Abstract
In this paper, we propose an optimal time and power allocation scheme in a wireless power supply full-duplex (FD) relay system, where we consider the number of relay antennas in the energy harvesting stage. At the same time, the energy efficiency optimization problem of the system is structured, where optimization issues related to time allocation factors and power allocation are established. For the FD dual-antenna and the FD single-antenna energy harvesting system, energy efficiency function is proven to be a concave function over the time-switch factor, and the optimal time-switching factor is theoretically obtained using the Lambert function. Then, according to the given value range of the optimal time switching factor, the optimal power distribution scheme is obtained by analyzing the derivative function of the system energy efficiency and using the properties of the Lambert function. The time-switching factor and transmission power are optimally selected at the wireless power supply FD relay. Results reveal that the performance of energy efficiency of the dual-antenna energy harvesting at the FD relay outperforms that of the single-antenna. Moreover, our results demonstrate that FD relay systems always substantially boost the energy efficiency compared with half-duplex (HD) relay systems.
Highlights
In some practical scenarios, the traditional energy-limited communication system has a limited operational life
This technology has the advantages of controllability and measurability, which can be used in wireless systems compared with traditional energy harvesting technologies, thereby providing an effective solution to solve the energy supply problem of energy-constrained nodes in harsh environments
The system energy efficiency performance for different α values is shown in Figure 3 under three schemes (FD dual-antenna energy harvesting, FD single-antenna energy harvesting, and HD) and fixed power splitting (PS) = {30 dB, 20 dB, 10 dB}
Summary
The traditional energy-limited communication system has a limited operational life. Because radio-frequency (RF) signals can simultaneously carry information and energy, technology involving the use of RF signals for energy collection has received extensive attention This technology has the advantages of controllability and measurability, which can be used in wireless systems compared with traditional energy harvesting technologies, thereby providing an effective solution to solve the energy supply problem of energy-constrained nodes in harsh environments. In [23], the authors studied wireless-powered FD relay systems based on a TS protocol, where the number of antennas of relay nodes in the energy harvesting phase was considered and the analytical expressions of throughput maximization in three different communication modes (instantaneous transmission, delay-constrained transmission, and delay-tolerant transmission) were derived by optimizing the TS factor.
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