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In the wideband regime, the performance of many of the popular modulation schemes such as code division multiple access and orthogonal frequency division multiplexing falls quickly without channel state information. Obtaining the amount of channel information required for these techniques to work is costly and difficult, which suggests the need for schemes which can perform well without channel state information. In this work, we present one such scheme, called wideband time frequency coding, which achieves rates on the order of the additive white Gaussian noise capacity without requiring any channel state information. Wideband time frequency coding combines impulsive frequency shift keying with pulse position modulation, which allows for information to be encoded in both the transmitted frequency and the transmission time period. On the detection side, we propose a non-coherent decoder based on a square-law detector, akin to the optimal decoder for frequency shift keying based signals. The impacts of various parameters on the symbol error probability and capacity of wideband time frequency coding are investigated, and the results show that it is robust to shadowing and highly fading channels. When compared to other modulation schemes such as code division multiple access, orthogonal frequency division multiplexing, pulse position modulation, and impulsive frequency shift keying without channel state information, wideband time frequency coding achieves higher rates in the wideband regime, and performs comparably in smaller bandwidths.

Wireless power and bidirectional wireless data transfer system using a conventional 2-coil inductive link is presented for Internet-of-Things (IoT) and mobile applications without any additional coil or antenna. The proposed system utilizes the dual-band frequency shift-keying (FSK) and the load shift-keying (LSK) for the downlink and uplink telemetries, respectively, while about 140 mW power is delivered to the Rx in the 2-coil inductive link. The data rates for downlink and uplink telemetries are 800 kbps and 14 kbps with bit error rate (BERs) of 3.1210^(-5) and less than 10^(-6) at 10 mm distance, respectively.

This article presents a 915-MHz ultra-low-power (ULP) sub-sampling phase-tracking receiver (SSPT-RX). It is targeted for the power-constrained devices that need short range but medium high-speed data receiving, such as the multi-channel neural stimulator with arbitrary waveform generation. The zero-intermediate frequency (zero-IF) phase-tracking receiver (PT-RX) topology is adopted to simplify the sub-sampling RX architecture with direct demodulation of frequency-shift keying (FSK) signal while improving the image frequency issue. The frequency of local oscillator (LO) is reduced by ten times with the proposed architecture, which leads to greatly reduced power consumption. Fabricated in 65-nm CMOS process, the RX chip occupies an active area of 0.58 mm2. The RX consumes one of the lowest power consumptions of 164 μW from 0.5-/1-V supplies. It achieves an energy efficiency of 32.8 pJ/bit at a data rate of 5 Mb/s, which is improved by ∼5.6× compared to the stateof- the-art RXs. The measured sensitivity of 915-MHz FSK signal receiving is -69.5 dBm with an LO frequency of 91.5 MHz, which is 1/10 of the carrier frequency. The achieved RX sensitivity figure-of-merit (FoM) is 174.3 dB. Agency for Science, Technology and Research (A*STAR) This work was supported in part by “Nanosystems at the Edge” through the Singapore A∗STAR SERC AME Program under Grant A18A4b0055, in part by the Minister of Science and Technology, China, through the National Science and Technology Major Project under Grant 2018AAA0103100, in part by the National Natural Science Foundation of China under Contract 61661166010, and the in part by the Shenzhen Science and Technology Program under Grant JCYJ20180306170435280.

Design scheme for embedding chipless radio-frequency identification (RFID) tag in quick response (QR) code is proposed and demonstrated. By searching for QR modules that can be metalized to form a loop resonator in the edge area and to load the loop in the central area, chipless RFID tag with optimized loaded-loop resonator can be designed in the QR code. Specific loop genetic operator is proposed for the optimization searching. The optimized loaded-loop resonator has sharp dominant resonant peak at frequency as low as possible and harmonic resonant peak at frequency as high as possible, which provides large space for data encoding of chipless RFID. By removing or de-metalizing the metalized loading modules, the resonant frequency can be tuned conveniently for FSK coding. For demonstration, chipless RFID tag embedded in QR code is designed and tested. It is shown that the RFID tag allows at least nine distinct resonant frequencies for simple FSK coding, which indicates a coding capacity of 3.17 bits and a normalization coding density of approximately 501.78 bits/λg2/GHz for the chipless RFID tag embedded in the QR code.

In this letter, an energy-efficient and low complexity method for capacitive-coupled human body communication (CCHBC) systems is proposed. In the proposed method, called impedance shift keying CC-HBC (ISK-CC-HBC), the change of impedance between the transmitters signal and the ground electrode is used to map information. In particular, the transmitter changes the condition of an electrical field generated by the receiver, by changing the impedance between its signal and ground electrodes. Subsequently, by detecting the changes in the electric field, the receiver can demodulate the information sent by the transmitter. The CC-HBC channel is obtained using the transfer function method, while the performance of the proposed scheme is compared with frequency shift keying (FSK) and on-off keying (OOK) modulations.

