On the achievable capacity of one-way NOMA based bi-directional full-duplex relay assisted cooperative networks

Abstract

In this paper, we investigate and derive new formulas for the individual and sum achievable capacities (rates) of a bi-directional non-orthogonal multiple access (NOMA)-based full-duplex one-way relay (FD-OWR) assisted network model, in which two sources in each direction are paired to perform NOMA and exchange information with the other two sources in the opposite direction via one shared full-duplex (FD) relay. Two common relaying protocols are considered: decode and forward (DF) and amplify and forward (AF) support the transfer of information between the two pair of sources. Only two time slots (phases) are sufficient to simultaneously perform a complete wireless communication by leveraging the NOMA based FD relaying technique. The proposed schemes are investigated, new closed form expressions for the achievable rates are derived and the simulation results are compared with the conventional one-way dual-hop cooperative relaying based orthogonal multiple access (OMA) schemes. The results demonstrate the effectiveness of our proposed schemes in saving time/frequency resources and improving the achievable rates. It is observed that the achievable rates can be further increased with the efficient cancellation of the residual self-interference (RSI). However, they exhibit an error floor due to inefficient elimination of RSI components at the relay.