On Reducing the Outage Probability in VFD-NOMA with Limited CSI at Source

Abstract

We study a virtual full-duplex (VFD) non-orthogonal-multiple-access (NOMA) system in which a source S transmits one message each to users R�1�and R�2�, and two messages to a destination D, in three time slots. In conventional VFD-NOMA, S follows a fixed sequence of transmission (SoT) for the messages of users and destination, leading to a higher outage probability (OP) at R�2�and D, and a higher overall system OP (O-OP). To this end, we propose a novel transmission scheme which significantly decreases the OP at R�2�and D, and the O-OP. We assume all the wireless links undergo Nakagami- m fading, and S only knows the instantaneous channel state information (CSI) of S-R�1�and S-R�2�links. We assume users suffer from imperfect successive interference cancellation (I-SIC) and residual inter-user interference (R-IUI). We derive closed-form results for the OP and show it matches with the simulations. Comparison with half-duplex and full-duplex multiple access schemes is done to demonstrate efficacy of the improved VFD-NOMA.