Showing papers on "Demodulation published in 2018"
TL;DR: This paper derives the explicit input–output relation describing OTFS modulation and demodulation (mod/demod) and analyzes the cases of ideal pulse-shaping waveforms that satisfy the bi-orthogonality conditions and those which do not.
Abstract: The recently proposed orthogonal time–frequency–space (OTFS) modulation technique was shown to provide significant error performance advantages over orthogonal frequency division multiplexing (OFDM) over delay-Doppler channels. In this paper, we first derive the explicit input–output relation describing OTFS modulation and demodulation (mod/demod). We then analyze the cases of: 1) ideal pulse-shaping waveforms that satisfy the bi-orthogonality conditions and 2) rectangular waveforms which do not. We show that while only inter-Doppler interference (IDI) is present in the former case, additional inter-carrier interference (ICI) and inter-symbol interference (ISI) occur in the latter case. We next characterize the interferences and develop a novel low-complexity yet efficient message passing (MP) algorithm for joint interference cancellation (IC) and symbol detection. While ICI and ISI are eliminated through appropriate phase shifting, IDI can be mitigated by adapting the MP algorithm to account for only the largest interference terms. The MP algorithm can effectively compensate for a wide range of channel Doppler spreads. Our results indicate that OTFS using practical rectangular waveforms can achieve the performance of OTFS using ideal but non-realizable pulse-shaping waveforms. Finally, simulation results demonstrate the superior error performance gains of the proposed uncoded OTFS schemes over OFDM under various channel conditions.
539 citations
TL;DR: A new indicator, Combined Squared Envelope Spectrum, is employed to consider all the frequency bands with valuable diagnostic information and to improve the fault detectability of the Autogram, and a thresholding method is also proposed to enhance the quality of the frequency spectrum analysis.
224 citations
TL;DR: In this article, the authors present a discrete-time formulation of an orthogonal frequency division multiplexing-based OTFS system, where they argue against deployment of window functions at the transmitter in realistic scenarios and thus limit any sort of windowing to the receiver.
Abstract: Orthogonal time frequency space (OTFS) modulation is a 2-D signaling technique that has recently emerged in the literature to tackle the time-varying (TV) wireless channels. OTFS deploys the Doppler-delay plane to multiplex the transmit data where the time variations of the TV channel are integrated over time and hence the equivalent channel relating the input and output of the system boils down to a time-invariant one. This signaling technique can be implemented on the top of a given multicarrier waveform with the addition of precoding and post-processing units to the modulator and demodulator. In this letter, we present discrete-time formulation of an orthogonal frequency division multiplexing-based OTFS system. We argue against deployment of window functions at the OTFS transmitter in realistic scenarios and thus limit any sort of windowing to the receiver side. We study the channel impact in discrete-time providing deeper insights into OTFS systems. Moreover, our derivations lead to simplified modulator and demodulator structures that are far simpler than those in the literature.
109 citations
15 Apr 2018
TL;DR: This paper reformulate the OTFS input-output relation in the vector form by placing some null symbols in the delay-Doppler grid thereby exploiting the block circulant property of the channel matrix and proposing a low complexity iterative detector based on the MRC scheme.
Abstract: We elaborate on the recently proposed orthogonal time frequency space (OTFS) modulation technique, which provides significant advantages over orthogonal frequency division multiplexing (OFDM) in Doppler channels. We first derive the input-output relation describing OTFS modulation and demodulation (mod/demod) for delay-Doppler channels with arbitrary number of paths, with given delay and Doppler values. We then propose a low-complexity message passing (MP) detection algorithm, which is suitable for large-scale OTFS taking advantage of the inherent channel sparsity. Since the fractional Doppler paths (i.e., not exactly aligned with the Doppler taps) produce the inter Doppler interference (IDI), we adapt the MP detection algorithm to compensate for the effect of IDI in order to further improve performance. Simulations results illustrate the superior performance gains of OTFS over OFDM under various channel conditions.
