sublayers accepts higher-layer protocol data units (PDUs) from ATM cell-based or packet-based network layers. The Common Part Sublayer (CPS) provides the core MAC functionality of system access, bandwidth allocation, connection establishment, and connection maintenance. The Security Sublayer provides authentication, secure key exchange, and encryption. The IEEE 802.16e (3) system is based on OFDMA physical structure, mobile subscriber stations (MSS) basically conduct three handoff methods: Hard Handoff (HHO), Fast Base Station Switching (FBSS) and Macro Diversity Handover (MDHO). The first method (HHO) is a mandatory while the other two methods are optional. In HHO, the Mobile Subscriber (MS) is connected to only one Base Station (BS) at any given time. If the MS decides to handover from the serving BS, it selects only one target BS from a subset of recommended BSs and starts connecting to it before disconnecting from the current serving BS. An important objective when designing a handover mechanism is to minimize the time spent in the handover transition to ensure that the MS does not experience service interruption during the handover.