Reliability-based type II hybrid ARQ schemes

Hybrid ARQ (HARQ) schemes use a combination of forward error correction and retransmissions to guarantee reliable packet data communications. In this work, we propose a HARQ scheme that exploits channel state information and received packet quality to improve system performance. Specifically, the receiver uses the average magnitude of the log-likelihood ratios corresponding to the received information bits, in order to determine the sizes of subsequent retransmissions. The proposed retransmission strategy attempts to maximize user throughput while satisfying a maximum packet delay constraint. The performance of our reliability-based type II HARQ (RBHARQ) scheme is evaluated in static and time-varying channels through simulations.