Spectrum efficiency and energy efficiency are two critical issues in designing wireless communication networks. In this paper, we consider cognitive spectrum sharing-based cooperation between a single-antenna primary system and a multi-antenna wireless-powered device-to-device (D2D) communication system. A novel joint time division and power splitting-based three-phase information and energy cooperation transmission scheme are proposed for cognitive spectrum sharing-based D2D communication system. In the proposed scheme, the cognitive D2D transceiver pair adopts the power splitting technique to receive information and energy simultaneously from the primary transmitter (PT) in the first phase. Then, they utilize the beamforming technique and the harvested energy as half-duplex (HD) relays to jointly forward the primary user (PU) signal in the second phase. Eventually, in the third phase, they can communicate directly with each other by using the licensed spectrum and their remaining energy. We focus on the design of time division ratios, power splitting ratios, and beamforming vectors, with the objective to maximize the data rate of the cognitive D2D communication system, subject to the quality of service (QoS) requirement of the primary system, and the cognitive D2D communication system's minimum energy harvesting requirements and maximum power consumption constraints. The simulation results demonstrate that our proposed scheme is the best and significantly improves the average data rate of the cognitive D2D communication system under different PU target rate requirements or PT rated transmit power. Furthermore, a large number of simulations are demonstrated to verify the feasibility and effectiveness of the proposed scheme. INDEX TERMS D2D communication system, cognitive spectrum sharing, energy harvesting, time division, power splitting.

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In this paper, we consider a spectrum sharing scheme that is a joint optimization of relay selection and power allocation at the secondary transmitter, which aims to achieve the maximum possible throughput for the secondary user. This paper considers the scenario where the primary user is incapable of supporting its target signal-to-noise ratio (SNR). More especially, the secondary transmitter tries to assist the primary user with achieving its target SNR by cooperative amplify-and-forward (AF) relaying with two-phase. By exhaustive search for all candidate secondary transmitters, an optimal secondary transmitter can be selected, which not only can satisfy the primary user's target SNR, but also maximize the secondary user's throughput. The optimal secondary transmitter acts as a relay for the primary user by allocating a part of its power to amplify-and-forward the primary signal over the primary user's licensed spectrum bands. At the same time, as a reward, the optimal secondary transmitter uses the remaining power to transmit its own signal over the remaining licensed spectrum bands. Thus, the secondary user obtains the spectrum access opportunities. Besides, there is no interference between the primary user and the secondary user. We study the joint optimization of relay selection and power allocation such that the secondary user's throughput is maximized on the condition that it satisfies the primary user's target SNR. From the simulation, it is shown that the joint optimization of relay selection and power allocation provides a significant throughput gain compared with random relay selection with optimal power allocation (OPA) and random relay selection with water-filling power allocation (WPA). Moreover, the simulation results also shown that our spectrum sharing scheme obtains the win-win solution for the primary system and the secondary system.

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