4.7 Inter-MSC Handover (GSM to UMTS)

29.0103GPPInformation element mapping between Mobile Station - Base Station System (MS - BSS) and Base Station System - Mobile-services Switching Centre (BSS - MSC)Release 17Signalling Procedures and the Mobile Application Part (MAP)TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

The general principles of the handover procedures are given in 3GPP TS 23.009 [2]. 3GPP TS 29.010 gives the necessary information for interworking between the 3GPP TS 25.413 [7] RANAP protocol, GSM handover procedures and the 3GPP TS 29.002 [9] MAP protocol. The RANAP protocol is used between the RNS and the 3G_MSC.

The following four principles apply for the Inter-MSC handover GSM to UMTS:

The BSSMAP parameters required for Inter-MSC handover GSM to UMTS are generated as in GSM.

Received RANAP parameters, e.g. cause code or transparent container, are mapped to the appropriate BSSMAP parameters, e.g. cause code or Handover command.

The RANAP parameters required for Inter-MSC handover GSM to UMTS are generated from received or stored GSM parameters.

When new parameters need to be added for transfer on the E-interface, the principles stated in the beginning of clause 4.5 shall be followed.

4.7.1 Basic Inter-MSC Handover

When a Mobile Station is handed over between two MSCs, the establishment of a connection between them (described in 3GPP TS 23.009 [2]) requires interworking between A-Interface, Iu-Interface and E-Interface.

The signalling at initiation, execution and completion of the Basic Inter-MSC handover procedure is shown in figures 37 to 42 with both possible positive or negative outcomes.

Additionally figure 37b shows the possible interworking when the trace related message is transparently transferred on the E-Interface at Basic Inter-MSC Handover initiation.

BSS-A MSC-A 3G-MSC-B

| | |

|HANDOVER | |

|————–>|MAP PREPARE HANDOVER |

|REQUIRED |————————>| +—————-+

| | | +—————-+

| | |

| | | RNS-B

| | | |

| | |RELOCATION REQUEST |

| | |——————>|

Figure 37a: Signalling for Basic Inter-MSC Handover initiation (no trace related messages transferred)

BSS-A MSC-A 3G-MSC-B

| (*) |

|HANDOVER | |

|————–>|MAP PREPARE HANDOVER |

|REQUIRED |————————>| +—————-+

| | | +—————-+

| | |

| | | RNS-B

| | | |

| | |RELOCATION REQUEST |

| | |——————>|

| | | |

| | |CN INVOKE TRACE |

| | |—————>(***)

Figure 37b: Signalling for Basic Inter-MSC Handover initiation (CN invoke trace message transferred)

(*): Tracing invocation has been received from VLR.

(**): In that case, HANDOVER REQUEST and MSC INVOKE TRACE messages are included within the AN-apdu parameter.

(***): CN INVOKE TRACE is forwarded to RNS-B if supported by 3G_MSC-B.

Possible Positive outcomes: successful radio resources allocation and handover number allocation (if performed):

BSS-A MSC-A 3G-MSC-B RNS-B

| | | |

| | |RELOCATION REQUEST |

| | |<——————|

| | |ACKNOWLEDGE |

| | |LOCATION REPORTING |

| | |——————>|

| | |CONTROL |

| | MAP PREPARE HANDOVER | |

| |<————————| |

| | response | |

| | | |

|HANDOVER COMMAND | |

|<————–| | |

Figure 38: Signalling for Basic Inter-MSC Handover execution (Positive outcome)

Possible Negative outcomes:

a) user error detected, or handover number allocation unsuccessful (if performed), or component rejection or dialogue abortion performed by 3G_MSC-B:

BSS-A MSC-A 3G-MSC-B RNS-B

| | | |

| |MAP PREPARE HANDOVER response |

| |negative result, MAP CLOSE |

| |<————————| |

| |MAP U/P-ABORT | |

| | | |

|HANDOVER REQUIRED | |

|<————–| | |

|REJECT (Note 1)| | |

| | | |

b) radio resources allocation failure:

BSS-A MSC-A 3G-MSC-B RNS-B

| | | |

| | |RELOCATION FAILURE |

| | |<——————|

| |MAP PREPARE HANDOVER | |

| |<————————| |

| | response | |

| | | |

|HANDOVER REQUIRED | |

|<————–| | |

|REJECT (Note 1)| | |

| | | |

c) unsuccessful handover execution (Reversion to the old radio resources):

BSS-A MSC-A 3G-MSC-B RNS-B

| | | |

|HANDOVER | | |

|————–>| | |

|FAILURE | | |

| |MAP U -ABORT | |

| |————————>| |

| | |IU RELEASE COMMAND |

| | |——————>|

Figure 39: Signalling for Basic Inter-MSC Handover execution (Negative outcomes)

NOTE 1: Possible rejection of the handover because of the negative outcome of MAP or RANAP procedure.

BSS-A MSC-A 3G-MSC-B RNS-B

| | | |

| | |RELOCATION COMPLETE|

| | |<——————|

| |MAP SEND END SIGNAL request |

| |<————————| |

|CLEAR COMMAND | | |

|<————–| | |

| | | |

Figure 40: Signalling for Basic Inter-MSC Handover completion

Positive outcome:

BSS-A MSC-A 3G-MSC-B RNS-B

| | | |

| |MAP SEND END SIGNAL | |

| |————————>| |

| | response |IU RELEASE COMMAND |

| | |——————>|

| | | (Note 2) |

Figure 41: Signalling for Basic Inter-MSC Handover completion (Positive outcome)

Negative outcome:

BSS-A MSC-A 3G-MSC-B RNS-B

| | | |

| | MAP U/P -ABORT | |

| |————————>| |

| | |IU RELEASE COMMAND |

| | |——————>|

| | | |

Figure 42: Signalling for Basic Inter-MSC Handover completion (Negative outcome)

NOTE 2: From interworking between MAP and RANAP point of view, when the call is released.

