Packet Control Unit (PCU2).pdf

Packet Control Unit (PCU2)Pooling

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# Nokia Siemens Networks 1 (23)

BSC3153Nokia GSM/EDGE BSS, Rel. BSS13, BSC andTCSM, Rel. S13, Product Documentation, v.4

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2 (23) # Nokia Siemens Networks DN70350136Issue 1-0 en20/02/2008

Packet Control Unit (PCU2) Pooling

Contents

Contents 3

1 Overview of Packet Control Unit (PCU2) Pooling 5

2 System impact of Packet Control Unit (PCU2) Pooling 92.1 Requirements 92.2 Restrictions 102.3 Impact on transmission 112.4 Impact on BSS performance 112.5 User interface 122.6 Impact on Network Switching Subsystem (NSS) 142.7 Impact on NetAct products 142.8 Impact on mobile stations 152.9 Impact on interfaces 152.10 Interworking with other features 16

3 Functionality of Packet Control Unit (PCU2) Pooling 19

4 Implementing Packet Control Unit (PCU2) Pooling overview 23

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Contents

1 Overview of Packet Control Unit (PCU2)Pooling

With Packet Control Unit (PCU2) Pooling, new packet control unit (PCU)plug-in units can be added to a live BSC easily. A group of PCU plug-inunits form a packet service entity (PSE), that is, one PSE can containseveral PCU plug-in units in a BSC.

A PSE is a logical concept that hides the physical PCU plug-in units fromthe logical network configuration. From the SGSN, a PSE looks like asingle PCU. The dynamic Abis pools (DAPs) and segments are attachedto a PSE instead of a PCU. When a new PCU is added to a PSE, the Gbinterface is configured automatically for the new PCU. The system thenallocates the DAPs and segments to the new PCU, based on themeasured peak GPRS/EDGE load of each cell.

With Packet Control Unit (PCU2) Pooling, the minimum size of a PSE istwo PCUs; the maximum is 50 PCUs. Packet Control Unit (PCU2) Poolingcan only be used with PCU2s and when IP is used as the transport methodon the Gb interface.

Figure Packet control pool in the BSC illustrates the concept of PacketControl Unit (PCU2) Pooling.

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Overview of Packet Control Unit (PCU2) Pooling

Figure 1. Packet control pool in the BSC

The IP configuration of an NSE under a PSE can be static or dynamic. Adynamic IP configuration in the network service entity (NSE) is therecommended configuration alternative on the Gb interface, as it makesconfiguration management easier at the BSC and the SGSN. Only onenetwork service virtual link (NS-VL) needs to be created per NSE.

When the NSE configuration changes, for example when a new PCU isadded to or removed from a PSE in a BSC or an IP endpoint is added orremoved in the SGSN, you do not need to make any changes to the logicalnetwork configuration at the other end. With Packet Control Unit (PCU2)Pooling you can use either IPv4 or IPv6 in the NSE but with inter-PCU LANyou can only use IPv4.

Figure IP endpoints shows the location of the IP endpoints in the BSC andthe SGSN.

Abisinterface

BTS SGSN

NSE

Gbinterface

BSC

NetAct

PSE

Q3 interface

PCU

PCU

Seg.

DAP

Seg.

DAP



Figure 2. IP endpoints

Benefits of Packet Control Unit (PCU2) Pooling

Packet Control Unit (PCU2) Pooling offers you the following benefits:

. increased data capacity in the NSE

. enhanced operability on the Gb and Abis interfaces

. more efficient Gb and Abis interface resource sharing

. New PCUs can be added dynamically, which makes it possible toincrease the GPRS/EDGE capacity easily.

. As the GPRS/EDGE load is shared automatically between the PCUswithin the PSE, all PCUs are used effectively.

All this leads to savings in both capital and operating expenditure.

RA

RA

Abisinterface

SGSN

BSC

Gb interfacePCU

BCSU

PCU

BCSU

PSE

IP endpoint

IP endpoint

IP endpoint

Inter-PCU LAN interface

NSE

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Overview of Packet Control Unit (PCU2) Pooling

Compliance

Packet Control Unit (PCU2) Pooling complies with the 3GPP standard,Release 5 Gb interface specifications.

