Impulse Radio Ultra-wideband Signals Research Articles

Design of Optical-Wireless IR-UWBoF Systems with Spectral Line Suppression Capabilities

Impulse-Radio Ultra-Wide Band (IR-UWB) over Fiber (IR-UWBoF) has been proposed to interconnect IR-UWB-based deployments separated by hundreds of meters or even kilometers. IR-UWB transmissions must comply with spectral masks provided by radio spectrum regulatory agencies. The maximum transmit power of an IR-UWB signal is adversely affected by the presence of spectral lines in its Power Spectral Density (PSD). Thus, it is desirable that the PSD of signals generated by IR-UWBoF systems does not show spectral lines. Previous works have shown the feasibility of deploying of optical-wireless IR-UWBoF systems. However, most of these proposals report PSDs showing spectral lines. To the best of our knowledge, spectral line suppression has not been previously studied for optical-wireless IR-UWBoF systems. This work shows the design and implementation of optical-wireless IR-UWBoF systems generating signals with Spectral Line-Free (SLF) PSDs. The proposal considers the use the use of a specifically designed convolutional code combined with Binary Phase Shift Keying (BPSK) or Quaternary Biorthogonal Pulse Position Modulation (Q-BOPPM) to provide a SLF PSD in IR-UWBoF systems. A testbed consisting of 30 km of single-mode optical fiber (SMF) concatenated to a 20 cm wireless link was physically implemented. The results show that a SLF PSD is achieved for both the optical and the wireless transmissions, even when the binary data source feeding the system is not perfectly random.

Respiration Based Non-Invasive Approach for Emotion Recognition Using Impulse Radio Ultra Wide Band Radar and Machine Learning.

Emotion recognition gained increasingly prominent attraction from a multitude of fields recently due to their wide use in human-computer interaction interface, therapy, and advanced robotics, etc. Human speech, gestures, facial expressions, and physiological signals can be used to recognize different emotions. Despite the discriminating properties to recognize emotions, the first three methods have been regarded as ineffective as the probability of human’s voluntary and involuntary concealing the real emotions can not be ignored. Physiological signals, on the other hand, are capable of providing more objective, and reliable emotion recognition. Based on physiological signals, several methods have been introduced for emotion recognition, yet, predominantly such approaches are invasive involving the placement of on-body sensors. The efficacy and accuracy of these approaches are hindered by the sensor malfunctioning and erroneous data due to human limbs movement. This study presents a non-invasive approach where machine learning complements the impulse radio ultra-wideband (IR-UWB) signals for emotion recognition. First, the feasibility of using IR-UWB for emotion recognition is analyzed followed by determining the state of emotions into happiness, disgust, and fear. These emotions are triggered using carefully selected video clips to human subjects involving both males and females. The convincing evidence that different breathing patterns are linked with different emotions has been leveraged to discriminate between different emotions. Chest movement of thirty-five subjects is obtained using IR-UWB radar while watching the video clips in solitude. Extensive signal processing is applied to the obtained chest movement signals to estimate respiration rate per minute (RPM). The RPM estimated by the algorithm is validated by repeated measurements by a commercially available Pulse Oximeter. A dataset is maintained comprising gender, RPM, age, and associated emotions which are further used with several machine learning algorithms for automatic recognition of human emotions. Experiments reveal that IR-UWB possesses the potential to differentiate between different human emotions with a decent accuracy of 76% without placing any on-body sensors. Separate analysis for male and female participants reveals that males experience high arousal for happiness while females experience intense fear emotions. For disgust emotion, no large difference is found for male and female participants. To the best of the authors’ knowledge, this study presents the first non-invasive approach using the IR-UWB radar for emotion recognition.

Attention-Based LSTM for Non-Contact Sleep Stage Classification Using IR-UWB Radar.

