Frequency Division Duplex Based Cooperative VFD: Outage Analysis and Relay Power Allocation

Due to high residual self-interference (RSI) problems in full-duplex (FD) systems, virtual full-duplex (VFD) has emerged as a smart and an attractive alternative to design co-operative networks and has drawn significant research attention. However, the VFD models studied in the literature are based on successive relaying (SR) that require an extra time phase and a double number of relays for each destination user in comparison to FD. Hence, in this work, we propose a novel frequency division duplex (FDD) based VFD (FDD-VFD) that not only matches FD in terms of resource utilization but also outperform both SR-VFD and FD. We consider two practical scenarios of absence of inter relay interference (A-IRI) and presence of IRI (P-IRI) and present outage probability expressions in closed-form for both over Nakagami-m fading channels. Next, to minimize the relay interferences in P-IRI scenario and further improve the outage performance, we utilize particle swarm optimization (PSO) algorithm for jointly allocating transmit power of the relays. Extensive evaluations are carried out over different system parameters to prove the efficacy of proposed FDD scheme and obtain key optimal design insights.