Chirp spread spectrum (CSS) is the modulation technique currently employed by Long-Range (LoRa), which is one of the most prominent Internet of things wireless communications standards. The LoRa physical layer (PHY) employs CSS on top of a variant of frequency shift keying, and non-coherent detection is employed at the receiver. While it offers a good trade-off among coverage, data rate and device simplicity, its maximum achievable data rate is still a limiting factor for some applications. Moreover, the current LoRa standard does not fully exploit the CSS generic case, i.e., when data to be transmitted is encoded in different waveform parameters. Therefore, the goal of this paper is to investigate the performance of CSS while exploring different parameter settings aiming to increase the maximum achievable throughput, and hence increase spectral efficiency. Moreover, coherent and non-coherent reception algorithm design is presented under the framework of maximum likelihood estimation. For the practical receiver design, the formulation of a channel estimation technique is also presented. The performance evaluation of the different variants of CSS is carried out by inspection of the symbol error ratio as a function of the signal-to-noise ratio together with the maximum achievable throughput each scheme can achieve., Summited to the IEEE Transactions on Green Communications and Networking. arXiv admin note: text overlap with arXiv:2009.10421

International audience; In this letter, we propose a near-optimal lowcomplexity frequency-domain (FD) harmonic receiver for visible light communication based unipolar frequency-shift keying (U-FSK). The time-domain (TD) maximum-likelihood (ML) receiver for U-FSK is computationally complex, while the sub-optimal receiver increases the noise variance. The proposed harmonic receiver determines the transmitted frequency from the crosscorrelations between the FD received waveform and the FD dictionary waveforms reduced to their strongest harmonics. The results shall demonstrate that besides affording a linerarithmic complexity, the performance of the harmonic receiver closely approaches that of TD ML receiver which exhibits quadratic complexity.

Due to the severe impact of dynamic plasma sheath on electromagnetic (EM) waves, the communication quality of hypersonic vehicles deteriorates, even resulting in communication blackouts during the reentry process. In this article, the hypersonic vehicle downlink integrated channels that cascade the plasma sheath channel and Rice fading channel, i.e., the downlink telemetry channels, are first established, and then the demodulation method and performance of typical telemetry modulations including the M-ary phase shift keying (MPSK), M-ary amplitude shift keying (MASK), and M-ary frequency shift keying (MFSK) are studied. Considering the high dynamics of the plasma sheath, the pilot signals are used to detect the signal correctly for MPSK, and the non-coherent demodulation is adopted for MASK and MFSK. Especially, an adaptive maximum likelihood (ML) receiver for ASK is proposed based on a reduced reversible jump Markov chain Monte Carlo (RRJ-MCMC) algorithm to estimate the probability density function (pdf) of the received signal. The simulation results show that the communication performance of PSK and ASK is improved with the modulation order $M$ decreasing; the performance of non-coherent FSK is improved with the modulation order $M$ increasing. Meanwhile, the performance follows the order of NC-MFSK (M ≥ 8) > BPSK > NC-4FSK > NC-2FSK > 2ASK. For NC-8FSK, when the electron density peak value ${Ne}_{\mathrm {peak}}$ = {2, 4, 6, 8, 10} $\times 10^{18}\,\,\text{m}^{-3}$ , the signal to noise ratio (SNR) required to reduce the bit error rate (BER) to 10−6 are 17, 18, 19, 21, and 34 dB, respectively.

An automatic method for classifying frequency shift keying (FSK), minimum shift keying (MSK), phase shift keying (PSK), quadrature amplitude modulation (QAM), and orthogonal frequency division multiplexing (OFDM) is proposed by simultaneously using normality test, spectral analysis, and geometrical characteristics of in-phase-quadrature (I-Q) constellation diagram. Since the extracted features are unique for each modulation, they can be considered as a fingerprint of each modulation. We show that the proposed algorithm outperforms the previously published methods in terms of signal-to-noise ratio (SNR) and success rate. For example, the success rate of the proposed method for 64-QAM modulation at SNR=11 dB is 99%. Another advantage of the proposed method is its wide SNR range; such that the probability of classification for 16-QAM at SNR=3 dB is almost 1. The proposed method also provides a database for geometrical features of I-Q constellation diagram. By comparing and correlating the data of the provided database with the estimated I-Q diagram of the received signal, the processing gain of 4 dB is obtained. Whatever can be mentioned about the preference of the proposed algorithm are low complexity, low SNR, wide range of modulation set, and enhanced recognition at higher-order modulations.

Reactive symbol-level jammer has attracted attention due to its low energy cost and high jamming efficiency. With the development of software-defined radio (SDR), the implementation of reactive symbol-level jamming has become more practical and efficient. To combat the reactive jammer, this paper proposes an index modulation based frequency hopping spread spectrum (IM-FHSS) scheme. Specifically, the current available frequencies are determined by multiple orthogonal frequency hopping (FH) patterns, and bit information is transmitted through the index of the active FH pattern. At the receiving side, we design an energy detector to distinguish the active and idle frequencies. With such implementation, IM-FHSS can obtain the improved resistance of reactive symbol-level jammer. Subsequently, we propose the alternative spectral efficiency (SE) mode of IM-FHSS in order to meet the high SE and low-power jamming scenarios. Furthermore, we analyze the BER of this scheme for the reactive symbol-level jamming under the cases of energy correlation, jamming rate, and phase offset. Theoretical analysis and simulation results show that IM-FHSS exhibits enhanced resistance to reactive symbol-level jamming than traditional FH scheme.

