Section: 4.3.4.2 IMSI detach procedure in the network
Content: When receiving an IMSI DETACH INDICATION message, the network may set an inactive indication for the IMSI. No response is returned to the mobile station. After reception of the IMSI DETACH INDICATION message the network shall release locally any ongoing MM connections, and start the normal RR connection release procedure (see 3GPP TS 44.018[ None ]  [84] subclause 3.5 (A/Gb mode only), 3GPP TS 25.331[ None ]  [23c] (UTRAN Iu mode only), or in 3GPP TS 44.118[ None ]  [111] (GERAN Iu mode only)). Only applicable for a network supporting VGCS: If an IMSI DETACH INDICATION message is received from the talking mobile station in a group call while the network is in service state MM CONNECTION ACTIVE (GROUP TRANSMIT MODE), the network shall release locally the ongoing MM connection and then go to the service state GROUP CALL ACTIVE.