A New Congestion Control Method for IEEE 802.16 Mesh Mode

With the increase of network service types and users’ broadband demand, broadband wireless access (BWA) has become the focus of people’s attention. The workgroup of IEEE 802 proposes the IEEE 802.16 standard to provide BWA. In IEEE802.16 mesh mode, all nodes are organized in an ad hoc fashion. Nodes use a pseudo-random function to compete for their transmission opportunities based on the scheduling information in the two-hop neighborhood. Meanwhile, they use “three-way handshaking” to achieve the allocation of data slot. In this paper, we present a novel congestion control method by adjusting the resources of MAC layer in a hop-by-hop way. A node, e.g. Base station (BS), which wants to send data to its neighbor, must detect congestion first. It will adjust the exponent of transmission holdoff time up to congestion state and send MSH-DSCH message with congestion information to its upstream node and downstream node, which also adjust the exponent or allocate minislot according to the information in the mesh message. Moreover, simulation results and analysis are given in this paper. With this method congestion has been controlled, packet loss rate and end-to-end delay have been decreased and throughput has been increased.