TSRS Strategy and Outage Performance Analysis of D2D Aided Cooperative Relaying NOMA System

‍ ‍In this paper， a D2D aided cooperative relaying system using non-orthogonal multiple access （DC-NOMA） is investigated， D2D communication link from relaying user （RU） to cell-center user （CCU） is exploited to transmit a new signal during the information forwarding of RU in the second phase. To improve the transmission reliability， a novel signal detection strategy is designed， which the side information is fully utilized to eliminate the inter-user interference. Based on the novel signal detection strategy， a two-stage relay selection strategy （TSRS） is proposed. In the subset of relays that satisfy cell-edge user （CEU） reliable reception， the relay with the greatest the successful decoding probability of CCU is selected. To evaluate the proposed DC-NOMA scheme， exact outage probabilities are derived for each user and verified by computer simulations. Simulation results demonstrate the outage performance of the proposed DC-NOMA using the TSRS based on the novel signal detection strategy outperforms that a partial relay selection scheme （PRSS） and the conventional DC-NOMA in the high signal-to-noise region. In particular， the increase in the number of relays can effectively improve the outage performance of the proposed system.