103 citations
TL;DR: Two algorithms are proposed for such an uncoordinated scenario where a communication receiver is to operate in the presence of a number of radars, which poses the problem of estimating the active waveforms and the relevant parameters thereof, so as to cancel them prior to demodulation.
Abstract: Most existing approaches to coexisting communication/radar systems assume that the radar and communication systems are coordinated, i.e., they share information, such as relative position, transmitted waveforms, and channel state. In this paper, we consider an uncoordinated scenario where a communication receiver is to operate in the presence of a number of radars, of which only a subset may be active, which poses the problem of estimating the active waveforms and the relevant parameters thereof, so as to cancel them prior to demodulation. Two algorithms are proposed for such a joint waveform estimation/data demodulation problem, both exploiting sparsity of a proper representation of the interference and of the vector containing the errors of the data block, so as to implement an iterative joint interference removal/data demodulation process. The former algorithm is based on classical on-grid compressed sensing, whereas the latter forces an atomic norm (AN) constraint: In both cases the radar parameters and the communication demodulation errors can be estimated by solving a convex problem. We also propose a way to improve the efficiency of the AN-based algorithm. The performance of these algorithms are demonstrated through extensive simulations, taking into account a variety of conditions concerning both the interferers and the respective channel states.
101 citations
TL;DR: A direct signal demodulation method is proposed, in which, the LPF is removed to improve system stability and dynamic property and a novel magnetic polarity detection method is put forward based on the magnetic saturation, which has a high signal-to-noise ratio.
Abstract: In a permanent magnet synchronous motor (PMSM) drive system, high-frequency (HF) pulsating voltage signal injection has demonstrated high accuracy to estimate the initial rotor position. However, a conventional signal demodulation method may face the problems of long convergence time and limited system stability, owing to the low-pass filter (LPF) used in signal demodulation process. Thus, a direct signal demodulation method is proposed, in which, the LPF is removed to improve system stability and dynamic property. A direct demodulation collection is generated to extract the position deviation signal from estimated q -axis HF current. Recursive discrete Fourier transform is employed to calculate the amplitude of estimated d -axis HF current, thus an amplitude normalized technique is implemented to reduce the effects of HF signal and PMSM. Meanwhile, the stability and dynamic property are compared between the conventional and proposed method, with the aid of D-partition technique and amplitude–frequency characteristics diagram. Furthermore, a novel magnetic polarity detection method is put forward based on the magnetic saturation, which has a high signal-to-noise ratio. Finally, the experimental results on three PMSM drive systems prove that the proposed method is practicable and effective.
87 citations
TL;DR: A novel turbo-coded 16-ary orbital angular momentum - shift keying-free space optical (OAM-SK-FSO) communication system combining a convolutional neural network (CNN) based adaptive demodulator under strong atmospheric turbulence is proposed for the first time.
Abstract: In this paper, a novel turbo-coded 16-ary orbital angular momentum - shift keying-free space optical (OAM-SK-FSO) communication system combining a convolutional neural network (CNN) based adaptive demodulator under strong atmospheric turbulence is proposed for the first time. The feasibility of the scheme is verified by transmitting a 256-grayscale two-dimensional digital image. The bit error ratio (BER) performance of the system is investigated and the effect of different factors such as turbulence strength, propagation distance, code rate, length of random interleaver and length of bit interleaver is also taken into account. An advanced encoder/decoder structure and mapping scheme are applied to diminish the influence of CNN misclassification and reduce the BER effectively. With the optimal encoder/decoder structure and CNN model settings, the BER varies from 0 to 4.89×10−4 when the propagation distance increases from 200m to 1000m for a given turbulence strength Cn2 equals 5×10−14m−2/3. For a determined propagation distance equals 400m, the BER ranges from 0 to 4.01×10−4 when Cn2increases from 1×10−15m−2/3 to 4×10−13m−2/3. Our numerical simulations demonstrate that the proposed system can provide better BER performance under strong atmospheric turbulence and conditions when the classification ability of CNN is limited.
