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Open USER DESCRIPTION 1 (65) Prepared (also subject responsible if other) No. EDD/XFF KBR 7/1553-APR 101 49/9 Uen Approved Checked Date Rev Reference EDD/XF (T. Funke) IXGEFDI 03/09/2010 B MSC in Pool in MSC Copyright © Copyright Ericsson GmbH 2010. All rights reserved. No part of this document may ...

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Open USER DESCRIPTION Prepared (also subject responsible if other)

1 (65)

No.

EDD/XFF KBR

7/1553-APR 101 49/9 Uen

Approved

Checked

Date

Rev

EDD/XF (T. Funke)

IXGEFDI

03/09/2010

B

Reference

MSC in Pool in MSC Copyright © Copyright Ericsson GmbH 2010. All rights reserved. No part of this document may be reproduced in any form without the written permission of the copyright owner. Contents Introduction..........................................................................................4   Glossary ..............................................................................................5  Concepts .............................................................................................5  Active MSC Blade ...............................................................................5  Anchor MSC ........................................................................................5  Blade ...................................................................................................5  Cluster Reconfiguration.......................................................................5  Consistent Cluster View ......................................................................5  Cooperating VLR Functionality............................................................6  CP Cluster State..................................................................................6  Global CN-Id........................................................................................6  Global Paging Flow Control.................................................................7  Gs-Interface.........................................................................................7  Mobile Subscriber Distribution Function ..............................................7  MSC Blade ..........................................................................................7  MSC Pool ............................................................................................8  MSC Server Blade Cluster ..................................................................9  N+1 Redundancy.................................................................................9  NB-LAI .................................................................................................9  Neighbouring MSC Group ...................................................................9  NRI ....................................................................................................10  Non-anchor MSC...............................................................................10  Null NRI .............................................................................................11  Outdated MSC Blade ........................................................................11  Overlapping Pool Area ......................................................................11  Passive MSC Blade...........................................................................12  Pool Area...........................................................................................12  Primary MSC Blade ...........................................................................13  Proxy MSC ........................................................................................13  Third MSC .........................................................................................13  TMSI ..................................................................................................14  Traffic Isolation ..................................................................................14  Subsequent Handover/SRNS Relocation..........................................14  Round Robin Algorithm .....................................................................14  Abbreviations.....................................................................................14

Open USER DESCRIPTION Prepared (also subject responsible if other)

2 (65)

No.

EDD/XFF KBR

7/1553-APR 101 49/9 Uen

Approved

Checked

Date

Rev

EDD/XF (T. Funke)

IXGEFDI

03/09/2010

B

                                            

Reference

Capabilities........................................................................................16 Advantages .......................................................................................16 Limitations .........................................................................................17 Failure Cases ....................................................................................17 Prerequisites .....................................................................................18 Technical Description ........................................................................19 General..............................................................................................19 Functions Needed in the MSC in the Pool.........................................21 Administration of NRI/Null NRI Values ..............................................21 TMSI Allocation, NRI .........................................................................23 CN-Id .................................................................................................23 Paging over Gs interface ...................................................................24 RANAP Procedures...........................................................................24 Subsequent Handover/SRNS Relocation to Third MSC, Anchor MSC ..................................................................................................25 Functions for Enhanced Access from Outer Nodes to the Pool ........25 Cooperating VLR ...............................................................................25 Proxy MSC ........................................................................................25 Cooperating VLR Enhancements ......................................................28 Handover/SRNS Relocation ..............................................................30 Neighbouring MSC Groups ...............................................................30 Handling of HANDOVER/SRNS RELOCATION in Non-anchor MSC ..................................................................................................30 MSC Pool Redistribution and Associated Functions .........................30 General..............................................................................................30 Initiation of an MSC Pool Redistribution Session ..............................32 Redistribution Actions due to First Phase..........................................33 Redistribution Actions due to Intermediate Phase.............................33 Redistribution Actions due to Third Phase ........................................34 Termination of an MSC Pool Redistribution Session.........................35 Reception of Location Update Requests with Null NRI and Own NB-LAI ...............................................................................................35 Mobile Terminated Requests for a Subscriber with Redistribution Actions Initiated ..........................................................36 Cooperating VLR/Proxy.....................................................................36 Functions Indirectly Affected due to MSC in Pool .............................36 Network Scenario Example ...............................................................37 Engineering Guidelines .....................................................................39 Building a Pool Network ....................................................................39 Running a Redistribution Session .....................................................43 Prerequisites/Conditions ...................................................................43 Redistribution Session Process.........................................................44 Exceptional Cases.............................................................................49 Use Cases .........................................................................................50 Use Case 1: Add a New NRI in an MSC ...........................................50 Use Case 2: Remove an NRI from an MSC ......................................51 Use Case 3: NRI Reassignment........................................................52 Use Case 4: Define Null NRI .............................................................52 Use Case 5: Null NRI Reassignment ................................................52