In this paper, we investigate multi user chirp spread spectrum with noncoherent detection as a continuation of our work on coherent detection in [1]. We derive the analytical bit error ratio (BER) expression for binary chirp spread spectrum (BCSS) in the presence of multiple access interference (MAI) caused by correlation with other user signals because of either asynchronism or Doppler shifts, or both, and validate with simulations. To achieve this we analyze the signal cross correlations, and compare traditional linear chirps with our recently-proposed nonlinear chirps introduced in [1] and with other nonlinear chirps from the literature. In doing so we illustrate the superior performance of our new nonlinear chirp designs in these practical conditions, for the noncoherent counterpart of [1]., Chirp spread spectrum, Noncoherent detection, Asynchronism, Doppler, Chirp, FMCW, Analysis, BER derivation

Standalone microgrids are used in various industrial operations to supply critical loads. The authors have proposed a stable and robust decentralized ac microgrid architecture that provides an automatic and equitable load sharing between distributed generators, without the use of droop control. To deal with faults or real-time changes in the distributed generation levels, a flexible reconfiguration of the microgrid can be advantageous. To achieve that, this article proposes the use of power line communication (PLC). Two PLC strategies are explored in this article: the first is based on using a single and constant PLC frequency, and the second is based on using a variable PLC frequency within a given range. This article details PLC injection, detection, and suppression methods, as well as the overall communication logic. It demonstrates the ability of the microgrid to adapt to changes while minimizing the amount of battery support. Findings of this article are supported by simulations and validated by experiments.

This paper proposes a new current-mode digital modulation circuit. The proposed circuit is MOS only hence, easily integrable. It employs an Extra X Current Conveyor (EX-CCII), two MOS transistors as switches, and a two MOS transistor-based active resistor. The amplitude shift keying/phase shift keying/frequency shift keying (ASK/PSK/FSK) modulator is obtained by proper selection of carriers (IC1, IC2). This circuit provides the current output signal at high output impedance, which is favorable for cascading. Also, the circuit is employing only MOS transistors, so it can be monolithically IC implementable. The effects of non-idealities and parasitics of the active element on the circuit performance are also investigated in detail. The functionality of the proposed digital modulator is verified through the Cadence Virtuoso tool using 0.18 μm Generic Process Design Kits parameters with the ±0.9 V supply voltage. The total area of the layout is 968.75 μm2. Also, the experimental results are verified by using the IC AD-844 and IC CD4007.

A wireless frequency shift keying (FSK) transceiver that can simultaneously transmit and receive over the same radio channel using a novel complex baseband technique is introduced. The proposed design combines a traditional FSK modulator with a new frame-based demodulation technique able to recover data without using traditional cancellation techniques. Self Interference (SI) level has no impact on demodulation and can be ignored. The mathematical equations are detailed and validated by simulation. The implementation through software defined radio (SDR) using Ettus B210 USRP and GNU Radio proves that the system works properly and enables the In-Band Full-Duplex (IBFD) for FSK. An example of one single hope real-world IBFD communication is presented. Energy efficiency and System performances have been also evaluated using the bit error rate (BER) curve and discussed. The proposed technique enhances the spectral efficiency by factor 2 and seems very useful for low-rate applications such many internet of things (IoT) devices.

This brief presents a 2.4-GHz crystal-less GMSK/GFSK phase-tracking receiver (PTRX) that employs a multiphase bang-bang PLL (BBPLL) as an auxiliary loop to perform multibit oversampled demodulation. A divider-less 30-MHz BBPLL with a 16-stage ring voltage-controlled oscillator (VCO) and 15 bang-bang phase detectors (BBPDs) works as a clock-less phase-to-digital converter (PDC) and improves demodulation SNR with control polarity reversal and frequency scaling. A prototype 2.4-GHz PTRX with the reference-less BBPLL is implemented in 65 nm and performs 1-Mb/s GMSK demodulation with −84-dBm sensitivity. Experimental results show that the proposed receiver can achieve high slew-rate transient performance for increased frequency deviation with the multiphase BBPLL-based demodulation.

In this article, fully integrated binary phase shift keying (BPSK) tags are presented to work in conjunction with narrowband frequency-shift keying (FSK) radar for concurrent multitarget range tracking and vital signs sensing. Without the employment of any radio frequency (RF) mixer, the developed BPSK tag introduces a frequency offset by generating periodic phase shifts to the radar carrier frequencies with optimized power level. The theory of BPSK tag-based range tracking and vital signs sensing in conjunction with FSK radar signal is developed. An impedance-modulated 24-GHz tag architecture without any active RF components is proposed and its implementation and characterization are presented. The system performance is evaluated in the following residential indoor scenarios: single tag ranging, concurrent multiple tags and an untagged human target detection, and multiple tagged human targets tracking. Promising ranging performance demonstrates the potential for the proposed system to be adopted in various indoor tracking applications.

