nokia - dynamic abis pool

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GSM/EDGE BSS, Rel.

RG20(BSS), Operating

Documentation, Issue 04

Feature description

BSS10045: Dynamic Abis

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Issue 5-0

Approval Date 2010-04-30

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Table of contentsThis document has 28 pages.

Summary of Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1 Overview of Dynamic Abis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2 System impact of Dynamic Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2 Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.3 Impact on transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.4 Impact on BSS performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.5 User interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.6 Impact on Network Switching Subsystem (NSS). . . . . . . . . . . . . . . . . . 14

2.7 Impact on NetAct products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.8 Impact on mobile stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.9 Impact on interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3 Technical description of Dynamic Abis . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.1 Capacity-related parameters of Dynamic Abis. . . . . . . . . . . . . . . . . . . . 16

3.2 Abis L1 frames. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.3 GPRS temporary block flow (TBF). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.4 EGPRS temporary block flow (TBF) . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4 Functionality of Dynamic Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.1 Dynamic Abis pool management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.2 EGPRS dynamic Abis pool connections . . . . . . . . . . . . . . . . . . . . . . . . 22

4.3 Dynamic Abis pool in a PCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23



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List of figuresFigure 1 An example of T1 allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 2 Equation 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 3 Equation 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 4 Equation 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 5 Equation 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 6 Equation 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 7 Equation 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 8 Equation 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 9 Equation 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 10 Equation 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28



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List of tablesTable 1 Required additional or alternative hardware or firmware . . . . . . . . . . . . 9

Table 2 Required software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 3 Impact of Dynamic Abis on BSC units . . . . . . . . . . . . . . . . . . . . . . . . . 12

Table 4 Counters of Dynamic Abis Measurement . . . . . . . . . . . . . . . . . . . . . . . 14

Table 5 Maximum number of DAPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Table 6 Coding schemes and need for master and slave channels on Abis. . . 17



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Summary of Changes

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

issue contains all changes made to previous issues.

Changes between issues 5-0 (2010/04/30, BSS15 RG20) and 4-1 (2000/02/02,

BSS14 RG10)

System impact of Dynamic Abis (2)

– Updated the section, Requirements for release RG20(BSS)

– Updated the section, User interface to include a new alarm- 3483 PCU

RESTARTED

Functionality of Dynamic Abis (4)

– Updated section Dynamic Abis pool management, EGPRS dynamic Abis pool con-

nections, and Dynamic Abis pool in a PCU to integrate the impact of BSS21232:

AUTOMATIC EDAP REALLOCATION IN PCU feature

Changes made between issues 4-1 and 4-0

Information on InSite BTS has been removed.

Changes made between issues 4-0 and 3-0

Information on Downlink Dual Carrier have been added.

Information on PCU2-E has been added and modified in sections System impact of

Dynamic Abis, Technical description of Dynamic Abis, and Functionality of Dynamic

Abis.

Information on PCU2-D/U has been modified in section Functionality of Dynamic Abis.



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BSS10045: Dynamic Abis Overview of Dynamic Abis

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1 Overview of Dynamic AbisDynamic Abis splits Abis E1/T1 transmission lines into:

• permanent 16 kbit/s sub-timeslots for signalling, voice, and data • Dynamic Abis pools (DAP) for radio timeslots that require more than 16 kbit/s

transmission capacity from Abis

The DAP area used by GPRS/EDGE is called the EGPRS dynamic Abis pool (EDAP).

The DAP can be shared by a number of EDGE-capable transceivers (TRXs) in the

same base control function (BCF) cabinet. The DAP and the TRXs sharing it have to

be allocated to the same Abis E1/T1 transmission line. The following figure illustrates an

example of T1 Dynamic Abis configuration; DAP 1 is shared by TRXs 1, 3, and 5:

Figure 1 An example of T1 allocation

In the BSC there can be two different GPRS/EDGE territory types:

1. GPRS territory with the following coding schemes:

TSL 1

TSL 12

TSL 13

TSL 18

TSL 24

MBCCH SDCCH TCHF TCHF

TCHFTCHFTCHFTCHF

TCHF TCHF TCHF TCHF

TCHDTCHF TCHDTCHD

TCHF TCHFSDCCHMBCCH

TCHF TCHFTCHFTCHF

TCHF

TCHF

TCHF TCHF TCHF

TCHDTCHDTCHD

TCHF TCHFSDCCHMBCCH

TCHF TCHFTCHFTCHF

TCHF

TCHF

TCHF TCHF TCHF

TCHDTCHDTCHD

TSIG5 TSIG6

TSIG4TSIG3

TSIG2TSIG1 OMU

EDGE TRX 1

TRX 2

EDGE TRX 3

TRX 4

EDGE TRX 5

TRX 6

BTS 1,SEGMENT 1

BTS 2,SEGMENT 2

BTS 3,

SEGMENT 3

BCF

DAP 16 X 64k

Signalling

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Overview of Dynamic Abis

• CS1 and CS2 packet data channels, no DAP required

• CS1 - CS4 packet data channels, DAP required

2. EGPRS territory with the following coding schemes:

• MCS1 - MCS9 and CS1 - CS2, DAP required • MCS1 - MCS9 and CS1 - CS4, DAP required

f

Sharing the EGPRS dynamic Abis pool (EDAP) between several cabinets may damage

the transceiver or transmission unit (TRU) hardware. One EDAP resource should not be

shared between several base control function (BCF) cabinets.

Benefits of Dynamic Abis

Dynamic Abis saves up to 60 per cent of the Abis transmission expansion cost, since it

allows Abis dimensioning to be performed closer to the average data rates instead of atpeak rates. This also applies to the reduced number of 2M BSC interfaces needed.

Related topics

Descriptions

• BSS20089: Extended Dynamic Allocation

• BSS9006: GPRS System Feature Description

• BSS10091: EDGE System Feature Description

• BSS20094: Extended Cell for GPRS/EDGE

• BSS21228: Downlink Dual Carrier Feature Description

Instructions

• Abis EDGE Dimensioning

• Testing and activating BSS10083: EGPRS

• Dynamic Abis Pool Handling

Reference

• ES - Abis Interface Configuration

• 1 Traffic Measurement

• 76 Dynamic Abis Measurement

• BSS Radio Network Parameter Dictionary

http://dn05115821.pdf/

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http://dn01444.pdf/









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BSS10045: Dynamic Abis System impact of Dynamic Abis

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2 System impact of Dynamic AbisThe system impact of BSS10045: Dynamic Abis is specified in the sections below.

