Amplify-and-Forward Relaying Based Spectrum Sharing in Both Time and Spectrum Domains With Wireless Powered Primary User

We propose a spectral and energy efficient cooperative spectrum sharing scheme with the primary user (PU) capable of harvesting wireless energy. Along with an access point (AP) transferring wireless power to PU, a secondary source (SS) and a secondary relay (SR) can cooperatively transmit data to a secondary destination (SD) using the amplify-and-forward protocol. The interference from secondary transmissions can boost the amount of harvested energy at PU. After the wireless power transfer phase, PU transmits data to AP using the harvested energy, and meanwhile SS transmits data to SD. The SR could simultaneously forward the data of both systems to improve their communication qualities. With the energy and data cooperations from SS and SR, more energy can be harvested by PU and the data reception at AP becomes more reliable, so the throughput performance of primary system can be satisfied more easily. As a result, a fraction of spectrum could be enough for the primary system and the remaining spectrum is released to the secondary system. The optimal time and bandwidth factors are determined to maximize the throughput of secondary system under the performance constraint of primary system. The numerical results show that our proposed scheme significantly outperforms the non-cooperative scheme in terms of system throughput.