13 BSC ReleaseAbout This Chapter

BSC release consists of the normal release and the local release.

13.1 Normal Release ProcedureNormal release is originated by the MS or the MSC. Upon onhook, the calling MS sends aDisconnect message to the MSC. Then the corresponding MSC sends the Disconnect messageto the called MS.13.2 Local Release ProcedureThe local release procedure is initiated by the BSC.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 13 BSC Release

Issue 01 (2007-11-26) Huawei Technologies Proprietary 13-1

13.1 Normal Release ProcedureNormal release is originated by the MS or the MSC. Upon onhook, the calling MS sends aDisconnect message to the MSC. Then the corresponding MSC sends the Disconnect messageto the called MS.

Signaling ProcedureAfter the access of the MS, the BSC initiates the release procedure upon service requests, forexample, MS onhook. Figure 13-1 shows the BSC normal release procedure.

13 BSC ReleaseHUAWEI BSC6000 Base Station Subsystem

BSS Signaling Analysis Guide

13-2 Huawei Technologies Proprietary Issue 01 (2007-11-26)

Figure 13-1 Normal release procedure

MS BTS MSC

Release Complete(3)

BSC

Disconnect(1)FACCH

Stop T3109

Stop T3109

Start T305Release(2)

FACCHStart T308

Start T305

Stop T308FACCH

Clear Command(4)Channel Release(5)

FACCH

Deactivate SACCH(8)DISC(6)

FACCH

UA(7)FACCH

Release Indication(9)

Start T3111

Stop T3111

RF Channel Release(10)Clear Complete(11)

RF Channel ReleaseAcknowledge(12)

RLSD(13)

RLC(14)

The BSC normal release procedure is as follows:1. Upon onhook, the calling MS sends a Disconnect message to the MSC and starts timer

T305. The Disconnect message carries the cause for disconnection.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 13 BSC Release

Issue 01 (2007-11-26) Huawei Technologies Proprietary 13-3

2. The MSC sends the calling MS a Release message and at the same time sends the calledMS a Disconnect message. The network starts timer T308.

3. Upon receiving the Release message, the calling MS stops timer T305, releases the MMconnection, and sends the MSC a Release Complete message.

4. Upon receiving the Release Complete message, the MSC stops timer T308, releases theMM connection, and sends the BSC a Clear Command message. The Clear Commandmessage notifies the BSC of releasing the resources on the A interface and the Um interface.

5. The BSC sends a Channel Release message and starts timer T3109. The Channel Releasemessage carries the RR cause filed and notifies the MS and the BTS of releasing the logicchannels on the Um interface.

6. Upon receiving the Channel Release message, the MS disconnects the uplink signaling linkand sends the BTS a DISC frame, indicating that the logic channels are released.

7. The BTS sends the MS a UA frame. Upon receiving the UA frame, the MS returns to theCCCH and enters the idle state.

8. The BSC sends the BTS a Deactivate SACCH message, deactivates the associated channels,and releases the downlink channel associated signaling.

9. Upon receiving the DISC frame, the BTS sends the BSC a Release Indication message,stops timer T3109, and starts timer T3111. The Release Indication message indicates thatthe MS has released the logic channels on the Um interface.

10. Upon timer T3111 expiry, the BSC sends the BTS an RF Channel Release message. TimerT3111 is used to reserve a period for the acknowledgement of disrupted connection.

11. The BTS sends the BSC an RF Channel Release Acknowledge message, indicating that theRF channels on the radio interface are released and can be used for re-assignment.

12. The BSC responds to the MSC with a Clear Complete message.13. The MSC sends the BSC an RLSD message to release the SCCP connection.14. The BSC responds to the MSC with an RLC message, indicating that the SCCP connection

is released.

Procedure Descriptionl Steps 1 through 3 shown in Figure 13-1 is the call connection release.

NOTE

Figure 13-1 shows the MS originating release procedure. For the network originating releaseprocedure, the directions of only the three transparent transmission messages are opposite.

l Steps 4 through 14 shown in Figure 13-1 is the radio resource release.After the connections at the CC layer and at the MM layer are released, the network sendsthe BSC a Clear Command message to request the release of the SCCP signaling link. TheClear Command message carries the clear causes such as the Handover Successful or CallControl. If the release is caused by radio interface message failures, radio link failures, orequipment failures, the BSC sends a Clear Request message to the system. Then, the MSCdelivers the Clear Command message.

13.2 Local Release ProcedureThe local release procedure is initiated by the BSC.Figure 13-2 shows the local release procedure.

13 BSC ReleaseHUAWEI BSC6000 Base Station Subsystem

BSS Signaling Analysis Guide

13-4 Huawei Technologies Proprietary Issue 01 (2007-11-26)

Figure 13-2 Local release procedure

Deactivate SACCH (1)

Release Request (2)

RF Channel Release(4)

RF Channel Release Acknowledge (5)

BTS BSC

Release Confirm (3)

l The BSC sends the BTS a Deactivate SACCH message to deactivate the associatedchannels.

l The BSC sends the BTS a Release Request message with the cause value Local End Release.In this case, the release procedure has nothing to do with the MS.

l Upon receiving the Release Request message with the cause value Local End Release, theBTS responds to the BSC with a Release Confirm message. If the Release Request messagecarries other cause values, the BTS sends a DISC frame to the MS. Only after receivingthe UA frame or DM frame from the MS, the BTS sends the Release Confirm message tothe BSC.

l The BSC sends an RF Channel Release message to the BTS.l The BTS sends an RF Channel Release Acknowledge message to the BSC.

HUAWEI BSC6000 Base Station SubsystemBSS Signaling Analysis Guide 13 BSC Release

Issue 01 (2007-11-26) Huawei Technologies Proprietary 13-5

13 BSC Release13.1 Normal Release Procedure13.2 Local Release Procedure