Dynamic Abis is always required with EGPRS, Coding Schemes CS-3 and CS-4,Extended Cell for GPRS/EDGE, and Downlink Dual Carrier.

2.1 Requirements

Hardware requirements

Software requirements

Frequency band support

The BSC supports Dynamic Abis on the following frequency bands:

• GSM 800

• GSM 900

• GSM 1800

• GSM 1900

Network element Hardware/firmware required

BSC Packet control unit (PCU) plug-in units

BTS Flexi EDGE BTS, Flexi Multiradio BTS, UltraSite EDGE

BTS, MetroSite EDGE BTS, and/or BTS plusTCSM No requirements

SGSN No requirements

Table 1 Required additional or alternative hardware or firmware

Network element Software release

required

BSC S15

Flexi EDGE BTS EX4

Flexi Multiradio BTS EXM4

UltraSite EDGE

BTS

CX8.0

MetroSite EDGE

BTS

CXM8.0

BTS plus BRG2

Talk-family BTS Not supported

MSC/HLR No requirements

SGSN SG8.0

NetAct OSS5.2 CD set3

Table 2 Required software



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System impact of Dynamic Abis

2.2 Restrictions

Only Flexi EDGE BTSs, Flexi Multiradio BTS, UltraSite EDGE BTSs, and MetroSite

EDGE BTSs are able to use Dynamic Abis allocation. Furthermore, only EDGE-capable

TRXs (EDGE TRXs) are capable of using shared EGPRS dynamic Abis pool (EDAP)resources.

PCUPCM allocation restrictions

• One EDAP cannot be divided to separate packet control unit pulse code modula-

tions (PCUPCMs).

• digital signal processor (DSP) HW restriction: one PCUPCM timeslot (TSL) (64

kbit/s = 4 x 16 kbit/s sub-timeslots (SUB-TSLs) must be handled in one DSP core.

• The system does not allow an EDAP area to overlap with another EDAP area or with

GPRS/EDGE channels on PCMs.

Internal PCU1 restrictions

• Not more than 204 EDAP channels can be configured in one PCU1. This is because

there must also be space for at least one EGPRS channel for every four EDAP

channels (51 EGPRS channels + 204 EDAP channels = 255 Abis channels).

• In one logical PCU1 there are 16 DSP cores identified by even or odd indexes. In a

PCU1, one DSP core can handle only one EDAP, but one EDAP can be shared by

several DSP cores. The DSP cores sharing an EDAP must be either even-indexed

or odd-indexed DSP cores. Therefore the maximum number of DSP cores per one

EDAP is eight.

• In the PCU1s, one DSP core can handle 0 to 20 channels (16 kbit/s), including active

EDAP channels, EGPRS channels, and GPRS channels. The maximum number of

16 kbit/s channels per PCU is 256. A DSP core attached to EDAP can handle 16 radio timeslots, so four slave channels

are needed to reach the maximum number of channels.

A GPRS-dedicated DSP core can handle 20 GPRS master channels because slave

channel reservation is not needed.

• All EGPRS channels of one EDGE TRX must be handled in the DSP core which

handles the related EDAP. If an EDAP is handled in several DSP cores, the EGPRS

channels of one EDGE TRX can be divided to several DSP cores in a PCU1.

• In the uplink direction, the PCU1 allocates uplink EDAP resources for the highest

CS/MCS granted for an MS during the TBF's lifetime.

• In PCU1 there is one synchronisation master channel (SMCH) for every EDAP.

Because of DSP restrictions, the SMCH must be allocated on PCUPCM0. To ensure

that each EDAP has SMCH candidates on PCUPCM0, the PCU1 reserves a number

of sub-timeslots from PCUPCM0 exclusively for each EDAP, that is, for the EGPRS

on the TRXs attached to the EDAP.

• PCU and PCU-S can handle 128 radio timeslots. This issue should be taken into

account in PCU dimensioning.

Internal PCU2-D and PCU2-U restrictions

• In one logical PCU2-D or PCU2-U there are eight DSP cores. In a PCU2-D or PCU2-

U, one DSP core can handle two EDAPs, but one EDAP can be shared by several

DSP cores.

• In the PCU2-D or PCU2-U, one DSP core can handle 0 to 40 channels (16 kbit/s),

including active EDAP channels, EGPRS channels, and GPRS channels. The















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maximum number of 16 kbit/s channels per PCU2-D or PCU2-U is 256. Note that

the maximum number of EGPRS channels and GPRS channels is 32 per DSP core.

To reach 40 channels there have to be at least eight EDAP channels.

• All EGPRS channels of one EDGE TRX must be handled in the single DSP core

which handles the related EDAP.

• In PCU2-D or PCU2-U, there is one SMCH for each EDAP in every DSP. The PCU2-

D or PCU2-U can allocate the SMCHs to both PCUPCMs 0 and 1.

Internal PCU2-E restrictions

• In the PCU2-E, one DSP core can handle up to 212 channels (16kbit/s), including

active EDAP channels, EGPRS channels, and GPRS channels. The maximum

number of Abis channels per PCU2-E is 512 in BSC3i 660, BSC3i 1000, and BSC3i

2000. In Flexi BSC, the maximum number of Abis channels per PCU2-E is 1024.

• Not more than 816 EDAP channels can be configured in one PCU2-E. This is

because there must also be space for at least one EGPRS channel for every four

EDAP channels (204 EGPRS channels + 816 EDAP channels = 1020 Abis chan-

nels).

• One EDAP cannot be divided between several DSPs but one DSP can have a

maximum of 10 EDAPs.

Common restrictions for both PCU1 and PCU2

• EDAP resource usage in a PCU dynamically reserves the DSP resources in the

PCU. When EGPRS and GPRS calls (TBFs) in EGPRS territory use EDAP

resources, allocation of the new packet switch (PSW) radio timeslots to the PCU

may fail due to the current EDAP and DSP resource load.

• When new PSW radio timeslots are added/upgraded to the PCU, the PCU DSP

resource capacity used for the EDAPs decreases. This may lead to a situationwhere the desired CS/modulation and coding scheme (MCS) cannot be assigned to

the TBFs. In downlink direction, the TBFs can adjust the downlink data according to

limited Dynamic Abis capacity. In uplink direction, the PCU DSP resource load situ-

ation may cause a situation in which the uplink transmission turns cannot be

assigned for the MSS, for example if adequate uplink Dynamic Abis resources

cannot be allocated.

