Performance Evaluation of Generalized Buffer-State-Based Relay Selection in NOMA-Aided Downlink

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.