Analysis and optimization of distributed cooperative multicast for wireless multimedia networks

In this paper, we systematically analyze the outage probability performance of the distributed cooperative multicast with randomized orthogonal space-time codes (OSTC) for wireless multimedia networks. The distributed cooperative multicast protocol with randomized OSTC enables users who successfully decode signals from base station or access point serving as relays to forward the signals to other users, and consequently the overall performance of wireless multimedia multicast can be greatly improved. We derive a closed-form expression for the outage probability for the distributed cooperative multicast with randomized OSTC. To get more insight, we further develop an asymptotically tight approximation for the outage probability which reveals the diversity order of the protocol as K + 1, where K is the size of the randomized OSTC used in the protocol. Based on the asymptotically tight approximation of the outage probability, we are able to determine an optimum power allocation for the distributed cooperative multicast protocol. It shows that in a statistic sense, we should allocate 1/(K + 1) of the total power budget to the BS/AP and evenly distribute the rest for the users as relaying power. Numerical and simulation results validate our theoretical development.