Partial automatic repeat request transceiver for bandwidth and power efficient multiple-input–multiple-output orthogonal frequency division multiplexing systems

In this study, the authors present a novel method to improve the performance of automatic repeat request (ARQ) protocol for multiple-input-multiple-output systems that use orthogonal frequency division multiplexing signalling by incorporating partial ARQ (PARQ) mechanism. As a typical ARQ frame has few number of errors, it is useful to retransmit partial sequence of symbols and recover from errors by consuming relatively low bandwidth. The observations from the first transmission and subsequent retransmission are used for joint detection. As a direct consequence of partial retransmission, the bandwidth and power efficiency of the overall system is improved considerably without substantial decrease in the performance. They achieve further bandwidth saving by omitting pilot sequence from the partial retransmission and acquire channel estimate in semi-blind fashion. Partial retransmission of the original information symbol sequence allows the authors to formulate second-order statistics based joint blind channel estimation problem by combining observations from two transmissions. Channel estimation ambiguity inherent to blind methods is resolved by combining cost functions of blind detection and least-square estimator. To evaluate efficacy of the proposed PARQ method, they compare throughput of chase-type hybrid-ARQ and the proposed PARQ methods.