We present a new analog-to-digital converter (ADC)-based architecture of a phase-tracking receiver (PT-RX) optimized for ultra-low-power (ULP) and ultra-low-voltage (ULV) operations for the Internet of Things (IoT). The RX employs a type-II loop configuration that offers improved stability compared with the previous type-I PT-RX solutions. In addition, the type-II loop is also very tolerant of long run-lengths of consecutive “1” or “0” symbol sequences. Fabricated in 28-nm CMOS, the prototype PT-RX targets Bluetooth low energy (BLE) standard consuming only 1.5 mW at a supply of ≤0.7 V. It maintains an adjacent-channel rejection (ACR) of ≥−11/3.5/17/27 dB at 0/±1/±2/±3 MHz offset and can tolerate out-of-band (OOB) blockers of minimum −21 dBm across 1.0–3.5 GHz while also offering a best-in-class figure of merit (FoM) of 181 dB, with a 1-Mb/s BLE sensitivity of −93 dBm.

We propose a novel simulation approach of the Middleton Class-A model for impulsive noise generation considering symbol-wise transmission in a real Power Line Communication environment. Then, we validate the proposed approach for both single carrier binary FSK based—and multi-carrier OFDM-based communication systems. Established analytical formulations and obtained simulation results for the impulsive noise variance distribution and the communication system error probability show that in a binary FSK system, the second order of the noise variance per symbol, as well as the error floor, are closely related to the impulsive index A. The error floor decreases when A becomes large, and its asymptotic value is equal to the Bit Error Rate (BER) for an additive white Gaussian noise channel with noise variance equal to the average variance of the impulse noise. However, in an OFDM-based system, the noise variance per symbol at the output of the demodulator, as well as the error floor in the BER curves, are fixed and independent of the impulsive index A. The proposed analysis allows us to compare binary FSK and OFDM under the same theoretical noise conditions.

In optical transmission technique using optical polarization, the change of state of polarization (SOP) and the rotation of SOP (RSOP) during optical transmission has a significant impact on the transmission performance. We propose polarized intensity rotational frequency shift keying (PIR-FSK) as a novel modulation technique in change of SOP and RSOP-tolerant optical transmissions. The proposed PIR-FSK signal does not affect the entire intensity of the optical carrier by modulating the sinusoidal signals on each X and Y-polarized optical carrier. Therefore, the proposed PIR-FSK modulation and optical carrier intensity modulation can operate at the same time. Moreover, since the proposed technique does not modulate the signal using the SOP unlike the PolSK, PIR-FSK is not affected by SOP changes that occur during transmission, and the signal does not be degraded even with RSOP. We demonstrated that the signals modulated using the proposed PIR-FSK modulation have higher signal capacity and efficiency compared to the signal modulated using PolSK modulation.

Communication system’s performance is sensitive to bandwidth, power, cost etc. There have been various solutions to improve the performance, out of them, one of the fundamental solutions over the years is design of optimum modulation schemes. As the research on beyond 5G heats up, we survey and explore power and bandwidth efficient modulation schemes for the next generation communication systems in details. In the existing literature, initially square quadrature amplitude modulation (SQAM) was considered. However, only square constellations are not sufficient for varying channel conditions and rate requirements, thus, efficient odd power of 2 constellations were introduced. For odd power of 2 constellations, rectangular QAM (RQAM) is most commonly used. However, RQAM is not a good choice and modified cross QAM (XQAM) constellation is preferred which provides improved power efficiency over RQAM due to its energy efficient two dimensional (2D) structure. The increasing demand for high data-rates has further encouraged research towards more compact 2D constellations which leads to hexagonal lattice structure based hexagonal QAM (HQAM) constellations. In this work, various QAM constellations are discussed and detailed study of star QAM, XQAM, and HQAM is presented. Generation, peak and average energies, peak-to-average-power ratio, symbol-error-rate, decision boundaries, bit mapping, Gray code penalty, and bit-error-rate of star QAM, XQAM, and HQAM constellations for different constellation orders are presented. Finally, a comparative study of various QAM constellations is presented which justifies the supremacy of HQAM over other QAM constellations for various wireless communication systems and a potential modulation scheme for future standards.

Automatic modulation recognition with deep learning (DL) is challenging in distinguishing high-order modulation modes and balancing complexity against recognition accuracy. In this paper, we propose a novel dual-path modulation recognition framework named IRLNet, which consists of the improved residual stacks (IRS) and long short-term memory (LSTM). The IRS maintains the more initial residual information, learns the signal features in deep and shallow, and achieves various degrees of feature extraction. The model learns from the time domain I/Q, amplitude and phase information presented in the training data. The simulation results on RadioML2016.10B show that IRLNet performs stable in the training stage and has low spatial-temporal complexity. It also achieves a recognition accuracy of more than 93% at high signal-to-noise ratios (SNRs). Transfer learning is introduced to improve the efficiency of retraining, and robustness is proved by transferring the model to RadioML 2018.01A and HisarMod 2019.1. The simulation result shows that the training time is greatly shortened by about 25.6% in RadioML 2018.01A by introducing transfer learning. Moreover, IRLNet improves the confusion of high-order modulations and achieves a recognition accuracy of more than 90% in high SNRs.

