Full-Duplex Cooperative Non-Orthogonal Multiple Access With Spectrum Sensing

This paper investigates a cooperative non-orthogonal multiple access (CNOMA) scheme based on spectrum sensing where a strong user works as a full-duplex (FD) relay to help a randomly located weak user to communicate with the base station. It overcomes resource wastage problems of the conventional orthogonal access method, i.e., the waste of spectrum holes and the underutilization of licensed spectrum bands, by adopting a spectrum sensing technique and a NOMA scheme. Expressions of outage probability and ergodic rate are derived. We then analytically obtain the optimal power allocations to maximize the strong user's ergodic rate on the condition that the weak user's outage performance requirement is satisfied. Finally, simulations validate theoretical derivation results, and illustrate that FD-CNOMA outperforms other cooperative benchmarks in practical scenarios. The effectiveness of the proposed power allocation method is also validated through comparing it with the enumeration method.