Adaptive Scheduling of Prioritized Traffic in IEEE 802.16j Wireless Networks

In this paper we propose an adaptive scheduling algorithm for IEEE 802.16j based wireless broadband networks. Computation of an optimal schedule for prioritized traffic in OFDMA based IEEE 802.16 wireless network is an NP-Hard problem. Hence, we propose a scheduling heuristic for an OFDMA based WiMAX relay network. The ORS (OFDMA Relay Scheduler) heuristic computes the zone boundaries (relay and access) in an uplink scheduling frame based on the number of RSs and MSs, the bandwidth demands and the link conditions. The ORS heuristic determines a schedule which assigns subchannels and timeslots to prioritized traffic based on the demand for various nodes while implementing frequency selectivity. The ORS adapts zone boundaries and the schedule to link and demand conditions at every scheduling period. We perform extensive simulations to demonstrate the effectiveness of adaptive zone scheduling and changes in rate conditions for various topologies.