Sum-Rate Maximization of Wireless Powered Primary Users for Cooperative CRNs: NOMA or TDMA at Cognitive Users?

• Published in: IEEE transactions on communications Vol. 69; no. 7; pp. 4862 - 4876
• Main Authors: Xu, Ding, Zhu, Hongbo
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.07.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Circuits; Cognitive radio; Cooperation; Copper; Energy; energy cooperation; Energy harvesting; Maximization; NOMA; non-orthogonal multiple access; Nonorthogonal multiple access; Optimization; Power consumption; Radio frequency; RF energy harvesting; Time Division Multiple Access; Wireless communication; Wireless sensor networks
• DOI: 10.1109/TCOMM.2021.3073952
• ISSN: 0090-6778

Recently, wireless powered cooperative cognitive radio networks (CRNs), which combine the technologies of radio frequency (RF) energy harvesting and CR, have drawn great attention. In such networks, energy cooperation between the cognitive users (CUs) and the wireless powered primary users (PUs) can be performed, where the CUs can charge the PUs wirelessly in exchange for the spectrum access. Specifically, energy cooperation and information transmission is executed in two phases, where the CUs transmit their data signals and the PUs harvest energy from these signals in the first phase, and the PUs transmit their data using the harvested energy in the second phase. In particular, we consider two multiple access schemes for the CUs, namely non-orthogonal multiple access (NOMA) and time-division multiple access (TDMA). For both NOMA and TDMA, the PU sum-rate maximization problems under the minimum CU sum-rate constraint are first simplified by exploring particular problem structure, then are transformed to convex problems, and finally are solved optimally. The PU sum-rates of the two schemes are compared theoretically as well as numerically. It is revealed that the circuit power consumption at the CUs, the required minimum CU sum-rate, and the PU energy harvesting sensitivity and saturation thresholds play key roles in the PU performance comparison of the two schemes.