Joint Transmit and Reflective Beamforming Design for IRS-Assisted Multiuser MISO SWIPT Systems

Abstract

This paper studies an intelligent reflecting surface (IRS)-assisted multiuser multiple-input single-output (MISO) simultaneous wireless information and power transfer (SWIPT) system. In this system, a multi-antenna access point (AP) uses transmit beamforming to send both information and energy signals to a set of receivers each for information decoding (ID) or energy harvesting (EH), and a dedicatedly deployed IRS properly controls its reflecting phase shifts to form passive reflection beams for facilitating both ID and EH at receivers. Under this setup, we jointly optimize the (active) information and energy transmit beamforming at the AP together with the (passive) reflective beamforming at the IRS, to maximize the minimum power received at all EH receivers, subject to individual signal-to-interference-plus-noise ratio (SINR) constraints at ID receivers, and the maximum transmit power constraint at the AP. Although the formulated SINR-constrained minenergy maximization problem is highly non-convex, we present an efficient algorithm to obtain a high-quality solution by using the techniques of alternating optimization and semi-definite relaxation (SDR). Numerical results show that the proposed IRSassisted SWIPT system with both information and energy signals achieves significant performance gains over benchmark schemes without IRS deployed and/or without dedicated energy signals used.Index Terms-Intelligent reflecting surface (IRS), simultaneous wireless information and power transfer (SWIPT), joint active and passive beamforming design, optimization.

Waveform and Beamforming Design for Intelligent Reflecting Surface Aided Wireless Power Transfer: Single-User and Multi-User Solutions

“…By leveraging jointly the frequency and spatial domains, and properly modeling the harvester nonlinearity, the proposed architecture exploits the combined benefits of the passive beamforming gain, the channel frequency selectivity and the rectenna nonlinearity. This contrasts with existing IRS-aided WPT papers [33], [34], [35], [36] whose architecture only benefits from the passive beamforming gain. This also contrasts with existing papers on waveform for WPT [7], [10], whose designs assume active antennas and are therefore not transferable to IRS-aided WPT due to the hardware constraints imposed by IRS.…”

“…This is particularly important in the context of wideband multi-band/carrier WPT since the choice of the passive beamforming phases across frequencies severely influences how much the channel frequency selectivity and the rectenna nonlinearity can be exploited by the waveform design to boost the harvested DC power. This also contrasts with existing IRS-aided WPT papers [33], [34], [35], [36] that ignore such consideration since their designs assume narrowband transmissions and frequency-flat channels.…”

“…Interestingly, the 2nd order term is essentially the linear based rectenna model which is widely addressed in existed IRS-aided WPT/SWIPT papers [33], [34], [35], [36] and is confirmed to be an inefficient and inaccurate in Section IV-A. 3…”

“…Aside communications, IRS brings some natural benefits to wireless power since IRS can help increasing the power level at the input of the rectenna. Existing IRS-aided WPT/SWIPT works focus on single tone, frequency-flat IRS, frequency-flat channel and jointly optimize transmit beamforming and passive IRS beamforming phases [33], [34], [35], [36].…”

Secrecy Rate Maximization for Intelligent Reflecting Surface Aided SWIPT Systems

“…Nevertheless, the randomness of wireless channels and severe channel attenuation will lead to weak energy and information received at receivers in SWIPT systems. Recently, intelligent reflecting surface (IRS) as an intelligent technology is proposed to overcome the harmful effects of wireless environments [9]- [13]. The IRS consists of many low-cost passive reflection units, and each of them can be controlled by software to change the phase and amplitude of incident signals.…”