Two-way relay assisted non-orthogonal multiple access

The use of two-way relaying in infrastructure network to support both downlink and uplink has not been considered in existing literature on cooperative non-orthogonal multiple access (NOMA). This paper proposes a novel cooperative NOMA that uses two-way relaying with analog network coding to improve the data rates of the users and the base station in an infrastructure based information exchange scenario, without utilizing additional channel resource. Analytical results on uplink and downlink ergodic rates are derived. In order to guarantee the rate of the proposed scheme always surpasses the orthogonal multiple access (OMA) scheme, a power allocation region is derived. Simulation and analytical results show that the proposed scheme achieves better sum rates when compared to the OMA scheme and existing cooperative NOMA scheme.