Rate-Energy Tradeoff Analysis in RIS-SWIPT Systems With Hardware Impairments and Phase-Based Amplitude Response

Abstract

This paper investigates the reconfigurable intelligent surface (RIS)-empowered dynamic power splitting designs for simultaneous wireless information and power transfer (SWIPT) systems while adopting various practical hardware issues. Specifically, we adopt the physical size of the RIS and the placement of the RIS plane to phase-align the reflected signals towards the desired direction. The analytical phase shift model for the reflecting elements is presented to characterize an intertwined relationship between amplitude and phase responses, which captures the amplitude variations depending on phase in RIS elements. Furthermore, an additive distortion noise incorporates the residual transceiver hardware impairments (RTHIs). The stringent signal-to-interference-plus-noise ratio requirement is facilitated using both the direct and indirect, i.e., RIS cascaded, links. To made complicated analysis become tractable, we exploit the statistical properties of the effective channel power which follows a Gamma distribution. The tight bounds for the achievable rates and residual energy are derived and the tradeoffs between the achievable rate and residual energy for the time switching and static power splitting designs are characterized. Finally, the numerical results confirm the accuracy of the developed framework and demonstrate the selection of the system parameters.INDEX TERMS RIS, SWIPT, RTHIs, phase-dependent amplitude response, rate-residual energy tradeoffs.

Performance Analysis of Wireless Communications with Nonlinear Energy Harvesting under Hardware Impairment and κ-μ Shadowed Fading

“…[25]. A few works [26][27][28][29] have studied wireless communications under concurrent consideration of energy-harvesting nonlinearity (EHNL) and hardware impairment. Nonetheless, these works have revealed several limitations.…”

“…To be more specific, the authors in ref. [ 26 ] considered transmission from S to D under the aid of the reconfigurable intelligent surface operated as a relay. Although the authors in [ 26 ] analyzed rate-energy tradeoff, it investigated simple Rayleigh fading channels without accounting for shadowing, and missed the throughput (TP) and the outage probability (OP) analyses.…”

“…[ 26 ] considered transmission from S to D under the aid of the reconfigurable intelligent surface operated as a relay. Although the authors in [ 26 ] analyzed rate-energy tradeoff, it investigated simple Rayleigh fading channels without accounting for shadowing, and missed the throughput (TP) and the outage probability (OP) analyses. Suffering from the same limitations as [ 26 ], the authors in [ 27 ] designed beamformers to obtain power efficiency and information security for direct transmission from S to multiple destinations.…”

“…Nevertheless, ref. [ 27 ] studied Rician fading for the channel from T to S. Similar to [ 26 , 27 ] in which no analysis of the TP and the OP was presented, the authors in ref. [ 28 ] assessed the TP of the secondary network in the context of cognitive radio over Nakagami- m fading without taking shadowing into account.…”

“…Recently, the authors in ref. [ 29 ] analyzed the TP and the OP of overlay networks over - shadowed fading which considers fading distributions (Rayleigh [ 26 , 27 ], Nakagami- m [ 28 ], Rician [ 27 ]) as special cases and accounts for shadowing and path loss. Nevertheless, only [ 27 ] considered multiple antennas at T for high energy efficiency and at S for beam-forming implementation, while [ 26 , 28 , 29 ] investigated the single antenna at T, therefore hardly improving energy-harvesting efficiency.…”