An adaptive algorithm for optimizing the packet size used in wireless ARQ protocols

We develop an algorithm that allows an ARQ protocol to dynamically optimize the packet size based on estimates of the channel bit-eiror-rate. Our algorithm is particularly useful for wireless and satellite channels where the bit-error-rates tend to be relatively high and time variable. Our algorithm uses the acknowledgment history to make estimates of the channel bit-error-rate, based on which the optimal packet size can be chosen. We develop a Markov chain model for the analysis of the system, under static channel conditions, and show that the algorithm can achieve close to optimal performance using a history of just 10,000 bits. We also use the Gilbert-Elliott two-state Markov channel to model dynamic channel conditions. We show, through simulation, that the algorithm performs well even under rapidly changing channel conditions. Finally, we discuss a maximum likelihood approach for choosing the packet size, which performs almost optimally but is much easier to implement.