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It is understood that in a network with an in-band full-duplex (FD) access point (AP) simultaneously serving multiple half-duplex clients, various kinds of interference may severely degrade the network spectral efficiency (SE). In this paper, we first address the problem of canceling the interclient interference (ICI) from multiple uplink clients to multiple downlink clients in such a scenario. The proposed ICI nulling approach, namely, multiuser ICI cancellation (MU-IC2), enables the AP to actively and completely eliminate the ICI for the downlink clients. With this method, the gain from FD processing can be achieved much efficiently. Design guideline is given and reduced-complexity implementation for use with a large number of antennas at the AP is also derived. Furthermore, in some circumstances, notable residual self-interference (SI) exists at the AP due to the imperfection of SI cancellation during the FD operation. This may enlarge the interference observed by the downlink clients. We provide new ways, i.e., two MU-SI-IC2 approaches, to deal with this case based on the possible knowledge of SI as well. As a result, both the SI-induced interference and ICI are effectively eliminated, and the overall throughput can still be benefited from FD and kept at a high level. The simulation results show that in terms of the network SE, our proposed MU-IC2 and MU-SI-IC2 can significantly outperform some baseline schemes and the state-of-the-art active ICI mitigation methods in various scenarios.

Non-orthogonal multiple access (NOMA)-based diamond relaying (NDR) is an efficient approach for combining NOMA and relaying techniques in such a way as to enhance the achievable rate from the source to the destination in the network. This paper examines the problem of joint power allocation among all the transmission phases during the operation of such networks. Based on the Karush-Kuhn-Tucker (KKT) condition and the second-order sufficient condition (SOSC), at least the local optimal solution is derived and analyzed. In addition, a new protocol for NDR networks based on cooperative communications is introduced and the associated joint power-allocation problem is examined. It is shown that this cooperative NDR (C-NDR) network further improves the achievable rate in some typical placements of the relays. Simulation results verify the correctness of the deviation and confirm the effectiveness of the proposed joint power-allocation method for both NDR and C-NDR networks. INDEX TERMS Non-orthogonal multiple access (NOMA), relay networks, NOMA-based diamond relaying (NDR), cooperative communications, Karush-Kuhn-Tucker (KKT) condition, second-order sufficient condition (SOSC), joint power allocation, achievable rate.

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