Section: 4.11.4 Support for enhanced discontinuous coverage
Content: If the UE and network support enhanced discontinuous coverage, the UE may provide unavailability information to the network in the tracking area updating procedure if the UE is registered over satellite E-UTRAN access (see 3GPP TS 23.401[ General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access ]  [10]). The unavailability information includes the unavailability period duration if known, and the start of the unavailability period if known. The support for the enhanced discontinuous coverage is negotiated in the attach procedure or the tracking area updating procedure. The MME may consider the unavailability period duration if provided by the UE to determine the unavailability period duration of the UE. The MME may provide the unavailability period duration to the UE in the TRACKING AREA UPDATE ACCEPT message. The MME may consider the unavailability period duration if provided by the UE to determine the unavailability period duration of the UE. If the UE provided unavailability information in the last tracking area updating procedure, the MME considers the UE unreachable until the UE registers for normal service without providing unavailability information. If the UE did not include a start of the unavailability period, the MME shall consider the start of the unavailability period to be the time at which MME received the TRACKING AREA UPDATE REQUEST message to the UE. The MME may determine the value of the periodic tracking area update timer (T3412) provided to the UE based on the unavailability period duration and the start of the unavailability period, if available. The MME releases the NAS signalling connection after the completion of the attach procedure or the tracking area updating procedure in which the UE provided unavailability information. If for discontinuous coverage the UE has stored a discontinuous coverage maximum time offset, upon returning in coverage after being out of coverage due to discontinuous coverage, the UE sets the discontinuous coverage maximum time offset value to a random value up to and including the stored discontinuous coverage maximum time offset for this PLMN and satellite E-UTRAN access and starts this timer. The UE shall not initiate any NAS signalling on that satellite E-UTRAN access and PLMN combination while the discontinuous coverage maximum time offset timer is running. The UE shall stop the discontinuous coverage maximum time offset timer and initiate NAS signalling if the UE receives a paging message, has pending emergency services, is establishing an emergency PDN connection, is performing emergency services fallback procedure or when the UE enters a new tracking area. When the unavailability period is activated, all NAS timers are stopped and associated procedures aborted except for timers T3412, T3346, T3447, T3396, any back-off timers, T3247, and the timer T controlling the periodic search for HPLMN or EHPLMN or higher prioritized PLMNs (see 3GPP TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [6]). When the UE provides unavailability information using the tracking area updating procedure without providing the start of the unavailability period, then after successful completion of the procedure the UE may deactivate the access stratum and enter the state EMM-REGISTERED.NO-CELL-AVAILABLE. Otherwise, if the UE provided the start of unavailability period, the UE may deactivate the access stratum and enter the state EMM-REGISTERED.NO-CELL-AVAILABLE only after the start of the unavailability period.