Published in Enchakilodil, S.M., Udar, N., & Viswanathan, R. (2006). A simple algorithm that adapts one of two packet sizes in a wireless ARQ protocol. 2006 40th Annual Conference on Information Sciences and Systems, 140-144. doi: 10.1109/CISS.2006.286450 ©2006 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.


A recent algorithm of Modiano selects packet sizes in a selective repeat ARQ protocol based on the acknowledgement history of the most recently transmitted packets. In this paper we modify this algorithm so that the choice of packet size is restricted to one of two pre-specified values. We provide a strategy for switching between these packet sizes and show that is optimal in the sense of maximizing the one step efficiency. The throughput efficiency of the proposed adaptive scheme is analyzed for a constant bit-error-rate channel and for two state Gilbert-Elliot channel. The results show that the throughput efficiencies of this scheme under high and moderate bit-error-rates are slightly less than that of Modiano's algorithm. However the scheme is attractive because of its simplicity.