• The EDAP size itself also limits the CS/MCS usage for both downlink and uplink

TBFs.

2.3 Impact on transmission

More transmission capacity is needed because Dynamic Abis splits Abis E1/T1 trans-

mission lines into:

• permanent 16 kbit/s sub-timeslots for signalling, voice, and data

• Dynamic Abis Pools (DAP) for radio timeslots that require more than 16 kbit/s trans-

mission capacity from Abis

2.4 Impact on BSS performance

OMU signalling

No impact.



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TRX signalling

No impact.

Impact on BSC units

Impact on BTS units

No impact.

2.5 User interface

BSC MMI

The following command groups and MML commands are used to handle dynamic Abis

pool:

• Abis Interface Configuration: ESE, ESM, ESG, ESI

In addition, the MML command ERM (Transceiver Handling) is used to modify trans-

ceiver (TRX) parameters, including the DAP parameter.

For more information on the command groups and MML commands, see MML com-

mands.

BTS MMI

Dynamic Abis cannot be managed with BTS MMI.

BSC parameters

Dynamic Abis Pool (DAP) radio network object parameters

• BCSU ID (BCSU)

• circuit (CRCT)

• new first time slot (NFT) • new last time slot (NLT)

BSC unit Impact

OMU No impact

MCMU No impact

BCSU No impact

PCU You can create a maximum of 16 DAPs in

one PCU1, PCU2-D, or PCU2-U. In case

of PCU2-E, the maximum number of

EDAPs is 60 in BSC3i 660, BSC3i 1000,

BSC3i 2000, and Flexi BSC.

There can be a maximum of 256 channels(including dedicated GPRS + default

GPRS + EDAP channels) in one PCU1,

PCU2-D, or PCU2-U, of which 204 can be

EDAP channels. The maximum number of

channels is 512 in PCU2-E in BSC3i 660,

BSC3i 1000, and BSC3i 2000. In Flexi

BSC, the maximum number of channels is

1024.

Table 3 Impact of Dynamic Abis on BSC units















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• packet service entity identifier (PSEI)

• PCU index (PCU)

• pool identification (ID)

• pool size (SIZE)

Transceiver (TRX) radio network object parameters

• TRX(s) connected to pool(s) (TRXS)

• dynamic abis pool ID (DAP)

For more information, see BSS Radio Network Parameter Dictionary .

Alarms

The following listed alarms can be generated in connection with Dynamic Abis:

For more information, see Failure printouts (2000-3999).

For an overview, see Overview of Dynamic Abis.

Measurements and counters

The following measurements and counters are related to Dynamic Abis:

1 Traffic Measurement

Traffic Measurement includes counters, for example, for partially successful and failed

territory upgrade requests.

76 Dynamic Abis Measurement

Alarm Type This alarm is set when...

3068 EGPRSDYNAMIC ABIS

POOL FAILURE

• BSC cannot attach DAP circuits to EDAP (all successfullyconnected DAP circuits are attached to EDAP)

• BSC cannot connect one DAP circuit to EDAP because of

connection failure

• EDAP configuration update or an EDAP modification to

PCU fails

The PCU capacity (for example, PCU DSP resource load

for ongoing EGPRS calls using EDAP resources) may

limit the EGPRS and GPRS RR procedures. It is possible

that new GPRS traffic channels (TCHs) cannot be added

to the PCU. Therefore, territory upgrades fail either partly

or completely.

3273 GPRS/EDGE

TERRITORY

FAILURE

GPRS/EDGE territory size in the BTS is below the limit spec-

ified by the BTS-specific radio network parameter default

GPRS capacity (CDEF). The BSC has not been able to

add more radio channels to the territory within informing

delay. The BSC's ability to transfer GPRS/EDGE traffic in the

BTS has been reduced or totally prevented.

For more information, see Problems with territory operations

in Handling Common Problem Situations in BSC .

3483 PCU

RESTARTED

PCU Hot restart is initiated and cancelled after restart is com-

pleted. During the DAP operation, the PCU Hot restart is per-formed to the PCU, where the DAP is connected













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The purpose of Dynamic Abis Measurement is to help you to monitor and control the use

of EDAPs and to give you a better possibility to configure and optimise, for example, the

EDAP sizes. There are separate counters for both uplink and downlink measurements.

For more information, see 1 Traffic Measurement and 76 Dynamic Abis Measurement .

2.6 Impact on Network Switching Subsystem (NSS)

No impact.

2.7 Impact on NetAct products

NetAct Administrator

No impact.

NetAct Monitor

NetAct Monitor can be used to monitor all alarms related to Dynamic Abis. For a list of

the alarms, see section Alarms.

NetAct Optimizer

No impact.

NetAct Planner

You may have to take Dynamic Abis into consideration in TRX dimensioning.

Name Number

TOTAL PCM SUBTSLS IN EDAP 076000

AVERAGE DL EDAP USAGE 076001

AVERAGE UL EDAP USAGE 076002

AVERAGE EDAP USAGE DEN 076003

PEAK DL EDAP USAGE 076004

PEAK UL EDAP USAGE 076005

UL TBFS WITHOUT EDAP RES 076006

DL TBFS WITHOUT EDAP RES 076007DL TBFS WITH INADEQUATE EDAP RES 076008

UL EDAP ALLOCATION REQUESTS 076009

DL EDAP ALLOCATION REQUESTS 076010

TOT NBR OF PCM STS IN EDAP UL 076017

DYNAMIC ABIS DENOM UL 076018

UL MCS LIMITED BY PCU 076019

DL MCS LIMITED BY PCU 076020

Table 4 Counters of Dynamic Abis Measurement





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NetAct Configurator

NetAct Configurator can be used to configure the radio network parameters related to

Dynamic Abis. For more information, see BSS RNW Parameters and Implementing

Parameter Plans in Nokia Siemens Networks NetAct Product Documentation. For a listof the radio network parameters, see section BSC parameters.

NetAct Reporter

NetAct Reporter can be used to view and create reports from measurements related to

Dynamic Abis. For a list of the measurements, see section Measurements and counters.

NetAct Tracing

No impact.

2.8 Impact on mobile stations

GPRS/EDGE-capable mobile stations are required.

2.9 Impact on interfaces

Impact on radio interface

No impact.

