1

Location management

Set of procedures to: track a mobile user find the mobile user to deliver it calls

Current location of MS maintained by 2-level hierarchical strategy with HLRs and VLRs.

2

Ways to obtain MSRN

1. Obtaining at location update – MSRN for the MS is assigned at the time of each location update, and is stored in the HLR. This way the HLR is in a position to immediately supply the routing info (MSRN) needed to switch a call through to the local MSC.

2. Obtaining on a per call basis – This case requires that the HLR has at least an identification for the currently responsible VLR. When routing info is requested from the HLR, it first has to obtain the MSRN from the VLR. This MSRN is assigned on a per call basis, i.e. each call involves a new MSRN assignment

3

Routing information: case when MSRN is selected per call by VLR/MSC

If MSRN is allocated to each subscriber visiting at an MSC, then the number of MSRNs required is large. If instead, an MSRN is allocated only when a call is to be established, then the number of MSRNs is roughly equal to number of circuits at MSC – a much smaller number – hence MSRNs typically allocated per call by VLR/MSC

MSISDN

GMSC

HLR

MSI

SDN

MSC/VLR

MSR

N

IMSI

MSR

N

MSISDNIMSI, VLR number

MSRN

4

Call routing to a mobile station: case when HLR returns MSRN

GMSC

BSC

BSC

EIR

HLR

AUCVLR

MSCBTS

BTS

BTS

LA 1

LA 2

ISDN1

MS

1

MSISDN

6

TMSI

4

MSRN

3

MSRN

2

MSISDN

7

TMSI

7

TMSI

7

TMSI

8

TMSI

5

MSRN

MSC

5

Messages exchanged: call delivery

PSTNGMSC

HLR VLR

Target

MSC

Originating Switch

GMSC HLR VLR

Target

MSC1. ISUP IAM

2. MAP_SEND_ROUTING_INFO

3. MAP_PROVIDE_ROAMING_NUMBER

4. MAP_PROVIDE_ROAMING_NUMBER_ack

5. MAP_SEND_ROUTING_INFO_ack6. ISUP IAM

1

2 3

45

6

6

Find operation in GSM

ISDN switch recognizes from the MSISDN that the call subscriber is a mobile subscriber. Therefore, forward the call to the GMSC of the home PLMN (Public Land Mobile Network)

GMSC requests the current routing address (MSRN) from the HLR using MAP

By way of MSRN the call is forwarded to the local MSC

Local MSC determines the TMSI of the MS (by querying VLR) and initiates the paging procedure in the relevant LA

After MS responds to the page the connection can be switched through.