BSS-A MSC-A 3G-MSC-B RNS-B

| | | |

| | |LOCATION REPORT |

| | |<——————|

| |MAP PROCESS ACCESS | |

| |<————————| |

| |SIGNALLING | |

Figure 42a: Signalling for updating of anchor MSC after change of location in RNS

The handover procedure is normally triggered by BSS-A by sending a HANDOVER REQUIRED message on A‑Interface to MSC-A. The invocation of the Basic Inter-MSC handover procedure is performed and controlled by MSC-A. The sending of the MAP Prepare-Handover request to 3G_MSC-B is triggered in MSC-A upon receipt of the HANDOVER REQUIRED message. The identity of the target RNC where the call is to be handed over in 3G_MSC-B area, provided in the HANDOVER REQUIRED message in the information element Cell Identifier List (Preferred), is mapped to the target RNC Id MAP parameter and the HANDOVER REQUEST message is encapsulated in the an-APDU MAP parameter of the Prepare‑Handover MAP request. 3G_MSC-B can invoke another operation towards the VLR-B (allocation of the handover number described in 3GPP TS 29.002 [9]).

Additionally, if tracing activity has been invoked, the trace related message can be transferred on the E-Interface encapsulated in the an-APDU MAP parameter of the Prepare-Handover Request. If transferred, one complete trace related message at a time shall be included in the an-APDU MAP parameter after the HANDOVER REQUEST message. Note: UMTS supports only CN initiated tracing.

The interworking between Prepare Handover and HANDOVER REQUIRED is as follows:

—————————————————————-

| 48.008 29.002 |Notes

——–┼————————————————-┼—–

Forward | HANDOVER REQUIRED MAP PREPARE HANDOVER request|

message | |

| -ho-NumberNotRequired| 1

| BSSMAP information -target RNC Id |

| elements -IMSI |

| -Integrity protection| 2

| info |

| -Encryption info |

| -an-APDU( | 3

| HANDOVER REQUEST, |

| MSC INVOKE TRACE) | 4

| GERAN classmark -GERAN classmark | 7

——–┼————————————————-┼—–

Positive| MAP PREPARE HANDOVER response|

result | | 5

| -handover number |

| -an-APDU( |

| HANDOVER REQUEST |

| ACKNOWLEDGE or |

| HANDOVER FAILURE) |

——–┼————————————————-┼—–

Negative| HANDOVER REQUIRED REJECT MAP PREPARE HANDOVER| 6

result | |

| equipment failure System Failure |

| equipment failure No Handover Number |

| available |

| equipment failure UnexpectedDataValue|

| equipment failure Data Missing |

| |

| equipment failure MAP CLOSE |

| equipment failure MAP U/P -ABORT |

| |

NOTE 1: The ho-NumberNotRequired parameter is included by MSC-A, when MSC-A decides not to use any circuit connection with 3G_MSC-B. No handover number shall be present in the positive result. Any negative response from 3G_MSC-B shall not be due to handover number allocation problem.

NOTE 2: Integrity protection information, encryption information and IMSI parameters are included by MSC-A, only when the MSC-A uses 29.002 as per release 99. These IEs are not included if the MSC-A is R98 or earlier.

NOTE 3: NOTE 3: The process performed on the BSSMAP information elements received in the HANDOVER REQUIRED message is described in the 3GPP TS 48.008 [12].

NOTE 4: The process performed on the BSSMAP information elements received in the MSC INVOKE TRACE message is described in clause 4.5.5.6.

NOTE 5: The response to the Prepare-Handover request can include in its an-APDU parameter, identifying the 3GPP TS 48.006 protocol, either a BSSMAP HANDOVER REQUEST ACKNOWLEDGE or a BSSMAP HANDOVER FAILURE.

In the first case, the positive result triggers in MSC-A the sending on A-Interface of the HANDOVER COMMAND.

In the second case, the positive result triggers in MSC-A optionally the sending of the HANDOVER REQUIRED REJECT.

(The possible sending of the HANDOVER REQUIRED REJECT message upon receipt of the HANDOVER FAILURE is out of the scope of 3GPP TS 29.010 and lies in 3GPP TS 48.008 [12]).

NOTE 6: The possible sending of the HANDOVER REQUIRED REJECT message is described in 3GPP TS 48.008 [12].

NOTE 7: If the GERAN Classmark was not received with the HANDOVER REQUIRED message initiating the handover, MSC-A shall include any previously received GERAN Classmark. See 3GPP TS 43.051 [17].

The interworking between Prepare Handover and RELOCATION REQUEST in 3G_MSC-B is as follows:

—————————————————————-

| 29.002 25.413 |Notes

——–┼————————————————-┼—–

Forward | MAP PREPARE HANDOVER RELOCATION REQUEST |

message | request |

| -ho-NumberNotRequired |

| -target RNC Id |

| -IMSI |

| -Integrity protection info | 1

| -Encryption info |

| -RANAP service handover |

| -UESBI |

| -an-APDU( |

| HANDOVER REQUEST, |

| MSC INVOKE TRACE) |

| |

| BSSMAP information RANAP information |

| elements: elements: |

| |

| Channel Type RAB parameters |

| Cause Cause |

| sRNC to tRNC container sRNC to tRNC container|

| SNA Access Information SNA Access Information| 3

| |

| info stored/generated |

| in/by 3G_MSC-B: |

| CN domain indicator |

| |

——–┼————————————————-┼—–

Positive| MAP PREPARE HANDOVER RELOCATION REQUEST ACK |

result | response |

| -an-APDU( |

| HANDOVER REQUEST ACK) |

| |

| BSSMAP information RANAP information |

| elements: elements: |

| |

| Layer 3 info tRNC to sRNC container|

| |

——–┼————————————————-┼—–

Negative| MAP PREPARE HANDOVER RELOCATION FAILURE |

result | response |

| -an-APDU( |

| HANDOVER FAILURE) |

| BSSMAP information RANAP information |

| elements: elements: |

| |

| GERAN classmark GERAN classmark | 2

| |

NOTE 1: Integrity protection information, encryption information, IMSI and RANAP service handover parameters are included by MSC-A only when the MSC-A uses 29.002 as per release 99. These IEs are not included if the MSC-A is R98 or earlier.

NOTE 2: If a handover to GERAN Iu-mode failed, the target RNS may include a GERAN classmark in the RELOCATION FAILURE message. See 3GPP TS 43.051 [17].

NOTE 3: SNA Access Information parameter is included by MSC-A only when the MSC-A uses 29.002 as per release 5. This IE is not included if the MSC-A is release 4 or earlier.

