nsn gsm edge abis dimensioning

Nokia Siemens Networks GSM/EDGE BSS, rel. RG10(BSS), operating documentation, issue 06

Plan and dimension

Abis EDGE Dimensioning

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The same text in German:

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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 24 pages.

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

1 Abis EDGE dimensioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.1 Definition of channels in EDGE transmission . . . . . . . . . . . . . . . . . . . . . 81.2 Dynamic Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2 Planning process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3 Key strategies for EDGE dimensioning . . . . . . . . . . . . . . . . . . . . . . . . . 12

4 Dimensioning process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.1 Dimensioning of network elements and interfaces . . . . . . . . . . . . . . . . 144.2 Abis EDGE dimensioning process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184.3 Inputs for Abis EDGE dimensioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . 204.4 Abis EDGE dimensioning calculations. . . . . . . . . . . . . . . . . . . . . . . . . . 214.5 Outputs of Abis EDGE dimensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . 224.6 Practical advice on detailed planning. . . . . . . . . . . . . . . . . . . . . . . . . . . 23

5 Abis traffic monitoring principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

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List of FiguresFigure 1 Allocation of Abis TSLs using different MCSs. . . . . . . . . . . . . . . . . . . . . 10Figure 2 Available data capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Figure 3 Required data capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Figure 4 Available data capacity process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Figure 5 Required data capacity process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Figure 6 Abis dimensioning process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

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List of TablesTable 1 BTS multiplexing factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

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Abis 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 5-0 and 4-1A note on BSS21226: Asymmetrical PCU HW Configuration has been added to section Available data capacity strategy in chapter Dimensioning of network elements and inter-faces.

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

Changes made between issues 4-0 and 3-0Updated the TRX dependency information.

Values of the bit rates for coding schemes were updated.

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Abis EDGE dimensioning

1 Abis EDGE dimensioningThese guidelines provide information on dimensioning the Abis interface for EDGE into an existing GSM network. The focus is on calculating the needed transmission capacity in the Abis interface for the successful operation of the EDGE network.

The dimensioning principles in EDGE networks differ quite dramatically from the trans-mission dimensioning in GSM/GPRS networks. This is due to the introduction of dynamic Abis, which makes it possible to transport higher data rate radio channels over the Abis interface more efficiently than static channel allocation in GSM/GPRS net-works. In GSM/GPRS networks, each timeslot in the radio interface has a corresponding timeslot in Abis where traffic (voice/data) is carried. Because higher data rates are sup-ported in EDGE networks than in GPRS networks, more capacity in Abis is needed in EDGE networks. This is handled by the EGPRS dynamic Abis pool (EDAP), which implements support for variable data rates.

Abis dimensioning results in a specific output that is used as input in the next dimension-ing phase, BSC EDGE dimensioning.

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. An example of BSS connectivity dimensioning is included in the BSC EDGE Dimensioning document.

1.1 Definition of channels in EDGE transmissionIn an EDGE transport network, the following channels must be carried via the available Abis links:

• transceiver (TRX) traffic channels (TCHs)TRX traffic channels carry user traffic (voice/data calls). Each TRX can contain a dif-ferent amount of these traffic carriers, but the maximum number of channels per TRX available for user traffic is eight (unless half rate is used). The actual number of these channels depends on the TRX TCH configuration. The number of the channels carrying user traffic can be less than eight if stand-alone dedicated control channels (SDCCH) or broadcast control channels (BCCH) are allocated to the TRX.The required Abis capacity for the given TRX is based on the channel allocation of the TRX. For each TCH on the TRX a 16k TCH channel is needed on Abis. In case a RTSL carries only signalling (BCCH, SDCCH) there is no need to reserve TCH on Abis for that particular RTSL. The signalling traffic of a TRX is carried by the TRX signalling link of the given TRX. Abis capacity is allocated for each TRX signalling link. If there is any feature activated which might change the role of a TRX dynamically it shall be taken into account when planning the Abis channel allocation.These channels are so called fixed allocation channels in Abis and the number of the channels does not change dynamically. The number of the fixed channels may change when the TRX channel configuration is changed.