Manual scoring of sleep stages from polysomnography (PSG) records is essential to understand the sleep quality and architecture. Since the PSG requires specialized personnel, a lab environment, and uncomfortable sensors, non-contact sleep staging methods based on machine learning techniques have been investigated over the past years. In this study, we propose an attention-based bidirectional long short-term memory (Attention Bi-LSTM) model for automatic sleep stage scoring using an impulse-radio ultra-wideband (IR-UWB) radar which can remotely detect vital signs. Sixty-five young (30.0 ± 8.6 yrs.) and healthy volunteers underwent nocturnal PSG and IR-UWB radar measurement simultaneously; From 51 recordings, 26 were used for training, 8 for validation, and 17 for testing. Sixteen features including movement-, respiration-, and heart rate variability-related indices were extracted from the raw IR-UWB signals in each 30-s epoch. Sleep stage classification performances of Attention Bi-LSTM model with optimized hyperparameters were evaluated and compared with those of conventional LSTM networks for same test dataset. In the results, we achieved an accuracy of 82.6 ± 6.7% and a Cohen's kappa coefficient of 0.73 ± 0.11 in the classification of wake stage, REM sleep, light (N1+N2) sleep, and deep (N3) sleep which is significantly higher than the conventional LSTM networks (p < 0.01). Moreover, the classification performances were higher than those reported in comparative studies, demonstrating the effectiveness of the attention mechanism coupled with bi-LSTM networks for the sleep staging using cardiorespiratory signals.

An Optimized IR-UWB Communication System with Interference Reduction on a Narrowband System Using Genetic Algorithm

This paper proposed a new impulse radio ultra wideband (IR-UWB) signal to reduce interference on narrowband systems at high usage 5.2 GHz frequency. The combination of 4th and 5th order derivatives of Gaussian pulses were employed to generate the signal so that satisfy the US Federal Communications Commission (FCC) mask. The genetic algorithm technique was used to find the pulse optimized parameters. In this paper, spectrum was optimized by changing the shape factor (sigma) and amplitude of Gaussian pulses so that the transmitted power spectrum density was minimized at a frequency of 5.2 GHz and maximized at the other frequencies from 3.1 to 10.6 GHz according to the FCC mask. The signal was applied in an IR-UWB transceiver system with binary-phase shift keying modulation. The IR-UWB waveform is generated by a programmable digital to analog based circuit. The proposed system was compared with conventional IR-UWB systems at the same condition. The simulation results in multipath channel showed that the proposed system not only reduced interference with the narrowband system, but also this was robust against narrowband interference at 5.2 GHz frequency.

Improvement of the Angle of Arrival Measurement Accuracy for Indoor UWB Localization

This paper shows that the accuracy of azimuth angle measurement for an interferometric localization system used to locate tags in its Line-of-Sight (LoS) can be improved by exploiting Impulse Radio-Ultra WideBand (IR-UWB) signals and without increasing the frequency bandwidth. This solution uses a Phase Correlation (PC) method, initially applied for Continuous Wave (CW) signals, adapted for Ultra WideBand (UWB) pulse signals. The obtained results are compared to those computed by a classical Energy Detection (ED) method where it becomes impossible to estimate azimuth angles for tag positions close to the orthogonal centered axis of the localization system baseline.

A Fully Configurable SoC-Based IR-UWB Platform for Data Acquisition and Algorithm Testing

Research and development of algorithms for processing impulse radio ultrawideband signals is a trending issue within remote sensing applications, personal area networks, and RF imaging among other areas. We have designed an SoC-based platform, conceived for scientific experimentation, with a fully modular and configurable design. Built with off-the-shelf components, our design achieves a configurable UWB-capable sampling rate through an equivalent-time sampling scheme. In this letter, we introduce the system architecture, its main interfaces, and the rationale behind each module implementation.

Image Reconstruction of Moving Objects Using Multiple IR-UWB Radar Signals

We propose an image reconstruction method to detect moving objects using multiple impulse radio ultra-wideband signals. In contrast with conventional methods, the proposed approach first reconstructs an image of changes of reflected ultra-wideband signals in the 2D domain, and then detects moving objects using the reconstructed 2D image. We believe that the proposed method is useful because not only it is based on effective 2D modeling of moving objects, but also it incorporates a priori information about the moving object images. We verified experimentally that the proposed method provided improved performance compared with the existing methods.

