A reliable broadcast algorithm with selected acknowledgements in mobile ad hoc networks

Mobile ad hoc networks (MANETs) suffer from transmission contention and congestion because of the broadcast nature of radio transmission. The broadcast operation, as a fundamental service in MANETs, will cause the broadcast storm problem if the forward nodes are not carefully managed. It is a major challenge to reduce broadcast redundancy while still providing high delivery ratio for each broadcast packet in a dynamic environment. In this paper, we propose a simple broadcast algorithm to provide high delivery ratio. Among the 1-hop neighbors of the sender, only selected forward nodes will send acknowledgements to confirm their receipt of the packet. Forward nodes are selected in such a way that all the senders 2-hop neighbors are covered. Moreover, no acknowledgment is needed from non-forward 1-hop neighbors, each of which is covered by at least two forward neighbors. The sender waits for the acknowledgements from all of its forward nodes. If not all acknowledgments are received, the sender will resend the packet until the maximum number of retries is reached. Simulation results show that the algorithm has high delivery ratio and low end-to-end delay for a broadcast operation.