Optimal Power Allocation for NOMA-based Cellular Two-Way Relaying

Abstract

This paper proposes a non-orthogonal multiple access (NOMA) based low-complexity relaying approach for multiuser cellular two-way relay channels (CTWRCs). In the proposed scheme, the relay detects the signal using successive interference cancellation (SIC) and re-generates the transmit signal with zero-forcing (ZF) transmit precoding. The achievable data rates of the NOMA-based multiuser two-way relaying (TWR) approach is analyzed. We further study the power allocation among different data streams to maximize the weighted sum-rate (WSR). We re-form the resultant non-convex problem into a standard monotonic program. Then, we design a polyblock outer approximation algorithm to sovle the WSR problem.The proposed optimal power allocation algorithm converges fast and it is shown that the NOMA-TWR-OPA scheme outperforms a NOMA benchmark scheme and conventional TWR schemes.