Adaptive contention resolution procedure for emerging WiMAX networks

Broadband Wireless Access (BWA) offers QoS-aware broadband access through a wireless medium, being IEEE 802.16 one of the BWA standards. In it, the Base Station (BS) is responsible of allocating the required bandwidth by the rest of nodes, acting as a central controller. The other nodes, Subscriber Stations (SSs), have to send a bandwidth request to give the BS the knowledge about their needs, taking part in a competition through a contention resolution procedure. The requests are located into the uplink subframe, using a period defined by the BS on frame by frame basis, allowing to send data in the rest of the uplink subframe not used by the contention period. So, a tradeoff between these two periods is needed to improve the operation of the system. This paper presents a study on the adaptation of the contention period size per frame by taking into account the number of competing connections. Simulation results confirm that our proposal improves throughput and end-to-end delay by increasing the part of uplink subframe dedicated to sent data.