Dynamic Contention Slot Allocation for 802.16 Broadband Wireless Access Systems

The IEEE 802.16 standard for broadband wireless access (BWA) is promising to offer high-speed wireless connectivity between base station (BS) and subscriber stations (SSs). The wireless link between BS and SSs is a two-way shared medium, where the downlink is a broadcast channel exclusively used by BS and the uplink channel is shared by all SSs on a demand basis. In each frame, BS allocates a number of contention slots (CSs) for SSs to send bandwidth reservation request through contention. This allocation of CS will directly affect the system throughput. However, how to calculate the number of CS is left open by the standard in terms of implementation. In this paper, we analyze the impact of contention slots allocation (CSA) on system throughput and thus propose an algorithm to optimize the utilization of uplink bandwidth by dynamically adjust the number of CSs. Analytical and simulation results show that the proposed CSA algorithm can efficiently improve throughput for 802.16 systems.