WiMAX Network Optimization - Analyzing Effects of Adaptive Modulation and Coding Schemes Used in Conjunction with ARQ and HARQ

The flexibility of WiMAX framework offers new dimensions for cross-layer optimization and can be exploited to optimize the application performance. This article focuses on identifiers that have direct impact on quality of service (QoS)and effect of such identifiers is evaluated through computer simulation using OPNET Modeler 14.5 Wireless Suite. In this paper we have used advanced WiMAX features such as adaptive modulation and coding (AMC), automatic repeat request (ARQ) and hybrid-ARQ to tune the WiMAX network MAC layer such that its adaptation improves both capacity and delay (thus optimize the performance). ARQ is treated as higher layer to HARQ. HARQ gives up after maximum retransmissions. HARQ performs fast retransmissions and ARQ takes over in cases HARQ fails after multiple retransmissions. This gives an added layer of protection to data. HARQ is proved to be most suitable (when used with aggressive modulation and coding) for WiMAX due to its hybrid nature as it takes into account both the MAC and link layer. Using ARQ in conjunction with HARQ gives slight improvement in BLER (Block Error Rate) but at the expense of high UL frame utilization.