 AAI_RNG-REQ (MS ID is transmitted over the air) AAI_RNG-RSP (STID is assigned by the BS) Data and Control Plane Establishment FIGURE 4-14 Summary of network entry procedures in IEEE 802.16m [2] whereas the BS associated with the MS after the handover is denoted as the target BS. The handover process involves a number of interactions and message exchanges between the MS and neighboring base stations for the purpose of scanning, ranging, parameter negotiation, and information exchange. In this process, which may take tens of milliseconds, the MS connection to the serving BS may be temporarily interrupted (i.e., handover interruption time). The handover process consists of the following five steps: 1. Cell reselection by scanning neighboring base stations and compiling a list of candidate base stations. The MS may use neighbor BS information acquired from a decoded neighbor advertisement message or may request to schedule scanning intervals or sleep intervals to scan (and possibly to perform ranging with) neighbor base stations for the purpose of evaluating MS interest in handover to a potential target BS. The cell reselection process does not need to occur in conjunction with any specific contemplated handover decision. 2. Handover decision that may be originated from the MS (mobile-initiated handover) or the serving BS (base station-initiated handover). The handover decision is carried out with a notification of MS or BS intent for handover through handover request messages. 3. Downlink synchronization with the target BS (if necessary). CHAPTER 4 IEEE 802. 16m System Operation and State Diagrams 4. Handover ranging uplink synchronization, and the subsequent network re-entry procedures with the target BS (i.e., basic capability negotiation, authorization, authentication, registration, and service flow establishment), some of which may be skipped or simplified if the target BS can obtain the MS context from the serving BS over the backbone. 5. Termination of the MS context at the serving BS that includes informatio