Presence Of Interfering Signals Research Articles

Real-time classification for Φ-OTDR vibration events in the case of small sample size datasets

Efficient classification of vibration signals detected by phase-sensitive optical time domain reflectometer (Φ-OTDR) based on small samples is an effective method to reduce the false alarm rate without GPU or large data sets. This paper proposes a fiber optic system vibration event recognition method based on a combination of image segmentation pre-processing, texture, statistical, morphological feature extraction, and weighted support vector machine (WSVM), which can effectively classify-five types of vibration events in high-speed railway perimeter intrusion detection with small sample data and no parallel processing units. Erosion and dilation operations are applied to vibration signal image feature enhancement in image pre-processing. The vibration signal region and background are separated by the maximum inter-class variance method, then 35 features of the vibration signal region are calculated and finally employed to construct a WSVM. Experiments show that the method achieves 99 FPS and 98.8% accuracy on the test set with 330 vibration images as the training set to build the model without GPU and in the presence of interference signals. It provides a generalized Φ-OTDR vibration event recognition method for small samples.

Online Own Voice Detection for a Multi-Channel Multi-Sensor In-Ear Device

Voice activity detection (VAD) aims for detecting the presence of speech in a given input signal, and is often the first step in voice -based applications such as speech communication systems. In the context of personal devices, own voice detection (OVD) is a sub-task of VAD, since it targets speech detection of the person wearing the device, while ignoring other speakers in the presence of interference signals. This article first summarizes recent single and multi-microphone, multi-sensor, and hearing aids related VAD techniques. Then, a wearable in-ear device equipped with multiple microphones and an accelerometer is investigated for the OVD task using a neural network with input embedding and long short-term memory (LSTM) layers. The device picks up the user’s speech signal through air as well as vibrations through the body. However, besides external sounds the device is sensitive to user’s own non-speech vocal noises (e.g. coughing, yawning, etc.) and movement noise caused by physical activities. A signal mixing model is proposed to produce databases of noisy observations used for training and testing the frame-by-frame OVD method. The best model’s performance is further studied in the presence of different recorded interference. An ablation study reports the model’s performance on sub-sets of sensors. The results show that the OVD approach is robust towards both user motion and user generated vocal non-speech sounds in the presence of loud external interference. The approach is suitable for real-time operation and achieves 90-96 % OVD accuracy in challenging use scenarios with a short 10 ms processing frame length.

On the performance of exploiting a full-duplex multi-antenna relay powered by wireless energy transfer and self-energy recycling with interference alignment

In this paper, the full-duplex (FD) relay transmission with simultaneous wireless information and power transfer in the presence of interference signals is investigated. A multiple-input multiple-output (MIMO) transmission in a small cell is considered, in which a half-duplex (HD) base station (BS) transmits data to the HD cell-edge user over an FD wireless powered relay. At the same time, BS transmits data to its near users. This concurrent data transmission to all nodes by BS causes signal interference at near users and relay. Relay harvests power from its received signals, including interference signals and the self-interference (SI) signal induced by the FD transmission, to forward the cell-edge user’s data. Power splitting (PS) and interference alignment (IA) techniques are used at the relay to jointly enable wireless energy transfer and interference management. The method introduced here is called the FD PS IA scheme. This method aims to find the PS ratio and beamforming matrices to maximize the cell-edge user and near users’ transmission rate. With this purpose, a closed-form expression for relay optimal PS ratio is derived. Furthermore, a method for choosing the proper precoding and decoding matrix at the relay and edge user, respectively, is proposed. Also, the IA matrices of BS, relay, and near users are optimized based on minimizing the mean square error iterative algorithm. Finally, numerical results demonstrate the rate gain from the combination of IA and PS at FD relay. Besides that, the performance improvement of information processing and energy harvesting by applying multiple antennas is presented. The significant benefits of harvesting the interference and SI signal power at the FD relay are exposed through analysis and simulations.

An objective measure of signal quality for pediatric lung auscultations.

A stethoscope is a ubiquitous tool used to 'listen' to sounds from the chest in order to assess lung and heart conditions. With advances in health technologies including digital devices and new wearable sensors, access to these sounds is becoming easier and abundant; yet proper measures of signal quality do not exist. In this work, we develop an objective quality metric of lung sounds based on low-level and high-level features in order to independently assess the integrity of the signal in presence of interference from ambient sounds and other distortions. The proposed metric outlines a mapping of auscultation signals onto rich low-level features extracted directly from the signal which capture spectral and temporal characteristics of the signal. Complementing these signal-derived attributes, we propose high-level learnt embedding features extracted from a generative auto-encoder trained to map auscultation signals onto a representative space that best captures the inherent statistics of lung sounds. Integrating both low-level (signal-derived) and high-level (embedding) features yields a robust correlation of 0.85 to infer the signal-to-noise ratio of recordings with varying quality levels. The method is validated on a large dataset of lung auscultation recorded in various clinical settings with controlled varying degrees of noise interference. The proposed metric is also validated against opinions of expert physicians in a blind listening test to further corroborate the efficacy of this method for quality assessment.

