Cooperative Spectrum Sharing With Wireless Energy Harvesting in Cognitive Radio Networks

We study cooperative spectrum sharing in cognitive radio networks with wireless energy harvesting (EH), where all the primary and secondary users are overlaid on the 2-D plane. Each primary user (PU) should harvest energy from the wireless signal sent by its access point (AP), whereas all the APs and the secondary users have stable power supply. To improve EH efficiency, an EH zone is applied around each PU, where the secondary transmitter (ST) with the shortest distance toward the PU is selected to transfer the wireless energy. Using the harvested energy, the PU can transmit its data over the reverse link to the AP, but the data transmission is more likely to fail due to the weak transmission power and the severe path loss. In this case, a cooperative region is applied between each PU and its corresponding AP, where a suitable ST with the best channel quality toward the AP is selected to forward the primary data. The performance requirement of the primary system can be easily satisfied with ST cooperation, and thus, a fraction of bandwidth can be released to the secondary-data transmission. The optimization problem is formulated to maximize the area throughput of the secondary system under the performance constraint of the primary system. By analyzing system performance using the stochastic geometry theory, we propose an algorithm to optimally allocate the bandwidth and time resources to facilitate both the EH and data transmission. Performance results are presented to validate our theoretical analysis and show the impacts of various system settings.