This paper mainly studies the data characteristics of high order cumulants using digitally modulated signals, and constructs the identification feature parameters that can distinguish the signal modulation type by the high-order cumulants data of the digital modulation signal. Set the identification signal modulation type determination threshold based on the value of the identification feature parameter. The identification feature parameter value of the signal modulation type is compared with the set determination threshold, to realize the recognition of digital modulation signal. This identification method is implemented based on MATLAB design, with a 2ASK (2-ary Amplitude Shift Keying) signal, 4ASK (4-ary Amplitude Shift Keying) signal, 2PSK (2-ary Phase Shift Keying) signal, 4PSK (4-ary Phase Shift Keying) signal, 2FSK (2-ary Frequency Shift Keying) signal, 4FSK (4-ary Frequency Shift Keying) signal. The second, fourth and sixth order cumulants of the six signals were analyzed. Calculate the selected identification feature parameter value and the determination threshold to identify the six signals. The six signals have made MATLAB identification simulation. Simulation results show that this method is feasible and has high recognition rate. Simulation results verify that such recognition methods maintain a high recognition rate under conditions with low signal-to-noise ratio. This identification method can be extended to more MASK (M-ary Amplitude Shift Keying), MPSK (M-ary Phase Shift Keying), MFSK (M-ary Frequency Shift Keying), MQAM (M-ary Quadrature Amplitude Modulation) signal identification.

Automatic modulation classification (AMC) is a method that supported different wireless communication systems for modulation type classification. Currently, orthogonal frequency division multiplexing, multiple-input, multiple-output systems are widely using this technique. Recent AMC methods are designed for a single-carrier system identifying a few modulation types. To motivate the AMC for the current communication systems, we present an intelligent pyramid model for automatic multi-carrier modulation classification (AMC2-pyramid) which alleviates the existing works challenges such as high degradation of accuracy for higher order modulation schemes, inefficient feature extraction and lack of effectiveness in low SNR environments. The proposed work contains three significant operations, namely, signal fortification, feature engineering and modulation classification. First, signal quality is estimated to reduce the complexity in classification because some signals are affected by noise and other environmental or channel artefacts. Hence, before pre-processing the signal, the quality is assessed according to the channel state information, signal to inference plus noise ratio, received signal strength indicator and spectral efficiency. For low quality, quality augmentation is applied. Then, quality augmentation is implemented with noise elimination, equalisation, quantisation and channel frequency offset compensation. In the feature engineering step, feature extraction and clustering are presented using the Gated Feature Response Pyramid Network (GaFP), and a twin-functioned human mental search algorithm is used. The modulation classification is implemented using a multi-distance-based nearest centroid classifier, and improved Q-learning is used to identify signals as any of 16QAM, 32QAM, 64QAM, 128QAM, QPSK, BPSK, DPSK, ASK and FSK. The performance of the proposed AMC2-pyramid is implemented using MatlabR2017b, where accuracy (6.8% – 23.15%) high when compared to sample size and (14% – 46%) high when compared to SNR at −10 dB, precision (4.96% – 29.5%) high when compared to sample size and (16.5% – 48.5%) high when compared to SNR at −10 dB, recall (2– 29.76%) high when compared to sample size and (14% – 45%) high when compared to SNR at −10dB, F-score (2– 30%) high when compared to sample size and (15.5%– 46.5%) high when compared to SNR at −10 dB, error rate (0.7% – 11.5%) low when compared to sample size and (4.5%– 17%) low when compared to SNR at −10 dB, computational time (170ms – 400ms) low when compared to sample size is computed for the proposed work including previous well-known methods. The proposed work proves that this method outperforms the previous ones.

A photonic approach to generate multiform microwave frequency shift keying (FSK) signal is proposed. In the scheme, a dual-polarization quadrature phase shift-keying (DP-QPSK) modulator along with a polarization controller (PC) is employed to generate two orthogonally polarized signals containing specific optical sidebands, and a following tunable filtering switch (TFS) serve as optical sidebands selector. From a theoretical analysis, when the modulators in the scheme are properly biased, we can obtain microwave FSK signal with frequency multiplication factors of 2/4 or microwave FSK signal with flexible tunable subcarrier frequencies. Simulations are conducted to verify the proposed scheme. 10/20GHz and 8/12GHz microwave FSK signals are successfully generated, and the frequency tunability is also demonstrated. In addition, the impact of the non-ideal parameters is analyzed, and the results show that the scheme has good immunity to the small parameters deviation (within 3°). The distinct advantage of our scheme is that we realize multiform microwave FSK signal generation based on a single system, which may find applications in high-frequency multifunction wireless communication system or radar system.

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 $N$ .

An approach for microwave signal generation with adjustable formats including ASK, PSK, FSK and FPSK (FSK-PSK) is proposed and demonstrated in this paper. In the proposed scheme, a phase modulator (PM) and an optical coupler form optically coupled selector switch (OCSS), which transmit the optical signal on specified path by adjusting its driving signal. Two parallel-placed Dual-Drive Mach-Zehnder modulators (DD-MZM) and a followed photodetector (PD) are employed to generate the multi-format microwave signals. From a theoretical analysis, the microwave signals with tunable formats can be obtained by properly adjusting the amplitude of the coding signals. The simulation and experimental results show that the ASK, PSK, FSK and FPSK signals are successfully generated, and the modulation format can be switched simply by adjusting the system parameters. In addition, the frequency and bit rate of generated signal can be adjusted according to the demand, so flexible tunability can be realized easily.

