Wireless Multicast Optimization: A Cross-Layer Approach

The problem of optimal scheduling of multicast traffic in time-varying wireless networks is studied in the framework of utility maximization. Since the wireless channel cannot be known exactly, only scheduling policies that take decisions based on a possibly inaccurate estimate of the wireless channel state are considered. A stationary, on-line, gradient-based scheduling and rate control policy is introduced which identifies at every decision instant the sources that should access the wireless medium along with their respective transmission rates. Furthermore, in the case that more than one optimal rate allocation is possible, the one that requires the minimum sum-power expenditure is selected by the policy. The optimality of the proposed policy among all policies that have access to the same estimate of the current wireless channel state is established through stochastic approximation arguments.