Cumulative acknowledgement multicast repetition policy for wireless LANs or ad hoc network clusters

For a wireless LAN or a cluster of nodes in an ad hoc wireless network, multicast transmissions from a controlling station must be acknowledged by the nodes that are addressed. To ensure reliable reception at all the nodes, the multicast packet may be repeated on different transmissions, or on the same transmission as a form of diversity, or both. In this paper, policies for repeat transmissions of multicast packets are analyzed in terms of the average number of repeat transmissions required and the corresponding efficiency of the signaling on the multicast channel. The analytical results are parametric in packet/ACK error probability, the number of nodes, and the number of required ACKs. It is shown that a policy of accumulating ACKs and addressing only unacknowledged nodes on repeated non-diversity transmissions is more efficient than simply using a higher order of diversity on the multicast transmissions. Methods are shown for avoiding unnecessary repetitions in the case of a missing node.