Related topics

. Test and activate. Data

. Activating and Testing BSS20106: Packet Control Unit(PCU2) Pooling



2 System impact of Packet Control Unit(PCU2) Pooling

The system impact of BSS20106: Packet Control Unit (PCU2) Pooling isspecified in the sections below.

Packet Control Unit (PCU2) Pooling is an application software product andrequires a valid licence in the BSC.

2.1 Requirements

Hardware requirements

Table 1. Required additional or alternative hardware or firmware

Network element Hardware/firmware required

BSC PCU2, PCU LAN cabling

BTS No requirements

TCSM No requirements

SGSN No requirements

Software requirements

Table 2. Required software

Network element Software release required

BSC S13

Nokia Flexi EDGE BTS No requirements

Nokia UltraSite EDGE BTS No requirements

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System impact of Packet Control Unit (PCU2) Pooling

Table 2. Required software (cont.)

Network element Software release required

Nokia MetroSite EDGE BTS No requirements

Nokia Talk-family BTS No requirements

Nokia InSite BTS No requirements

MSC/HLR No requirements

SGSN SG6.0

Nokia NetAct OSS4.2 CD1

Frequency band support

The BSC supports Packet Control Unit (PCU2) Pooling on the followingfrequency bands:

. GSM 800

. GSM 900

. GSM 1800

. GSM 1900

2.2 Restrictions

The following restrictions apply to Packet Control Unit (PCU2) Pooling:

. PCU1 is not supported

. Gb over frame relay is not supported

. PCU selection algorithm cannot move chained dynamic Abis pools(DAPs) from one PCU to another PCU inside one packet serviceentity (PSE). This means that if several DAPs are connected to asegment, the DAPs and the segment cannot be moved from onePCU to another PCU.

. Inside one network service entity (NSE) you can only use either IPv4or IPv6 on the Gb interface. The PCUs in the PCU pool must haveIPv4 addresses even if the NSE uses IPv6 because IPv4 is alwaysused for the inter-PCU LAN interface.



. Frequent PSE reallocation is not recommended because moving ofDAPs from one PCU to another PCU may cause fragmentation ofthe packet control unit pulse code modulation (PCUPCM) circuit.

. GPRS segments that are not connected to a DAP cannot be movedfrom one PCU to another PCU inside the pool with an MMLcommand.

2.3 Impact on transmission

IP is required on the Gb interface.

2.4 Impact on BSS performance

OMU signalling

No impact.

TRX signalling

No impact.

Impact on BSC units

Table 3. Impact of Packet Control Unit (PCU2) Pooling on BSC units

BSC unit Impact

OMU No impact

MCMU No impact

BCSU No impact

PCU Packet Control Unit (PCU2) Poolingincreases the load on the PCU slightly.

Impact on BTS units

No impact.

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2.5 User interface

BSC MMI

The following command groups and MML commands are used to handlePacket Control Unit (PCU2) Pooling:

. Abis Interface Configuration: ESE, ESM, ESI

. Base Station Controller Parameter Handling in BSC: EEO, EEQ

. Base Transceiver Station Handling in BSC: EQC, EQO, EQV

. Frequency List and GPRS Objects Handling: EBF, EBH, EBP

. Gb Interface Handling: FXA, FXE, FXF, FXH, FXI, FXJ, FXK, FXL

. Licence and Feature Handling: W7M, W7I

For more information on the command groups and MML commands, seeMML commands under Reference/Commands in the PDF view.

BTS MMI

Packet Control Unit (PCU2) Pooling cannot be managed with BTS MMI.

