Optimal power allocation for non‐orthogonal multiple access enabled full‐duplex underlay cognitive relay networks under partial relay selection

Abstract

This article considers non-orthogonal multiple access (NOMA) enabled full-duplex (FD) underlay cognitive relay networks (ie, NOMA-FDCRNs) with partial relay selection scheme. The secondary network, where NOMA is used, consists of a secondary base station (SBS) sending messages to two secondary users (SUs), that is, a near SU (SU1) and a far SU (SU2), by utilizing a dedicated relay selected from a set of FD decode-and-forward nodes. We obtain analytical expressions for the outage probabilities (OPs) of the SUs and then deduce the asymptotic OP expressions as well. Further, expressions are obtained for the optimal power allocation (OPA) coefficients at the SBS and at the relay that separately maximizes the throughput of the secondary network in NOMA-FDCRN.Furthermore, the jointly optimal power allocation (JOPA) coefficients that maximize the throughput are also determined. The analyses consider (i) imperfect successive interference cancelation conditions, (ii) the tolerable interference limit of the primary receiver, (iii) the secondary nodes' maximum transmit power values, (iv) interference generated by the primary transmitter, and (v) the residual self-interference (RSI) at the FD relay. It is shown that the proposed OPA coefficients at the SBS and the JOPA can mitigate the impact of RSI and significantly improve the OP and throughput performance. The numerical results show that the proposed JOPA approach provides 32% and 106% improvement of throughput compared to random power allocation (RPA) and equal power allocation (EPA) strategies, respectively. The OP of SU1 and SU2 reduce by 68% and 73%, respectively, under the proposed JOPA compared to RPA, while compared to EPA, the OP of SU1 and SU2 reduce by 96% and 97%, respectively.

Investigations on Secrecy Performance of Downlink Overlay CR-NOMA System With SIC Imperfections

“…This system enables multiple SUs to send and receive signals concurrently while still adhering to primary interference power limitations. The work in [13] explores the performance of a NOMA based underlay CR framework with partial relay selection (PRS). In this setup, the secondary network employs NOMA, utilizing K half-duplex (HD), decode-and-forward (DF) relays to assist the SBS in serving SUs.…”

Algorithms and throughput analysis of cognitive radio‐based MIMO‐NOMA for the next generation of wireless communications

“…Moreover, regarding merging the three techniques in one system, that is, MIMO, NOMA, and CR, the performance of the cooperative sensing on the conventional and superior selective reporting types are investigated in reference 18, in which the error probability of the false alarm is derived and optimization constraints are studied for the sake of enhancing the sum rates of the proposed schemes. In reference 19, NOMA with underlay cognitive radio based on in‐band full duplex is proposed and investigated, where a scheme of partial selection of decode‐and‐forward relays is considered, and expressions for obtaining the optimal coefficients of the power allocation are evaluated for maximizing the throughput of the secondary network. Furthermore, the authors in reference 20 suggest the utilization of multiple carrier filter‐band‐based spectral sensing of cooperative NOMA‐CR networks.…”

Best Relay Selection Strategy in Cooperative Spectrum Sharing Framework with Mobile-Based End User

“…The obtained results demonstrated that the system performance can be enhanced using multiple relays. An optimal power allocation scheme using partial relay selection was considered in [51] for the sake of enhancing the performance of underlay CRNs. In this work, NOMA was used for transmission and one relay was selected among several DF relays.…”