Cognitive Non-Orthogonal Multiple Access with Cooperative Relaying: A New Wireless Frontier for 5G Spectrum Sharing

Abstract

Two emerging technologies towards 5G wireless networks, namely non-orthogonal multiple access (NOMA) and cognitive radio (CR), will provide more efficient utilization of wireless spectrum in the future. In this article, we investigate the integration of NOMA with CR into a holistic system, namely cognitive NOMA network, for more intelligent spectrum sharing. Design principles of cognitive NOMA networks are perfectly aligned to functionality requirements of 5G wireless networks, such as high spectrum efficiency, massive connectivity, low latency, and better fairness. Three different cognitive NOMA architectures are presented, including underlay NOMA networks, overlay NOMA networks, and CR-inspired NOMA networks. To address inter-and intra-network interference which largely degrade the performance of cognitive NOMA networks, cooperative relaying strategies are proposed.For each cognitive NOMA architecture, our proposed cooperative relaying strategy shows its potential to significantly lower outage probabilities. Furthermore, we discuss open challenges and future research directions on implementation of cognitive NOMA networks.

Performance analysis of nonorthogonal multiple access‐based underlay cognitive relay network

“…Likewise, selecting P max < I th makes the ergodic sum rate to increase with P max . Moreover, the results in (10) to (13) establish that the ergodic rate decreases significantly when transmission from PT is considered for the analysis. Figures 14 and 15 show the dependence of on ergodic rates of SU 1 and SU 2 , respectively.…”

“…Consider the definition of system outage (P out ) given in (13). In the absence of primary interference, we use modified expressions for 11 , 12 and 22 by setting P p = 0 in (8) to (10).…”

“…In underlay spectrum sharing CR networks, the secondary users (SUs) are allowed to coexist with the primary users (PUs) by accessing the licensed frequency band such that the interference induced on the PUs because of transmissions by the SUs remains below the tolerable limit . To further improve the spectrum utilization efficiency, the idea of cognitive NOMA (C‐NOMA) has been proposed in the study of Lv et al that can provide more intelligent spectrum sharing, by combining CR and NOMA technologies. The C‐NOMA networks aim to enhance the spectrum efficiency by simultaneously serving multiple PUs and/or SUs in one resource block with different power levels …”

“…To further improve the spectrum utilization efficiency, the idea of cognitive NOMA (C‐NOMA) has been proposed in the study of Lv et al that can provide more intelligent spectrum sharing, by combining CR and NOMA technologies. The C‐NOMA networks aim to enhance the spectrum efficiency by simultaneously serving multiple PUs and/or SUs in one resource block with different power levels …”

“…The C-NOMA networks aim to enhance the spectrum efficiency by simultaneously serving multiple PUs and/or SUs in one resource block with different power levels. 13 Despite many benefits, C-NOMA networks suffer from both inter as well as intra-network interference. In underlay C-NOMA networks where the secondary transmitters (STs) simultaneously serve multiple secondary receivers (SRs) by employing NOMA signaling, the STs need to choose their transmission powers such that the interference induced at the primary receivers (PRs) does not go beyond the maximum tolerable limit.…”