Evaluation of multicast efficiency in random clustered networks under antenna selection combining

In multicast networks it is necessary to secure the successful reception of the packet by all the intended receivers, which often calls for the retransmission of the packet up to a number of times. When each receiver is subject to signal deterioration due to fading and unrestrained inter-cluster interference, retransmissions however renders unacceptable large delay that eventually undermines the utility of multicasting. In this paper, we attempt to understand the impact of a practically attractive multi-antenna communication scheme viz. antenna selection combining (ASC) on enhancing the performance of a random multicast network under delay requirement. Since during retransmission attempts the transmitters and the receivers in each cluster likely stay stationary, igniting substantial interference correlation across antennas, the potential diversity of ASC may be dramatically destructed. We, here scrutinize the effect of this diversity loss on the multicast performance by analytically evaluating the multicast coverage efficiency (MCE), which measures the percentage of receivers who experience multicast coverage during the retransmission procedure. We provide a number of approximations on MCE as the main system parameters, and further study their accuracies. Our simulations show that ASC has benefits in improving MCE, however not as pronounced as one may otherwise experience when interference is de-correlated across antennas and retransmission attempts.