Dual Notched Band Quad-Element MIMO Antenna With Multitone Interference Suppression for IR-UWB Wireless Applications

Ultrawideband (UWB) signals are extremely power limited due to the severe power spectral density constraints obligated by the Federal Communications Committee. Therefore, the design of radiation efficient antennas for UWB signaling is a challenging step in the design and development of impulse radio UWB (IR-UWB) communication systems, especially when these signals coexist with previously standardized narrowband (NB) wireless services. In this paper, a dual-band-notched quad-element UWB multiple-input multiple-output (MIMO) antenna design is presented. The proposed design is capable of suppressing NB interference (NBI). The NBI suppression capability of the proposed design is tested both experimentally and through simulations. Moreover, the experimentally measured spectral characteristics of the proposed design are employed in simulating the bit error rate (BER) performance of IR-UWB systems, considering the biphase modulation (BPM) scheme. Both experimental and simulation results show that the proposed design is capable of improving the BER performance of BPM-modulated IR-UWB systems in an NBI environment by suppressing the NBI signals located at six different frequencies within the bandwidth of the two band notches of the proposed design, while introducing a negligible distortion to the IR-UWB signaling waveforms.

Photonic generation and transmission of on–off keying ultra-wideband impulse radio signals over a fiber link utilizing a delay interferometer and a semiconductor optical amplifier

Photonic generation and transmission of on–off keying ultra-wideband impulse radio signals over a fiber link utilizing a delay interferometer and a semiconductor optical amplifier

An Efficient Method of Power Spectral Density Estimation for On-Chip IR-UWB Transmitter Self-Calibration

In ultra-wideband impulse radio communications, process, voltage, and temperature variations may impact the operation of emitters by modifying the emitted power spectral density. In order to compensate the impact of such variations and to respect the spectral emission masks, self-calibration systems able to estimate the output power spectral density have to be integrated in ultra-wideband impulse radio transmitters. In this paper, a new power spectral density estimation method for ultra-wideband impulse radio signals is presented. Unlike the discrete Fourier transform classically used to estimate the power spectral density, the proposed method, which is based on the measurement of the time varying envelope and instantaneous frequency of the emitted pulse, preserves a link between the time and the frequency domain thanks to a piece-wise approximation of these waveforms. This time-to-frequency link enables a straightforward pulse shape control by using simple control methods and allows to comply with spectral masks required by ultra-wideband communication regulations and standards such as the IEEE 802.15.4a. Thus, both envelope and instantaneous frequency extraction techniques are introduced for acquisition of these time domain waveforms in ultra-wideband impulse radio domain. The proposed techniques are validated and allow to consider future hardware implementation in order to build on-chip calibration systems for ultra-wideband transmitters.

Joint Estimation of TOA and PPM Symbols Using Sub-Nyquist Sampled IR-UWB Signal

Impulse radio ultra wideband (UWB) signals are used in various applications which require joint localization and communication. Due to the large bandwidth of the UWB signal, the estimation of time of arrival (TOA) and data symbols requires high sampling rates. This letter describes a sub-Nyquist rate receiver, which can jointly estimate TOA and data symbols. We first represent the received UWB signal in a new domain in which it is sparse. Then, we design physical layer waveforms and estimation algorithms to exploit this sparsity for joint estimation of TOA and pulse position modulation data symbols. The performance of the receiver is compared against the maximum likelihood (ML)-based receiver using an IEEE 802.15.4a CM1 line of sight UWB channel model. The proposed algorithm yields performance similar to the ML-based algorithms with only a fraction of sampling rate at high SNRs (> 25 dB).

