Wireless information and power transfer over an AWGN channel: Nonlinearity and asymmetric Gaussian signaling

Abstract

Simultaneous transmission of information and power over a point-to-point flat-fading complex Additive White Gaussian Noise (AWGN) channel is studied. In contrast with the literature that relies on an inaccurate linear model of the energy harvester, an experimentally-validated nonlinear model is considered. A general form of the delivered Direct Current (DC) power in terms of system baseband parameters is derived, which demonstrates the dependency of the delivered DC power on higher order statistics of the channel input distribution. The optimization problem of maximizing Rate-Power (R-P) region is studied. Assuming that the Channel gain is available at both the receiver and the transmitter, and constraining to independent and identically distributed (i.i.d.) channel inputs determined only by their first and second moment statistics, an inner bound for the general problem is obtained. Notably, as a consequence of the harvester nonlinearity, the studied inner bound exhibits a tradeoff between the delivered power and the rate of received information. It is shown that the tradeoff-characterizing input distribution is with mean zero and with asymmetric power allocations to the real and imaginary dimensions. DRAFT rate and delivered power. Just to name a few, frequency-selective channel [2], MIMO broadcasting [3], interference channel [4], [5], relaying [6], [7].One of the major efforts in a Simultaneous Wireless Information and Power Transfer (SWIPT) architecture is to increase the Direct-Current (DC) power at the output of the harvester without increasing transmit power. The harvester, known as rectenna, is composed of a rectifier 1 followed by a low-pass filter.In [8], [9], it is shown that the RF-to-DC conversion efficiency is a function of rectenna's structure, as well as its input waveform. Accordingly, in order to maximize rectenna's DC power output, a systematic waveform design is crucial to make the best use of an available RF spectrum. In [9], an analytical model for rectenna's output is introduced via the Taylor expansion of the diode characteristic function. As one of the main conclusions, it is shown that the rectifier's nonlinearity is key to design efficient wireless powered systems. The design of an efficient SWIPT architecture fundamentally relies on designing an efficient Wireless Power Transfer (WPT) structure as an important building block of SWIPT. The SWIPT literature has so far focused on the linear model of the rectifier, e.g., [2]-[7], whereas, it is expected that considering nonlinearity effect changes the SWIPT design, signalling and architecture significantly. Indeed, in [10],[11], the design of SWIPT waveforms is studied accounting for rectenna's nonlinearity with a power splitter at the receiver. It is shown that superposing deterministic multisines (for power transfer purposes) with Orthogonal Frequency Division Multiplexing (OFDM) symbols modulated with Circularly Symmetric Complex Gaussian (CSCG) zero-mean inputs (for information purposes) enlarges the Rate-Power (R-P) region, compared ...

Conditional Capacity and Transmit Signal Design for SWIPT Systems With Multiple Nonlinear Energy Harvesting Receivers

“…i.e., we use the low-power approximation of the rectifier's input impedance 10 . Our numerical results in Section V confirm that both the exact and the approximate output DC power functions in (6) and (14), respectively, are in good agreement with circuit simulations, cf.…”

“…For example, setting the maximum received amplitude to A R,sat l ∆ = 2P in,sat , ∀ l ∈ L, ensures that 10 We note that the harvested DC power function in (15) depends on the circuit parameters Rs, C j , C L , and R L since P l (x) is a function of B = 1/(ηV T {1/Za(R j 0 ) * }) and the rectifier's input impedance Za(R j 0 ) in (13) is a function of these circuit parameters. none of the EH Rxs operates in saturation 11 .…”

“…In addition to their capability to convey information, radio frequency (RF) signals can transfer energy for wirelessly charging low-power devices. This property of RF signals has attracted significant attention to the study of simultaneous wireless information and power transfer (SWIPT) systems [2]- [10]. In [2], the author defined a rate-energy (R-E) function that characterizes the tradeoff between wireless information transfer (WIT) and wireless power transfer (WPT).…”

SWIPT Signaling Over Frequency-Selective Channels With a Nonlinear Energy Harvester: Non-Zero Mean and Asymmetric Inputs

“…Nonlinearity leads to various energy harvester models [7], [11], [12], new designs of modulation and input distribution [13]- [15], waveform [16], RF spectrum use [16], transmitter and receiver architecture [14], [16], [17] and resource allocation [11], [18], [19]. Of particular interest is the role played by nonlinearity on SWIPT signalling in single-carrier and multi-carrier transmissions [1], [13], [14], [16], [20]. In multi-carrier transmissions, it is shown in [16] that inputs modulated according to the Circular Symmetric Complex Gaussian (CSCG) distributions, improve the delivered power compared to an unmodulated continuous waves.…”

“…In multi-carrier transmissions, it is shown in [16] that inputs modulated according to the Circular Symmetric Complex Gaussian (CSCG) distributions, improve the delivered power compared to an unmodulated continuous waves. Furthermore, in [13], it is shown that for an AWGN channel with complex Gaussian inputs under average power and delivered power constraints, depending on the receiver demand on information and power, the power allocation between real and imaginary components is asymmetric. As an extreme point, when the receiver merely demands for power requirements, all the transmitter power budget is allocated to either real or imaginary components.…”