Small and Adaptive Antennas and Arrays for GNSS Applications

This paper reviews Global Navigation Satellite Systems (GNSS) antennas and arrays for robust coverage in presence of interference signals with a focus on antenna design aspects. A number of small antenna designs are presented that cover multiple current and future GNSS frequency bands (1150–1610 MHz) with sizes as small as 1 in (25 mm) in diameter. Several arrays are presented with a size as small as 3.5 in (8.9 cm) in diameter and approximately 0.5 in (13 mm) thick as compared to commercially available apertures 14 in (35.6 cm) and 5.5 in (14.0 cm) in diameter. These small arrays are shown to satisfy the gain requirements of GNSS receivers while simultaneously offering four to six antenna elements for adaptive interference suppression.

Multiband FM‐based passive bistatic radar: target range resolution improvement

FM-based passive bistatic radars (PBRs), exploiting a single broadcasted channel, have limited range resolution due to low modulation bandwidth and high dependence on the content broadcasted from an FM station. This may be alleviated by exploiting multiple broadcasted channels from a single transmitter. To reach these goals, the authors formulate the problem of detecting a target in the presence of interference signals, such as receiver noise, direct signal, multipath/clutter echoes, and interfering targets, as a composite hypothesis test. So, they derive a multiband uniformly most powerful invariant test. In the proposed detector, they analytically show how the exploitation of the multiple broadcasted channels can improve the target range resolution. The false alarm rate and detection probability of the proposed detector are also derived in the closed-form expressions. Finally, they provide some simulation examples to validate the authors’ theoretical analysis. Simulation results show that a multiband PBR system offers advantages in terms of coherent combined diversity gain and target range resolution improvement as compared to a single band PBR system.

Impact of Distinctive Jamming Signals on WiMAX System

In this recent era wireless communication industries have focused on the uses of broadband system having high quality functions. Because of this issue new advances with high transmission capability technologies are designed. The broadband wireless access turns into the best approach to satisfy the high business interest for expanding the web connection. WiMAX (Worldwide Interoperability for Microwave Access) is a broadband wireless technology is developed to meet the growing demand of increased data rate and accessing the internet at high speeds as well as low cost maintenance. It is based on the IEEE 802.16-2004 standard family. In this system allows using an efficient bandwidth in a wide frequency range, and last mile solution for broadband internet access. The jamming and scrambling are two important threats in WiMAX system. This paper presents the simulation of WiMAX system with and without impact of jamming signals. The performance parameter BER of the system is analyzed in all conditions and the result implies the enormously changes with the utilization of distinctive jamming signals. The aim of this paper is to analyze and simulate WIMAX OFDM system in the presence of interference signals. MATLAB Simulink software is used to simulate and analyze the WIMAX system. The simulation results include the performance analysis based on bit error rate (BER) versus signal to noise rate (Eb/No).

GNSS space-time interference mitigation and attitude determination in the presence of interference signals.

The use of Space-Time Processing (STP) in Global Navigation Satellite System (GNSS) applications is gaining significant attention due to its effectiveness for both narrowband and wideband interference suppression. However, the resulting distortion and bias on the cross correlation functions due to space-time filtering is a major limitation of this technique. Employing the steering vector of the GNSS signals in the filter structure can significantly reduce the distortion on cross correlation functions and lead to more accurate pseudorange measurements. This paper proposes a two-stage interference mitigation approach in which the first stage estimates an interference-free subspace before the acquisition and tracking phases and projects all received signals into this subspace. The next stage estimates array attitude parameters based on detecting and employing GNSS signals that are less distorted due to the projection process. Attitude parameters enable the receiver to estimate the steering vector of each satellite signal and use it in the novel distortionless STP filter to significantly reduce distortion and maximize Signal-to-Noise Ratio (SNR). GPS signals were collected using a six-element antenna array under open sky conditions to first calibrate the antenna array. Simulated interfering signals were then added to the digitized samples in software to verify the applicability of the proposed receiver structure and assess its performance for several interference scenarios.

Interference rejection in quadrature band-pass $$\varSigma \varDelta $$ Σ Δ modulators

Interference is a major concern in surface acoustic wave-less receiver architectures. This paper presents an architectural solution to design a quadrature band-pass $$\varSigma \varDelta $$ΣΔ modulator in presence of interference signals. These interferences are rejected by using the built-in signal transfer function (STF) filtering action inside the quadrature modulator. The implementation of the STF filtering is achieved by means of feed-forward paths and does not require any additional active blocks. Simulations at the behavioral level on different design examples verify the architecture implementation and the effectiveness of the approach.

Direction Finding of a Compromised Node in a Wireless Network

When a spread-spectrum receiver in a network discovers that it is processing a jamming signal transmitted by a compromised node, its first response is to attempt to identify the compromised node. In this paper, an adaptive array is used to find the direction to the jamming source despite the presence of interference signals transmitted by both legitimate network nodes and external sources. Unlike other direction-finding algorithms, the desired-signal classification (DESIC) algorithm requires no information or special assumptions about the interference signals to effectively cancel them and find the desired direction. Simulation experiments show that the DESIC algorithm provides an excellent performance in many scenarios, even when the received signals cannot be resolved by the widely used MUSIC algorithm.

