Traditional link-layer automatic repeat request (ARQ) protocols attempt to retransmit the corrupted frames regardless of the channel state. Since this channel-state unaware behavior may cause unnecessary retransmissions, traditional ARQ protocols may not be energy efficient. Some channel-adaptive ARQ ideas have been proposed, such as, channel probing based ARQ and stochastic learning automaton based ARQ. However, these algorithms do not make use of the channel fading properties. Instead, the retransmission decision is made according to a binary feedback - whether the previous frame was successful or not. In this paper, we present four algorithms, which incorporate the channel state estimate in the feedback process to judiciously select a frame transmission/retransmission timing instant. Proposed protocol designs have been applied on stop-and-wait (S-W) ARQ, and the performance have been compared with respect to simple S-W ARQ and the probing based S-W ARQ. Our simulation based performance results show significant improvement on energy saving and throughput performance when the channel fading knowledge is applied in the link layer ARQ strategy.
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