• link access procedure on the D-channels (LAPD)LAPD channels (TRXSIG, OMUSIG) are used for signalling or managing the traffic between the BSC and BTS. There is one TRXSIG LAPD channel for each TRX. The capacity of the channel may vary. For example, the use of half rate affects the required capacity of the TRXSIG LAPD channels.

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Abis EDGE Dimensioning Abis EDGE dimensioning

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• channels in the EGPRS dynamic Abis pool, used to carry EGPRS data dynamicallyEDAP channels belong to the EGPRS dynamic Abis pool that is used for EGPRS data traffic. The dynamic Abis pool is used by EDGE traffic (MCS2-MCS9) or by GPRS with CS2 - CS4 (CS-2 only if an EDGE TRX is used). Voice and high speed circuit switched data (HSCSD) traffic use the statically allocated TRX traffic chan-nels.The amount of these channels depends on the data traffic (especially EGPRS). The amount of the channels may vary. In Flexi EDGE BTS the maximum number of EDAP channels in a single EDAP is 116 (29 DS0 or 64 kbit/s channel). In UltraSite and MetroSite BTSs, the maximum number is 48 channels (12 x 64 kbit/s PCM timeslots). Multiple pools can be created within one PCM circuit, within the limits of the physical capacity of the PCM.

• other channels (for example, E911 in the ANSI environment, Q1 management channel, and synchronisation control bits)Other channels that must be carried via Abis must be taken into account when dimensioning Abis. The other channels can include a management channel for addi-tional transmission equipment.All channels mentioned above are transported in the timeslots of the PCM frame. One 64 kbit/s timeslot can be divided into four 16 kbit/s timeslots. These 16 kbit/s timeslots are referred to as sub-timeslots. The timeslots in the radio interface are referred to as radio timeslots. The throughput of a radio timeslot depends on the used coding scheme.

1.2 Dynamic AbisThe Abis interface is static in GSM and GPRS with coding schemes 1 and 2. This means that the TRX TCH allocation onto the PCM timeslot does not change, regardless of whether there is traffic. Because of more efficient modulation and the use of higher coding schemes, EDGE networks are capable of delivering higher data rates than GPRS. For this reason, the concept of dynamic Abis has been introduced in Nokia Siemens Networks EDGE networks. In EDGE, some traffic timeslots are statically allo-cated as in GSM/GPRS, while other timeslots are allocated dynamically when needed. This enables a more efficient way of allocating Abis resources. It also makes it possible to share available resources from the EDAP during peak traffic.

Dynamic Abis is mandatory for EDGE and CS-3/CS-4.

For more information on Dynamic Abis, see chapter Dynamic Abis in (E)GPRS System Feature Description.

Allocation of Abis timeslotsIn Dynamic Abis, each timeslot in the radio interface has one corresponding fixed sub-timeslot in the Abis PCM frame. These statically allocated channels are called master channels. When the data rates go beyond 16 kbit/s (when the coding scheme is in the range from MCS2 to MCS9 and CS-3 and CS-4), extra traffic channels are required to handle the traffic, and these are allocated from the EDAP. The extra channels are called slave channels. This also applies to GPRS CS-2, if the GPRS temporary block flow (TBF) is set via a TRX that is connected to an EDAP. This is caused by the BTS-BSC inband signalling on the Abis interface. The inband signalling increases and the size of the radio link control (RLC) block increases from 268 bits to 368 bits (268 bps / 20 ms = 13.4 kbit/s, 368 bps / 20 ms > 16 kbit /s ).

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Abis EDGE dimensioning

Figure Allocation of Abis TSLs using different MCSs depicts the data rates of different coding schemes and the required amount of 16 kbit/s timeslots from the EDAP.

Figure 1 Allocation of Abis TSLs using different MCSs

Dynamic Abis capabilitiesThe following lists the capabilities of the Abis interface implementation:

• The maximum size of the dynamic Abis pool is 12 timeslots. • The master 16 kbit/s timeslots in the fixed part and the timeslots for the EDAP must

be located in the same PCM frame.If partial E1/T1 switching is used, the PCM timeslots that are supposed to be on the same E1/T1 frame must always be switched to the same path.

