DELAY ANALYSIS FOR ADAPTIVE HYBRID ARQ PROTOCOL.

Abstract

The authors analyze transmission delays of an adaptive hybrid automatic repeat request (ARQ) communications protocol used with a discrete-time two-state Markovian channel; this channel model allows for both time-varying noise levels and memory. The analysis shows that for some channels with moderate or long dwell times, i. e. , infrequent changes of channel state, the adaptive hybrid ARQ protocol can dramatically reduce transmission delays; the regime of channel parameters for which this protocol is useful is thus wider than indicated by previous analyses of throughput improvement along. For some channels evaluated, both the mean and standard deviation of the delay were reduced by factors of more than three, and the reduction in the standard deviation was sometimes more than four.