Open USER DESCRIPTION Prepared (also subject responsible if other)

3 (65)

No.

EDD/XFF KBR

7/1553-APR 101 49/9 Uen

Approved

Checked

Date

Rev

EDD/XF (T. Funke)

IXGEFDI

03/09/2010

B

                       

Reference

Use Case 6: Add NB-LAI...................................................................53 Use Case 7: Change NB-LAI ............................................................53 Use Case 8: Take an MSC Out of Service ........................................53 Use Case 9: Take a Proxy MSC Out of Service................................54 Use Case 10: Add a New MSC to the Pool .......................................54 Use Case 11: Add a New RAN (BSC/RNC) Node to the Pool ..........55 Parameters ........................................................................................55 Main Controlling Parameters .............................................................55 Parameters for Special Adjustments .................................................56 Value Ranges and Default Values ....................................................57 ADMHOMSCPOOL ...........................................................................57 GPFCRATEGSM...............................................................................57 GPFCRATEWCDMA .........................................................................57 MSCREQNUM ..................................................................................58 NBLAC ..............................................................................................58 NBMCC .............................................................................................59 NBMNC .............................................................................................59 OWNCNID .........................................................................................59 PAGREP1LA .....................................................................................60 PAGREPCT1LA ................................................................................61 PAGREPGLOB .................................................................................61 TIMNRICHGM ...................................................................................62 TMSIPAR ..........................................................................................62 References ........................................................................................63

Open USER DESCRIPTION Prepared (also subject responsible if other)

EDD/XFF KBR

7/1553-APR 101 49/9 Uen

Approved

Checked

Date

Rev

EDD/XF (T. Funke)

IXGEFDI

03/09/2010

B



4 (65)

No.

Reference

Introduction The continuous growth of subscribers, and consequently traffic, in certain GSM/WCDMA markets stresses the capability to scale up MSC capacity. A pool area is a radio coverage area served by a number of MSCs. Every BSC/RNC within the service area is connected, through the A/Iu interface, to each MSC in the pool. When more capacity is needed, additional MSC nodes can be added to the pool without the need to change the network configuration (move BSCs/RNCs from one MSC to another) and thus avoid a lot of configuration effort and traffic disturbances. The new MSC nodes must be connected through A/Iu -interface to all the BSC/RNC nodes respectively in the pool area. The BSC/RNC nodes in the pool area are set up to take the new MSC into account in their traffic distribution procedure. When partial or full load removal is needed in one MSC node (for example, to perform scheduled maintenance or to perform load redistribution among pool members) with minimal impact to end users, the MSC pool redistribution function can be used. The feature MSC in pool is supported for GSM and WCDMA in MSC-S, classical MSC and MSC-S BC. In the rest of the document “MSC” will be used. Whenever a differentiation is applicable between MSC-S, classical MSC and MSC-S BC it will be explicitly stated using the corresponding term. Also MS corresponds to UE in WCDMA. The MSC in pool function supported by the MSC is compliant with the 3GPP Intra Domain Connection of RAN Nodes to Multiple CN Nodes (TS 23.236) for GSM/WCDMA. That means that Ericsson MSCs could work together with other vendor nodes (MSCs or BSCs/RNCs) in a pool. The purpose of this user description is to give an overview about: 

MSC in pool feature in the MSC



the functions that are working in a specific way due to the MSC in pool feature.

The Gs interface is not supported in MSC-S BC environment.

Open USER DESCRIPTION Prepared (also subject responsible if other)

5 (65)

No.