Joint Multiple Symbol Differential Detection and Channel Decoding for Noncoherent UWB Impulse Radio by Belief Propagation

This paper proposes a belief propagation (BP) message passing algorithm-based joint multiple symbol differential detection (MSDD) and channel decoding scheme for noncoherent differential ultra-wideband impulse radio (UWB-IR) systems. MSDD is an effective means to improving the performance of noncoherent differential UWB-IR systems. To optimize the overall detection and decoding performance, this paper proposes a novel soft-in soft-out (SISO) MSDD scheme for noncoherent differential UWB-IR. We first propose a new sampling mechanism for the noncoherent auto-correlation receiver to sample the received UWB-IR signal. The proposed sampling mechanism can exploit the dependences (imposed by the differential modulation) among data symbols throughout the whole packet. The signal probabilistic model has a hidden Markov chain structure. We use a factor graph to represent this hidden Markov chain. Then, we apply BP message passing algorithm on the factor graph to develop an SISO MSDD scheme, which is easy to integrate with SISO channel decoding to form a joint MSDD and channel decoding scheme. Performance results of bit error rate simulations and EXIT chart analyses indicate the performance advantages of our scheme over the previous MSDD scheme.

Frequency Extended-MUSIC Method for DOA Estimation in Indoor IR-UWB Environment

In recent years, many researchers have been developed in order to ensure an accurate localization. So many techniques have been used the direction of arrival to estimate and track of IR-UWB signals. In this study, we propose a new direction of arrival estimation method for impulse radio UWB signals. This technique based on Extended-Music algorithm. The proposed method has high performances in the multipath channels. Simulation results show that it has more accuracy then others high resolution algorithms, moreover, It is compared the performance corresponding to the Cramer-Rae bound (CRB).

Impulse radio ultra wideband wireless transmission of dopamine concentration levels recorded by fast-scan cyclic voltammetry.

This paper demonstrates the feasibility of utilizing impulse radio ultra wideband (IR-UWB) signaling technique for reliable, wireless transmission of dopamine concentration levels recorded by fast-scan cyclic voltammetry (FSCV) at a carbon-fiber microelectrode (CFM) to address the problem of elevated data rates in high-channel-count neurochemical monitoring. Utilizing an FSCV-sensing chip fabricated in AMS 0.35μm 2P/4M CMOS, a 3-5-GHz, IR-UWB transceiver (TRX) chip fabricated in TSMC 90nm 1P/9M RF CMOS, and two off-chip, miniature, UWB antennae, wireless transfer of pseudo-random binary sequence (PRBS) data at 50Mbps over a distance of <;1m is first shown with bit-error rates (BER) <; 10(-3). Further, IR-UWB wireless transmission of dopamine concentration levels prerecorded with FSCV at a CFM during flow injection analysis (FIA) is also demonstrated with transmitter (TX) power dissipation of only ~4.4μW from 1.2V, representing two orders of magnitude reduction in TX power consumption compared to that of a conventional frequency-shift-keyed (FSK) link operating at ~433MHz.

Nonparametric TOA estimators for low-resolution IR-UWB digital receiver

Nonparametric time-of-arrival (TOA) estimators for impulse radio ultra-wideband (IR-UWB) signals are proposed. Non-parametric detection is obviously useful in situations where detailed information about the statistics of the noise is unavailable or not accurate. Such TOA estimators are obtained based on conditional statistical tests with only a symmetry distribution assumption on the noise probability density function. The nonparametric estimators are attractive choices for low-resolution IR-UWB digital receivers which can be implemented by fast comparators or high sampling rate low resolution analog-to-digital converters (ADCs), in place of high sampling rate high resolution ADCs which may not be available in practice. Simulation results demonstrate that nonparametric TOA estimators provide more effective and robust performance than typical energy detection (ED) based estimators.