The interworking between Send End Signal and RELOCATION COMPLETE in 3G_MSC-B is as follows:

—————————————————————-

| 25.413 29.002 |Notes

——–┼————————————————-┼—–

Forward | RELOCATION COMPLETE MAP SEND END SIGNAL request |

message | |

| -an-APDU( |

| HANDOVER COMPLETE)|

| |

——–┼————————————————-┼—–

Positive| IU RELEASE COMMAND MAP SEND END SIGNAL response|

result | -Normal release | 1

——–┼————————————————-┼—–

Negative| IU RELEASE COMMAND |

result | -Normal release MAP CLOSE | 2

| -Normal release MAP U/P -ABORT|

| |

NOTE 1: The positive empty result triggers the clearing of the Radio Resources on the Iu-Interface and the release of the SCCP connection between 3G_MSC-B and RNS-B. If a circuit connection is used between MSC-A and 3G_MSC-B, the ‘Normal release’ clearing cause shall only be given to RNS-B when 3G_MSC-B has received a clearing indication on its circuit connection with MSC-A.

NOTE 2: The abortion of the dialogue or the rejection of the component triggers in 3G_MSC-B the clearing of its circuit connection with MSC-A, if any, of the Radio Resources on the Iu-Interface and the release of the SCCP connection between 3G_MSC-B and RNS-B.

The interworking between Send End Signal and CLEAR COMMAND in MSC-A is as follows:

—————————————————————-

| 29.002 48.008 |Notes

——–┼————————————————-┼—–

Forward | MAP SEND END SIGNAL CLEAR COMMAND |

message | request |

| -an-APDU( – Handover |

| HANDOVER COMPLETE) Successful |

——–┼————————————————-┼—–

Positive| |

result | |

——–┼————————————————-┼—–

Negative| |

result | |

The interworking between HANDOVER FAILURE in case of reversion to old channel of the MS and User Abort in MSC-A is as follows:

—————————————————————-

| 48.008 29.002 |Notes

——–┼————————————————-┼—–

Forward | HANDOVER FAILURE MAP U -ABORT |

message | |

| – Reversion to old |

| channel |

——–┼————————————————-┼—–

Positive| |

result | |

——–┼————————————————-┼—–

Negative| |

result | |

4.7.2 Subsequent Inter-MSC Handover from MSC-B back to 3G_MSC-A

When a Mobile Station is being handed over back to 3G_MSC-A, the procedure (described in 3GPP TS 23.009 [2]) requires interworking between A-Interface, Iu-Interface and E-Interface.

The signalling at initiation, execution and completion of the Subsequent Inter-MSC handover procedure is shown in figures 43 to 47.

BSS-A MSC-B 3G-MSC-A

| | |

|HANDOVER | |

|————–>|MAP PREPARE SUBSEQUENT |

|REQUIRED |————————>|

| |HANDOVER request |

| | | RNS-B

| | | |

| | |RELOCATION REQUEST |

| | |——————>|

Figure 43: Signalling for Subsequent Inter-MSC Handover back to 3G_MSC-A initiation

Possible Positive outcomes: successful radio resources allocation:

BSS-A MSC-B 3G-MSC-A RNS-B

| | | |

| | |RELOCATION REQUEST |

| | |<——————|

| | |ACKNOWLEDGE |

| | MAP PREPARE SUBSEQUENT | |

| |<————————| |

| | HANDOVER response | |

|HANDOVER COMMAND | |

|<————–| | |

Figure 44: Signalling for Subsequent Inter-MSC Handover back to 3G_MSC-A execution (Positive outcome)

Possible Negative outcomes:

a) user error detected, or component rejection or dialogue abortion performed by 3G_MSC-A:

BSS-A MSC-B 3G-MSC-A RNS-B

| |MAP PREPARE SUBSEQUENT HANDOVER |

| |<————————| |

|HANDOVER REQUIRED response negative result |

|<————–| | |

|REJECT (Note 1)| | |

| | | |

b) component rejection or dialogue abortion performed by 3G_MSC-A:

BSS-A MSC-B 3G-MSC-A RNS-B

| |MAP CLOSE, MAP U/P ABORT | |

| |<————————| |

|CLEAR COMMAND | | |

|<————–| | |

| | | |

c) radio resources allocation failure:

BSS-A MSC-B 3G-MSC-A RNS-B

| | | RELOCATION FAILURE|

| | |<——————|

| |MAP PREPARE SUBSEQUENT | |

| |<————————| |

|HANDOVER REQUIRED HANDOVER response | |

|<————–| | |

|REJECT (Note 1)| | |

d) unsuccessful relocation execution (reversion to the old radio resources):

BSS-A MSC-B 3G-MSC-A RNS-B

|HANDOVER | | |

|————–>| | |

|FAILURE |MAP PROCESS ACCESS | |

| |————————>| |

| | SIGNALLING request |IU RELEASE COMMAND |

| | |——————>|

| | | |

Figure 45: Signalling for Subsequent Inter-MSC Handover back to 3G_MSC-A execution
(Negative outcome)

NOTE 1: Possible rejection of the handover because of the negative outcome of MAP or BSSMAP procedure.

RNS-B 3G-MSC-A MSC-B BSS-A

| | | |

|RELOCATION | | |

|————–>|MAP SEND END SIGNAL | |

|COMPLETE |————————>| |

| | response | |

| | |CLEAR COMMAND |

| | |——————>|

Figure 46: Signalling for Subsequent Inter-MSC Handover back to 3G_MSC-A completion
(Successful completion of the procedure)

NOTE: Positive outcome case shown in figure 41.

RNS-B 3G-MSC-A MSC-B BSS-A

| | | |

| |MAP U/P -ABORT | |

| |<————————| |

| | |CLEAR COMMAND |

| | |——————>|

| | |(Note 1) |

Figure 47: Signalling for Subsequent Inter-MSC Handover back to 3G_MSC-A completion (Unsuccessful completion of the procedure)

NOTE 1: Abnormal end of the procedure that triggers the clearing of all resources in MSC-B.

