Research On Mobile Handover Technology In WiMAX

Based on the performance analysis of mobile handover in WiMAX, an improved handover mechanism is proposed in this thesis.At the beginning, the handover mechanism and models in WiMAX are discussed in detail in this thesis, especially the hard handover process. And the disadvantages of handover performance are indicated, e.g., the low efficiency of handover trigger rule and target BS choice rule. So, based on the hard handover mechanism, an absolute & relative threshold handover trigger rule named CSSTH is proposed. The CSSTH requires that the downlink carrier interference noise ratio CINR must meet the handover threshold and the hysteresis. It can avoid the"ping-pong"effect as well as satisfy QoS requirements during the handover process. Meanwhile, in HTBS, a modified algorithm, the HO_process_optimization field is checked during choosing the target BS. This can shorten the re-entry process at the target BS, and reduce the handover delay introduced by hard handover.To evaluate the improved handover mechanism, the simulations are made with network simulator software-OPNET. The simulation results show that, compared with the IEEE802.16e standard algorithm and single CSSTH algorithm, CSSTH & HTBS can obviously reduce the handover delay and downlink packets dropped of MS, and improve the MS's total data traffic during the handover process.