ABSTRACT
One major challenge in broadband wireless access networks is to provide fast, reliable services for real-time communication. This chapter describes the hybrid automatic repeat request (HARQ) scheme for the worldwide interoperability for microwave access (WiMAX). It also proposes an enhanced HARQ that would greatly reduce the latency while providing reliable transmissions. The new scheme follows the multiple-channel stop-and-wait chase combining HARQ adopted by WiMAX, yet it enables the base station (BS) to proactively react to poor channel conditions. The BS would sendmultiple copies of the same data burst to the subscriber station (SS) over multiple HARQ channels available to the SS, and thereby effectively reduces the total time needed for a successful
transmission. Simulation results show that on comparing with the original WiMAX HARQ the new scheme significantly reduces latency while maintaining a comparable level of throughput. This work is most significant for time-critical applications that need fast, reliable services, such as VoIP, interactive communications, and media streaming.
