Partial-DF Full-Duplex D2D-NOMA Systems for IoT With/Without an Eavesdropper

摘要

The massive connectivity and information exchange in the Internet of Things (IoT) pose great challenges to the bandwidth efficiency. To overcome this issue, this article investigates a cooperative full-duplex device-to-device system with nonorthogonal multiple access (NOMA) and partial decode-and-forward (P-DF). In the proposed system, the base station simultaneously transmits signals to all receiving nodes. Two kinds of scenes are considered depending on the locations of the users, where the cases with and without an eavesdropper are respectively studied. According to the P-DF protocol, three kinds of relay forwarding strategies are studied, where only the correctly decoded symbol will be forwarded to the user equipments to avoid performance loss. For the full-duplex relay, it is allowed to forward its own signal by superposing the partial correctly decoded symbol from the previous phase to other users, to further improve the spectral efficiency. Closed-form expressions of the ergodic sum rate, outage probability and secrecy rate are derived. Simulation results verify the analytical results especially in the high signal-to-noise ratio region, and show the superiority of our proposed P-DF-NOMA scheme in terms of outage probability performance.