Multitone QAM Modulation Design for Simultaneous Wireless Information and Power Transfer

Abstract

Future Internet of Things (IoT) networks are expected to realize far-field wireless power transfer (WPT) to mitigate the sensors’ dependence on batteries. Recently, simultaneous wireless information and power transfer (SWIPT) has gained attention by utilizing RF signals for both information as well as power transfer. In this paper, a novel N-tone multitone quadrature-amplitude-modulation (QAM) transmission waveform carrying $(N-1)$ information symbols, is proposed for an integrated information-energy receiver with a lower power consumption compared to conventional separated information-energy receiver architectures. The multitone QAM signal is designed by exploiting the non-linearity of the receiver-rectifier, and both amplitudes and phases are used for information transfer offering an advantage of a higher degree of freedom to optimize WPT and wireless information transfer (WIT) performances. It is shown that the power performance of the designed waveform varies with the orientation of the symbol constellation. Two asymmetric QAM constellation designs, expanded symbol constellation and compressed symbol constellation, are proposed to enhance WPT performance according to the application-specific requirement, such as whether a higher level of minimum continuous power transfer is critical or if a high-power transfer in short bursts is preferred for the SWIPT’s operation. It has been shown that WPT and WIT performances can be enhanced according to the IoT node’s requirements by varying the transmission probabilities of inner symbols and outer symbols of the QAM constellation.