On the delay performance of selective-repeat ARQ for underwater acoustic channels

There are few approaches for the delay analysis of ARQ in underwater acoustic links owing to the fact that only the worst efficient SW-ARQ can function over the half-duplex channel. Meanwhile, many approaches for the delay analysis of the most efficient SR-ARQ in terrestrial communications have appeared to be impractical because of the static channel assumption and/or much high computational complexity. In this paper, we first characterize the time-varying underwater acoustic channel by a two-state Markov model; then we perform SR-ARQ protocol based on the transmission scheme that is tailored for underwater acoustic channels and, in turn, analyze the mean delivery delay, which consists of transmission and resequencing delays. A closed-form expression of delivery delay whose computational complexity is insensitive to round-trip delay is derived. Both numerical and simulation results are finally provided to highlight the accuracy of the delivery delay analysis.