Performance Analysis of an ARQ Initialized Cooperative Communication Protocol in Shadowed Nakagami-m Wireless Channel

We develop and analyze an ARQ (Automatic Repeat reQuest) initialized transmit diversity protocol for cooperative communications. Medium access control (MAC) layer packet retransmission limit (similar to aShortRetryLimit or aLongRetryLimit in 802.11-1997) has been used as an actuator for transmit cooperative diversity initialization. We take the channel state information (CSI) as a function of retransmission tries. Relays close to the source node are chosen for the transmit cooperation. Closed form expressions are obtained for symbol error rate (SER) and outage probability for the proposed scheme in shadowed fading channels. This cooperative scheme achieves lower signal-to-noise ratio (SNR) values for desired symbol error rate, stumpy outage probability and high bandwidth efficiency as compared to the preceding ARQ based cooperative protocols. Finally, the results of computer simulations are included to demonstrate the efficacy of the proposed scheme and to verify the accuracy of analytical expressions.