Tactical data links are becoming more widely used in the military, as they can greatly improve the efficiency of various combat units. Such tactical data links must be able to transmit large volumes of data at high speed in complex communication environments while ensuring reliability. This paper studies the influence of 16-ary Quadrature Amplitude Modulation (16QAM) and Minimum Frequency-shift Keying(MSK) modulation on the transmission performance of data chain system. The simulation results show that 16QAM modulation can meet the requirements of tactical data link system for BER and data transmission rate, and the technical complexity is in the middle; the system BER of MSK modulation is lower, and a large number of data transmission can be realized at high speed. When the SNR reaches 50dB, the BER of MSK modulation can be reduced to $10^{-4}$ order of magnitude, which is better than Quadrature Phase Shift Keying (QPSK) modulation, that is, the data chain system based on MSK modulation can meet the transmission requirements of data chain when the signal-to-noise ratio is large.

Magnetic communication is a promising technique in harsh environments, such as seawater. To enable efficient communication, transmitting and receiving coils are conventionally operated as part of resonant circuits. However, this results in narrow bandwidths and the associated disadvantages. Thus, most digital modulation schemes cannot be used efficiently on these systems. In this contribution, a mixed hardware/software approach for efficient frequency shift keying is presented. With this energy-efficient modulation concept, the full available bandwidth of a receiver can be utilized for data transmission, while all advantages of using a resonant circuit on the transmitter side can be retained. Towards this goal, a transmitter-side resonant circuit is designed, which supports discrete switching between multiple resonant frequencies. The data symbols are mapped onto these unique resonant frequencies. This prevents the parasitic amplitude modulation associated with conventional frequency shift keying applied to narrow bandwidth circuits, resulting in maximum transmitted magnitude and minimum symbol distortion without need for any further measures. Furthermore, the frequency spacing and/or the cardinality of the symbol alphabet can be increased considerably. At the receiver side, the classical pick-up coil is replaced by a high-sensitivity broadband magnetic field sensor. Numerical results of the mixed hardware/software scheme are provided, and are verified by an experimental setup. This setup is constructed using principles from the field of power electronics and demonstrates, how this modulation concept can be implemented with relatively simple and highly energy efficient electronics and without the use of linear amplifiers in particular.

A novel photonic scheme of binary modulated microwave signals generation based on a dual-polarization quadrature phase-shift keying (DP-QPSK) modulator is proposed and experimentally demonstrated. The scheme is highly reconfigurable, amplitude keying signal (ASK), phase-shift keying signal (PSK) or frequency-shift keying (FSK) signal can be generated by appropriately setting the amplitude of the binary coding signal. The coding signal and local oscillator (LO) signals are independent with each other, binary modulated microwave signals can be generated with arbitrary coding rate and carrier frequency. The frequency deviation of the FSK signal can also be adjusted flexibly. No filter is used in the scheme and the tuning range is large. A proof-of-concept experiment is carried out to verify the feasibility of the proposed system. A 1-Gbps 8-GHz microwave ASK signal, a 0.5-Gbps 6-GHz microwave PSK signal, and a 0.5-Gbps 8/12-GHz microwave FSK signal are g[enerated in the experiment.

In this work we propose a simple approach to realize the direct frequency modulation of a semiconductor distributed feedback (DFB) laser. The directly frequency-modulated DFB laser (DFL) is biased by a direct current (DC) on a normal electrode along the laser cavity to define the output power. The signal current is applied on an extra short electrode placed in the center section of the DFB laser, isolated from the DC electrode. The varying of the material refractive index in the center section with the signal current introduces an effective grating phase change, thereby alters the lasing frequency. Small-signal simulation shows that a frequency modulation efficiency of 26GHz/mA from 0 to 100GHz and 17GHz/mA from 100GHZ to 200GHz can be achieved, respectively. Large-signal simulation of the waveform and eye-diagram of a frequency-shift keying (FSK) signal generated by the DFL is also performed by converting it to an intensity modulated signal through an optical slope filter.

This brief proposes and demonstrates a reliable power and data transfer scheme for biomedical implants through a resonant capacitive link. Flexible, conformable, and biocompatible patches are adopted with an automatic resonant frequency calibration technique for the first time. A voltage feedback network, a Class- ${D}$ driver, and a custom algorithm have been developed for the low overhead calibration. An ex vivo chicken skin tissue-based experiment with 4 cm2 flexible, conformal capacitive patches demonstrated the method. Experimental results show that the power delivered to the load (PDL) of the link extends up to 150 mW and maximum power transfer efficiency (PTE) of the link is 54%. A simultaneous data transfer with a rate of up to 170 kbps alongside power transfer using 1.5 to 2 mm-thick biological skin tissue has been achieved.