EDD/XFF KBR

7/1553-APR 101 49/9 Uen

Approved

Checked

Date

Rev

EDD/XF (T. Funke)

IXGEFDI

03/09/2010

B

Reference



Glossary



Concepts



Active MSC Blade The active MSC blade is the MSC blade that is handling traffic of a certain mobile subscriber at a certain time. It is a logical role that is automatically assigned to an MSC blade for each mobile subscriber by the mobile subscriber distribution function. The active MSC blade of a subscriber is either the primary MSC blade or the buddy MSC blade of that subscriber. The selection whether primary MSC blade or buddy MSC blade is the active MSC blade can change in the course of time and depends on the ability of the two MSC blades to execute traffic. The active MSC blade allocates a TMSI for the subscriber (if the TMSI function is available). There can be only one active MSC blade per subscriber at the same time.



Anchor MSC Anchor-MSC is the MSC where the transaction is originally established.



Blade A blade in terms of the MSC Server Blade Cluster is an IS adapted single-sided APZ Central Processor (CP). In an MSC Server Blade Cluster it can be configured either as MSC blade or as TSC blade. Depending on its configuration, it has different tasks within the MSC Server Blade Cluster. The term CP is used synonymously.



Cluster Reconfiguration A cluster reconfiguration is the automatic process of redistributing the registered mobile subscribers between the MSC blades according to a new cluster configuration. It is always preceded by the calculation of new load vectors. A cluster reconfiguration is initiated due to a cluster extension, due to a cluster reduction or due to a permanent failure of an MSC blade.



Consistent Cluster View The consistent cluster view is a set of data that is known by all blades within an MSC Server Blade Cluster. The main purpose of the consistent cluster view is that all blades have the same information about the existing blades. The main data included in the consistent cluster view is: 

The CP cluster state of each blade



The APT sub-state of each blade

Open USER DESCRIPTION Prepared (also subject responsible if other)

EDD/XFF KBR

7/1553-APR 101 49/9 Uen

Approved

Checked

Date

Rev

EDD/XF (T. Funke)

IXGEFDI

03/09/2010

B



6 (65)

No.

Reference



The IP address of each blade for internal inter-blade communication



The relative capacity of each blade



The role of each blade

Cooperating VLR Functionality The cooperating VLR functionality permits the MSC node to configure for each LA one cooperating VLR address or more than one cooperating VLR address. For the purposes of this document, the latter is referred to by the term ‘enhanced cooperating VLR functionality’. The advantage with this functionality in an MSC is that the new MSC does not have to contact a cooperating MSC in the old LA through a cooperating proxy MSC. Instead the new MSC can directly contact a cooperating MSC in the old LA and therefore save the routing through the cooperating proxy MSC.



CP Cluster State The CP cluster state indicates the status of a blade within the MSC Server Blade Cluster. It is part of the consistent cluster view. Possible CP cluster states are:





Non-Op



Passive



Active



Intermediate

Global CN-Id The global CN-Id is used on the Gs-interface (BSSAP+ protocol) and Iuinterface in order to inform the radio access network about the CN node that issued the respective message. The global CN-Id is used in the case that the radio access network cannot obtain from the NRI the CN node where it should respond. A unique global CN-Id needs to be defined in case Iu-interface is used or CS paging over Gb-interface is performed. This is needed to enable the BSC/RNC to identify the paging MSC.

Open USER DESCRIPTION Prepared (also subject responsible if other)

EDD/XFF KBR

7/1553-APR 101 49/9 Uen

Approved

Checked

Date

Rev

EDD/XF (T. Funke)

IXGEFDI

03/09/2010

B



7 (65)

No.

Reference

Global Paging Flow Control The Global Paging Flow Control (GPFC) function offers a mechanism to regulate the amount of global pagings sent by the MSC in order to prevent a possible overload of paging channels of the connected BSC/RNC nodes. In MSC in Pool environment an overload of the radio network might occur especially after an almost simultaneous large restart with reload on several MSCs. The operator can define the allowed rate of global pagings for GSM access and WCDMA access separately and thereby adjust the configuration of the GPFC function to the capacity of the radio network. Global paging requests beyond the allowed rate are rejected by the MSC. For more information about the Global Paging Flow Control functions refer to [Ref. 57] and [Ref. 58].



Gs-Interface Gs-interface is the signalling interface between the MSC and SGSN.



Mobile Subscriber Distribution Function The mobile subscriber distribution function implements the internal distribution algorithm. It has tw...