BSC parameters

Base Station Controller (BSC) radio network object parameters

. PSE overload alarm threshold (POAT)

. PSE PCU selection algorithm threshold (PSAT)

Network Service Entity (NSE) radio network object parameters

. local UDP port number (LPNBR)

. network service entity identifier (NSEI)

. NSE type

Network Service Virtual Connection (NSVC) radio network objectparameters

. network service virtual link identifier (NSVLI)

. network service virtual link name (NAME)

. preconfigured SGSN IP endpoint (PRE)



. remote data weight (RDW)

. remote host name (RHOST)

. remote IP address (RIP)

. remote signalling weight (RSW)

. remote UDP port number (RPNBR)

Packet Control Unit (PCU) radio network object parameters

. BCSU ID (BCSU)

. Gb interface type

. packet service entity identifier (PSEI)

. PCU identifier (PCU ID)

. PCU index (PCU)

. plug-in unit type

For more information on radio network parameters, see BSS RadioNetwork Parameter Dictionary under Reference/Parameters in the PDFview.

Alarms

The following alarms can be generated in connection with Packet ControlUnit (PCU2) Pooling:

. 3322 IP ENDPOINT CONFIGURATION OF NSE HAS FAILED

. 3324 FAILURE IN UPDATING CONFIGURATION DATA TO PCU

. 3415 GPRS/EDGE LOAD IS VERY HIGH IN PCU OF PSE

. 3482 SUB NETWORK SERVICE ADD PROCEDURE FAILED

For more information, see Failure Printouts (2000-3999) under Reference/Alarms in the PDF view.

Measurements and counters

Packet Control Unit (PCU2) Pooling does not introduce newmeasurements or counters. For a list of measurements and countersrelated to GPRS/EDGE, see chapter System impact of EDGE in GPRS/EDGE System Feature Description under Feature descriptions/Data in thePDF view.

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You can use the counters of Gb over IP Measurement to monitor the Gbinterface. For more information, see 98 Gb over IP Measurement underReference/Counters/performance indicators/Packet-switchedmeasurements in the PDF view.

2.6 Impact on Network Switching Subsystem (NSS)

Nokia Combi SGSN supports both static and dynamic IP configurations onthe Gb interface. However, the dynamic IP configuration is highlyrecommended, as Nokia Combi SGSN supports only four remote IPendpoints in the NSE with the static IP configuration.

If the dynamic IP configuration is used, the system creates a full meshconfiguration automatically between the BSC and the SGSN. If the staticIP configuration is used, you need to create remote IP endpoints for theNSE at the SGSN separately. Also with the dynamic IP configuration, youdo not need to configure the SGSN end at all when you add a new PCU tothe PSE or remove a PCU from the PSE.

The SGSN must support the resource distribution function. The SGSNmay send the protocol data unit (PDU) to the wrong PCU inside the NSEand then the PCU transfers the PDU to the right PCU. The PCU uses theresource distribution function and requests the SGSN to send next PDUsto the right PCU.

To get the full benefit of Packet Control Unit (PCU2) Pooling, you shoulduse Large RA Support (LRAS) on Nokia Combi SGSN. Using LRAS easesnetwork management and provides more subscriber capacity. For moreinformation on LRAS, see Feature SG01060: Nokia SGSN Large RASupport in Nokia SGSN SG6.0 Product Documentation.

2.7 Impact on NetAct products

NetAct Administrator

No impact.

NetAct Monitor

NetAct Monitor can be used to monitor all alarms related to Packet ControlUnit (PCU2) Pooling. For a list of the alarms, see section Alarms.



NetAct Optimizer

NetAct Optimizer provides automated packet-switched traffic capacityanalysis functionality over the critical radio interface - BTS - Abis interface -PCU - Gb interface chain. It combines the network performance and trafficwith the used and available capacity information in those elements andinterfaces. You can use NetAct Optimizer to gain a complete and accurateunderstanding of capacity bottlenecks. When Packet Control Unit (PCU2)Pooling is used in the network, NetAct Optimizer notices this and includesit in the analysis.

NetAct Planner

No impact.

NetAct Radio Access Configurator (RAC)

NetAct Radio Access Configurator (RAC) can be used to configure theradio network parameters related to Packet Control Unit (PCU2) Pooling.For more information, see BSS RNW Parameters and ImplementingParameter Plans in Nokia NetAct Product Documentation. For a list of theradio network parameters, see section BSC parameters.