A frequency reconfigurable patch antenna is dynamically tuned to transmit frequency-shift keying (FSK) signals over a range of frequencies much broader than the static impedance bandwidth of the antenna. Experiments are conducted for two binary FSK schemes having different carrier spacing. In both cases, dynamic tuning of the antenna is shown to increase the amplitude of the radiated signal by providing a better match than the static antenna. However, the average energy of the radiated bit at each carrier frequency decreases as the symbol rate increases beyond the 3 dB bandwidth of the antenna. Therefore, the bandwidth of the antenna is found to be a limiting factor for the maximum achievable data rate in this scheme. As an alternative to shorter bit durations, the authors show that a higher level FSK scheme using dynamic tuning is able to increase throughput beyond what is possible with a static antenna.

In this article, a miniaturized dual-resonant antenna system at MHz-band operating at around 20 and 50 MHz is proposed for frequency-shift keying impulse radio (FSK-IR) intrabody communications. This antenna system comprises a swallowable helix-coil in-body antenna with a hollow cylindrical shape of 10 mm diameter and 30 mm length, and two single band on-body matched planar spiral-coil antennas with a compact size of 79 mm $\times\,\,72$ mm $\times\,\,2.8$ mm. For in-body antenna design, a nonuniform helical pitch structure is utilized to produce dual-resonant frequencies. The soft ferrite magnetic sheet with high relative permeability and low dissipation factor is used as a flexible conformal substrate to realize antenna miniaturization without lumped element loading. Simulation results for antenna performance, electromagnetic field distribution, and specific absorption rate are presented with different tissue-type phantoms, as well as an anatomical numerical human model. In addition, experimental verification of antenna performance and implant transmission characteristics is also conducted in a liquid phantom. At an implant depth of 50 mm, the measured maximum transmission coefficients are −33 and −45 dB at the dual-resonant frequency bands, respectively. Simulation and measurement results demonstrate that the proposed dual-resonant antenna is suitable for the FSK-IR system and can be expected to realize a data rate as high as 10 Mb/s for biomedical implant applications at MHz-band.

Radio-frequency (RF) energy harvesting is a promising technology that obtains energy from electromagnetic waves. As an alternative energy source, this modern technology can provide power wirelessly enabling the practical use of battery-free devices and it is also expected to be widely used in future applications. Many studies have examined the effects of different modulation techniques on power or efficiency in RF energy-harvesting systems. In this article, the effects of different modulation techniques, such as amplitude shift keying (ASK), quadrature amplitude modulation (QAM), phase-shift keying (PSK), and frequency shift keying (FSK) on charging time, were measured and theoretically analyzed in detail. The measurement system was designed using a signal generator, an RF energy-harvesting circuit, and other auxiliary devices. The signal generator produced four different modulated signals as transmit power signals from 1 to 10 dBm at the interval of 1 dBm, and then, the RF energy-harvesting circuit was fed with these power signals. According to the measurement results, four different modulation techniques charged the RF energy-harvesting circuit at different times. It was observed that the 4-ASK modulation technique had the shortest charging time in the range of 1–10 dBm when comparing to QAM, PSK, and FSK modulation techniques, and thus, it was evaluated to be the most suitable modulation technique for the RF energy-harvesting system among these modulation techniques in terms of charging time.

We are interested in a communication system that operates under stringent power constraints, but is flexible with bandwidth constraints. Our approach is to consider some of the key elements in a transceiver and optimize them for low power consumption, as opposed to optimizing them to minimize, say, average probability of error. An obvious consequence of this is that high complexity components of the system, such as matched filters, forward error correction that employs iterative decoders, coherent demodulators, and bandwidth-efficient modulation formats, are not feasible for this research. Rather, our system is designed using $M$ -ary FSK with non-coherent detection, optimized two-pole bandpass filters (BPF), and Reed-Solomon (RS) codes with hard-decision decoding. Among other things, we show that by properly optimizing the key parameters of the BPFs and RS codes, we can design the system to be significantly less complex than an optimal one, and only lose about 1.2 ( $M$ =16) to 1.5 ( $M$ =2) dB in terms of performance.

The “magnetic window” is considered to be an effective technique for alleviating a vehicle’s atmospheric reentry blackout, whereas the dynamic variation characteristic of the plasma sheath is critical for the vehicle’s communication. In this article, the effects of dynamic plasma sheath on electromagnetic wave propagation and the bit error rate (BER) of two typical modulation signals under an external magnetic field are investigated. First, the hybrid matrix method is used to calculate the transmission coefficients of right-handed circularly polarized (RHCP) waves with different magnetic fields and plasma electron density fluctuation. Then, the average BER of two typical modulations signals, namely M-ary phase-shift keying (MPSK) and noncoherent M-ary frequency shift keying modulation (NC-MFSK) is numerically simulated based on the magnetized plasma sheath channel response. The results show that the magnitude in dB scale and phase of the RHCP transmission coefficient follow Gaussian distribution when the probability density function of the electron density is a Gaussian distribution. The BER performance of binary phase-shift keying (BPSK) and NC-MFSK is relevant to the incident wave frequency, the plasma stopband, and the intensity of electron density variation. Owing to the insensitivity of phase jitter, the NC-8FSK has a better performance than BPSK, followed by NC-4FSK and NC-2FSK.

