A Hybrid-ARQ Scheme with Codeword Combining in Random and Burst Error Channels

Data link protocols such as hybrid-ARQ of type II are overlaid on digital data links in order to reduce the bit errors to zero while keeping the average throughput and time delay at reasonable levels. The paper begins with an introduction to a protocol which can be realized using BCH codes. It then shows that further improvements, particularly at high error rates, may be achieved by combining the received codewords. It explains one method of combining, out of many possible, and derives the average throughput and the time delay. In addition to random error channels, this paper considers burst error channels, modelled with bits occurring either as single non-error bits or as part of a contiguous error sequence of arbitrary length. The results are compared to those of the scheme which does not use any codeword combining