72 citations
TL;DR: The capability of the technique to quantify distributed dynamic phase change due to a generic external impact is experimentally demonstrated by measuring the phase change induced by a nonlinear actuator generating a 2 kHz perturbation at a distance of 1.5 km on a standard singlemode fiber with an SNR of ~24 dB.
Abstract: We propose and experimentally demonstrate a stable homodyne phase demodulation technique in a ϕ-OTDR using a double-pulse probe and a simple direct detection receiver. The technique uses selective phase modulation of one of a pair of pulses to generate a carrier for dynamic phase changes and involves an enhanced phase demodulation scheme suitable for distributed sensing by being robust against light intensity fluctuations, independent of the modulation depth, and convenient for analogue signal processing. The capability of the technique to quantify distributed dynamic phase change due to a generic external impact is experimentally demonstrated by measuring the phase change induced by a nonlinear actuator generating a 2 kHz perturbation at a distance of 1.5 km on a standard singlemode fiber with an SNR of ~24 dB. The demodulated nonlinear response is shown to have a spectrum consistent with one obtained using an FBG sensor and a commercial reading unit.
71 citations
TL;DR: In this article, a modulation signal bispectrum (MSB) based robust detector for bearing fault detection is proposed, which allows effective suppression of both stationary random noise and discrete aperiodic noise.
71 citations
TL;DR: A continuous wave Doppler radar, operating as a phase-locked-loop in phase demodulator configuration, is proposed and in vivo demonstrated for noncontact vital signs monitoring and exhibits a unique precision in tracking the phase modulation caused by human cardiopulmonary activity.
Abstract: A continuous wave Doppler radar, operating as a phase-locked-loop in phase demodulator configuration, is proposed and in vivo demonstrated for noncontact vital signs monitoring. The radar architecture exhibits a unique precision in tracking the phase modulation caused by human cardiopulmonary activity from which heartbeat and respiration can simultaneously be extracted. The single mixer architecture is immune to the null point and does not require small-angle approximation conditions, which distinguishes it from pre-existing other approaches. This enables the proposed radar to behave highly linear, with very precise detection of phase modulations induced by any kind of movement, independently from amplitude and speed. After simulations and technical tests to validate functionality and safety of the proposed architecture, a practical setup was demonstrated on human volunteers. Wavelet independent component analysis was applied to successfully retrieve respiratory and heart rate information from the radar baseband signal.
66 citations
TL;DR: An adaptive iterative generalized demodulation (AIGD) is proposed, which is highly adaptive to reveal the frequency contents and track their time variability of a signal, and provides an effective approach to nonstationary complex multi-component signal analysis.
TL;DR: A 320×240 back-illuminated Time-of-Flight CMOS image sensor with 10μm CAPD pixel structure maximizes the fill factor, allows for flexible transistor position and makes the light path independent of the metal layer.
Abstract: A $320\times 240$ back-illuminated (BI) time-of-flight CMOS image sensor with 10- $\mu \text{m}$ current-assisted photonic demodulator (CAPD) pixels has been developed. The BI pixel structure maximizes fill factor, allows for flexible transistor positioning, and makes the light path independent of the metal layers. The BI-CAPD pixel, which has relatively thinner substrate than that of front-illuminated CAPD, makes it possible to generate steeper electric-potential gradient in the vertical direction of the substrate, and results in 80% modulation contrast at 100-MHz modulation frequency. A higher modulation contrast contributes to suppress system power consumption as the sensor integration time for reaching specific signal-to-noise ratio is reduced. Alternatively, it contributes to improve depth accuracy when integration time is fixed.
TL;DR: In this paper, an atom-based receiver for AM and FM microwave communication with a 3-dB bandwidth in the baseband of $\sim$100~kHz that provides optical circuit-free field pickup, multi-band carrier capability, and inherently high field sensitivity was demonstrated.
