The Suspend and Resume procedure for intra-SGSN is illustrated in Figure 99.
Step 1.
The MS enters dedicated mode and the MS or the network limitations make it unable to support Class A mode of operation, or during CS connection, a DTM MS performs handover from a cell supporting DTM to a cell not supporting DTM.
Step 2.
The MS sends an RR Suspend (TLLI, RAI) message to the BSS. The BSS may terminate any ongoing GPRS traffic for this TLLI.
Step 3.
The BSS sends a Suspend (TLLI, RAI) message to the SGSN, and the SGSN acknowledges by returning Suspend Ack. The BSS shall store TLLI and RAI in order to be able to request the SGSN to resume GPRS services when the MS leaves dedicated mode.
Step 4.
Eventually, the BSS may determine that the conditions for the GPRS suspension have disappeared. If the BSS is able to request the SGSN to resume GPRS services, the BSS shall send a Resume (TLLI, RAI) message to the SGSN. The SGSN acknowledges the successful outcome of the resume by returning Resume Ack.
Step 5.
If the circuit switched radio channel is to be released, the BSS sends an RR Channel Release (Resume) message to the MS. The Resume message indicates whether the BSS has successfully requested the SGSN to resume GPRS services for the MS, i.e., whether Resume Ack was received in the BSS before the RR Channel Release message was transmitted. The MS leaves dedicated mode.
Step 6.
The MS shall resume GPRS services by sending a Routeing Area Update Request message to the SGSN:
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if the BSS did not successfully request the SGSN to resume GPRS services,
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if the RR Channel Release message was not received before the MS left dedicated mode,
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if the MS locally determines that the conditions for the GPRS suspension have disappeared
The Update Type depends on the mode of operation of the network in use e.g. in mode I Combined RA/LA Update is made and in mode II Routeing Area Update is made.
The full handling of suspended MSs in the BSS and the SGSN is implementation dependent. Typically, the SGSN should not page suspended MSs.
If the MS performs an inter-BSC handover while suspended, the TLLI and RAI should be transferred as BSC-to-BSC information in the Handover Required and Handover Request messages, see
TS 48.008. This allows the new BSC to initiate the Resume request procedure to the SGSN. If the BSC-to-BSC information was not transferred or not understood, the MS doesn't receive an indication that resumption has been successful, and the MS shall resume GPRS services by initiating a Routeing Area Update or Combined RA/LA Updating procedure as described in step 6.
The Suspend and Resume procedure for inter-SGSN is illustrated in Figure 100.
This describes the scenario where the old cell and the new cell are handled by different SGSN's, i.e. suspend message is received in an SGSN that is different from the SGSN currently handling the packet data transmission.
Step 1.
During CS connection, a DTM MS performs handover from a cell supporting DTM to a cell not supporting DTM.
Step 2.
The MS sends an RR Suspend (TLLI, RAI) message to the BSS.
Step 3.
The BSS sends a Suspend (TLLI, RAI) message to the SGSN.
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Since the SGSN that receives the Suspend message is not the one currently handling the packet data transmission, an indication to perform suspend will be sent to the old SGSN by means of a SUSPEND REQUEST message on the Gn interface. The address of the old SGSN is derived by "old RAI" received in Suspend message. If the SGSN that receives the Suspend message provides functionality for Intra Domain Connection of RAN Nodes to Multiple CN Nodes, the SGSN that receives the Suspend message from the BSS may derive the old SGSN from the old RAI and the old TLLI and send the Suspend Request message to this old SGSN. Otherwise, the SGSN that receives the Suspend message from the BSS derives the old SGSN from the old RAI. In any case the SGSN that receives the Suspend message from the BSS will derive an SGSN that it believes is the old SGSN. This derived SGSN is itself the old SGSN, or it is associated with the same pool area as the actual old SGSN and it will determine the correct old SGSN from the TLLI and relay the Suspend Request message to that actual old SGSN.
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The Old SGSN returns a SUSPEND RESPONSE.
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The new SGSN then returns Suspend Ack to the BSS.
Step 4.
After CS connection is terminated, the BSS may send a Resume (TLLI, RAI) message to the new SGSN, but since resume is not needed against the old SGSN, the new SGSN acknowledges the resume by Resume Nack.
(Resume is not needed against the old SGSN since the MS in this case always will perform an RA Update for updating of GPRS services when the CS connection is terminated and the MM context will be moved from the old to the new SGSN.)
Step 5.
The BSS sends an RR Channel Release message to the MS, indicating that the BSS has not successfully requested the SGSN to resume GPRS services for the MS. The MS leaves dedicated mode.
Step 6.
The MS shall resume GPRS services by sending a Routeing Area Update Request message to the SGSN. The Update Type depends on the mode of operation of the network in use e.g. in mode I Combined RA/LA Update is made and in mode II Routeing Area Update is made.