The interworking between Prepare Subsequent Handover and HANDOVER REQUIRED is as follows:

—————————————————————-

| 48.008 29.002 |Notes

——–┼————————————————-┼—–

Forward |HANDOVER REQUIRED MAP PREPARE SUBSEQUENT HANDOVER|

message | request | 1

| |

| -target MSC number |

| BSSMAP information -target RNC Id |

| elements -an-APDU( |

| HANDOVER REQUEST) |

| GERAN classmark -GERAN classmark | 4

——–┼————————————————-┼—–

Positive|HANDOVER REQUIRED MAP PREPARE SUBSEQUENT HANDOVER|

result | response | 2

| -an-APDU( |

| HANDOVER REQUEST |

| ACKNOWLEDGE or |

| HANDOVER FAILURE) |

——–┼————————————————-┼—–

Negative| HANDOVER REQUIRED REJECT MAP PREPARE SUBSEQUENT| 3

result | HANDOVER response |

| equipment failure Unknown MSC |

| equipment failure Subsequent Handover|

| Failure |

| equipment failure UnexpectedDataValue|

| equipment failure Data Missing |

| |

| CLEAR COMMAND |

| |

| equipment failure MAP CLOSE |

| equipment failure MAP U/P -ABORT |

| |

NOTE 1: The processing performed on the BSSMAP information elements received in the HANDOVER REQUIRED message is out of the scope of the present document. The target MSC number is provided to 3G_MSC-A by MSC-B based on the information received from RNS-B.

NOTE 2: The response to the Prepare-Subsequent-Handover request can include in its an-APDU parameter, identifying the 3GPP TS 48.006 protocol, either a BSSMAP HANDOVER REQUEST ACKNOWLEDGE or a BSSMAP HANDOVER FAILURE.

In the first case, the positive result triggers in MSC-B the sending on A‑Interface of the HANDOVER COMMAND.

In the second case, the positive result triggers in MSC-B optionally the sending of the HANDOVER REQUIRED REJECT.

(The possible sending of the HANDOVER REQUIRED REJECT message upon receipt of the HANDOVER FAILURE is out of the scope of 3GPP TS 29.010 and lies in 3GPP TS 48.008 [12]).

NOTE 3: The possible sending of the HANDOVER REQUIRED REJECT message is described in 3GPP TS 48.008 [12].

NOTE 4: If the GERAN Classmark was not received with the HANDOVER REQUIRED message initiating the handover, MSC-B shall include any previously received GERAN Classmark. See 3GPP TS 43.051 [17].

The interworking between Prepare Subsequent Handover and RELOCATION REQUEST in 3G_MSC-A is as follows:

—————————————————————-

| 29.002 25.413 |Notes

——–┼————————————————-┼—–

Forward | MAP PREPARE SUB HANDOVER RELOCATION REQUEST |

message | request |

| -ho-NumberNotRequired |

| -target RNC ID |

| -an-APDU( |

| HANDOVER REQUEST, |

| MSC INVOKE TRACE) |

| |

| BSSMAP information RANAP information |

| elements: elements: |

| |

| Cause Cause |

| sRNC to tRNC container sRNC to tRNC container|

| |

| info stored/generated |

| in/by 3G_MSC-A: |

| CN domain indicator |

| RAB parameters |

| Permanent NAS UE id |

| Encryption info |

| Integrity protection |

| info |

| |

——–┼————————————————-┼—–

Positive| MAP PREPARE SUB HANDOVER RELOCATION REQUEST ACK|

result | response |

| -an-APDU( |

| HANDOVER REQUEST ACK) |

| |

| BSSMAP information RANAP information |

| elements: elements: |

| |

| Layer 3 info tRNC to sRNC container|

| |

——–┼————————————————-┼—–

Negative| MAP SUB PREPARE HANDOVER RELOCATION FAILURE |

result | response |

| -an-APDU( |

| HANDOVER FAILURE) |

| |

| BSSMAP information RANAP information |

| elements: elements: |

| |

| GERAN classmark GERAN classmark | 1

| |

NOTE 1: If a handover to GERAN Iu-mode failed, the target RNS may include a GERAN classmark in the RELOCATION FAILURE message. See 3GPP TS 43.051 [17].

The interworking between HANDOVER FAILURE and MAP Process Signalling Request in 3G_MSC-B is as follows:

—————————————————————-

| 48.008 29.002 |Notes

——–┼————————————————-┼—–

Forward | HANDOVER FAILURE MAP PROCESS-SIGNALLING |

message | request |

| -an-APDU( |

| HANDOVER FAILURE) |

| |

——–┼————————————————-┼—–

Positive| |

result | |

——–┼————————————————-┼—–

Negative| |

result | |

| |

The interworking between Send End Signal Response and RELOCATION COMPLETE in 3G_MSC-A is as follows:

—————————————————————-

| 25.413 29.002 |Notes

——–┼————————————————-┼—–

Forward | RELOCATION COMPLETE MAP SEND END SIGNAL |

message | response |

| |

——–┼————————————————-┼—–

Positive| |

result | |

——–┼————————————————-┼—–

Negative| |

result | MAP U/P -ABORT | 1

| |

NOTE 1: The abortion of the dialogue ends the handover procedure with MSC-B.

4.7.3 Subsequent Inter-MSC Handover to third MSC

When a Mobile Station is being handed over to a third MSC, the procedure (described in 3GPP TS 23.009 [2]) does require one specific interworking case in MSC-A (figure 49) between E-Interface from MSC-B and E-Interface from 3G_MSC‑B’ other than the combination of the ones described in the clause 4.5.1 and 4.7.2.