Impact on Abis interface

• Abis Telecom interface

No impact.

• Abis O&M interfaceDynamic pool info IE has been added to the following Abis O&M messages:

• BTS_CONF_DATA

• AC_BSC_CIRCUITS_ALLOCATED

Impact on A interface

No impact.

Impact on Gb interface

No impact.



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Technical description of Dynamic Abis

3 Technical description of Dynamic Abis

3.1 Capacity-related parameters of Dynamic AbisDynamic Abis pool (DAP) is a continuous block of 64 kbit/s timeslots reserved from

external pulse code modulation line (ET-PCM). The maximum size of one DAP in a

packet control unit (PCU) is 24 timeslots but the BTSs, with the exception of Flexi EDGE

BTS, limit the usable size into 12 timeslots. The maximum number of all DAPs in one

PCU is 51 timeslots in PCU1, PCU2-D, and PCU2-U. The maximum number of DAPs in

one PCU is 204 timeslots in PCU2-E in Flexi BSC. In BSC3i 1000 and BSC3i 2000, the

maximum number of DAPs is 102 timeslots in PCU2-E.

There can be a maximum of 16 DAPs per PCU in PCU1, PCU2-D, and PCU2-U. The

maximum number of DAPs per PCU is 60 in PCU2-E in BSC3i 660, BSC3i 1000, BSC3i

2000, and Flexi BSC. Table Maximum number of DAPs lists the maximum number of

DAPs in different BSC variants. The value range of DAP identifier is from 1 to 1800.

The theoretical maximum number of transceivers (TRXs) per DAP is 20. However, since

TRXs using DAP resources must be allocated to the same Abis external pulse code

modulation (ET-PCM) line with EGPRS dynamic Abis pool (EDAP), the maximum TRX

count for a DAP is 12 in the ETSI environment and 8 in the ANSI environment.

The capacity of a specific EDAP depends on:

• the total number of EDAPs in the PCU

• the EDAP size

• the number of EDGE TRXs and EGPRS channels/packet data channels (PDCHs)

connected to the EDAP • the modulation and coding schemes (MCS) used in data transmission.

The MCSs that are used are selected by the PCU based on the radio link quality mea-

surements and link adaptation algorithms. Operator parameters for initial MCSs are also

taken into account when selecting an MCS for data transmission. However, Dynamic

Abis capacity (EDAP size and available PCU digital signal processor (DSP) resources)

also affects MCS usage and because of this, Dynamic Abis and PCU capacity limitations

are also taken into account in MCS selection.

Dynamic Abis counters monitor EDAP usage and Dynamic Abis limitations. You may

have to consider the following actions if the Dynamic Abis counters indicate problems in

Dynamic Abis usage:

BSC variant Number of DAPs

BSCi 128

BSC2i 256

BSC3i 660 384

BSC3i 1000 800

BSC3i 2000 1600

Flexi BSC 1800

Table 5 Maximum number of DAPs










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• increasing EDAP size

This may help, for example, in cases where the EDAP counters indicate that tem-

porary block flows (TBFs) are left without requested EDAP resources, EDAP peak

usage is 100%, EDAP average usage is high, but EDAP resource limitations are not

caused by the lack of PCU resources.

• decreasing the number of EDGE TRXs and/or EGPRS channels attached to EDAP

• sharing the load between PCUs, that is moving EDAP(s) and/or GPRS channels

from one PCU to another

• changing the radio network (RNW) configuration and EDAP configuration so that

PCU1 dedicates DSP resources for GPRS usage

For more information, see section Dynamic Abis pool in a PCU .

The last three actions may help, for example, in cases where the EDAP counters

indicate that TBFs are left without requested EDAP resources and EDAP resource

limitations are caused by the lack of PCU resources.

Note that the EDAP size is the same for both downlink and uplink directions. It is notpossible to set different EDAP sizes for downlink and uplink directions.

3.2 Abis L1 frames

In Nokia Siemens Networks GPRS/EDGE implementation, PCU frames (based on

transcoding and rate adaptation unit (TRAU) frames in circuit switched (CS) traffic)

are used to carry the packet switched (PS) traffic over the Abis interface. One PCU

frame uses a 16 kbit/s sub-timeslot. There are the following PCU frame types:

• PCU data frame

is used when TRX is not in EDGE mode and is able to carry CS-1 and CS-2

• PCU master data frameis used when TRX is in EDGE mode and carries CS-1 or MCS-1 on its own and CS-

2...CS-4 and MCS-2...MCS-9 with the help of slave frame(s)

• PCU slave data frame(s)

is used to carry additional data that does not fit in PCU master data frames

• PCU random access frame

is used only in uplink direction to carry access burst information

• PCU synchronisation frame

is used after territory upgrade for synchronising PCU with BTS radio timeslots

Master and slave channels with different coding schemes

PCU slave data frames are transferred in the EDAP area and they are always associ-ated with the PCU master data frames transferred in the permanent 16 kbit/s sub-

timeslots. The following table displays the number of 16 kbit/s sub-timeslots required by

different coding schemes.

CS/MCS

Need for master

(M) and slave (S)

channels

CS-1 M

CS-2 M+S

Table 6 Coding schemes and need for master and slave channels on Abis.























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Technical description of Dynamic Abis

The MS may use a lower coding scheme (CS)/modulation and coding scheme (MCS)

for uplink data transmission than the CS/MCS for which uplink EDAP resources have

been reserved.

3.3 GPRS temporary block flow (TBF)In the BSC, there can be separate territories for GPRS and EGPRS. In GPRS load sit-

uations or when a GPRS territory does not exist, it is possible that GPRS traffic (GPRS

TBFs) uses EGPRS territory. When a GPRS TBF is via GPRS territory (via a non-EDGE

TRX), the CS-2 coding scheme needs only 16 kbit/s from Abis. When a GPRS TBF is

via CS-3 and CS-4 capable GPRS territory or via EGPRS territory (via an EDGE TRX),

the CS-2 coding scheme needs a 16 kbit/s master Abis channel and one 16 kbit/s slave

channel from the EDAP. This is because the EDGE TRX uses different PCU frame

formats. Coding Schemes CS-3 and CS-4 always uses EDAP.

If a 16 kbit/s slave channel for a GPRS TBF cannot be found, for example, because of

EDAP load situations, the coding schemes CS-2 - CS-4 cannot be used. In the uplink

direction, the MS's transmission turn may have to be rejected. In the downlink direction,CS-1 may be used instead of CS-2 - CS-4 in certain cases. Applicable counters are

updated.

