Mobile computing implies reliance on a portable, self-contained power source and increased difficulty of communications due to the highly-variable radio channel. In order to ensure reliable, verified, error-free delivery of data in the presence of multipath fading, automatic repeat request (ARQ) schemes are used to synchronize and acknowledge the transmission of data between the base station and the mobile node. In this paper, we build upon previous designs of energy-conserving variants of theclassical Selective Repeat protocol to design a dynamic, asymmetric energy-conserving protocol. Primarily, in this work, we move the complexity of the protocol to the base station, which can optimally assign on a packet-by-packet basis the set ofenergy-conserving ARQ protocol and parameters which is best suited to the current radio channel, traffic and energy requirements. In this manner, the best delay vs. energy trade-off of previously proposed protocols can be incorporated in a practical,dynamic way. Through simulation we evaluate the average packet delay of different classes of service under strict energy constraints and varying channel characteristics. The results derived here show the significant advantage of quickly adapting theprotocol to changing channel fading characteristics so as to maintain a required energy vs. delay trade-off between multiple priority classes of traffic.
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