Abstract: Radio reception relies on antennas for the collection of electromagnetic fields carrying information, and receiver elements for demodulation and retrieval of the transmitted information. Here we demonstrate an atom-based receiver for AM and FM microwave communication with a 3-dB bandwidth in the baseband of $\sim$100~kHz that provides optical circuit-free field pickup, multi-band carrier capability, and inherently high field sensitivity. The quantum receiver exploits field-sensitive cesium Rydberg vapors in a centimeter-sized glass cell, and quantum-optical readout of baseband signals modulated onto carriers with frequencies ranging over four octaves, from C-band to Q-band. Receiver bandwidth, dynamic range and sideband suppression are characterized, and acquisition of audio waveforms of human vocals demonstrated. The atomic radio receiver is a valuable receiver technology because it does not require antenna structures and is resilient against electromagnetic interference, while affording multi-band operation in a single compact receiving element.
02 Sep 2018
TL;DR: This paper explores speech demodulation-based features using Hilbert transform (HT) and Teager Energy Operator (TEO) for replay detection and proposes features, namely, HT-based Instantaneous Amplitude (IA) and Instantaneous Frequency (IF) Cosine Coefficients and Energy Separation Algorithm (ESA) based features.
Abstract: Replay attack presents a great threat to Automatic Speaker Verification (ASV) system. The speech can be modeled as amplitude and frequency modulated (AM-FM) signals. In this paper, we explore speech demodulation-based features using Hilbert transform (HT) and Teager Energy Operator (TEO) for replay detection. In particular, we propose features, namely, HT-based Instantaneous Amplitude (IA) and Instantaneous Frequency (IF) Cosine Coefficients (i.e., HT-IACC and HT-IFCC) and Energy Separation Algorithm (ESA)-based features (i.e., ESA-IACC and ESA-IFCC). For adapting instantaneous energy w.r.t given sampling frequency, ESA requires 3 samples whereas HT requires relatively large number of samples and thus, ESA gives high time resolution.The experiments were performed on ASV spoof 2017 Challenge database for replay spoof speech detection (SSD).The experimental results shows that ESA-based features gave lower EER. In addition, linearlyspaced Gabor filterbank gave lower EER than Butterworth filterbank. To explore possible complementary information using amplitude and frequency, we have used score-level fusion of IA and IF. With HT-based feature set, the score-level fusion gave EER of 5.24 % (dev) and 10.03 % (eval), whereas ESA-based feature set reduced the EER to 2.01 % (dev) and 9.64 % (eval).
16 Apr 2018
TL;DR: StripComm is proposed, interference-resilient CTC in coexisting environments that contains both presence and absence of packets in one symbol and strips the interference from the interested signal by exploiting the self-similarity of StripComm signals.
Abstract: Cross- Technology Communication (CTC) is an emerging technique to enable the direct communication among different wireless technologies. A main category of the existing proposals on CTC propose to modulate packets at the sender side, and demodulate them into 1 and 0 bits at the receiver side. The performance of those proposals is likely to degrade in a densely coexisting environment. Solely judged according to the received signal strength, a symbol 0 that is modulated as packet absence is generally indistinguishable from dynamic interference. In this paper, we propose StripComm, interference-resilient CTC in coexisting environments. A sender in StripComm adopts an interference-resilient coding scheme that contains both presence and absence of packets in one symbol. The receiver strips the interference from the interested signal by exploiting the self-similarity of StripComm signals. We prototype StripComm with commercial WiFi, ZigBee devices and a software radio platform. The theoretical and experimental evaluation demonstrate that StripComm offers a data rate up to 1.1K bps with a SER (Symbol Error Rate) lower than 0.01 and a data rate of 0.89K bps even against strong interference.
TL;DR: The experimental results show that the elliptical parameters of the quadrature components can be achieved precisely in real time and nanometer accuracy was realized in displacement measurements.
