Reliability-based hybrid ARQ as an adaptive response to jamming

We consider the use of selective-retransmission automatic repeat request (ARQ) protocols to improve communication performance on partial-time jamming channels. The schemes that we propose are based on reliability-based hybrid ARQ (RB-HARQ), in which the set of bits to be retransmitted is adaptively selected based on the estimated a posteriori probabilities at the output of a soft-input, soft-output decoder. For channels with bursty partial-time jamming, the RB-HARQ techniques are particularly appropriate because these techniques can identify which symbols need to be retransmitted, and the bursty nature of the jamming reduces the overhead required to relay this information to the source. We extend our reliability measure to incorporate not only a posteriori probability information but also estimates of the probability that a bit was jammed. We compare the performance of the proposed scheme with that of conventional approaches, in which a predetermined set of bits is retransmitted in response to a packet failure. The results show that RB-HARQ schemes can achieve higher throughput than these conventional approaches in several scenarios.