On the power allocation of non-orthogonal multiple access for 5G wireless networks

This paper addresses the power allocation issue in non-orthogonal multiple access (NOMA) systems. In NOMA, multiple paired users can simultaneously utilize the frequency bands of each other such that the message signals of all these users are superimposed by the transmitter by allocating different powers to all users. As the paired users communicate over the same frequency band, high amount of interference is faced by them. Thus, some paired users perform successive interference cancellation to decode and cancel the signals of other users while some users recover their signals by simply treating signals of other users as noise. Inefficient power allocation may increase the interference significantly, which causes degradation in data recovery at the user ends. We propose a novel power allocation strategy that can optimize the system ergodic sum capacity while minimizing the mutual interference between the paired users. It is shown through simulations that the proposed scheme outperforms conventional power allocation in terms of bit error rates at the user ends with negligible effect on the system ergodic sum capacity.