The Research And Optimization Of Initial Ranging Mechanism In IEEE 802.16e Standard

IEEE 802.16 (WiMAX) is developed by the IEEE 802 workgroup as the wireless access air interface standards, including IEEE 802.16d—the fixed wireless access standard, IEEE 802.16e—mobile wireless access standard and IEEE 802.16m—high speed mobile wireless access standard.Random Access Part is a important technology in the MAC Layer of a communication system, and system performances mainly depend on the performance of random access. In order to meet demands of connection delay and usage of resources in WiMAX, the research of random access comes to be one key part of WiMAX. And initial ranging mechanism is used as the random access technology.The paper identified the principle, function and categories of ranging mechanism, then researched mainly in the performance, including ranging codes, backoff algorithm and connection delay. Because of no clear definition to the allocation methods of initial ranging resources, based on the above analysis, the paper proposed a method which used pseudo-random codes as ranging codes and dynamically allocated methods of initial ranging resources. This improved initial ranging mechanism constructed a joint optimization function based on connection delay and the ratio of initial ranging resources and dedicated data resources, then derived the optimization allocation methods of initial ranging resources. Then it is analyzed by simulation which the decrease of connection delay using pseudo-random ranging code and construction method of joint optimal function, and proved the correctness of dynamical allocation initial ranging resources'method. Meanwhile, a backoff algorithm adapting the method and allocation methods of ranging codes which focus on initial ranging are introduced briefly.