New look on relay selection strategies for full-duplex multiple-relay NOMA over Nakagami-m fading channels

This is an accepted manuscript of an article published by Springer in Wireless Networks on 07/07/2021, available online: https://doi.org/10.1007/s11276-021-02676-1 The accepted version of the publication may differ from the final published version.By removing the orthogonal use of radio-resources, non-orthogonal multiple access (NOMA) has been introduced to improve the spectral efficiency of fifth generation (5G) and beyond networks. This paper studies the system performance in a dual-hop multi-relay NOMA using decode-and-forward (DF) scheme over Nakagami-m fading channels. A group of NOMA users is considered, i.e. the near and far users which are decided by how strong these related channels are. Specifically, we obtain a closed-form expression of the outage probability of the near/far NOMA users when the several relay selection schemes are adopted for selecting the best among M intermediate relays. As main finding, this paper introduces three strategies including two-stage relay selection, max-min and power allocation based relay selection schemes. As main benefit, the NOMA users are considered to employ selection combining technique in order to improve signal transmissions for an increased reliability in the context of massive connections in 5G wireless communications. By conducting numerical simulations, we evaluate the impact of the number of intermediate relays, the NOMA power allocation factor, and the Nakagami-m fading severity parameter on the outage performance of the NOMA users. Finally, the outage probability along with throughout in delay-limited transmission mode are provided via numerical results and the necessary comparisons are provided.Published onlin

Study on Generalized Buffer-State-Based Relay Selection in Cooperative Cognitive Radio Networks

学位の種別: 修士University of Tokyo(東京大学

Delay-and diversity-Aware buffer-Aided relay selection policies in cooperative networks

In this paper, we propose novel relay selection policies that aim at reducing the average delay by incorporating the buffer size of the relay nodes into the relay selection process. More specifically, we propose two delay-Aware protocols that are based on the max-link relay selection protocol. First, a delay-Aware only approach while it reduces the delays considerably it starves the buffers and increases the outage probability of the system. Towards this end, we propose a delay-and diversity-Aware buffer-Aided relay selection policy that aims at reducing the average delay considerably and at the same time maintaining good diversity. The protocols are analyzed by means of Markov Chains and expressions for the outage, throughput and delay are derived. The performance and use of our proposed algorithms is demonstrated via extensive simulations and comparisons

Delay- and Diversity-Aware Buffer-Aided Relay Selection Policies in Cooperative Networks

Buffer-Aided (BA) relaying has shown tremendous performance improvements in terms of throughput and outage probability, although it has been criticized of suffering from long delays that are restrictive for applications, such as video streaming, Web browsing, and file sharing. In this paper, we propose novel relay selection policies aiming at reducing the average delay by incorporating the buffer size of the relays into the decision making of the relay selection process. More specifically, we first propose two new delay-aware policies. One is based on the hybrid relay selection algorithm, where the relay selection takes into account the queue sizes so that the delay is reduced and the diversity is maintained. The other approach is based on the max - link relay selection algorithm. For the max - link algorithm, a delay-aware only approach starves the buffers and increases the outage probability of the system. Thus, for max - link, we propose a delay- and diversity-aware BA relay selection policy targeting the reduction of the average delay, while maintaining the diversity of the transmission. The proposed policies are analyzed by means of Markov Chains and expressions for the outage, throughput, and delay are derived. The asymptotic performance of the policies is also discussed. The improved performance in terms of delays and the use of the proposed algorithms are demonstrated via extensive simulations and comparisons, signifying, at the same time, the need for adaptive mechanisms to handle the interplay between delay and diversity.Peer reviewe