Presence Of Multiple Interference Research Articles

CFAR-Based Interference Mitigation for FMCW Automotive Radar Systems

In this paper, constant false alarm rate (CFAR) detector-based approaches are proposed for interference mitigation of Frequency modulated continuous wave (FMCW) radars. The proposed methods exploit the fact that after dechirping and low-pass filtering operations the targets’ beat signals of FMCW radars are composed of exponential sinusoidal components while interferences exhibit short chirp waves within a sweep. The spectra of interferences in the time-frequency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$t$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f$ </tex-math></inline-formula> ) domain are detected by employing a 1-D CFAR detector along each frequency bin and then the detected map is dilated as a mask for interference suppression. The proposed approaches are applicable to the scenarios in the presence of multiple interferences. Compared to the existing methods, the proposed methods reduce the power loss of useful signals and are very computationally efficient. Their interference mitigation performances are demonstrated through both numerical simulations and experimental results.

Gait and Respiration-Based User Identification Using Wi-Fi Signal

The ever-growing security issues in various scenarios create an urgent demand for a reliable and convenient identification system. Traditional identification systems request users to provide passwords, fingerprints, or other easily stolen information. Existing works show that everyone’s gait and respiration have unique characteristics and are difficult to imitate. But these works only use gait or respiration information to achieve identification, which leads to low accuracy or long identification time. And they have no strong anti-interference ability, which leads to the limitation in practical application. Toward this end, we propose a new system which uses both gait and respiratory biometric characteristics to achieve user identification using Wi-Fi (GRi-Fi) in the presence of interferences. In our system, we design a segmentation algorithm to segment gait and respiration data. And we design a weighted subcarrier screening method to improve the anti-interference ability. In order to shorten the identification time, we propose a feature integration method based on the weighted average. Finally, we use a deep learning method to identify users accurately. Experimental results show that GRi-Fi can identify the users identity with an average accuracy of 98.3% in noninterference environments. Even in the presence of multiple interferences, the average identification accuracy also reaches 91.2%. In future applications, our system can be applied to many fields of Internet of Things, such as smart home systems and clocking in at companies.

Spectral efficiency and quantum limit of BPSK transmission in a WDM system in presence of multiple interferers

Spectral efficiency and quantum limit of BPSK transmission in a WDM system in presence of multiple interferers

Highly sensitive and stable sensor for the detection of capsaicin using electrocatalytic carbon dots grafted onto indium tin oxide

In this work, a highly sensitive and stable capsaicin sensor was developed from carbon dots synthesized from iota-carrageenan. The carbon dots were grafted onto an indium tin oxide (ITO) substrate via a novel one-step thermal annealing process. This was used as an electrode for the electrochemical detection of capsaicin. The carbon dot-grafted ITO electrode was sensitive across a wide linear range from 0.05 to 500 μM, with a remarkably low detection limit of 5.4 nM. The electrode showed excellent recyclability over 450 cycles, suggesting that it was electrochemically stable and can be reused for several hundred times. It demonstrated good selectivity towards capsaicin in the presence of multiple interferences: d-(+)-glucose, citric acid, l-ascorbic acid, Na+, K+, Mg2+, Ca2+, Fe2+, and Cl−. A recovery test was performed using Cayenne pepper, Tabasco sauce, and Thai chili, yielding the recovery in the range 92–108 %. In addition to high sensitivity, stability, and selectivity, the sensor could produce the detection results within 5 min. The novel capsaicin sensor developed here has potential uses for quality control in the agricultural, food, and pharmaceutical sectors.

Partial relay selection for combating the effects of co-channel interference in RF/FSO cooperative relaying

In this research work, mixed radio frequency (RF)/free space optical (FSO) communication systems have been investigated in the presence of multiple interferers at the relay node. The considered system incorporates partial relay selection (PRS) using the available outdated channel state information (CSI) at the relay node to combat the effect of interference. The fading on the PRS-aided RF link has been modeled using the Rayleigh distribution whereas the statistics of the co-channel interferers (CCIs) at the relay node has been modeled using Nakagami-m fading distribution. On the other hand, FSO link has been assumed to undergo α−μ distributed atmospheric turbulence with pointing errors. To this end, the model on the FSO link considers the impact of both kinds of optical demodulation schemes i.e., intensity modulation direct detection (IM/DD) and coherent demodulation. For the system under study, exact closed-form expressions for the outage probability, bit error rate (BER) and ergodic capacity have been presented. Further to this, asymptotic high signal to noise ratio (SNR) approximate expressions have been derived for outage probability, BER and ergodic capacity to extract quick insights into the results. Finally, numerical examples have been demonstrated to validate the findings of the research work.

Organic Electrochemical Transistors/SERS-Active Hybrid Biosensors Featuring Gold Nanoparticles Immobilized on Thiol-Functionalized PEDOT Films.

