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Next generation wireless networks are expected to support several bandwidth expensive multimedia applications, e.g., distance learning, video conferences etc., which are inherently multicast in nature. Group communication is also the main-stay of several specialized adhoc networks such as sensor networks, disaster recovery networks and military communications. We discuss the design of bandwidth efficient strategies for MAC layer multicast. Bandwidth efficiency of wireless multicast can be improved substantially by exploiting the fact that several receivers can be reached at the MAC layer by a single transmission. However, this feature can be effectively exploited only by resolving several decision problems and protocol challenges. Interestingly, fundamental relations between qos parameters such as throughput, loss and stability change on account of the multicast nature of transmissions, e.g., a strategy which maximizes system throughput does not necessarily minimize packet loss. Similarly, there is a tradeoff between maximizing the throughput and attaining the maximum possible stability region. We explore these trade-offs from a theoretical standpoint, and provide optimal transmission strategies which maximize system throughput subject to loss and stability constraints. The strategies we present are online and adaptive, and yet attain maximum possible throughput even among offline and statistics aware policies. Simulation based performance evaluations demonstrate significant improvement in system performance as compared to existing MAC layer multicast strategies.
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