Abstract: A precision PGC demodulation for homodyne interferometer modulated with a combined sinusoidal and triangular signal is proposed Using a triangular signal as additional modulation, a continuous phase-shifted interference signal for ellipse fitting is generated whether the measured object is in static or moving state The real-time ellipse fitting and correction of the AC amplitudes and DC offsets of the quadrature components in PGC demodulation can be realized The merit of this modulation is that it can eliminate thoroughly the periodic nonlinearity resulting from the influences of light intensity disturbance, the drift of modulation depth, the carrier phase delay, and non-ideal performance of the low pass filters in the conversional PGC demodulation The principle and realization of the signal processing with the combined modulation signal are described in detail The experiments of accuracy and rate evaluations of ellipse fitting, nanometer, and millimeter displacement measurements were performed to verify the feasibility of the proposed demodulation The experimental results show that the elliptical parameters of the quadrature components can be achieved precisely in real time and nanometer accuracy was realized in displacement measurements
TL;DR: In this paper, the authors proposed a PGC demodulation scheme with the carrier phase delay compensation based on the basic PGC-Atan scheme, which provides the real-time carrier phasedelay compensation over the all possible phase delay range from 0° to 360° without using phase adjustments of the carrier signal.
Abstract: Phase generated carrier (PGC) demodulation schemes are widely used in fiber-optic interferometric sensors. All known PGC schemes use carrier signals to obtain in-phase and quadrature components from the interference signal. The unwanted phase delay between the reference carrier signal and the modulation signal in the interference signal might exist. This effect might lead to the incorrect measurement of the phase signal in the PGC scheme. In this paper, the original PGC demodulation scheme with the carrier phase delay compensation based on the basic PGC-Atan scheme is presented. The proposed scheme provides the real-time carrier phase delay compensation over the all possible phase delay range from 0° to 360° without using phase adjustments of the carrier signal. Theoretical analysis and mathematical modeling of the proposed scheme and the basic PGC-Atan demodulation scheme were performed to compare their performance under the same conditions. The proposed scheme, the basic PGC-Atan demodulation scheme, and the PGC synchronous carrier restoration scheme were implemented in the FPGA-based electronic processing circuit of the single interferometric fiber Bragg grating sensor. Experimental results showed that the proposed scheme provides carrier phase delay compensation without using phase adjustments of the carrier signal.
TL;DR: This work demonstrates and analyzes the performance of the VLC link using CMOS camera for different LED luminaires for the first time in this knowledge and proposes and demonstrates to use contrast limited adaptive histogram equalization to extend the transmission distance and mitigate the influence of the background noise.
TL;DR: A new system for the detection of human respiration behind obstacles using impulse ultra-wideband (UWB) radar is presented and a frequency accumulation (FA) method is proposed to suppress mixed products of the heartbeat and respiration signals and spurious respiration signal harmonics.
Abstract: This paper presents a new system for the detection of human respiration behind obstacles using impulse ultra-wideband (UWB) radar. In complex environments, low signal-to-noise ratios (SNRs) as they can result in significant errors in the respiration, heartbeat frequency, and range estimates. To improve the performance, the complex signal demodulation (CSD) technique is extended by employing the signal logarithm and derivative. A frequency accumulation (FA) method is proposed to suppress mixed products of the heartbeat and respiration signals and spurious respiration signal harmonics. The respiration frequency is estimated using the phase variations in the received signal, and a discrete short-time Fourier transform (DSFT) is used to estimate the range. The performance of the proposed system is evaluated along with that of several well-known techniques in the literature.
TL;DR: The proposed demodulator has a potential to be integrated with the AIA in a multilayered printed-circuit board for the realization of a compact wearable self-injection-locked radar sensor.
