Adaptive successive transmission in virtual full-duplex cooperative NOMA

In this paper, we propose a novel virtual full-duplex cooperative non-orthogonal multiple access (NOMA) technique for a downlink two-hop cellular network which consists of a single base station (BS), two mobile stations (MSs), and K half-duplex decode-and-forward (DF) relay stations (RSs). In the proposed technique, the BS sends super-imposed signals for two MSs via the RSs in each transmission phase, while a selected RS via two-stage relay selection sends the signals to two MSs. Thus, the multiplexing loss due to half-duplex operation of RSs can be overcome by allowing for both the BS and a selected RS to send data at the same time. In the proposed cooperative NOMA, we adaptively reset the successive transmission according to decoding status at RSs. As main results, we mathematically analyze outage probability and diversity-multiplexing tradeoff (DMT) of the proposed technique. Extensive computer simulations show that the proposed technique significantly outperforms the existing schemes in terms of both outage probability and DMT.