Abstract
In this paper, we propose a spectrum-sharing protocol for a cooperative cognitive radio network based on non-orthogonal multiple access technology, where the base station (BS) transmits the superimposed signal to the primary user and secondary user with/without the assistance of a relay station (RS) by adopting the decode-and-forward technique. RS performs discrete-time energy harvesting for opportunistically cooperative transmission. If the RS harvests sufficient energy, the system performs cooperative transmission; otherwise, the system performs direct transmission. Moreover, the outage probabilities and outage capacities of both primary and secondary systems are analyzed, and the corresponding closed-form expressions are derived. In addition, one optimization problem is formulated, where our objective is to maximize the energy efficiency of the secondary system while ensuring that of the primary system exceeds or equals a threshold value. A joint optimization algorithm of power allocation at BS and RS is considered to solve the optimization problem and to realize a mutual improvement in the performance of energy efficiency for both the primary and secondary systems. The simulation results demonstrate the validity of the analysis results and prove that the proposed transmission scheme has a higher energy efficiency than the direct transmission scheme and the transmission scheme with simultaneous wireless information and power transfer technology.
Highlights
With the promotion of 5G, Cognitive radio (CR) has gradually attracted researchers’ attention, which is regarded as an important technology to improve the spectrum utilization efficiency of 5G networks [1]
We proposed a cooperative transmission protocol in a non-orthogonal multiple access (NOMA)-cognitive radio network (CRN), which improved the spectrum efficiency of the overall system and reduced the interference between primary users (PUs) and secondary users (SUs) at the same time
An Markov chain (MC) model based on discrete-time energy harvesting was developed to analyze the charging and discharging performance of the relay node, and the analytical expressions of the outage probabilities and the outage capacities for the primary system and the secondary system were derived
Summary
With the promotion of 5G, Cognitive radio (CR) has gradually attracted researchers’ attention, which is regarded as an important technology to improve the spectrum utilization efficiency of 5G networks [1]. The CR uses complex signal processing and coding to maintain or improve the communication between nodes [3]. It allows primary users (PUs) and secondary users (SUs) to utilize the same frequency band for communication to realize effective spectrum utilizing. The interference from the SUs will affect the PU performance To solve this problem, we combine non-orthogonal multiple access (NOMA) technology with CR. NOMA technology supports the simultaneous information transmission of multiple users under the same time-frequency resource by allocating different power domain levels [4,5]. The cooperative relay strategy is added to extend the transmission distance and reduce the interference within the network
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