NetAct Reporter

No impact.

NetAct Tracing

No impact.

2.8 Impact on mobile stations

No impact.

2.9 Impact on interfaces

Impact on radio interface

No impact.

Impact on Abis interface

No impact.

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Impact on A interface

No impact.

Impact on Gb interface

With Packet Control Unit (PCU2) Pooling, the resource distributionfunction is available also to the uplink direction, that is, from the PCU to theSGSN.

2.10 Interworking with other features

Gb over IP

Packet Control Unit (PCU2) Pooling can be used only when the transportmethod of the Gb interface is IP.

For more information on Gb over IP, see Gb over IP under Featuredescriptions/Data in the PDF view.

Multipoint Gb Interface

When Multipoint Gb Interface is used with Packet Control Unit (PCU2)Pooling, there is more than one network service entity (NSE) in a packetservice entity (PSE). Figure Packet Control Unit (PCU2) Pooling andMultipoint Gb Interface illustrates this concept.



Figure 3. Packet Control Unit (PCU2) Pooling and Multipoint Gb Interface

If you are planning on activating both Packet Control Unit (PCU2) Poolingand Multipoint Gb Interface, activate Packet Control Unit (PCU2) Poolingfirst. If you activate Multipoint Gb Interface first, you cannot move thePCUs that have Multipoint Gb Interface activated to the PCU pool becausethe moved PCUs get the NSE configuration of the PCU pool. ActivatingPacket Control Unit (PCU2) Pooling first also makes it easier to configurethe Gb interface in Multipoint Gb.

For more information on Multipoint Gb Interface, see Multipoint GbInterface under Feature descriptions/Data in the PDF view.

RA

RA

Abisinterface

Inter-PCU LAN interface

PCU

PCU

NSE1 NSE2

BCSU

BCSU

PSE

BSC

SGSN2Gb interface

IP endpoint

IP endpoint

SGSN1

NSE1IP endpoint

NSE2IP endpoint

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3 Functionality of Packet Control Unit(PCU2) Pooling

Gb configuration in Packet Control Unit (PCU2) Pooling

When the Gb interface is configured for a network service entity (NSE) inthe packet service entity (PSE) and the operator adds a new packetcontrol unit (PCU) into the PSE, the BSC creates a new PCU object underthe PSE object in the radio network database. The BSC then creates thewhole NSE configuration for the new PCU.

If either static or dynamic IP configuration is used, the BSC creates allSGSN IP endpoints of the NSE to the new PCU. If a dynamic IPconfiguration is used, the new PCU configures its own IP endpoint for theSGSN NSE automatically. The BSC informs the existing PCUs in the PSEabout the new PCU's IP address and the new PCU about the existingPCUs' IP addresses.

Abis configuration in Packet Control Unit (PCU2) Pooling

When dynamic Abis pools (DAPs) and segments are configured for thePSE and the operator adds a new PCU into the PSE, the PCU selectionalgorithm in the BSC moves the DAPs and the segments to a new PCUautomatically if the operator is allowed to make PSE rearrangement in thePSE modify command. The DAPs and the segments are moved to a newPCU from those PCUs of the PSE in which the GPRS/EDGE load is veryhigh.

Also when the operator removes the PCU from the PSE, the PCUselection algorithm moves the DAPs and the segments from the removedPCU to the other PCUs in the PSE. The DAPs and the segments aremoved one by one. During the move, GPRS/EDGE is disabled from everycell in the PCU and the MSs that are attached to the cells are withoutGPRS/EDGE services. Each time the cell configuration has been changedin the PSE, the BSC informs every PCU in the PSE about each PCU's cellconfiguration.

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Functionality of Packet Control Unit (PCU2) Pooling

PCU selection algorithm

The PCU selection algorithm is based on GPRS/EDGE load and channelusage in a PCU. The PCU selection algorithm calculates the cell’s total PSload from the cell's downlink data. The channel usage is EDAP size +GPRS default channels in the PCU.