For more information, see BSS9006: GPRS System Feature Description and

BSS10091: EDGE System Feature Description.

3.4 EGPRS temporary block flow (TBF)

The GPRS RR procedures apply to EGPRS as well. The difference is that the EGPRS

needs more than 16 kbit/s Abis transmission capacity. The master Abis channel is

always linked to a packet data traffic channel (PDTCH). The rest of the required Abis

transmission is allocated from the EDAP in 16-64 kbit/s blocks, depending on the codingscheme (MCS) used. The Dynamic Abis resource information and coding scheme is

CS-3 M+SCS-4 M+S

MCS-1 M

MCS-2 M+S

MCS-3 M+S

MCS-4 M+S

MCS-5 M+S

MCS-6 M+ 2*S

MCS-7 M+ 3*S

MCS-8 M+ 4*S

MCS-9 M+ 4*S

CS/MCS

Need for master

(M) and slave (S)

channels

Table 6 Coding schemes and need for master and slave channels on Abis. (Cont.)





















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transmitted to the BTS by in-band signalling in the PCU master data frame transferred

on the master Abis channel.

If enough 16 kbit/s slave channels for the coding scheme (MCS) used by the EGPRS

TBF cannot be found because of the EDAP load situation, the desired coding schemecannot be used. In the uplink direction, the MS's transmission turn may have to be

rejected. In the downlink direction, a lower coding scheme may be used instead of the

desired coding scheme in certain cases. Applicable counters are updated.





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Functionality of Dynamic Abis

4 Functionality of Dynamic Abis

4.1 Dynamic Abis pool managementDynamic Abis is mandatory when EGPRS, Coding Schemes CS-3 and CS-4, Extended

Cell for GPRS/EDGE, or Downlink Dual Carrier support in the BSC and in the Packet

Control Unit (PCU) is enabled. If Dynamic Abis is used, you must define the pool to be

used by the Transceiver (TRX). It must be located on the same Abis external PCM circuit

(ET-PCM) as the TRX channel (TRXSIG) and the fixed traffic timeslots.

Activating dynamic Abis pool for GPRS/EDGE use

You can allocate common transmission resources for EDGE-capable TRXs from the

Abis ET-PCM. This common resource is called the Dynamic Abis Pool (DAP) and it is

comprised of consecutive Abis ET-PCM timeslots. There can be several DAPs in one

Abis ET-PCM but normally only one is needed. The DAP has to be created before theEDGE TRXs that use the DAP are created to the Abis ET-PCM. If you want to change

the TRX's usage of Dynamic Abis, a DAP can be attached or detached from the TRX.

When a DAP is created, the BSC reserves the corresponding block of timeslots from the

Packet Control Unit Pulse Code Modulation (PCUPCM) line. These PCUPCM circuits

are needed when DAP circuits are connected to EGPRS use. Following the DAP cre-

ation, the BSC updates the database for DAP configuration and then initiate the PCU

Hot restart in PCU. During the PCU Hot restart process, the BSC turns off the GPRS

traffic from all segments configured to the PCU, releases all EDAP connections from the

PCUPCM and then restarts the PCU. After the completion of PCU restart, BSC recon-

nects all EDAPs again to PCUPCM and turns on the GPRS traffic in all segments con-

figured to the PCU. This short interruption ensures that the BSC can find a block of freetimeslots from the PCUPCM, as all EDAPs are consecutively connected in PCUPCM

and there are no free timeslots (TSLs) between the EDAPs. PCU Hot restart also

ensures the optimized PCU Digital Signal Processor (DSP) resource usage for each

EDAP connected to the PCU. If Packet Control Unit (PCU2) Pooling is in use and the

DAP is created for a Packet Service Entity (PSE), this kind of interruption in the GPRS

traffic takes place in the PCU where the PCU selection algorithm attaches the DAP. For

instructions on how to handle dynamic Abis pools in the BSC, see Dynamic Abis Pool

Handling .

Dynamic Abis pool modification

You can change the size of the DAP by adding Abis ET-PCM timeslots to the DAP, or

by removing Abis ET-PCM timeslots from the DAP. However, such changes must firstbe performed on the BTS side.

The integrity of the DAP is kept up in the modification operations. This means that new

Abis ET-PCM timeslots are added to either upper or lower edge of the DAP and Abis

ET-PCM timeslots are removed from either upper or lower edge of the DAP.

When new Abis ET-PCM timeslots are added to the DAP, the BSC reserves a corre-

sponding block of timeslots from the PCUPCM. These PCUPCM circuits are needed

when DAP circuits are connected to EGPRS use. When the DAP is modified, the BSC

updates the database for DAP configuration and then initiate the PCU Hot restart in

PCU. During the PCU Hot restart process, the BSC turns off the GPRS traffic from all

segments configured to the PCU, releases all EDAP connections from the PCUPCM

and then restarts the PCU. After the completion of PCU restart, BSC reconnects all









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EDAPs again to PCUPCM and turns on the GPRS traffic in all segments configured to

the PCU. This short interruption ensures that the BSC can find a block of free timeslots

from the PCUPCM, as all EDAPs are consecutively connected in PCUPCM and there

are no free timeslots (TSLs) between the EDAPs. PCU Hot restart also ensures the opti-

mized PCU DSP resource usage for each EDAP connected to the PCU.

You can also change the controlling PCU of the DAP. When the DAP's PCU is changed,

the BSC initiates the hot restart for both the old and new PCU and then upgrades these

same traffic channels to packet switched use again. This short interruption ensures opti-

mized PCU DSP resource usage for each DAP connected to those PCUs. If there are

one or more TRXs attached to that pool, the packet switched channels of the segments

of the TRXs are upgraded to the new PCU. If Packet Control Unit (PCU2) Pooling is in

use, the controlling PCU of the DAP can be changed also during PSE reallocation. For

operating instructions on how to handle dynamic Abis pools in the BSC, see Dynamic

Abis Pool Handling .