Abstract: This paper presents a new wearable self-injection-locked sensor with a self-oscillating active integrated antenna (AIA) and a differentiator-based envelope detector for detecting vital signs from the chest wall and the wrist. The AIA is designed to radiate the electromagnetic signal and sense the scattered-back signal, which is phase modulated by the physiological movement of the human chest and wrist. The received self-injection signal from the subject under test locks the AIA and simultaneously introduces a variation in the output magnitude (amplitude modulation) and a shift in the oscillation frequency (frequency modulation). In other words, the output signal of the AIA is a frequency-modulated carrier with an amplitude-varying envelope. To acquire the vital signs from the modulated signal, an envelope detector is integrated with a microwave differentiator to form a differentiator-based envelope detector, which demodulates signal. The heartbeat and wrist pulse rates measured by the proposed sensor agree well with the results acquired by a finger pulse oximeter. Since the proposed demodulator has a simple architecture, it has a potential to be integrated with the AIA in a multilayered printed-circuit board for the realization of a compact wearable self-injection-locked radar sensor.
TL;DR: Results demonstrate that the proposed FrFT waveform presents performance close to a LFM pulse in terms of probability of detection and probability of false alarm, in exchange for slightly worse range and Doppler resolution, to maintain comparable communication performance with respect to the OFDM waveform.
TL;DR: The results obtained with an 80 kW interior (I)-PMSM intended for EV propulsion show that the proposed algorithms allow a better machine control performance in terms of a smaller torque ripple generation and a faster current control loop.
Abstract: This paper investigates the performance of two novel half-switching frequency signal injection (HSFSI) demodulation algorithms for encoderless field-oriented control (FOC) of permanent magnet synchronous machines (PMSMs) intended for electric vehicle (EV) propulsion. The proposed rotating and pulsating HSFSI demodulation algorithms do not require voltage measurements or approximations for estimating the rotor position angle. The proposed HSFSI algorithms have been quantitatively and qualitatively compared by MATLAB-SimPowerSystems simulations, as well as experimentally against the two equivalent classical high-frequency signal injection (HFSI) approaches. A 2.5 kW PMSM with radially inset rotor magnets has been used for experimentally evaluating and validating the performance analysis and the comparison of the four algorithms fully implemented to work in real-time on a TI C2000 digital signal processor (DSP). The results obtained with an 80 kW interior (I)-PMSM intended for EV propulsion also show that the proposed algorithms allow a better machine control performance in terms of a smaller torque ripple generation and a faster current control loop.
TL;DR: In this paper, the authors proposed a method for spatially distributed temperature measurement with Chirped Fiber Bragg Grating (CFBG) fiber-optic sensors, which is based on an iterative optimization that aims at minimizing the mismatch between the measured CFBG spectrum and a CFBG model perturbed by a temperature gradient.
TL;DR: In this article, a photonics-based Terahertz wireless communication system for the transmission of uncompressed 4K video feed that is built using all commercially available system components is presented.
Abstract: Taming the Terahertz waves (100 GHz–10 THz) is considered the next frontier in wireless communications. While components for the ultra-high bandwidth Terahertz wireless communications were in rapid development over the past several years, however, their commercial availability is still lacking. Nevertheless, as we demonstrate in this paper, due to recent advances in the microwave and infrared photonics hardware, it is now possible to assemble a high-performance hybrid THz communication system for real-life applications. As an example, in this paper, we present the design and performance evaluation of the photonics-based Terahertz wireless communication system for the transmission of uncompressed 4K video feed that is built using all commercially available system components. In particular, two independent tunable lasers operating in the infrared C-band are used as a source for generating the Terahertz carrier wave using frequency difference generation in a photomixer. One of the IR laser beams carries the data which is intensity modulated using the LiNbO3 electro-optic modulator. A zero bias Schottky diode is used as the detector and demodulator of the data stream followed by the high-gain and low-noise pre-amplifier. The Terahertz carrier frequency is fixed at 138 GHz and the system is characterized by measuring the bit error rate for the pseudo random bit sequences at 5.5 Gbps. By optimizing the link geometry and decision parameters, an error-free ( $\text {BER} ) transmission at a link distance of 1 m is achieved. Finally, we detail the integration of a professional 4K camera into the THz communication link and demonstrate live streaming of the uncompressed HD and 4K video followed by the analysis of link quality.
