This time we are going to talk about next three rejection causes for GMM. Rejection causes are related to Combined Attach, routing and updating procedures.
The description for IMSI attach for GPRS services will follow. In addition, the following description for IMSI attach for non-GPRS services applies.
Only difference in Combined Attach successful for GPRS services only and Combined Routing and Updatting successful for GPRS services only is in next two messages listed below:
1. The MS receiving the ATTACH ACCEPT message takes one of the following actions depending on the reject cause:
2. The MS receiving the ROUTING AREA UPDATE ACCEPT message takes one of the following actions depending on the reject cause:
# 16 (MSC temporarily not reachable)
# 17 (Network failure)
# 22 (Congestion)
Message exchange, status change and counter increments are the same for both procedures.
The MS shall change to state GMM-REGISTERED.ATTEMPTING-TO-UPDATE-MM. Timer T3310 shall
be stopped if still running. The routing area updating attempt counter shall be incremented.
If the routing area updating attempt counter is less than 5, and the stored RAI is equal to the RAI of the current serving cell and the GMM update status is equal to GU1 UPDATED:
- the MS shall keep the GMM update status GU1 UPDATED and changes state to GMMREGISTERED. ATTEMPTING-TO-UPDATE-MM. The MS shall start timer T3311. When timer T3311 expires the combined routing area update procedure indicating "combined RA/LA updating with IMSI attach" is triggered again.
If the routing area updating attempt counter is greater than or equal to 5:
- the MS shall start timer T3302 and shall change to state GMM-REGISTERED.ATTEMPTING-TO-UPDATE-MM;
- a GPRS MS operating in MS operation mode A shall then proceed with appropriate MM specific procedure; a GPRS MS operating in MS operation mode B may then proceed with appropriate MM specific procedures. The MM sublayer shall act as in network operation mode II as long as the combined GMM procedures are not successful and no new RA is entered. The new MM state is IDLE.
Other values are considered as abnormal cases. The combined attach procedure shall be considered as failed for GPRS and non-GPRS services.
Additional cause codes for GMM
Cause value = 16 MSC temporarily not reachable
This cause is sent to the MS if it requests a combined GPRS attach or routing are updating in a PLMN where the MSC is temporarily not reachable via the GPRS part of the network.
Causes related to PLMN specific network failures and congestion/Authentication Failures
Cause value = 17 Network failure
This cause is sent to the MS if the MSC cannot service an MS generated request because of PLMN failures, e.g. problems in MAP.
Cause value = 22 Congestion
This cause is sent if the service request cannot be actioned because of congestion (e.g. no channel, facility busy/congested etc.).