Optimization of rateless-coded asynchronous multimedia multicast

We investigate the optimization of asynchronous multimedia multicast to heterogenous users. A priority encoding transmission (PET) based packetization scheme in combination with rateless coding has recently been proposed for multicasting. In previous work, a suboptimal greedy search algorithm is proposed to find the allocation of source symbols over different layers. However, the complexity of the algorithm is high for large numbers of user classes and the optimality of the algorithm is not proven. In this paper, we first show that the problem can be transformed to an equivalent convex optimization problem under the relaxation of integer constraints. In addition, a solution is found analytically for the optimal allocation. Numerical results demonstrate that the optimal analytical solution matches the results using the greedy search algorithm as well as results obtained using convex optimization software.