Peak avoidance and collision control for contention-based bandwidth requests in WiMAX systems

There are two fundamental bandwidth-request mechanisms specified in the IEEE 802.16 standard: contention-based random access and contention-free polling. For example, non-real-time polling and best-effort services mainly rely on the contention-based mechanism to submit bandwidth requests to the base station (BS). However, the performance degrades considerably when the number of requests is high and they collide with each other. To avoid collision, the standard supports a truncated binary exponential backoff resolution. Nevertheless this resolution is inefficient in dispersing the requests when the network traffic is overloaded. In order to improve the efficiency of the random-access mechanism in the standard, the authors propose a new mechanism that aids mobile stations (MSs) in sending bandwidth requests more efficiently and also avoiding peak traffic. By using the mechanism, MSs send bandwidth requests under low loads, thus avoiding collisions.