• All timeslots that belong to an EDAP should be contiguous. • One EDAP cannot be shared between several base control function (BCF) cabi-

nets. Sharing an EDAP between several cabinets may damage the TRX or the transmission unit (DTRU) hardware.

• The EDAP can be shared between the TRXs in the same BCF; it cannot be shared by the TRXs in different BCFs. As soon as a new BCF is added, a new pool is needed to take care of the packet-switched data handled by the BCF.

For more information on the connectivity restrictions of the PCU, see the BSC EDGE Dimensioning document.

There are also different BTS hardware restrictions for implementing the Abis interface. For more information on these restrictions, see the applicable BTS documentation.

Related topics

• BTS EDGE Dimensioning • BSC EDGE Dimensioning • Gb EDGE Dimensioning

CS-1CS-2CS-3CS-4

MCS-1MCS-2MCS-3MCS-4MCS-5MCS-6MCS-7MCS-8MCS-9

9050134001560021400

8,80011,20014,80017,60022,40029,60044,80054,40059,200

GPRS

EDGE

Coding scheme Bit rate (bps) Abis PCM allocation (fixed + pool)

Slavegroups

GMSK

GMSK

8-PSK

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Abis EDGE Dimensioning Planning process

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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

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

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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Key strategies for EDGE dimensioning

3 Key strategies for EDGE dimensioningThe 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 2 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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Abis EDGE Dimensioning Key strategies for EDGE dimensioning

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Figure 3 Required data capacity

Input information:

Current network configuration

Current equipment'sEDGE capability

Current network's voiceperformance

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

Required EDGE capacity

Required EDGE performance

Planned EDGE dataresources may be fully 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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Dimensioning process

4 Dimensioning process

4.1 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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Abis EDGE Dimensioning Dimensioning process

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• 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, 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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Dimensioning process

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. • Define the 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. • 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

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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• 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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4.2 Abis EDGE dimensioning processAbis dimensioning can be divided into the following steps:

1. Gather the necessary inputs.Note that if the input values are exaggerated, Abis capacity is unnecessarily wasted. Respectively, if the input values are too low, Abis capacity may become the bottle-neck of the BSS throughput when EDGE traffic is high.

2. Define the EGPRS dynamic Abis pool (EDAP) size based on the given inputs.Choose the minimum EDAP size from the multislot classes needed to be supported or from the maximum default territory size of a single BTS. Choose the option that requires a higher number of TSLs.If the EDAP has more than one BTS attached, the BTS multiplexing factor can be taken into account when calculating the sufficient EDAP size for multiple BTSs.

3. In detailed planning, check that the defined EDAPs fit into the existing E1/T1 links. Also check whether it would be beneficial to adjust the EDAP size based on the PCU connectivity (when upgrading an existing EGPRS BTS). Resize the EDAP, if needed, according to the principles described in the BSC EDGE Dimensioning doc-ument.

After the dimensioning and implementation of the EDAP in the Abis interface, it is impor-tant to monitor and evaluate the performance of the Abis interface by using certain traffic counters and key performance indicators (KPIs). With traffic monitoring, it is possible to verify the dimensioning traffic assumptions and to initiate re-dimensioning process according to traffic needs. For more information on the principles of traffic monitoring, see chapter Traffic monitoring principles in the EDGE and GPRS Key Performance Indi-cators document and chapter Abis traffic monitoring in this document.

The Abis dimensioning process is illustrated in a flowchart format in Figure Abis dimen-sioning process.

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Figure 6 Abis dimensioning process

Inputs for EDAPdimensioning

1. Site configurations2. Territory sizes3. MS multislot classes

STEP1

STEP2

Inputs for detailedplanning

1. Existing Abis configuration2. Possibility to add E1/T1 links

Capacity limitations of the BSC1. PCU capacity

Adjust the EDAPsize according toBTS multiplexing

STEP3

Resizing may havean impact on throughput

Doesthe EDAP

fit into the existingE1/T1 links?

Calculate theminimum EDAPsize

Enlarge the EDAPsize (if needed)

Abis dimensioning planis ready for implementation

Yes

No

Is itpossible toadd a newE1/T1 link?

