tion Not successful AAI REG- Obtained AAISBC-REQ/Process AAI_SBC-REQ re-transmission (Send AAI_SBC-RSP) ObtainedAAI_REG-REQ/ Send AAI_RNG-RSP Send AAI_REG-RSP with (Abort) or AAI_RES-CMD Wait for ObtainedAAI REG-REQ ACK for Process AAI_REG-REQ AAI REG- re-transmission (Send AAI_REG-RSP with STID) Obtainedimplicit or explicit ACK for Send AAI_RNG-RSP AAI_REG-RSP (Abort), Establish AAI_RES-CMD or Connection/ AAI_DREG-CMD Network Entry Completed FIGURE 4-13 Initial network entry procedures in the base station [1,2] 4.2 Network entry expired in the network, and consequently the MS must perform the normal network re-entry procedures. If the serving ASN has the MS context or the context in the serving BS is not revoked before the management resource holding timer expires, the procedures for the MS to exit Idle State can be further simplified. The serving BS releases the MS context and the data paths for this MS only upon expiration of this timer. In this case, if the MS has maintained downlink synchronization with the BS during Idle State and if the system information at the MS is up-to-date, the MS may skip Initialization State procedures and directly transition to Access State and perform a light ranging, re-authentication, and re-registration with the serving BS. This form of network re-entry is referred to as fast network re-entry. Note that in the IEEE 802.16 standard, an MS is deregistered with the serving BS prior to entering the Idle State. In addition, during handover, the MS must search and select a target BS and perform network re-entry process in order to establish a data-plane with the target BS and detach from the serving BS. Since the MS context may remain in the network when the MS transitions to the Idle State for a limited time, there is no need for a full authentication and registration on transition from the Idle State. Cell reselection is the process where an MS scans and associates with one or more base stations in order to determine their suitability, along with other performance considerations, 