BSS-A MSC-B MSC-A 3G-MSC-B’

| | | |

|HANDOVER | | |

|———–>|MAP PREPARE SUBSEQUENT| |

|REQUIRED |———————>| |

| |HANDOVER request |MAP PREPARE |

| | |—————>|

| | |HANDOVER request|

| | | |+——-+

| | | ||Possib.|

| | | ||Alloc. |

| | | ||of ho. |

| | | ||number |

| | | || VLR-B |

| | | |+——-+

| | | | RNS-B’

| | | | |

| | | |RELOCATION

| | | |——–>|

| | | |

Figure 45: Signalling for Subsequent Inter-MSC Handover to third MSC (3G_MSC-B’) initiation

Possible Positive outcomes: successful radio resources allocation:

BSS-A MSC-B MSC-A 3G-MSC-B’

| | | |

| | | | RNS-B’

| | | | |

| | | |RELOCATION

| | | |<——–|

| | | ACKNOWLEDGE

| | | | |

| | | |——–>|

| | | | |

| | |MAP PREPARE HANDOVER |

| | |<—————| |

| |<———————| | |

|<———–| | | |

| | | | |

Figure 46: Signalling for Subsequent Inter-MSC Handover to third MSC (3G_MSC-B’) execution
(Positive outcome)

Possible Negative outcomes:

a) user error detected, or component rejection or dialogue abortion performed by MSC-B’:

BSS-A MSC-B MSC-A 3G-MSC-B’

| | | |

| | | | RNS-B’

| | |MAP PREPARE HANDOVER |

| | |response negative result |

| | |<—————| |

| |<———————| | |

| |HANDOVER response negative | |

|<———–| | | |

b) radio resources allocation failure:

BSS-A MSC-B MSC-A 3G-MSC-B’

| | | |

| | | | RNS-B’

| | | | |

| | | |RELOCATION

| | | |<——–|

| | | | |

| | |MAP PREPARE HANDOVER |

| | |<—————| |

| |<———————| | |

|<———–| | | |

Figure 47: Signalling for Subsequent Inter-MSC Handover to third MSC (3G_MSC-B’) execution (Negative outcome)

NOTE 1: Possible rejection of the handover because of the negative outcome of MAP or BSSMAP procedure.

Positive outcome:

BSS-A MSC-B MSC-A 3G-MSC-B’

| | | |

| | | | RNS-B’

| | | | |

| | | |RELOCATION

| | | |<——–|

| | | | |

| | |MAP SEND END SIGNAL |

| | |<—————| |

| |<———————| | |

|<———–| | | |

Figure 48: Signalling for Subsequent Inter-MSC Handover to third MSC (3G_MSC-B’) completion (Successful completion of the procedure)

Negative outcome:

BSS-A MSC-B MSC-A 3G-MSC-B’

| | | |

|HANDOVER | | | RNS-B’

|———–>| | | |

| |———————>| | |

| |SIGNALLING request (Note 1) | |

| | | | |

| | |—————>| |

| | | |IU RELEASE

| | | |——–>|

| | | | |

Figure 49: Signalling for Subsequent Inter-MSC Handover to third MSC (3G_MSC-B’) completion (Unsuccessful completion of the procedure)

NOTE: Specific interworking case detailed below.

BSS-A MSC-A 3G-MSC-B’ RNS-B’

| | | |

| | |LOCATION REPORT |

| | |<——————|

| |MAP PROCESS ACCESS | |

| |<————————| |

| |SIGNALLING | |

Figure 49a: Signalling for updating of anchor MSC after change of location in RNS

The specific interworking case in MSC-A compared to the clauses 4.5.1 and 4.7.2 occurs between HANDOVER FAILURE encapsulated in a Process Access Signalling from MSC-B and the abortion of the dialogue with 3G_MSC-B’ in the case of a reversion to old channel of the MS:

—————————————————————-

| 29.002 29.002 |Notes

——–┼————————————————-┼—–

Forward | MAP PROCESS-SIGNALLING |

message | request |

| |

| -an-APDU( MAP U -ABORT | 1

| HANDOVER FAILURE) |

| |

——–┼————————————————-┼—–

Positive| |

result | |

——–┼————————————————-┼—–

Negative| |

result | MAP U/P -ABORT | 2

| |

NOTE 1: The abortion of the dialogue triggers in 3G_MSC-B’ the clearing of the circuit connection with MSC-A, if any, and of the Resources between 3G_MSC-B’ and RNS-B’. The abortion of the dialogue ends the handover procedure with 3G_MSC-B’.

NOTE 2: The abortion of the dialogue ends the handover procedure with MSC-B.

4.7.4 BSSAP Messages transfer on E-Interface

The handling is described in clause 4.5.4, additional cases are described in this clause.

4.7.4.1 Assignment

The interworking between the BSSMAP assignment messages in MAP and the RANAP RAB assignment messages is as follows:

—————————————————————-

| 29.002 25.413 |Notes

——–┼————————————————-┼—–

Forward | MAP PREPARE HANDOVER RAB ASSIGNMENT REQ|

message | request |

| -RANAP service Service handover |

| handover |

| -an-APDU( |

| ASSIGNMENT REQUEST) |

| |

| BSSMAP information RANAP information |

| elements: elements: |

| |

| Channel Type RAB parameters |

| |

——–┼————————————————-┼—–

Positive| MAP PREPARE HANDOVER |

result | request |

| -an-APDU( |

| ASSIGNMENT COMPLETE RAB ASSIGNMENT |

| RESPONSE |

| or (positive result)|

| ASSIGNMENT FAILURE) RAB ASSIGNMENT |

| RESPONSE |

| (negative result)|

| |

| BSSMAP information RANAP information |

| elements: elements: |

| |

| Cause Cause | 1

| |

——–┼————————————————-┼—–

Negative| |

result | MAP U/P –ABORT |

| |

NOTE 1: For the mapping between the cause codes see clause 4.7.6.

4.7.4.2 Cipher Mode Control

The interworking between the BSSMAP cipher mode messages in MAP and the RANAP security mode messages is as follows:

—————————————————————-

| 29.002 25.413 |Notes

——–┼————————————————-┼—–

Forward | MAP FORWARD ACCESS SIGN. SECURITY MODE CMD |

message | request |

| -an-APDU( |

| CIPHER MODE CMD) |

| |

| BSSMAP information RANAP information |

| elements: elements: |

| |

| Encryption information Integrity |

| protection info|

| Encryption info |

| |

——–┼————————————————-┼—–

Positive| MAP PROCESS ACCESS SIGN. |

result | request |

| -an-APDU( |

| CIPHER MODE COMPLETE SECURITY MODE |

| or COMPLETE |

| CIPHER MODE REJECT) SECURITY MODE |

| REJECT |

| |

| BSSMAP information RANAP information |

| elements: elements: |

| |

| Encryption information Integrity |

| protection info|

| Encryption info |

| Cause Cause | 1

| |

——–┼————————————————-┼—–

Negative| |

result | MAP U/P –ABORT |

| |

NOTE 1: For the mapping between the cause codes see clause 4.7.6.

