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Soc Classification level1 Nokia Siemens Networks RN28121EN14GLN0

BSS overviewBSS S14

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Soc Classification level3 Nokia Siemens Networks RN28121EN14GLN0

GSM subsystems

Control flowUser data flow

PSTN

PLMN

PSPDN

CSPDN

ISDN

PSTN Public Switched Telephone NetworkPSPDN Packet Switched Public Data NetworkPLMN Public Land Mobile NetworkCSPDN Circuit-Switched Public Data Network

ISDN Integrated Services Digital Network

OSS

NSSBSS

Mobile Station

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Soc Classification level4 Nokia Siemens Networks RN28121EN14GLN0

BSS Network Elements

OSS

MSC orMGW/MSS

SGSN

BSCTCSM

BTS

BTS

BTS

MS

BSS

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Soc Classification level6 Nokia Siemens Networks RN28121EN14GLN0

Multipoint A IF- Solution ArchitectureIntroduction

Basic idea

One BSC connect to several MSC servers in order to:

Increase the network performance in terms of scalability (easier capacity expansion)

Distributing the network load among the serving entities (MSS/MSCresiliency, if one MSS/MSC fails, the whole BSC wont be lost )

Reducing the required signaling as the MS roams (less inter-MSCHandover and less Location Update Request to HLR lesssignaling load).

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Soc Classification level7 Nokia Siemens Networks RN28121EN14GLN0

Multipoint A IFconfiguration example

MSC-2MSC-1

MSC-3

POOL-1

MSC-1 MSC-5MSC-4

MSC-6

POOL-2

MSC-7MSC-8

POOL-3

Area 1

BSC

Area 2

BSC

Area 3

BSC

Area 4

BSC

Area 5

BSC

Area 6

BSC

Area 7

BSC

Area 8

BSC

PoolArea 1

PoolArea 2 PoolArea 3

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Soc Classification level8 Nokia Siemens Networks RN28121EN14GLN0

Network Resource Identifier (NRI) identifies an individual MSC/MSS andenables the BSC to route traffic to one of the MSC/MSSs to which it is

connected. The NRI is part of the TMSI which the serving MSC/MSS assigns to a mobilestation.

After NRI assigned, future transactions between MS and MSC are donetowards the same MSC.

In BSC MML, it is needed to define NRI for each MSC/MSS. NRI length can be from 0 to 10 bits. NRI is located in bit 14 to 23 in TMSI.

Selection of MSC

Method 1: based on NRI

Multipoint A IFRouting Mechanism (1/2)

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Soc Classification level9 Nokia Siemens Networks RN28121EN14GLN0

In NAS node selection the BSC routes the traffic to an available MSC/MSS onthe basis of the circuit group load of each SPC or or by using a weightedround robin method .

It is used in the following cases: The NRI cannot be derived from the TMSI or t he null NRI is received in the TMSI The MS indicates an NRI for which an MSC/MSS has not been configured. The BSC cannot find direct mapping between the NRI and MSC/MSS for some other

reasons. NAS node selection has been defined to be used for all traffic with the forced mode

parameter.

NAS node selection is automatic and cannot be configured or controlled by anyparameters.

Selection of MSC

Method 2 : NAS (Non Access Stratum) Node Selection function

Multipoint A IFRouting Mechanism (2/2)

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Location Update AttachProcedure (IMSI/IMEI)

Multipoint A if Routing Example

BSC

MSS-1

MSS-2

Location Update AttachProcedure (IMSI/IMEI)

NAS Node selectionfunction

Pool area 1

Encode TMSI sothat it contains NRI

TMSI(NRI)TMSI(NRI)

NRI: Network Resource Identifier

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Soc Classification level11 Nokia Siemens Networks RN28121EN14GLN0

Multipoint A-InterfaceFailure Cases

If MSC breaks down, the NRI value(s) belonging to this MSC are mapped tothe other available MSCs if load balancing parameter is set in use

The Load Balancing algorithm will be informed about the fault situationand new mobiles will not be allocated to that MSC any more

In failure situation existing 2241 SCCP SUBSYSTEM PROHIBITED alarmrises

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Soc Classification level12 Nokia Siemens Networks RN28121EN14GLN0

Exercise: Network Elements and interfaces

BSS