A finite HARQ-based non-orthogonal multiple access for reliable communications

ABSTRACTReliability is one big concern for future communication networks such as 5G and beyond to support massive machine-type communications. These networks face reliability issues due to the frequent movement of users or/and a deep fading environment, particularly in urban areas. To overcome this bottleneck, a reliable communication protocol is proposed in this paper by incorporating the hybrid automatic repeat request (HARQ) along with non-orthogonal multiple access (NOMA) schemes. The NOMA scheme helps in improving spectral efficiency and maintaining fairness among the users, while HARQ initiates a retransmission of the user signal in case of unsuccessful decoding of the received signal. Unlike existing work, the proposed scheme allows the base station (BS) to utilise the available resources most efficiently by initiating the retransmission of the signal of the user who failed to decode the received signals. A two-user scenario is considered in this framework and all the possible combinations of positive and negative acknowledgement feedback from users are analysed. Depending upon the feedback received from the receiver, BS exploits transmission mode diversity during signal retransmission. The extensive Monte Carlo simulations are executed to analyse the outage performance of the proposed communication system. To validate the efficacy of the proposed scheme, numerically simulated results are compared with the existing research works.KEYWORDS: Non-orthogonal multiple access (NOMA)outage probabilityreliabilityhybrid automatic repeat request (HARQ)retransmission Disclosure statementNo potential conflict of interest was reported by the author(s).