Dynamic Abis pool deletion

You can delete a DAP when there are no TRXs attached to it. The BSC releases all

resources reserved for the DAP when it is deleted. Following the DAP deletion, the BSC

updates the database for DAP configuration and then initiate the PCU Hot restart in

PCU. During the PCU Hot restart process, the BSC turns off the GPRS traffic from all

segments configured to the PCU, releases all EDAP connections from the PCUPCM

and then restarts the PCU. After the completion of PCU restart, BSC reconnects all

EDAPs again to PCUPCM and turns on the GPRS traffic in all segments configured to

the PCU. This short interruption ensures that the BSC can find a block of free timeslots

from the PCUPCM, as all EDAPs are consecutively connected in PCUPCM and there

are no free timeslots (TSLs) between the EDAPs. PCU Hot restart also ensures the opti-

mized PCU DSP resource usage for each EDAP connected to the PCU. For operatinginstructions on how to handle dynamic Abis pools in the BSC, see Dynamic Abis Pool

Handling .

Dynamic Abis pool circuit routings

Circuit routings are needed for Abis ET-PCM circuits to use Dynamic Abis in the BSC.

The BSC makes these routings automatically when a DAP is created, modified, or

deleted.

The BSC adds Abis ET-PCM circuits to a circuit group called ET-PCM at the same time

as the Abis ET-PCM circuits are added to the DAP. This prevents other use of these

Abis ET-PCM circuits while they belong to the DAP. The ET-PCM circuit group is shared

by all DAP circuits.The BSC also has a specific circuit group for every DAP. These DAP circuit groups are

called DAPxxxx , where 'xxxx' indicates the dynamic Abis pool number with four digits.

The DAP circuit group is specially designed for Dynamic Abis and it enables hunting and

connection methods required by Dynamic Abis. The BSC adds DAP circuits to the DAP

circuit group as one-bit wide circuits which are in ascending order according to timeslots

and sub-timeslots. The BSC changes the states of these circuits from BA to WO at the

same time as the circuits are added to the circuit group.

g Removing Dynamic Abis Pool (DAP) routings causes malfunction of the dynamic Abis.

Do not change DAP routings manually even if it is possible with MML commands

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4.2 EGPRS dynamic Abis pool connections

The procedure where Dynamic Abis Pool (DAP) circuits are connected to EGPRS use

is called the EGPRS dynamic Abis pool (EDAP) upgrade procedure and the procedure

where DAP circuits are removed from EGPRS use is called the EDAP downgrade pro-cedure. If GPRS service is provided with an EDGE TRX, EDAP circuits may also be

used for GPRS. In the EDAP upgrade and downgrade, the BSC downgrades all packet

switched traffic channels from the PCU and then upgrades these same traffic channels

to packet switched use again. This short interruption ensures optimized PCU DSP

resource usage for each DAP connected to the PCU.

EGPRS dynamic Abis pool upgrade

The BSC performs the EDAP upgrade procedure, when:

1. DAP is created

2. new circuits are added to a DAP

3. switchover is made for the Base Station Controller Signalling Unit (BCSU)

4. BCSU is restarted

5. PSE is reallocated (Packet Control Unit (PCU2) Pooling)

6. PCU is restarted

The upgrade procedures for PCU1 and PCU2 are different.

• PCU1

There are two phases in the EDAP upgrade procedure for PCU1. In the first phase

the BSC makes connections between Abis ET-PCM circuits and packet control unit

pulse code modulation (PCUPCM) circuits. In the second phase the BSC attaches

DAP circuits to EDAP by informing the PCU1 about mappings between the Abis ET-

PCM circuits and the PCUPCM circuits.The BSC searches for a continuous block of free timeslots for the EDAP starting

from the end of the second PCUPCM and continuing from the end of the first

PCUPCM. The search is stopped when a free block is found or the area reserved

for the EDAP-dedicated timeslots is reached. The EDAP is then connected to the

free place found in the PCUPCM.

• PCU2

At the start-up phase, the BSC searches for a free place for EDAP from the ET-

PCMs and PCUPCMs and informs the PCU2 about EDAP count and sizes. After all

EDAP resources have been assigned to the PCU2, the BSC sends the EDAP infor-

mation messages for all EDAPs to the PCU2. These messages contains the ET-

PCM mappings and suggestions for PCUPCM mappings.

When the PCU2 receives the messages, it starts to perform reverse PCUPCM

resource allocation algorithm. This algorithm is used by the PCU2 to search for the

best place for EDAP from the PCUPCM. The PCU2 can accept or reject the sug-

gested PCUPCM mapping. If the PCU2 accepts the suggestion for EDAP, it

responds to the EDAP information message with the same PCUPCM mappings. If

the PCU2 finds a better place for EDAP, it responds with the new PCUPCM map-

pings. When the BSC receives the response, it makes the connection between the

ET-PCM and PCUPCM circuits assigned to EDAP.

EGPRS Dynamic Abis Pool downgrade

The BSC starts the EDAP downgrade procedure, when:

1. DAP is deleted























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2. circuits are removed from a DAP

3. switchover is made for the Base Station Controller Signalling Unit (BCSU)

4. BCSU is restarted

5. PSE is reallocated (Packet Control Unit (PCU2) Pooling)6. PCU is restarted

The downgrade procedures for PCU1 and PCU2 are different:

• PCU1

There are two phases in the EDAP downgrade procedure. In the first phase the BSC

detaches DAP circuits from the EDAP by informing the PCU about changed

mappings between Abis ET-PCM circuits and PCUPCM circuits. In the second

phase the BSC releases connections between the Abis ET-PCM circuits and the

PCUPCM circuits.

• PCU2

As in the upgrade procedure, PCU2 also uses the reverse PCUPCM allocation algo-

rithm in the EDAP downgrade. This ensures that the EDAP area in the PCUPCM is

as consecutive as possible, because removing PCUPCM timeslots from the begin-

ning of the EDAP could lead to PCUPCM fragmentation.

PCU restart

When the PCU is restarted, the BSC releases all EDAP connections related to the PCU.

After the PCU becomes operational again, the BSC runs an upgrade procedure for each

EDAP controlled by the PCU. The PCU shares the DSP resources optimally for all the

EDAPs when the PCU is restarted.

BCSU restart

When the BCSU is restarted, the BSC releases all EDAP connections related to theBCSU. After the PCU becomes operational again, the BSC runs an upgrade procedure

for each EDAP controlled by the PCU. The PCU shares the DSP resources optimally for

all the EDAPs when the BCSU is restarted.

BCSU switchover

If a switchover is made for the BCSU, the BSC releases all EDAP connections related

to the old BCSU and then starts an upgrade procedure to recover the EDAP connections

in the new BCSU. The PCU shares the DSP resources optimally for all the EDAPs in the

BCSU switchover.

