Energy-efficient congestion control on contention-based BW-REQ in WiMAX system

The IEEE 802.16 standard for broadband wireless metropolitan area network supports diverse real time and non-real time services. The standard defined the contention-based bandwidth request mechanism for the nonreal time (nrt-PS) and Best-Effort (BE) services. Before using the resource of base station (BS), the mobile station (MS) or subscriber station (SS) should send the bandwidth request (BW-REQ) in the allocated contention time interval. For avoiding collision, the standard supports truncated binary exponential backoff resolution. However this mechanism works inefficiently while the network traffic is overloading, and then the result will cause MSs waste power. In this paper we propose a new mechanism at MS, for BE service, to help the MS send the bandwidth request more efficiently and also avoid the traffic peak. By using the mechanism, the MS sends the bandwidth request in the low loading time and it reduces the power consumption of the MS. Additionally, the method balanced the burst of traffic loading and smoothed the traffic loading that brings the bandwidth request efficiency and higher power utilization.