4.7.4.3 Location Reporting Control

The interworking between the RANAP location report message and the BSSMAP handover performed message in MAP is as follows:

—————————————————————-

| 25.413 29.002 |Notes

——–┼————————————————-┼—–

Forward | LOCATION REPORT MAP PROC. ACC. SIGNALLING |

message | |

| -an-APDU( |

| HANDOVER PERFORMED)|

| |

| RANAP information BSSMAP information |

| elements: elements: |

| |

| Area identity (SAI) Cell identifier |

| Cause Cause |

| |

——–┼————————————————-┼—–

Positive| |

result | |

——–┼————————————————-┼—–

Negative| |

result | |

4.7.5 Processing in 3G_MSC-B, and information transfer on E-interface

The following parameters require processing (e.g. to store the parameter, to internally generate the parameter) in MSC‑B. The relevant BSSMAP procedures are mentioned to ease the comprehension, their detailed description is the scope of 3GPP TS 48.008 [12]. Each BSSMAP message listed in 3GPP TS 49.008 [14] being transferred on E-interface shall use the mechanisms given in clause 4.5.4 and is described in 3GPP TS 48.008 [12].

4.7.5.1 Encryption Information

3G_MSC-B shall remove algorithms not allowed by 3G_MSC-B from the list of GSM algorithms received from MSC-A. The modified list of algorithms, the ciphering key and the chosen algorithm shall be stored by 3G_MSC-B and used for generating the UMTS parameters Encryption Information and Integrity Protection Information if they are not received in MAP Prepare Handover Request (the generation of the UMTS parameters from the GSM parameters is described in TS 33.102).

Transfer of Information:

If ciphering has not been performed before Inter-MSC Handover, this will be controlled by MSC-A after the completion of Inter-MSC Handover.

Ciphering control towards 3G_MSC-B:

If Ciphering has been performed before Inter-MSC Handover:

– in the Handover Request BSSMAP message (information included).

The Handover Request Acknowledge should in this case NOT contain the indication of the chosen algorithm.

If Ciphering has NOT been performed before Inter-MSC Handover:

– in the Cipher Mode Command procedure between MSC-A and 3G_MSC-B.

4.7.5.2 Channel Type

The Channel Type shall be stored by 3G_MSC-B and used for generating RAB parameters.

Transfer of Information:

Independently of the type of resource (Signalling only or traffic channel) assigned to the MS, the Channel Type Information is transferred to 3G_MSC-B in:

– the Handover Request BSSMAP message.

Chosen Channel and/or Speech Version shall NOT be reported back to MSC-A in the Handover Request Acknowledge

If a new type of resource is to be assigned after Inter-MSC Handover, this can be made with:

– the BSSMAP Assignment procedure between MSC-A and 3G_MSC-B.

4.7.5.3 Classmark

This information shall be stored by 3G_MSC-B and might be received from MSC-A.

Transfer of Information due to Classmark received from MSC-A:

This information shall be stored by 3G_MSC-B and is received:

– in the Handover Request BSSMAP message.

If a new type of resource is to be assigned after Inter-MSC Handover, Classmark Information MAY be included:

– in the BSSMAP Assignment procedure.

4.7.5.4 Priority

The parameter shall be stored by 3G_MSC-B and used for generating RAB parameters. It is received as detailed below:

Transfer of Information:

Received by 3G_MSC-B from MSC-A in:

– the Handover Request BSSMAP message.

If a change is needed after an Inter-MSC Handover with:

– the BSSMAP Assignment procedure.

4.7.5.5 MSC-Invoke Trace Information Elements

The process to be performed by 3G_MSC-B on the information elements of the MSC Invoke Trace BSSMAP messages is left for further study.

Note that MSC-A does not forward BSC Invoke Trace in case of GSM to UMTS handover.

4.7.5.6 Selected UMTS Algorithm

A sequence of possible encryption and integrity protection algorithms, received from the 3G_MSC-A, can be sent to an RNS in Relocation Request or in Security Mode Command in case of cipher mode setting after inter-MSC handover from GSM to UMTS. The RNS chooses one of the listed algorithms and reports this back to the 3G_MSC in Relocation Request Acknowledge or Security Mode Complete respectively. The MSC-B provides the Selected UMTS algorithm information to the MSC-A. The Selected UMTS algorithms IE in the MAP Process Access Signalling Request and MAP Prepare Handover Response messages refers to the Chosen Integrity Protection Algorithm and Chosen Encryption Algorithm, defined in RANAP specification 3GPP TS 25.413 [7]

The selected algorithm shall be stored by 3G_MSC-B, and sent to 3G_MSC-A.

Transfer of Information:

If ciphering has not been performed before Inter-MSC Handover, this will be controlled by 3G_MSC-A after the completion of Inter-MSC Handover.

If Ciphering has been performed before Inter-MSC Handover, Selected UMTS algorithm information is received by 3G_MSC-A from 3G_MSC-B in:

– The Prepare Handover Response MAP message.

If Ciphering has NOT been performed before Inter-MSC Handover, Selected UMTS algorithm information is received by 3G_MSC-A from 3G_MSC-B in:

– The Process Access Signalling Request MAP message.

4.7.5.7 Allowed UMTS Algorithms

In case of GSM-subscriber, the Integrity Protection Information and UMTS Encryption Information are not transferred to the MSC-B during inter-MSC handover from GSM to UMTS. Allowed UMTS algorithms is UMTS information that is required in RANAP Relocation Request and RANAP Security Mode Command, and shall be provided by 3G_MSC-A. 3G_MSC-B needs this information in case of an inter-MSC GSM to UMTS handover and in subsequent security mode setting, after an inter-MSC GSM to UMTS handover. Therefore 3G_MSC-A must provide this information in case of an inter-MSC GSM to UMTS handover. The Allowed UMTS algorithms IE in the MAP Prepare Handover and in the MAP Forward Access Signalling Request messages refers to the Permitted Integrity Protection Algorithms in Integrity Protection Information and Permitted Encryption Algorithms in Encryption Information, defined in RANAP specification 3GPP TS 25.413 [7].

