Design and optimization of wireless information and power transfer networks

Abstract

Energy harvesting from the Radio Frequency (RF) has been identified as one of the solution to alleviate the power constraint in wireless device. RF can carry both information and power. In recent years, the studies of Wireless Information and Power Transfer (WIPT) has attracted significant interest among researchers. WIPT has appeared in multiple forms such as simultaneous wireless information and power transfer (SWIPT), wireless powered communication and wireless powered backscatter communication.

First, we analysed the trade-off between harvested energy and communication reliability in SWIPT in a K-user Orthogonal Frequency Division Multiplexing (OFDM) interference channel. When the transmitters are non-cooperative, it was found that the necessary condition for the optimal transmission strategy at high SNR is for each energy transmitter to transmit its signal on a single subcarrier. Based on one-subcarrier selection method at the energy transmitter, an iterative algorithm has been proposed to optimize the power allocation at all transmitters. Moreover, with a low-rate feedback from the information transmitters to the energy transmitters and with full cooperation among the transmitters respectively, the transmission strategy maximizing the trade-off region has been proposed.

Secondly, we analysed the coordinated waveform design in SWIPT. The waveform was designed by taking into account the the non-linearity of the rectifier. The trade-off between harvested energy and achievable rate was investigated. It was found that deterministic waveform has a better RF-DC efficiency and results in enlarged trade-off region compared to the modulated waveform. Accordingly, the superposition of modulated and deterministic waveform at the information transmitter was proposed. Another observation was that by accounting for the non-linearity of the rectifier, it increases the resource efficiency that leads to a larger trade-off region than those obtained by ignoring the non-linearity of the rectifier.

Finally, backscatter communication has emerged to be a promising technology for power limited devices. In this thesis, we analysed the trade-off between harvested energy and reliability of backscatter communication for wireless powered backscatter system. It was found that the performance of wireless powered backscatter is subject to a trade-off between harvested energy and SINR. The result highlights the importance of addressing the non-linearity of the diode for wireless powered backscatter system.