Yes

No

Reduce theEDAP size

Resize the EDAP

Anybenefit to

resize the EDAPbased on

PCU?

Yes

No

Collect the inputs

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4.3 Inputs for Abis EDGE dimensioningThe following are the inputs for Abis EDGE dimensioning:

• the highest (or average) multislot class of the mobile stations (MSS) needed to be supported in the network

• the maximum default territory size of the BTSs attached to the EGPRS dynamic Abis pool (EDAP)

As choosing the highest multislot class may lead to overdimensioning of the EDAP, you may want to choose a value closer to the average multislot class in use in the network. Note that choosing the average multislot class in use means that users with higher than average multislot class MSS never achieve the maximum throughput.

Define the default territory size according to the principles described in the BTS EDGE Dimensioning document.

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4.4 Abis EDGE dimensioning calculationsChoose the minimum EGPRS dynamic Abis pool (EDAP) size from the multislot classes needed to be supported or from the maximum default territory size of a single BTS, whichever requires a higher number of TSLs. You can use the following calculation formula:

min_EDAP_size = max(MS_multislot_capability, max_default_territory_size_of_one_BTS)

If the EDAP has more than one BTS attached, the BTS multiplexing factor can be taken into account if the EDAP peak load is estimated to exceed one BTS. The BTS multiplex-ing factor (k) is chosen according to the number of attached BTSs and can be estimated, for example, with the following formula:

k = 2/(1+1/x)

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

The EDAP can be dimensioned using the following formula:

EDAP_size = k x min_EDAP_size

You can adjust the EDAP size in the detailed planning phase according to your needs.

Number of BTSs k

1 1.0

2 1.3

3 1.5

Table 1 BTS multiplexing factor

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4.5 Outputs of Abis EDGE dimensioningThe result of the Abis EDGE dimensioning process is the size of each EGPRS dynamic Abis pool (EDAP). The output is used as input in the next dimensioning phase, BSC EDGE dimensioning.

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4.6 Practical advice on detailed planningAfter the dimensioning of the Abis interface, the following need to be taken into consid-eration in the detailed planning phase:

• All the traffic channels (TCHs) of each transceiver (TRX) and their signalling links which are associated to the EGPRS dynamic Abis pool (EDAP) must be on the same E1/T1.

• There are two options for the Abis timeslot (TSL) allocation: TRXs can be grouped either by function or by cell. • Grouping by function so that all EDGE TRXs and EDAPs are allocated to one

E1, while the non-EDGE resources are mapped to another E1 frame. All cells are served by one EDAP.This option saves the packet control unit (PCU) resources and reduces the need for total Abis capacity because the maximum trunking gain of the EDAP is achieved. Careful consideration in the maintenance and upgrades of the config-uration is needed to maintain the functional split.

• Grouping by cell so that, for example, two cells are allocated to one E1 and the third one to a second E1. EDAPs are created for both groups.This approach is straightforward to maintain and upgrade. Smaller trunking gain of the EDAPs requires more total Abis capacity. In addition, the higher number of EDAPs uses more PCU resources.

• The use of several pools should be avoided, that is, one EDAP per base control function (BCF) is recommended.

• Only TRXs from one BCF can be connected to the same EDAP.

24 DN7032309Issue 5-0


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Abis traffic monitoring principles

5 Abis traffic monitoring principlesThe sufficiency of the downlink EGPRS dynamic Abis pool (EDAP) resources is the most important performance indicator to be followed in Abis traffic monitoring. Typically, downlink EDAP congestion starts before uplink EDAP congestion. If there is downlink congestion, it is important to monitor uplink congestion too. For information on key per-formance indicators (KPIs), see EDGE, GPRS, and GSM Voice Key Performance Indi-cators.

Counters 076000-076008 can be used to understand Abis traffic in more detail. For more information, see 76 Dynamic Abis Measurement.

To provide excellent end user throughput performance, it is important to ensure that dynamic Abis does not limit system throughput unnecessarily. If there is Abis conges-tion, the packet control unit (PCU) asks the mobile station to use lower modulation and coding scheme (MCS) classes to be able to get the data through Abis interface.

nsn gsm edge abis dimensioning

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