Power Allocation in Cellular Systems with Multicast and Unicast Hybrid Service

In this paper we present a hybrid multicast and unicast transmission scheme with superposition coding (SC), i.e., the multicast and unicast signals are overlaid across the entire time and frequency domain. In the SC scheme, the multicast and unicast signals are superimposed and transmitted by BS, in each transmission the superimposed multicast signals are transmitted to a multicast group, while the superimposed unicast signals are transmitted to the best channel user among unicast users. At user side the multicast signals are first demodulated and decoded under the interference of the unicast signals. The reconstructed multicast signals are then cancelled from the overall received signals, obtaining clean unicast signals that are free from any interference. In this paper, we propose a power allocation algorithm to provide QoS guarantee for multicast and unicast services concurrently. The optimization objective is to maximize the rate of unicast service under the constraints of power and the outage requirement of multicast service. Numerical results show the optimal power allocation coefficient and the maximum rate of unicast transmission for the SC scheme.