4.3 Dynamic Abis pool in a PCU A PCU shares DSP resources optimally for EDAPs when a new dynamic Abis pool is

created or an existing pool is deleted or modified. The DSP resources are also shared

after PCU restart, BCSU restart or switchover. The PCU shares all (working) DSP cores

between all EDAPs connected to the PCU by using a PCU internal algorithm. The PCU

DSP resources for an individual EDAP depends on the total number of EDAPs for the

PCU and on EDAP-specific properties (EDAP size and attached default EGPRS

channel count).

Since there are some differences between PCU1 and PCU2 in the DSP allocation for

EDAPs algorithm, the description is divided into two parts.











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PCU1

First PCU1 calculates the ideal DSP core count for each EDAP by using equation 1

(which is the same for PCU1 and PCU2).

Figure 2 Equation 1

where

• EDAPsizeIn16kbit/sChs is the EDAP size in 16 kbit/s PCM sub-timeslots (SUB-

TSLs)

• DefaultEGPRSchs is the sum of the default EGPRS channels of all the TRXs (BTSs)

attached to the EDAP

• 20 is in the case of PCU1 the channel handling capacity of a single DSP core in 16

kbit/s Abis channels and in the case of PCU2 the channel handling capacity of a half

DSP core in 16 kbit/s Abis channels

The result of the ideal DSP core count calculation is rounded up.

If the result of the algorithm that calculates the ideal DSP core counts for each EDAP

indicates that all available DSP cores are not needed for EDAPs, the PCU1 may

dedicate DSP cores also for GPRS channels, that is for the radio timeslots of TRXs not

attached to any EDAP. The PCU1 calculates the maximum number of GPRS-dedicated

DSP cores by using the equation 2.

Figure 3Equation 2

where

• def_gprs_tchs_no_dap is the number of default GPRS channels connected to a

PCU (default channels of the TRXs that are not attached to any EDAP)

• ch_capacity_dsp_core is the 16 kbit/s channel handling capacity of a single DSP

core

The result of the equation 2 is rounded down.

For each EDAP, the PCU1 calculates the EDAP DSP load based on the ideal DSP core

count for that EDAP. For EDAP DSP load calculation, the PCU is using equation 3

(which is the same for PCU1 and PCU2).

Figure 4 Equation 3

If the sum of ideal DSP core counts for all EDAPs in the PCU1 differs from the available

DSP core count, the PCU1 adjusts the DSP resources for each EDAP according to the

available DSP core count as follows:

• If the sum of ideal DSP core counts for all the EDAPs in PCU1 is less than the avail-

able DSP core count, the PCU1 dedicates DSP cores for GPRS as mentioned

above, and if there are still unassigned DSP cores after GPRS dedication, the extra

DSP cores are allocated to the EDAPs, starting from the EDAP with the highest DSP

EDAP load.

IdealDSPcoreCountForEDAP=EDAPsizeIn16kbit/sChs + DefaultEGPRSchs

20

DSP_need_for_GPRS =def_gprs_tchs_no_dap

ch_capacity_dsp_core

DSP_EDAPload=EDAPsizeIn16kbit/sChs + DefaultEGPRSchs

IdealDSPcoreCountForEDAPs







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• If the sum of ideal DSP core counts for all the EDAPs in PCU1 is more than the avail-

able DSP core count, the PCU1 decreases the DSP core count for the EDAPs that

have the lowest DSP EDAP loads until the sum of allocated DSP core counts equals

the available DSP cores. However, each EDAP gets at least one DSP core. The

PCU1 tries to minimize the relative effect with more than one EDAP with the same

DSP EDAP load, as the PCU1 decreases the highest DSP core count first.

Sometimes the parity of DSP indexing limits the optimal sharing of DSP resources to the

EDAPs. In such cases, the PCU1 tries to minimize the relative effect.

The PCU DSP resources assigned to an EDAP may limit the usage of EDAP resources

and PCU capacity for new GPRS channels.

Special configurations for algorithm:

• If there are no EDAPs defined for a PCU, all DSPs are dedicated for GPRS.

• If there is only one EDAP for the PCU, one DSP group (even or odd) is for the EDAP

and the others are dedicated for GPRS (PCU1 only).

• If there are 16 EDAPs for the PCU, all DSPs must be used for the EDAPs and there

are no GPRS dedicated DSPs.

Only GPRS channels are allowed to GPRS-dedicated DSPs. Both GPRS and EGPRS

channels are allowed to a DSP assigned for EDAPs.

PCU2-D and PCU2-U

You should take the following differences between PCU2-D/U and PCU1 into account

when the DSP allocation for EDAPs algorithm is examined:

• PCU2-D/U has only eight DSP cores whereas PCU1 has 16 DSP cores. Based on

this difference, a single DSP core of a PCU2-D/U has to handle a maximum of two

different EDAPs. This also means that the PCU2-D/U calculates and allocates thehalves of the DSP cores.

• In PCU2-D/U, the DSP is not divided into even and odd DSP groups. This enables

a more flexible DSP allocation for EDAPs.

• PCU2-D/U does not dedicate any DSPs to the GPRS use, that is the GPRS dedi-

cated DSP core concept does not exist in PCU2-D/U.

PCU2-D/U begins the DSP allocation for EDAPs by calculating the DSP count for

EDAPs. Equation 4 is used for calculation when a TRX from at least one BTS that has

Downlink Dual Carrier activated is attached to the EDAP.

Figure 5 Equation 4

where

• edap_size is the size of EDAP in 64 kbit/s PCM timeslots

• edap_tch_count is the sum of the default EGPRS channels of all the TRXs (BTSs)


• logical_ch_per_edap_per_dsp is the half of the amount of the channels in single

DSP core (one DSP core can handle up to two EDAPs)

logical_ch_per_edap_per_dsp = 20

=dsp_need_for_edap MAXi logical_ch_per_edap_per_dsp

2 * edap_dldc_bts_count + (edap_bts_count - edap_dldc_bts_count) / 2

(4* edap_size) + edap_tch_count



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• edap_dldc_bts_count is the sum of the BTS associates with EDAP (Downlink Dual

Carrier enabled)

• edap_bts_count is the sum of the BTS associates with EDAP

The result of the equation 4 is rounded up. Nokia Siemens Networks recommends thatthe minimum size of the default territory should be 4 or 13 timeslots. When the PS terri-

tory size is 13 (PS territory is accommodated on 2 TRX and territory size is at least 5 on

both the TRXs), Downlink Dual Carrier service is immediately available.

