Power Allocation in CoMP-Empowered C-NOMA Networks

In this letter, the dynamic power allocation problem of a cellular network consisting of two adjacent and coordinating cells is investigated. The joint transmission coordinated multipoint (JT-CoMP) between the two-cell is introduced to assist users experiencing high inter-cell interference, where each cell invokes cooperative non orthogonal multiple access (C-NOMA) to serve its associated devices. Both effects of imperfect successive interference cancellation (SIC) and imperfect channel estimation are considered within the proposed scheme. A power allocation framework is formulated as an optimization problem with the objective of maximizing the network sum-rate while guaranteeing a certain quality-of-service (QoS) for each user. The formulated optimization problem is neither concave nor quasi-concave, which is difficult to be solved directly unless using heuristic methods, which comes with the expense of high computational complexity. To overcome this issue, a near-optimal closed-form expressions for the power allocation are derived. The simulation results show that our purposed scheme achieves an average sum-rate that is 3% less than the one of the optimal power control but it can save up to 99% in the computational time. In addition, the superiority of the proposed CoMP C-NOMA scheme is demonstrated when compared to the well known C-NOMA scheme.