Optimal Power Allocation and Performance Analysis of Cooperative Multicast Systems Using Non-Orthogonal Multiple Access

For cooperative multicast systems using nonorthogonal multiple access, we propose optimal power allocation to maximize the achievable rate, and present its performance analysis in terms of average achievable rate and outage probability assuming Rayleigh fading channels. To perform the optimal power allocation, the source requires instantaneous channel information for a subset of the links. In the performance analysis, we provide approximate expressions for the average achievable rate and outage probability of the optimal power allocation using high signal-to-noise ratio (SNR) approximation. From the high SNR performance analysis, we show that the performances for the optimal power allocation are not affected by the number of destinations, while those for the fixed power allocation become worse as the number of destinations increases, which can be a remarkable finding although the optimal power allocation requires the overhead for the channel information feedback and the complexity for computing the power allocation coefficients.