A Novel Cooperative Network Using Down-link Non-orthogonal Multiple Access Scheme

A novel downlink cooperative non-orthogonal multiple access (DC-NOMA) scheme is proposed in this paper to achieve higher performance in the spectral efficiency compared to the classical NOMA schemes. The communication system consists of one base station and two users (e.g., strong user and weak user). In down link phase, the base station transmits a superimposed signal to both users, and in the cooperative phase, the weak user sends its decoded message to the strong user. The main idea is how the weak user can help the strong user to improve the performance of both users. This occurs by enabling the weak user to perform a cooperative transmission with the strong user during the cooperative phase. The outage probability, outage throughput, and diversity order are derived and analyzed. Numerical results are provided to show that the spectral efficiency gain achieved through our proposed scheme is better than the conventional cooperative NOMA schemes.