A Markov Analysis of Selective Repeat ARQ with Variable Round Trip Time

Many papers analyze selective repeat automatic repeat request schemes by means of a Markov chain representation for the channel and, by extension, the whole transmission system. This Markov approach precisely characterizes the queueing behavior and the statistics of several delay terms. In the vast majority of the investigations, the round-trip time of the channel, which determines the instant of reception of the feedback from the receiver, is taken as a fixed value. This letter explores the relaxation of this assumption, still framing the system within a Markov chain. The main conclusion is that the impact of a variable round trip time on the delay statistics is rather limited. The used approach can be promptly applied to any similar analysis of retransmission-based error control systems.