Adaptive Decode-and-Forward Protocol Based Cooperative Spectrum Sensing in Cognitive Radio with Interference at the Secondary Users

In this paper a novel multiple-user cooperative spectrum sensing scheme (MCSS) based on hybrid relay is proposed to achieve the spatial diversity gain in detection of the primary user (PU) in a cognitive radio (CR) network. A practically important case where co-channel interference signals are present at the network is considered for the analysis. Closed-form expressions of detection probability $$(\hbox {P}_{\mathrm{d}})$$ ( P d ) and false alarm probability $$(\alpha )$$ ( ? ) for the proposed adaptive decode-and-forward based multiple-user cooperative spectrum sensing scheme (ADF-MCSS) using energy detector over Rayleigh fading sensing channels is derived in presence of co-channel interference at the secondary user which is far away from the PU. Further we extend the concept of two user amplify-and-forward (AF) and decode-and-forward (DF) cooperative spectrum sensing schemes in multiple-user scenario (i.e. AF-MCSS and DF-MCSS) over Rayleigh fading channels when the secondary user (which is far away from PU) is affected by interference. Closed-form expressions of AF-MCSS and DF-MCSS schemes over a Rayleigh fading channels are also evaluated and compared with that of proposed ADF-MCSS in presence of interference signals at the secondary user. Further the performance analysis of AF-MCSS, DF-MCSS and ADF-MCSS schemes are compared with the existing non-cooperative spectrum sensing schemes in presence of interference at the secondary user. Our analysis is validated by numerical and simulation results for multiple-user CR network. The impact of number of cooperative relays, SNR in sensing channel, energy of interference signal, false alarm on detection probability in proposed ADF, AF and DF schemes is shown.

End-to-end channel capacity of MAC-PHY cross-layer multiple-hop MIMO relay system with outdated CSI

For high end-to-end channel capacity, the amplify-and-forward scheme multiple-hop multiple-input multiple-output relay system is considered. The distance between each transceiver and the transmit power of each relay are optimized to prevent some relays from being the bottleneck and guarantee high end-to-end channel capacity. According to the proposed transmission environment coefficient, the path loss can be described in a new way, and then the distance of multiple-hop relay system can be optimized more simply than the original one. However, when the system has no control on media access control (MAC) layer, performance of the system deteriorates because of the presence of interference signal. Thus, the specific transmission protocol on the MAC layer for multiple-hop system is proposed to reduce the power of interference signal and to obtain high end-to-end channel capacity. According to the proposed transmission protocol on the MAC layer, the system indicates the trade-off between the end-to-end channel capacity and the delay time. The end-to-end channel capacity of the outdated channel state information system is also analyzed.

Analysis of Injection Pulling in Phase-Locked Loops With a New Modeling Technique

A new formulation is presented for the analysis of phase-locked loops (PLL). It is based on the use of a realistic reduced-order model for the voltage-controlled oscillator, extracted from harmonic-balance (HB) simulations. An HB formulation of the reduced-order PLL equations enables an efficient analysis of the PLL in unlocked conditions, and therefore, prediction of common hysteresis phenomena. The injection-pulling effects in the presence of interference signals are analyzed taking into account the nonlinearity of the phase detector. The interfered PLL in locked conditions is analyzed with a single-tone HB formulation of the reduced-order system, whereas a two-tone HB analysis is used for the analysis in unlocked conditions. The frequency-domain formulation enables an accurate and efficient prediction of the effect of the interferer on the hold-in and lock-in ranges, here investigated, to our knowledge, for the first time. The analysis has been successfully applied to a PLL operating at 5.3 GHz.

GLRT-Based CFAR Detection in Passive Bistatic Radar

The work presented here addresses the problem of detecting a target in a passive bistatic radar (PBR) in the presence of interference signals, including receiver noise, direct signal, multipath/clutter echoes, and interfering targets. To this end, after outlining the model of the detection problem in the surveillance channel as a composite hypothesis test, a generalized likelihood ratio test (GLRT) is derived. Its performance is expressed in the closed forms for both the interference-alone case, the probability of false alarm, and the signal-plus-interference case, the probability of detection. A thorough performance assessment is also given, and the results show the superiority of the proposed detector in detection performance and false alarm regulation, and so the proper cancellation of the direct signal, multipath/clutter echoes, and interfering targets occur.

A Statistical Signal Prediction Model for Communication Receivers

Many communication receivers receive the desired signal in presence of interference signal. A statistical antenna and propagation model is described which predicts the expected values of the desired and undesired signal levels Ŝ and Î, respectively, the standard deviations of the desired and undesired signals σs and σI, respectively, and their correlation coefficients PSI. The expected values of the signal levels are expressed in terms of the random parameters of the radio frequency power fed into the transmitting antenna, its efficiency, gain, propagation path loss, receiving antenna gain, receiving antenna loss, and input impedance of the receiver.