Peak to Average Power Ratio Based Signal Detection for Frequency Shift Multitone SWIPT System

Abstract

In this paper, we investigate a multitone simultaneous wireless information and power transfer (SWIPT) based modulation scheme for battery-less Internet of Things (IoT) nodes that works in the ultra high frequency (UHF) region. The conventional SWIPT system is assumed to have power-consuming communication modules. Having such modules on to the IoT nodes whose power is harvested from radio frequency (RF) power sources is too unrealistic. In addition, waveform design from the aspect of power harvesting through SWIPT still has room for consideration. Recent studies have explored multitone based SWIPT to increase the power conversion efficiency (PCE). In these schemes, information is modulated by changing each tone's nature or varying the number of tones. Among these methods, we focused on modulation schemes known as frequency-shift multitone based SWIPT, which shifts frequencies among the tones for information encoding. Unlike previously proposed methods where demodulation requires some power-consuming fast Fourier transfers (FFTs), especially under small communication bandwidths, we applied a signal detection method by measuring output peak to average power ratios (PAPRs) for frequency-shift multitone based SWIPT to reduce power consumption. Based on our analysis, different tone configurations in the frequency domain would yield varieties of nonlinear outputs during the rectification process. In addition, these specific nonlinear output patterns depend on the tone configurations. With this feature, it is possible to demodulate in the time domain at the receiver side using PAPR based measurements, which could eliminate FFT operation. This paper describes how measuring PAPRs enables the detection of signals in theory and validates this through simulations and experiments. We also estimate the communication rates. Based on our results, we achieved 0.46 bits/s/Hz when the number of tones was 6 and estimated that there were (N − 1)(N − 2)/2 + 1 different PAPRs from a given multitone waveform whose number of tones was N .INDEX TERMS Energy harvesting, frequency shift keying, multisine based waveforms, peak to average ratio, simultaneous wireless information and power transfer.

Unified Simultaneous Wireless Information and Power Transfer for IoT: Signaling and Architecture with Deep Learning Adaptive Control

“…6(a). Using the Fourier transform pair y env (f ) of the envelope signal in (11), the frequency-domain expression of the input signal at the FS PAPR estimator is given by…”

“…Meanwhile, it was shown that the RF to direct current (RFto-DC) power conversion efficiency (PCE) in EH circuits of SWIPT receivers depends not only on the input power but also the shape of the input signal, i.e., peak-to-average power ratio (PAPR), due to the nonlinearity of the rectifier, such as diode small signal [5], [6] and saturation effect [7]. Following this observation, new modulation schemes which utilize multi-tone waveforms for boosting the PCE were proposed in [8]- [11]. The authors in [8] proposed the PAPR modulation for SWIPT using distinct levels of signal PAPR to convey information.…”

“…These multi-tone SWIPT schemes utilize an envelope detection that requires less power consumption and low complexity for ID since the receiver can be implemented without power-hungry devices (e.g., mixer, I/Q demodulator). Also, the authors in [10], [11] proposed multi-tone FSK based SWIPT by using the relationship between the input frequency spacing and rectifier output intermodulation frequencies. But most of the multi-tone SWIPT schemes suffer lower data rate compared to conventional information modulation, hence the rate-energy tradeoff should be optimized jointly with the operational range of IoT devices.…”

Multitone PSK Modulation Design for Simultaneous Wireless Information and Power Transfer

“…To minimize these ripples, a multitone frequency shift keying (FSK) scheme is introduced, where the tones' frequency spacings are varied according to the transmitted information, and information decoding is performed by Fast Fourier Transform (FFT) [27]. Another way of decoding information from multitone FSK is considering the fact that multitones with different frequency spacings result in different PAPR levels, which further helps in reducing the receiver power consumption by the removal of FFT [28]. A way of utilizing the phase of 2-tone signal is introduced in [25].…”

Internet of Things Networks: Enabling Simultaneous Wireless Information and Power Transfer

“…13). Further, decoding at the receiver can be performed in two ways: either by using Fast Fourier Transform (FFT) for identifying the strongest baseband signal, or by evaluating multitone PAPR levels with the changing frequency spacings to lower the power consumption at the receiver [59]. In this way, a 0.55 V output voltage can be attained, which is higher than the amplitude based biased-ASK waveform.…”