Cooperative Uplink NOMA in D2D Communications

In this work, we propose and investigate a novel hybrid cellular and bidirectional device-to-device (D2D) transmission scheme that exploits cooperative non-orthogonal multiple access (termed as BD2D-CNOMA). In BD2D-CNOMA, two far users can transmit their messages to the base station (BS) via a relaying node, while simultaneously they exchange D2D messages. Analytical expressions for the ergodic capacity, ergodic sum capacity (ESC) and outage probability of all data streams are derived under both perfect and imperfect successive interference cancellation (SIC). Furthermore, it is proved that ESC under perfect SIC scales as \frac {2}{3}\log _{2}\rho as transmit signal-to-noise ratio \rho increases. Simulation results validate the accuracy of the presented analysis, illustrate the superiority of BD2D-CNOMA over conventional benchmarks under perfect SIC and provide useful insights for the case of imperfect SIC.