Research On Key Swipt Technology In Cognitive Radio Systems

With the explosive growth of wireless data services, wireless communications systems are faced with double pressure, the spectrum scarcity and the sharp increase in energy consumption. Cognitive radio technology allows the primary users share the licensed spectrum with secondary users, which greatly improves the spectrum utilization. The SWIPT technology realizes the simultaneously information and power transfer, which will significantly prolong the lifetime of the energy-constrained networks, such as the wireless sensor networks. Therefore, the combination of the cognitive radio and SWIPT provides a new solution for the current wireless communication systems. This paper will investigate the cognitive SWIIPT-enabled system, by introducing the one-way relay and the two-way relay to improve the throughput of the networks. The main work of this paper includes:Firstly, this paper considers a cognitive AF one-way relaying network, where the relay SU (Secondary User) forwards the source information to the destination with the energy harvested from the RF signal, aiming at maximizing the throughput by a deadline of N slots. Supported by a proposed SWEPT-enabled cognitive relay architecture, the problem is formulated and approximated with its upper bound. A suboptimal power splitting factor and relay power allocation jointly-management algorithm based on the solution of the upper bound is developed. The simulation results indicate that the proposed algorithm performs closely to the optimal solution, and yields a significant gain compared to the separate management algorithm.Secondly, this paper considers a cognitive two-way AF relaying network, where the SWIPT-enabled-relay helps two secondary nodes exchange information with the energy harvested from the received signals. The rate maximization problem for the relaying network is formulated under the constraint that interference to the primary user resulting from the transmission of the secondary relaying network cannot exceed the threshold. Based on the mathematical analysis of the problem, this paper proposes a suboptimal joint relay selection and power allocation scheme with the Bisection Search method. Numerical simulations confirm the near-optimality of the proposed scheme by comparing with the optimal solution. Specially, the best two-way relay location is also revealed in simulations.