setup

Configuration CDED CDEF EDAP

Configuration 1 2 4 6

Configuration 2 2 6 9

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




Table 17. PCU usage

Number ofPCUs

PCUconfigurations

Usage of AbisTSLs

Gb link size per PCUconfiguration

5 C 77% 11

4 H 70% 8



8 BSC traffic monitoring principles

When the BSC dimensioning has been done accurately, traffic flow is at anoptimal level, that is, traffic flow is as high as possible. You can use countersrelated to the radio interface to monitor the use and congestion level of the BSC.It is also useful to monitor the performance of all hardware units of the BSC.Good tools for this are EDGE key performance indicators (KPIs) and overloadalarms related to the hardware units. For more information on EDGE KPIs, seethe EDGE and GPRS Key Performance Indicators document.

To check whether dimensioning has been successful, you need to compare realtraffic against the traffic estimations done during the dimensioning. If there is aserious discrepancy, you have to re-plan the network.



BSC traffic monitoring principles

BSC EDGE Dimension Ing

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