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.

Reliability-based hybrid ARQ (RB-HARQ) is a recently developed form of incremental-redundancy ARQ. The RB-HARQ technique can be used with codes that use soft-input, soft-output (SISO) decoders, such as convolutional codes and turbo codes. In RB-HARQ, the bits that are to be retransmitted are adaptively selected at the receiver based on the estimated bit reliabilities at the output of a SISO decoder. This technique has the potential to improve performance and minimize retransmission size by targeting those bits that are likely to be in error. It has already been shown that RB-HARQ achieves significant performance improvement provided that large retransmission-request (NACK) packets can be afforded on the feedback link. In this paper, we propose and evaluate the performance of a RB-HARQ technique that uses rate-compatible punctured convolutional (RCPC) codes in the forward channel and source coding in the feedback link. The proposed technique uses source coding to achieve small request packets, thus leading to better performance. The performance of the proposed technique is evaluated in terms of probability of bit error, probability of packet error and throughput. We also compare the performance of the proposed scheme with the common approach to hybrid-ARQ that uses punctured convolutional codes and code combining. The results show that the proposed RB-HARQ scheme achieves better performance than a hybrid-ARQ scheme that uses only RCPC codes.

Reliability-based hybrid ARQ (RB-HARQ) is a recently introduced approach to incremental-redundancy ARQ. In RB-HARQ, the bits that are to be retransmitted are adaptively selected at the receiver based on the estimated bit reliabilities. This technique has the potential to improve performance and minimize retransmission size by targeting those bits that are likely to be in error. However, previous versions of the RB-HARQ algorithm have resulted in large request (NACK) packets that made the technique appropriate only for systems that can tolerate large request packets on the feedback link. In this paper, we show that RB-HARQ is effective with convolutional codes, and we exploit the time-correlation properties of these codes to significantly reduce the size of the retransmission requests.