Optimal power allocation and harvesting duration for mixed RF/FSO using Non Orthogonal Multiple Access

In this paper, we suggest to optimize power allocation coefficients and harvesting duration in mixed Radio Frequency (RF)/Free Space Optical (FS0) communications using Non Orthogonal Multiple Access (NOMA). The system model contains three time slots. In the first time slot, relay nodeRharvests energy from RF signal received from nodeH. NodeHcan be any node transmitting RF signals. In the second time slot, an FSO transmitterTtransmits a linear combination of symbols ofKusers to relay nodeRusing NOMA. In the third and last slot, relayRdetects the receive symbols and sends a linear combination of detected symbols toKusers using NOMA. We show that power allocation and harvesting duration optimization allow to increase the throughput of RF/FSO communications. We consider two users' ranking techniques using average or instantaneous channel gains.