On MAC And Network Layers Protocol Of WiMAX System

BWA (Broadband Wireless Access) is atracted more and more attention as one of the most promising techniqes in the Wireless Metropolitan Area Networks(WMANs). IEEE802.16 standard( also be called WiMAX)is proposed for the development of BWA and as a global standard.Research in this paper was based on the IEEE 802.16d standard.In order to satisfy the various needs in the coming WiMAX times, we focus on two aspects:he MAC and multi-gateways access protocol in WMANs.The numerical deduction and simulations are used to rarity the proposed algorithms.This paper introduce the two topology structures of WiMAX:PMP and Mesh. Further more, we discusse the assignment of bandwidth in sharing wireless channel. This paper mainly sdudy the channel use state in the Mesh model,and also introduced the frames tructure in Mesh network and the two channel competition states in MAC, which are centralizing and distributing scheduling algorithms. At the same time,this paper also proposes a scheduling algorithm: Mesh Centralized Scheduling(Mesh CS) Based on Tree (MCT) under the WiMAX Mesh MeshCS model and a Coordination Distributed Mesh Scheduling Algorithm(CDMSA) under the Mesh Distributed Scheduling (Mesh DS) model. This paper gives simulation results about the length of scheduling of MCT,the average channel utilization ratio, and the average transmission delay and the average success ratio and the average delay in coordination and non-coordination scheduling algorithms. The results verifies that in the case of giving SS nodes a high priority, which is close to Mesh BS, the length of scheduling and transmission delay, and improve channel utilization ratio will be reduced. It also is approved the CDMSA has a good performance in the connection probability and delay.The paper also discuss the problem of multi-gateways selection in WMANs:the rapid development of wired internet bought big progress for the whole society, as people could easily access resource and service through the internet. In nowadays, the highly developing of wireless network has a close touch with the resource in the wired internet. So we should connect to the wired internet to get what we want when we correlating in the wireless terminals. The paper presente the routing algorithm of how to select the wired gateways.