Photonic envelope detection and fiber transmission of 24 GHz IR-UWB signal based on phase modulation

A novel scheme for photonic envelope detection and fiber transmission of 24 GHz impulse radio ultra-wideband (IRUWB) signal is proposed based on phase modulator (PM). In the system, an optics assisted envelope detection unit (OAEDU) is used for filtering one of the first sidebands at the output of PM, then this narrow band optical signal transfers over single-mode fiber (SMF), and the envelope of 24 GHz IR-UWB signal is obtained after photodetection (PD) and low pass filter (LPF). The numerical simulation results show that the combination of PM and OAEDU can alleviate the fiber chromatic dispersion (CD) effectively. The proposed system may provide a simple and cost-effective solution for IR-UWB receiver.

Joint Ranging and Clock Parameter Estimation by Wireless Round Trip Time Measurements

In this paper we develop a new technique for estimating fine clock errors and range between two nodes simultaneously by two-way time-of-arrival measurements us- ing impulse-radio ultra-wideband signals. Estimators for clock parameters and the range are proposed that are robust with respect to outliers. They are analyzed numerically and by means of experimental measurement campaigns. The technique and derived estimators achieve accuracies below 1Hz for frequency estimation, below 1 ns for phase estimation and 20 cm for range estimation, at 4m distance using 100MHz clocks at both nodes. Therefore, we show that the proposed joint approach is practical and can simultaneously provide clock synchronization and positioning in an experimental system.

Transmission Performance Investigation of IR-UWB Signals over Existing optical fiber Transmission link

Recently there is increasing interest in using optical fiber links to distribute impulse radio-ultrawideband (IR-UWB) signals in order to increase the coverage area. This paper investigates the transmission performance of these signals over existing fiber links and addresses the possibility of increasing the coverage area beyond 30 km.The transmission link consists of a single- mode fiber, dispersion compensating fiber (DCF) and, optical amplifiers. Simulation results are presented using Optisystem (version 13.0) software package for both Gaussian monocycle and 5th-order derivative Gaussian systems, each operating with ON-OFF keying (OOK) and biphase modulation (BPM) formats. The results reveal that extending the coverage area for 625 Mb/s UWB signal toward 100 km is possible for the UWB signals and modulation formats adopted in this study.

A cross-layer energy efficiency optimization model for WBAN using IR-UWB transceivers

An energy efficiency optimization model for the IEEE 802.15.6 standard based wireless body area network is described in this paper. Cross-layer approach has been used here by focusing on physical (PHY) and medium access control (MAC) layers taking into account relevant characteristics therein. Studied PHY is based on impulse radio ultra wideband (IR-UWB) signaling with mandatory on---off keying modulation and non-coherent energy detection receiver. The analyzed MAC protocol is slotted Aloha which is used in the contention based mode of the IEEE 802.15.6 std. using IR-UWB PHY. The proposed model can be used to compare the energy efficiency of uncoded and coded transmissions using different Bose---Chaudhuri---Hocquenghem code rates. The model enables joint code rate and packet length optimization in AWGN channel when using the path loss model for hospital scenario, defined by the IEEE P802.15 working group. Results clearly show the most energy efficient code rate and packet length as a function of distance.

Narrow-Band Interference Suppression in Impulse-Radio Ultrawideband Systems

For impulse-radio ultrawideband (IR-UWB) communications, pulse overlap often occurs in indoor dense multipath environments, where the time separation between adjacent received multipaths is typically less than one pulsewidth. Moreover, due to its low power spectral density (PSD) and its overlay usage model, the IR-UWB signal is also vulnerable to narrow-band interference (NBI) of a high power level. Taking the effect of pulse overlap into account, this paper presents an optimal prerake/postrake UWB transceiver design to counteract NBI. The prerake/postrake uses rake structures at both the transmitter and the receiver. The optimum weights for the prerake and postrake are derived by maximizing the signal-to-inference-plus-noise ratio (SINR). Furthermore, an adaptive scheme is proposed to achieve the optimal solution iteratively. Simulations show that the proposed prerake/postrake and the adaptive scheme can significantly eliminate the adverse effect of NBI and thus perform well even in the presence of severe NBI.