Allowed UMTS algorithms shall be stored by 3G_MSC-B.

Transfer of information:

If ciphering has not been performed before Inter-MSC Handover, this will be controlled by 3G_MSC-A after the completion of Inter-MSC Handover.

Ciphering control towards 3G_MSC-B:

If Ciphering has been performed before Inter-MSC Handover:

– The Prepare Handover Request MAP message.

If Ciphering has NOT been performed before Inter-MSC Handover:

– The Forward Access Signalling Request MAP message.

4.7.5.8 BSSMAP Service Handover

This information shall be stored by 3G_MSC-B and sent to a BSS in Handover Request, when 3G_MSC-B performs handover to GSM.

Transfer of information:

The BSSMAP Service Handover information is transferred to 3G_MSC-B in:

– the Handover Request BSSMAP message.

If a new assignment of a TCH after an inter-MSC handover is to be performed, the BSSMAP Service Handover information is transferred to 3G_MSC-B in:

– the BSSMAP Assignment procedure.

4.7.5.9 RANAP Service Handover

This information shall be stored by 3G_MSC-B and sent to an RNS in Relocation Request during the basic inter-MSC handover or when 3G_MSC-B performs a subsequent relocation or handover to UMTS.

Transfer of information:

The RANAP Service Handover information is transferred to 3G_MSC-B in:

– the Prepare Handover Request MAP message.

If a new assignment of a Radio Access Bearer after an inter-MSC handover is to be performed, the information is transferred to 3G_MSC-B in:

– the Forward Access Signalling Request MAP message

and sent by 3G_MSC-B to the RNS in RAB Assignment Request.

4.7.5.10 GERAN Classmark

The GERAN Classmark shall be stored by 3G_MSC-B and can be received from MSC-A, from the serving BSS or serving RNS, or from the target RNS. The GERAN Classmark shall be used together with other parameters, e.g. the Channel Type, for selecting a service and for generating RAB parameters for handover to GERAN Iu-mode, subsequent relocation or handover to GERAN Iu-mode, and RAB (re-)assignment when the MS is in GERAN Iu-mode.

Transfer of Information due to GERAN Classmark received from MSC-A:

Received by 3G_MSC-B in:

– the Prepare Handover Request MAP message.

Transfer of Information due to GERAN Classmark received from the serving BSS or serving RNS:

Received by 3G_MSC-B in:

– the Handover Required BSSMAP message;

– the Initial UE RANAP message; or

– the RAB Assignment Response RANAP message.

Transfer of Information due to GERAN Classmark received from the target RNS:

Received by 3G_MSC-B in:

t- he Relocation Failure RANAP message.

4.7.5.11 SNA Access Information

This information shall be stored by 3G_MSC-B and sent to an RNS in the Relocation Request message when 3G_MSC-B performs handover to UMTS.

Transfer of information:

The SNA Access Information is transferred to 3G_MSC-B in:

– the Handover Request BSSMAP message.

4.7.5.12 UESBI

This information shall be stored by 3G_MSC-B and sent to an RNS in Relocation Request during the basic inter-MSC handover or when 3G_MSC-B performs a subsequent relocation or handover to UMTS.

Transfer of information:

The UESBI information is transferred to 3G_MSC-B in:

– the Prepare Handover Request MAP message.

4.7.5.13 Alternative Channel Type

This information shall be stored by 3G_MSC-B and from this information 3G_MSC-B shall generate Alternative RAB Parameters Value IE sent to an RNS in Relocation Request, when 3G_MSC-B performs relocation or handover to UMTS.

Transfer of information:

The Alternative Channel Type information is transferred to 3G_MSC-B in:

– the Prepare Handover Request MAP message.

If a new assignment of a Radio Access Bearer after an inter-MSC handover is to be performed, the information is transferred to 3G_MSC-B in:

– the Forward Access Signalling Request MAP message.

4.7.5.14 Trace parameters

This information shall be stored by 3G_MSC-B and 3G_MSC-B shall use this information for trace activation for MSC-S, MGW, RNC or BSC.

Transfer of information:

The Trace Parameter List information for MSC-S, MGW and RNC tracing is transferred to 3G_MSC-B in:

– the Prepare Handover Request MAP message.

The Trace Reference and Trace Type information for BSC tracing is transferred to 3G_MSC-B in:

– the MSC Invoke Trace BSSMAP message.

4.7.6 Cause Code Mapping

When a Mobile Station is handed over between GSM and UMTS, a mapping of the cause codes used in the BSSMAP and the RANAP protocols is needed. The mapping described here is applicable to the BSSMAP protocol even when used inside MAP in the E-interface.

The mapping between the cause codes received in BSSMAP Handover Required and the cause codes sent in RANAP Relocation Request is as follows:

—————————————————————-

48.008 25.413 |Notes

——————————————————-┼——–

HANDOVER REQUIRED RELOCATION REQUEST |

-Better Cell -Relocation Desirable |

for Radio Reasons |

-Directed retry -Directed retry |

-Distance -Time critical reloc. |

-Downlink quality -Time critical reloc. |

-Downlink strength -Time critical reloc. |

-O and M intervention -O and M intervention |

-Preemption -RAB pre-empted |

-Response to MSC invocation -Network Optimisation |

-Switch circuit pool | 1

-Traffic -Resource Optimisation |

Relocation |

-Uplink quality -Time critical reloc. |

-Uplink strength -Time critical reloc. |

-Reduce Load in -Reduce Load in |

serving cell serving cell |

-Any other value -Relocation Desirable |

For Radio Reasons |

NOTE 1: Cause code not used at inter-system handover.

The mapping between the cause codes received in BSSMAP Handover Request and the cause codes sent in RANAP Relocation Request is as follows (the mapping is only used for the MAP-E interface):

—————————————————————-

48.008 25.413 |Notes

——————————————————-┼——–

HANDOVER REQUEST RELOCATION REQUEST |

-Better Cell -Relocation Desirable |

for Radio Reasons |

-Directed retry – Directed retry |

-Distance -Time critical reloc. |

-Downlink quality -Time critical reloc. |

-Downlink strength -Time critical reloc. |

-O and M intervention -O and M intervention |

-Preemption -RAB pre-empted |

-Response to MSC invocation -Network Optimisation |

-Switch circuit pool | 1

-Traffic -Resource Optimisation |

Relocation |

-Uplink quality -Time critical reloc. |

-Uplink strength -Time critical reloc. |

-Reduce Load in -Reduce Load in |

serving cell serving cell |

-Any other value -Relocation Desirable |

For Radio Reasons |

NOTE 1: Cause code not used at inter-system handover.