TL;DR: A new optimal demodulation subband selection method (ODSSM) for fault diagnosis of planetary gearbox is proposed that can detect the gear fault in both simulation signals and experiment signals, and achieves improved demodulated performance than the other two methods.
TL;DR: Experimental results show that the nonlinear error of phase demodulation reduced to less than ± 1° with real-time normalization, and nanometer displacement measurement is realized.
Abstract: In order to reduce the nonlinearity caused by an error of phase modulation depth, carrier phase delay and non-ideal performance of the low pass filters in the sinusoidal phase modulating interferometer (SPMI), a modified EOM-based SPMI is proposed in this paper to realize real-time normalization of the quadrature components for the arctangent approach of phase generated carrier (PGC-Arctan) demodulation. To verify the effectiveness of the real-time normalization technique, a fixed-phase-difference detection method is presented to evaluate the periodic nonlinearity in real time. The modified EOM-based SPMI is consisted of a monitor interferometer and a probe interferometer. The two interferometers share a reference corner cube, which is mounted on a slowly moving stage, thus periodic interference signals are generated for real-time normalization of the quadrature components in PGC demodulation. Subtracting the demodulated phase of the monitor interferometer from the phase of the probe interferometer, the phase to be measured can be obtained. The fixed-phase-difference detection method is realized by detecting an interference signal with two photodetectors, which are placed at an interval of quarter fringe, and the variation of the fixed-phase-difference can reflect the nonlinear error in PGC demodulation. Experiments of real-time normalization, nonlinear error evaluation of PGC demodulation, and displacement measurement were implemented to demonstrate the effectiveness of the proposed method. Experimental results show that the nonlinear error of phase demodulation reduced to less than ± 1° with real-time normalization, and nanometer displacement measurement is realized.
TL;DR: This paper proposes a novel magnitude ratio modulation, utilizing two-tone signals, and describes the IRR’s to show the symbol diagram considering the influence of nonlinearity of the circuit and its limitation on modulation.
Abstract: Using the wireless signals to extend the sensors’ battery life in a network or make them battery-free becomes prominent with the high number of sensors and circuits that are desired in the Internet of Things. Decreasing the power consumption of the sensors is also a valid point. Colocating information signals and power signals at the same frequency further decreases the size of the sensor and the used bandwidth. To fulfill all the mentioned requirements, we used an integrated rectifier–receiver (IRR) to decrease the power consumption and fully utilize all the received signals without splitting signals. We propose a novel magnitude ratio modulation, utilizing two-tone signals. We extend this paper by introducing the ratio phase modulation (PM) and, finally, merging the ratio amplitude–PM. The main advantage of the proposed modulations is the degree of freedom that it is possible to deliver a constant dc power to the sensor even with symbol variations, that is not possible by using M-ASK or ON–OFF keying modulations. If the channel is narrowband, the demodulation of our proposed modulation is possible even by not knowing the channel’s attenuation. Since the IRR is highly nonlinear and this feature is used to fulfill our goals to receive power and information, we characterize the IRR’s to show the symbol diagram considering the influence of nonlinearity of the circuit and its limitation on modulation. We report the power conversion efficiency to prove that the IRR is harvesting RF energy well with the proposed modulation.
TL;DR: This paper designs two classes of energy-efficient time-dimensional constellations that are addition-unique and have remarkable performance gains over the currently available zero-forcing, minimum mean square error and time-division multiple access methods for the multiuser multi-input-single-output VLC broadcast systems.