Equation 5 is used for calculation when the TRXs that are attached to the EDAP are from

BTSs that have Downlink Dual Carrier deactivated.

Figure 6 Equation 5

where

• logical_ch_per_edap_per_dsp = 20

The result of the equation 5 is rounded up. Nokia Siemens Networks recommends 4 as

the size of the PS territory, if Downlink Dual Carrier is not used.

If the result of the ideal DSP count for all EDAPs differs from the available DSP core

count, the PCU2-D/U proceeds by calculating the EDAP DSP load for each EDAP by

using equation 6. This equation is used when a TRX from at least one BTS that has

Downlink Dual Carrier activated is attached to the EDAP. Otherwise the PCU2-D/U allo-

cates the DSPs for EDAP according to DSP need.

Figure 7 Equation 6

where




• dsp_need_for_edaps is the result of the equation 4

• edap_dldc_bts_count is the sum of the BTS associates with EDAP (Downlink Dual

Carrier enabled)

• edap_bts_count is the sum of the BTS associates with EDAP

The result of the equation 6 is rounded up. Nokia Siemens Networks recommends at

least 4 as the size of the PS territory. When the PS territory size is 13 (PS territory is

accommodated on 2 TRX and territory size is at least 5 on both the TRXs), Downlink

Dual Carrier service is immediately available.

Equation 7 is used for calculation when the TRXs that are attached to the EDAP are from

BTSs that have Downlink Dual Carrier deactivated.

=dsp_need_for_edap i

logical_ch_per_edap_per_dsp

(4* edap_size) + edap_tch_count

= MAXi

100 * ((4* edap_size) + edap_tch_count)

dsp_need_for_edap i

dsp_need_for_edap i

100 * ((4* edap_size) + edap_dldc_bts_count * 13 + (edap_bts_count - edap_dldc_bts_count) * 4)dsp_payload_for_edap



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Figure 8 Equation 7

The result of the equation 7 is rounded up. Nokia Siemens Networks recommends 4 as

the size of the PS territory, if Downlink Dual Carrier is not used.

After PCU2-D/U has calculated EDAP DSP load for each EDAP, it adjusts the DSP

resources for each EDAP according to the available DSP core count as follows:

• If the sum of the ideal DSP core count for all EDAPs in the PCU2-D/U is less than

the available halves of the DSP cores, the PCU2-D/U allocates the extra halves of

the DSP cores for EDAPs, starting from the EDAP with the highest DSP EDAP load.

• If the sum of the ideal DSP core count for all EDAPs in the PCU2-D/U is more than

the count of the available halves of the DSP cores, the PCU2-D/U decreases the

DSP core count for the EDAPs that have the lowest DSP EDAP loads until the sumof allocated DSP core counts equals the available DSP cores. However, each EDAP

gets at least one half of the DSP core. The PCU2-D/U tries to minimize the relative

effect with more than one EDAP with the same DSP EDAP load, as the PCU2-D/U

decreases the highest DSP core count first.

Special configurations for the algorithm:

• If there are no EDAPs defined for a PCU, none of the DSPs are allocated to EDAPs.

• If there are 16 EDAPs defined for a PCU, all EDAPs have only one half of a DSP

core.

You should note that there is no fixed boundary for EDAPs in the DSP resources when

a single DSP core handles two different EDAPs at a time.

PCU2-E

PCU2- E shares DSP resources optimally for EDAPs when a new dynamic Abis pool is

created or an existing pool is deleted or modified. The DSP resources are also shared

after a PCU restart, BCSU restart or a switchover. However, the DSP resource alloca-

tion for EDAPs with PCU2-E is different from other PCU variants, because with PCU2-

E the DSPs are not allocated to EDAPs but the EDAPs are allocated to the DSPs. This

difference originates from the fact that in PCU2-E one EDAP cannot be shared between

multiple DSPs but one DSP can have multiple EDAPs to handle.

At the initial stage of the DSP allocation, the PCU2-E calculates a payload value for each

EDAP. This payload value indicates how much the EDAP increases the payload for theDSP. The used equation for calculation depends on whether Downlink Dual Carrier is

enabled in some BTS that is attached with the EDAP. For more information, see

BSS21228: Downlink Dual Carrier Feature Description.

Equation 8 is used if the dldc_bts_range_count field is not zero for the DAP (Downlink

Dual Carrier enabled):

Figure 9 Equation 8

=dsp_payload_for_edap i100 * ((4* edap_size) + edap_tch_count)

dsp_need_for_edap i

=dsp_payload_for_edap MAXi

100 * ((4* edap_size) + edap_tch_count)

100 * ((4* edap_size) + edap_dldc_bts_count * 13 + (edap_bts_count - edap_dldc_bts_count) * 4)



BSS10045: Dynamic AbisFunctionality of Dynamic Abis

where



attached to the EDAP • edap_dldc_bts_count is the sum of the BTS attached with the EDAP (Downlink Dual

Carrier enabled)

• edap_bts_count is the sum of the BTS attached with the EDAP

Nokia Siemens Networks recommends that the minimum size of the default territory

should be 4 or 13 timeslots. When the PS territory size is 13 (PS territory is accommo-

dated on 2 TRX and territory size is at least 5 on both the TRXs), Downlink Dual Carrier

service is immediately available.

Equation 9 is used if the dldc_bts_range_count field is zero for the EDAP (Downlink Dual

Carrier disabled):

Figure 10 Equation 9

where

• edap_size is the size of the EDAP in 64 kbit/s PCM timeslots



Nokia Siemens Networks recommends 4 as the size of the PS territory, if Downlink Dual

Carrier is not used.

After the PCU2-E has calculated the payload for every EDAP, it begins to allocate the

EDAPs to DSPs. The target is to allocate all EDAPs to DSPs so that the sum of payload

that one DSP carries is even for all DSPs.

Special configuration for the algorithm:

• When a PCU2-E has less than six EDAPs configured, the DSPs that have no EDAP

are dedicated to the GPRS use. Only GPRS channels can be connected to the

GPRS dedicated DSP.

=dsp_payload_for_edap i 100 * ((4* edap_size) + edap_tch_count)

nokia - dynamic abis pool

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