Tuning holdoff exponents for performance optimization in IEEE 802.16 Mesh Distributed Coordinated Scheduler

The IEEE 802.16/WiMAX mesh standard is a promising technology to support next generation wireless broadband metropolitan area networks. The medium access control (MAC) layer of IEEE 802.16 mesh supports both centralized and distributed scheduling mechanisms. The coordinated distributed scheduling mechanism uses a pseudo-random election algorithm to determine the transmission times of the nodes. The holdoff exponent is an important parameter of scheduling and determines the channel contention time of a node. In this paper, we propose a novel distributed search protocol that each node uses to select the holdoff exponent that minimizes the expected delay between its two successive transmissions in the control channel. We analyze the scheduler performance in NS-2 for various kinds of traffic including TCP, UDP and VoIP. Simulation results show that our scheme performs better than the standard algorithm and other comparable schemes in terms of throughput and delay.