Abstract: In this paper, we investigate the design of energy-efficient space-time modulation for peak-limited MISO broadcast visible light communication (VLC) systems by cooperatively managing the non-negative multiuser interference. We first characterize a constellation-optimal structure that maximizes the worst-case minimum Euclidean distance of all users for a general space-time modulation design. It turns out that the optimal space-time constellation can be constructed via the spatial repetition of the optimal multidimensional constellation in time dimension over ideal additive white Gaussian noise channels. Then, based on this structure, we specifically design two classes of energy-efficient time-dimensional constellations: 1) for the integer overall bit rate, we design the optimal linear precoded block design, which admits fast maximum likelihood demodulation algorithms. 2) for the non-integer case, we propose a nonlinear precoding scheme called block coded modulation , which sums the code word sets of the optimal linear design and a block channel code. In addition, we show that these two classes of designs are addition-unique, thus, generating an energy-efficient mapping from users’ data to the transmitted constellations. This property enables the efficient demodulation of the sum signal from a noisy received signal as well as the decoding of individual signal from the estimated sum signal. Extensive computer simulations indicate that our addition-unique designs have remarkable performance gains over the currently available zero-forcing, minimum mean square error and time-division multiple access methods for the multiuser multi-input-single-output VLC broadcast systems.
01 Jan 2018
TL;DR: This work shows how much the DCNN would provide substantial benefit as the demodulator of a Rayleigh-faded wireless data signal, and a comparative study has been applied between DCNN and other machine learning classifiers.
Abstract: This paper demonstrates exceptional performance of approximately 10.0 dB learning-based gain using the Deep Convolutional Neural Network (DCNN) for demodulation of a Rayleigh-faded wireless data signal. We simulate FSK demodulation over an AWGN Rayleigh fading channel with average signal to noise ratios (SNR) from 10 dB to 20 dB. The most recent and accurate classifier is the Deep Convolutional Neural Network (DCNN) which resulted in the lowest error bit probabilities between 0.00128 to 0.00019 for the range of SNRs. A comparative study has been applied between DCNN and other machine learning classifiers such as Support Vector Machine (SVM), Linear Discriminant Analysis (LDA), Multi-Layer Perceptron (MLP) which give bit error probabilities between 0.021 to 0.002, and Quadratic Discriminant Analysis (QDA) which gives bit error probabilities between 0.027 to 0.003. Frequency-shift keying (FSK) demodulation using matched filtering showed bit error probabilities between 0.025 to 0.0025. We also discuss the complexity issues with the DCNN regarding decoding rates and training set sizes. This work shows how much the DCNN would provide substantial benefit as the demodulator.
TL;DR: Since the sensing and demodulation are implemented at the same time, the complexity for detection reduces significantly compared with traditional RF/microwave sensing techniques which need complicated frequency spectrum monitoring equipment.
Abstract: This paper presents a fully combined sensor-antenna transmitter system for sensing relative permittivity of material at microwave frequencies The transmit (Tx) antenna senses the relative permittivity of specimen and loads the radio frequency (RF) oscillator which translates the relative permittivity to the operational frequency of the carrier signal At the same time, independent data, which can be the Radio Frequency Identification (RFID) information, are ON–OFF keying modulated over the carrier At the receiver, a demodulator system extracts the data stream as well as recovers the carrier frequency using a zero-crossing detector Therefore, the relative permittivity of the sample can be obtained from the extracted frequency shift as a digital number As all the sensing elements in the proposed structure are passive, the sensor does not increase the power consumption of the system The sensor-transceiver capability at low powers makes it ideal for sensor nodes in the Internet of Things applications Since the sensing and demodulation are implemented at the same time, the complexity for detection reduces significantly compared with traditional RF/microwave sensing techniques which need complicated frequency spectrum monitoring equipment The output of the system is a digital number correlated to the dielectric constant of the specimen and the independent data stream for communication The proposed sensor node is fabricated at the 245-GHz ISM band as an evaluation and the measurement results with some known samples are presented