In this paper, we propose a novel buffer-aided relay selection scheme that is capable of amalgamating the concepts of non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA) in the context of two-hop cooperative networks supporting multiple relays. This is enabled by allowing relay nodes to share a common information packet in their buffers with the aid of a source-to-relay broadcasting mode. Hence, the proposed relay selection scheme switches between diverse modes of uplink NOMA, downlink NOMA, unicast, source broadcasting, and cooperative beamforming. The theoretical bounds of the outage probability, throughput, average delay, and diversity order are derived for the proposed scheme, based on a Markov chain model. Through our analytical and numerical results, it is demonstrated that the proposed scheme is capable of switching to one of the best modes in an adaptive manner while outperforming the conventional buffer-aided cooperative schemes.

In this paper, we propose a novel buffer-state-based (BSB) non-orthogonal multiple access (NOMA)-aided downlink scheme for a two-hop cooperative network supporting multiple relay and destination nodes. More specifically, in the broadcast phase, the source node broadcasts information packets to multiple selected relay nodes. In the relaying phase, a selected relay node transmits packets to multiple destination nodes based on the NOMA principle. Here, the use of buffer at the relay nodes allows us to achieve a flexible relay selection. Furthermore, with the aid of buffer-state-based relay selection, the detrimental effects of empty-and full-buffer states are avoided. The theoretical outage probability and average packet delay are derived for our proposed scheme, based on the Markov-chain model. Our simulation results demonstrate that the proposed scheme outperforms the existing max-link and BSB relay selection benchmarks.INDEX TERMS Broadcast, buffer, Markov chain, non-orthogonal multiple access (NOMA), outage probability, packet delay, successive interference cancellation, theoretical bound.

This paper proposes a buffer-aided relay selection that is capable of exploiting both half-duplex and virtual full-duplex (VFD) transmissions in a hybrid manner. In the proposed scheme, we consider a two-hop cooperative network where each node is equipped with a single antenna, and no direct link between the source to the destination exists. The proposed scheme consists of five relay selection modes: two unicast modes, a broadcast mode, a cooperative beamforming mode, and a VFD mode. Owing to the broadcast mode, multiple relay nodes can seamlessly have a common packet; this mode is capable of solving the inter-relay interference problem imposed on the VFD mode. The proposed scheme's theoretical performance bounds on the throughput, the outage probability, and the delay are derived. It is demonstrated in our simulations that the proposed scheme attains higher performance in terms of a throughput and an outage probability than the conventional schemes while maintaining an acceptable average end-to-end delay profile.

This paper proposes novel buffer-aided relaying selection in a two-hop cooperative network based on virtual full-duplex (VFD) and half-duplex transmission. The proposed scheme consists of five relay selection modes, i.e., two unicast modes, a broadcast mode, a cooperative beamforming mode, and a VFD mode. The broadcast mode allows multiple relay nodes to seamlessly share a common packet, which allows us to solve the inter-relay interference problem imposed on the VFD mode.

This paper proposes novel buffer-aided relaying selection in a two-hop cooperative network based on virtual full-duplex (VFD) and half-duplex transmission. The proposed scheme consists of five relay selection modes, i.e., two unicast modes, a broadcast mode, a cooperative beamforming mode, and a VFD mode. The broadcast mode allows multiple relay nodes to seamlessly share a common packet, which allows us to solve the inter-relay interference problem imposed on the VFD mode.