The PCUs that have a lot of channels in use and high total PS load areselected to be the source PCUs. The DAPs and segments that are movedfrom the source PCUs are selected by the cell's total PS load and thenumber of segment's neighbour cells inside the source PCUs. The DAPand the segment that have the highest PS load and least neighbours in thecurrent PCU are moved first.

The PCUs that have a lot of free channels and low total PS load areselected to be the target PCUs. The target PCU is selected on the basis oftotal PS load and the number of neighbour cells. The DAP and thesegment are moved to the target PCU that has the lowest total PS loadand most neighbour cells.

Also the number of DAPs in the target PCU is defined in the PCU selectionalgorithm. The recommended maximum number of DAPs in one PCU iseight but there can be up to 16 DAPs in the PCU if there are several DAPsin the PSE.

GPRS/EDGE load balancing

The operator reallocates DAPs and segments within the PSE to balancethe GPRS/EDGE load between the PCUs in the PSE. When thereallocation command has been given, the PCU selection algorithm movesDAPs and segments from a high load PCU to a low load PCU. This waythe GPRS/EDGE load is shared between the PCUs in the PSE.

The GPRS/EDGE load is also shared when the operator allows the PSErearrangement when a new PCU is added to the PSE and when theoperator removes the PCU from the PSE.

Protocol data unit (PDU) transferring within Packet Control Unit(PCU2) Pooling

Each PCU in a PSE has its own IP endpoint. When the SGSN sends aPDU in the downlink direction, it selects one of the BSC IP endpoints in theNSE.

When the SGSN sends the subnetwork service protocol data unit (SNSPDU) to a PCU, the PCU updates the NSE configuration and transfers theSNS PDU to every PCU in the PSE.



When the SGSN sends the base station system GPRS protocol (BSSGP)PDU to a PCU, the PCU transfers the BSSGP PDU to PCUs that need it. Ifthe SGSN sends the data PDU to a PCU in which the cell and mobilestation (MS) context do not exist, the PCU transfers the data PDU to thetarget PCU in which the cell and MS context exist. The target PCUrequests the SGSN to change the IP endpoint for the MS with the resourcedistribution function. The SGSN then changes the destination IP endpointfor the MS. After this, the SGSN sends the rest of the data PDUs directly tothe correct PCU, provided that the SGSN has location information for theMS on cell level.

PDUs are transferred between the PCUs of the PSE using the inter-PCULAN interface. IPv4 is always used for the inter-PCU LAN. If PCU2-D'sboth logical PCUs are in the same PSE, the routing PCU must be definedfor the PCUs that can transfer the PDU to another logical PCU in the sameplug-in unit (PIU).

For more information on inter-PCU LAN, see BSC Site IP ConnectivityGuidelines under Plan/Site in the PDF view.

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Functionality of Packet Control Unit (PCU2) Pooling

4 Implementing Packet Control Unit(PCU2) Pooling overview

Steps

1. Check the SGSN configuration.

Check that the pre-configured IP endpoint and the network serviceelement (NSE) are created in the SGSN if you are using a dynamicIP configuration. If you are using a static IP configuration, you needto create all BSC IP endpoints for the NSE in the SGSN. For moreinformation, see FW - GPRS NS Layer Handling in Nokia SGSNSG6.0 Product Documentation.

If you are planning on creating a large PCU2 pool in the BSC, it isrecommended that Large RA Support (LRAS) is used in NokiaCombi SGSN. For more information on LRAS, see FeatureSG01060: Nokia SGSN Large RA Support in Nokia SGSN SG6.0Product Documentation.

2. Activate Packet Control Unit (PCU2) Pooling in the BSC.

For detailed activation instructions, see Activating and TestingBSS20106: Packet Control Unit (PCU2) Pooling under Test andactivate/Data in the PDF view.

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Implementing Packet Control Unit (PCU2) Pooling overview

Packet Control Unit (PCU2).pdf

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