Modeling and Transmission Optimization of Full-Duplex Energy Harvesting Enabled Hybrid Relaying

Energy harvesting (EH) enabled relaying has attracted lots of interests recently, as the network energy consumption can be reduced and the coverage range can be extended simultaneously. In most existing literatures, the Harvest-Store-Use (HSU) model is utilized to describe the energy flow behavior of the EH system. However, the half-duplex (HD) constraint of HSU that harvested energy can only be used for powering load after being temporally stored in energy storage unit may reduce the effective transmission time. Thus, we first model the full-duplex (FD) energy flow behavior of the EH system where harvested energy can be tuned to power load and being stored simultaneously, and then prove the FD model is equivalent to the HSU model when time interval is small enough. With consideration of some key physical variabilities, e.g., the wireless channel and the amount of harvested energy, and the energy consumption difference between FD and HD relaying protocols, we further model the transmission optimization problem to improve the utilization of harvested energy by optimizing the short-term throughput. Finally, to numerically obtain the optimized short-term throughput, we propose the joint power adaption, relay selection and transmission protocol switching algorithm. Results show that the performance of the proposed algorithm outperforms that of fixed relaying algorithms, e.g., the short-term throughput of the proposed algorithm is improved by about 40% comparing with fixed HD relaying algorithm, with 20 user equipments, and loop interference power and EH rate equal to 23 dB and 120 J/s, respectively.