Improving multicast throughput in mobile ad-hoc networks using cross-layer signaling mechanism

A significant portion of communication across tactical edge networks includes multicast traffic to support collaboration among many separate multicast groups. In order to provide a reliable and scalable network, it is critical to optimize its multicast performance. However, multicast traffic performance in radio networks is limited by the data link layer design for distribution of multicast traffic to its neighbors. In many situations, local distribution is derived by the neighbor with weakest RF link. For example, when the Network layer forwards a multicast packet the MAC layer will use the lowest link state among all its neighbors to transmit that packet. This can result in reduction of available bandwidth for multicast transmission in situations when at least one neighbor with the lowest link state exists. One method to alleviate this problem is to disable lowest state for data delivery and routing. However this approach can result in network fragmentation when a neighbor is in line of sight but only available at the lowest state. An extreme example of this is when the lowest state link is the only link available between two network partitions (bridge), in this case the network will be fragmented. In this paper we examine the possibilities for cross layer optimization by using the lowest link state judicially, only at times when performance with other neighbor nodes is not affected. We will explore the benefit and tradeoff of different approaches in this paper and analyze the performance benefits that we can expect to achieve.