In this article, we propose an index modulation system suitable for optical communications, where the intensity of the light is modulated along the time, space and frequency dimensions, building a Frequency-Hopping Spatial Multi-Pulse Position Modulation (FH-SMPPM). We analyze its performance from the point of view of its efficiency in power and spectrum, and its implementation complexity and required receiver latency. We analyze its error probability in the case of the non-turbulent free-space optical (FSO) channel. We derive formulas for the average symbol and bit error probabilities, and the simulation results show that they are tight enough for a wide range of signal-to-noise ratios and system parameters. We compare FH-SMPPM with other proposed index modulated systems of the same nature, and we highlight its distinctive advantages, like the flexibility to build an appropriate waveform under different constraints and objectives. Moreover, FH-SMPPM shows to be better performing in BER/SER and/or offer advantages in efficiency with respect to those alternatives, thus offering the possibility to be adopted for a variety of contexts., 14 pages, 8 figures, accepted for publication at IEEE Transactions on Communications

A low-power and small chip-area multi-rate human body communication (HBC) discontinuous-phase FSK (DPFSK) transceiver applied for wearable devices is presented. The transceiver is implemented in UMC $0.18~\mu \text{m}$ CMOS process with a small chip area of only 0.46 mm2. DPFSK modulation is adopted to reduce the hardware complexity of the transceiver. In the receiver, a direct-conversion front-end is adopted to eliminate polarization voltage of the electrode-skin interface. A delay line (DL)-based variable phase shifter used in the demodulator of the receiver is proposed for accomplishing of multi-rate DPFSK demodulation. In the transmitter, a digital frequency interpolator is adopted for achieving multi-rate DPFSK transmission. At a data rate of 1 Mb/s, the receiver and the transmitter consume the power of 1.79 mW and $700~{\boldsymbol{\mu }}\text{W}$ , respectively. Therefore, energy consumption per received and transmitted bit are 1.79 nJ/bit and 0.7 nJ/bit, respectively.

Phase coherent, frequency hopping direct digital synthesizer (DDS) and Type-II phase locked loop (PLL) circuits are presented in this paper. The proposed approach eliminates the memory effects of prior frequency states in the phase (DDS) and fractional (PLL) accumulators by employing a master accumulator with a fixed increment and multiplying its output to generate the appropriate phase and fractional outputs. This approach allows for an arbitrary sequence of frequency hops, since it is not based on multiple simultaneous accumulators to store phase. We present phase coherent topologies for standard and parallelized DDS circuits, a fractional-N PLL and a multistage sigma-delta modulator (MASH)-111 fractional-N PLL, along with mathematical analysis showing phase coherency. We also present measured results of parallelized DDS and MASH-111 fractional-N PLL hardware.

This paper presents a detailed study of multiple access ultrawideband communications based on M-ary frequency-shift keying modulation of impulse-like carrier waveforms. The proposed signal model is described using expressions of duty cycle, energy, and correlation coefficient analytically derived and analyzed in terms of signal parameters. The frequency sets for coherent as well as non coherent detection utilized in narrow band communications are extended to impulse communications, and the resultant signals' correlation properties are investigated. Analytic expression of the frequency spectrum for continuous transmission is obtained, and a parametric study of the spectrum is carried out to analyze its properties. System performance analysis in terms of error probability curves is given for different signal model parameters. For single user communications, error probability curves for M-ary system are plotted using the union bound, while for multiple access communications, analytic expression of binary error probability in Rayleigh fading channel is given and plotted. The plots demonstrate the advantages of multiple access coding and signal design in improving system performance. Comparison between the bit error performance of impulse frequency shift keying, impulse phase shift keying, pulse position, and binary phase shift keying modulation schemes is presented too.

Power & signal multiplex transmission (P&SMT) is a technique that uses power electronic circuits for communication signal transmission. In this paper, a three-phase cascaded multilevel inverter-based P&S MT system is proposed. The proposed method can transmit communication signals without using a Controller Area Network bus, thereby reducing the wiring cost of the conventional electric vehicle (EV) communication system. The designed system can achieve motor speed regulation and battery balance discharging for EVs. With the combined pulse width modulation scheme and frequency shift keying method, both power and communication signals are transmitted successfully in a simulation model implemented in Matlab/Simulink. By evaluating the bit error rate of the transmitted signal, the maximum signal rate of the proposed system is determined as 600 bit/s.

In this research, the authors extract features from intermediate frequency band radar signals in the time-frequency domain for classification. The extracted features are classified via support vector machine and K-nearest neighbour classifiers. They show the accuracy of classification is above 99% for different classes of radar signals except for frequency shift keying signal with accuracy 83% in negative signal-to-noise ratio (SNR). To identify the radars with the same class, the classification accuracy is 91% for SNR between 5 to 15 dB and 64% in the worst case for SNR between -1 to 10 dB. The proposed method is compared with some methods based on the empirical mode decomposition (EMD), cumulant and Zhao Atlas Mark Distribution (ZAMD). The results show that the classification error in the proposed method is less than that of EMD method 55% in the best case and 9% in the worst case. The performance of the cumulant-based method is weaker than that of the proposed method in common designed scenarios becoming almost similar only in one scenario. The ZAMD-based method could only distinguish the signals with different modulations in high SNR while it is unable to classify the signals with the same modulation but different parameters.