Cross-Layer Error Control Optimization in WiMAX

WiMAX is one of the most promising emerging broadband wireless technologies. As a consequence, data transfer performance optimization represents a crucial issue due to TCP limitations in wireless environment. In this study, we focus on the overhead deriving from the multilayer ARQ employed at the link and transport layers. To the aim of reducing unnecessary burden on the wireless link, we propose a cross-layer ARQ approach, called ARQ proxy, which substitutes the transmission of TCP ACK packet with a short MAC layer request on the radio link. Packet identification is achieved through the use of hash functions applied to the packet headers. Performance of the ARQ proxy is evaluated using an IEEE 802.16e system level simulator which includes realistic physical layer implementation. The results demonstrate good agreement with the design objectives and achieve the expected levels of system capacity increase, reduction of round trip time, and higher error rate tolerance.