Underlay Spectrum Sharing with Wireless Power Transfer Towards Primary User

We propose a wireless power transfer (WPT) based underlay spectrum sharing scheme, where a primary user (PU) needs to harvest wireless energy from an access point (AP) and then transmit its data to AP using the harvested energy. In the same area, a secondary transmitter (ST) intends to communicate with a secondary receiver (SR). The secondary data can be transmitted along with the WPT, which can on one hand improve the spectral efficiency of the secondary data transmission and on the other hand improve the WPT efficiency towards PU. In the primary data transmission period, ST continuously transmits its data to SR by properly adjusting its power under the interference constraint of primary system. The interference cancelation technique is used by SR to retrieve its desired secondary data. We analyze the outage probability and throughput of both systems. Numerical results show that our scheme can well accommodate the secondary data transmissions while greatly improving the performance of primary system.