WLC10-2: Analytic Optimization of Hybrid ARQ Performance in Wireless Packet Data Systems

We propose an analytical framework that optimizes the performance of various Hybrid Automatic Repeat reQuest (HARQ) schemes in wireless packet data systems. The optimization framework lends itself to maximizing the user throughput without assuming a specific HARQ scheme, a target packet error rate, and a mapping of signal-to-interference-noise ratios (SINR) into modulation and coding scheme (MCS) sets. Thus, a user selects an optimal amount of redundancy bits used for retransmissions, an optimal packet error rate, and an optimal SINR-MCS mapping such that the user throughput would be maximized. We show that there exists an optimal redundancy block size of incremental redundancy (IR) scheme when the number of retransmissions is limited, while as small as possible redundancy size is optimal when the number of retransmissions is unlimited. Our analytical results are verified through extensive simulations of the IEEE 802.16e system.