Cooperative Beamforming for the Joint Unicast and Multicast Transmission with Decode-and-Forward Full-Duplex Relaying

We study the cooperation for the joint unicast and multicast (JUMC) transmission system through a full-duplex (FD) decode-and-forward (DaF) mode relay and propose sub-optimal beamforming schemes for this cooperative JUMC FD relay channel. The beamforming vectors at the access point (AP) and at the full-duplex relay (FDR) are optimized with the metric based on the end-to-end information rate. The cooperation lets the user terminals (UT) outside of the direct coverage of the AP to be served by JUMC from the AP, and hence, the focus of this paper is on the sum rate resulting from the cooperation. As a reference scheme, a zero-forcing-based (ZF) beamforming algorithm is proposed, which suppresses the self-interference (SI) at the FDR perfectly. The SI at the FDR and the minimum operation for the signal-to-interference power ratios (SINR) at involved nodes of the DaF protocol are leveraged in designing and optimizing the second beamforming algorithm, which is the regularized beamforming scheme, since it allows an optimal amount of the SI at the FDR. This algorithm relies on the iterative applications of a quadratically constrained quadratic problem (QCQP) in its central part, while a few one-dimensional searches are running for the optimal SI levels for the individual rates. We consider three different scenarios depending on the existence of an FDR unicast message and the multiple UTs in the coverage of FDR for the application of the proposed algorithms, with some necessary modifications. Corroborating simulation results are presented to show the strengths and weaknesses of the proposed algorithms for the cooperative JUMC system.