The mapping between the cause codes received in BSSMAP Handover Failure and the cause codes sent in RANAP Iu Release Command is as follows:

—————————————————————-

48.008 25.413 |Notes

——————————————————-┼——–

HANDOVER FAILURE IU RELEASE COMMAND |

-Ciphering algorithm not | 2

supported |

-Circuit pool mismatch | 1

-Equipment failure -Relocation cancelled |

-Invalid message contents -Abstract Syntax Error |

-No radio resource available | 2

-O and M intervention -O and M intervention |

-Radio interface failure, -Relocation cancelled |

reversion to old channel |

-Radio interface message -Relocation cancelled |

failure |

-Requested speech version | 2

unavailable |

-Requested terrestrial | 2

resource unavailable |

-Requested transcoding/rate | 2

adaption unavailable |

-Switch circuit pool | 1

-Terrestrial circuit already -Relocation cancelled |

allocated |

-Any other value -Relocation cancelled |

NOTE 1: Cause code not used at inter-system handover.

NOTE 2: Cause code not applicable to this traffic case.

The mapping between the cause codes received in RANAP Relocation Failure and the cause codes sent in BSSMAP Handover Failure is as follows (this mapping is only used for the MAP-E interface):

—————————————————————-

25.413 48.008 |Notes

——————————————————-┼——–

RELOCATION FAILURE HANDOVER FAILURE |

-GERAN Iu-mode failure -GERAN Iu-mode failure |

-Traffic load in the target -Traffic load in the |

cell higher than in the target cell higher |

source cell than in the source |

cell |

-Any other value -No radio resource |

available |

The mapping between the cause codes received in RANAP Relocation Failure and the cause codes sent in BSSMAP Handover Required Reject is as follows:

—————————————————————-

25.413 48.008 |Notes

——————————————————-┼——–

RELOCATION FAILURE HANDOVER REQUIRED REJECT |

-GERAN Iu-mode failure -GERAN Iu-mode failure |

-Incoming Relocation -Incoming Relocation |

Not Supported Due To Not Supported Due To |

PUESBINE Feature PUESBINE Feature |

-Traffic load in the target -Traffic load in the |

cell higher than in the target cell higher |

source cell than in the source |

cell |

-Any other value -No radio resource |

available |

The mapping between the RANAP and the BSSMAP assignment messages is used in the MAP-E interface. RANAP RAB Assignment Response with successful result is mapped to BSSMAP Assignment Complete; RANAP RAB Assignment Response with unsuccessful result is mapped to BSSMAP Assignment Failure. The mapping between the cause codes received in RANAP RAB Assignment Response and the cause codes sent in BSSMAP Assignment Failure is as follows (this mapping is only used for the MAP-E interface):

—————————————————————-

25.413 48.008 |Notes

——————————————————-┼——–

RAB ASSIGNMENT RESPONSE ASSIGNMENT FAILURE |

-Requested traffic class not –No radio resource |

available available |

-Invalid RAB parameters value –Invalid msg. contents |

-Requested max bit rate not –No radio resource |

available available |

-Requested max bit rate for DL –No radio resource |

not available available |

-Requested max bit rate for UL –No radio resource |

not available available |

-Requested guaranteed bit rate –No radio resource |

not available available |

-Requested guaranteed bit rate –No radio resource |

for DL not available available |

-Requested guaranteed bit rate –No radio resource |

for UL not available available |

-Requested transfer delay not –No radio resource |

achievable available |

-Invalid RAB param. combination–Invalid msg. contents |

-Condition violation for SDU –Invalid msg. contents |

parameters |

-Condition violation for –Invalid msg. contents |

traffic handling priority |

-Condition violation for –Invalid msg. contents |

guaranteed bit rate |

-User plane not supported –No radio resource |

available |

-Iu UP failure –Equipment failure |

-Tqueuing expiry –Radio interface message|

failure |

-Invalid RAB id –Invalid msg. contents |

-Request superseeded –No radio resource |

available |

-Relocation triggered -Relocation triggered |

-GERAN Iu-mode failure -GERAN Iu-mode failure |

-Any other value –Radio interface message|

failure |

The mapping between the cause codes received in RANAP Security Mode Reject and the cause codes sent in BSSMAP Cipher Mode Reject is as follows (this mapping is only used for the MAP-E interface):

—————————————————————-

25.413 48.008 |Notes

——————————————————-┼——–

SECURITY MODE REJECT CIPHER MODE REJECT |

-Requested ciphering and/or –Ciphering algorithm |

integrity protection not supported |

algorithms not supported |

-Failure in the radio –Radio interface message|

interface procedure failure |

-Change of ciphering and/or -Invalid msg. contents |

integrity protection is |

not supported |

-Relocation triggered -Relocation triggered |

-Any other value –Radio interface message|

failure |

The mapping between the cause codes received in RANAP Location Report and the cause codes sent in BSSMAP Handover Performed is as follows (this mapping is only used for the MAP-E interface):

—————————————————————-

25.413 48.008 |Notes

——————————————————-┼——–

LOCATION REPORT HANDOVER PERFORMED |

-User restriction start ind. –O&M intervention |

-Requested report type not | 1

supported |

-Any other value -Better cell |

NOTE 1: In this case, no Handover Performed is sent.

The mapping between the cause codes received in RANAP Iu Release Request and the cause codes sent in BSSMAP Clear Request is as follows:

—————————————————————-

25.413 48.008 |Notes

——————————————————-┼——–

IU RELEASE REQUEST CLEAR REQUEST |

-O and M intervention -O and M intervention |

-Unspecified failure -Equipment failure |

-Repeated integrity checking -Invalid message |

failure contents |

-Release due to UE generated -Call control |

signalling connection release |

-Radio connection with UE lost –Radio interface |

failure |

-Access restricted due -Access restricted due |

to shared networks to shared networks |

-Any other value -No radio resource |

available |