In this study we immobilized gold nanoparticles (AuNPs) onto thiol-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) films as bioelectronic interfaces (BEIs) to be integrated into organic electrochemical transistors (OECTs) for effective detection of dopamine (DA) and also as surface-enhanced Raman scattering (SERS)—active substrates for the selective detection of p-cresol (PC) in the presence of multiple interferers. This novel PEDOT-based BEI device platform combined (i) an underlying layer of polystyrenesulfonate-doped PEDOT (PEDOT:PSS), which greatly enhanced the transconductance and sensitivity of OECTs for electrochemical sensing of DA in the presence of other ascorbic acid and uric acid metabolites, as well as amperometric response toward DA with a detection limit (S/N = 3) of 37 nM in the linear range from 50 nM to 100 μM; with (ii) a top interfacial layer of AuNP-immobilized three-dimensional (3D) thiol-functionalized PEDOT, which not only improved the performance of OECTs for detecting DA, due to the signal amplification effect of the AuNPs with high catalytic activity, but also enabled downstream analysis (SERS detection) of PC on the same chip. We demonstrate that PEDOT-based 3D OECT devices decorated with a high-density of AuNPs can display new versatility for the design of next-generation biosensors for point-of-care diagnostics.

Third-Order Intermodulation Effects and System Sensitivity Degradation in Receive-Mode 5G Phased Arrays in the Presence of Multiple Interferers

Electronically scanned phased-array antennas need to function in an interference-rich environment as an integral part of millimeter-wave 5G networks. In these scenarios, multiple interferers’ incident from different directions can create intermodulation products that can severely degrade the system sensitivity. This paper first presents the theoretical analysis of intermodulation effects in a receive-mode phased array and then shows the detailed experimental verification of multiple interferer effects on a 28-GHz 5G phased array. It is shown that the third-order intermodulation products generated by the interferers peak at certain predictable scan angles depending on the interferer directions of arrival and can limit the sensitivity of the phased array. The interferers degrade the system sensitivity even if incident in the direction of pattern nulls. Two scan-angle-dependent third-order input intercept point (IIP3) definitions are given for a phased array and their implications are discussed. It is shown that while a phased array does result in an input P1dB improvement as the number of elements increases (handles more incident power than a single channel), it does not result in an IIP3 improvement over a single channel as the number of elements increases. Theoretical predictions are also verified by extensive numerical simulations and measurement results for multiple interferers from different directions. Finally, the IIP3 degradation in mechanically scanned antennas is analyzed and it is shown that such antennas are much more robust than phased arrays for wide angle interferers.

Are Seat and Aisle Interferences Affecting the Overall Airplane Boarding Time? An Agent-Based Approach

Seat and aisle interferences are assumed to be linked with a prolonged boarding time along with several other aspects related to airplane boarding such as: luggage handling, luggage distribution inside the cabin, number of passengers, passengers’ physique characteristics, group behavior, seat selection, aircraft occupancy, aircraft design, etc. Based on these assumptions, a series of proposed boarding methods, underlying their efficiency starting from the absence or limited presence of these types of interferences, are proposed. The present paper aims to analyze whether the different types of seat or aisle interferences do matter for the overall boarding time by considering 24 boarding methods proposed in the literature. A series of specific elements related to interferences, such as: the average waiting time, the average number of interferences based on their types, and the average number of interference-affected passengers, have been considered. Also, the presence of multiple interferences in different parts of the aircraft has been analyzed in order to offer a complete picture of the considered situation. An agent-based model in NetLogo 6.0.4, fed with values form field trials within the literature is created and used for simulations, which enables the agents to act like real passengers involved in an airplane boarding process.

Performance analysis of scheduled STBC using statistical CSI under multiple interferers with different power in CR-MIMO systems

This paper studies the impact of the multiple interferers with different power on performance of a scheduled space–time block coding (STBC) using the statistical channel state information (CSI) in cognitive radio-multiple input multiple output (CR-MIMO) systems. This paper derives the exact closed-form cumulative density function (CDF) expression of the instantaneous post-processing signal to noise plus interference ratio (SINR) random variable at the user terminal of the proposed system. Using the derived CDF, the exact closed-form symbol error rate (SER) expression of the proposed system is derived for M-ary quadrature amplitude modulations (QAM). Further, this paper derives the exact closed-form expressions of outage probability and capacity for the proposed system. From the results, we know that the performance of the proposed system is saturated at different peak power constraint depending on the peak interference constraint. Also, the performance floor gets better by multi-user diversity and receive spatial diversity below the peak interference constraint in the presence of multiple interferers.

Performance analysis of scheduled TAS‐MRC MIMO systems with multiple interferers

The authors present the performance analysis of a scheduled transmit antenna selection with maximal ratio combining (TAS-MRC) for multiple-input multiple-output transmission in the presence of multiple interferers. They derive the probability density function of the instantaneous post-processing signal to interference plus noise ratio for the scheduled TAS with MRC over the Rayleigh fading channels under multiple interferers. Using the distribution, the closed-form expressions of the scheduled TAS with MRC are derived for symbol error rate (SER), outage probability and ergodic capacity in the presence of multiple interferers. From the analysis results, the performance of the scheduled TAS-MRC in the presence of multiple interferers is mainly determined by the signal-to-interference ratio. The performance of SER and ergodic capacity is less sensitive to the number of interferers.

Passive beamforming with coprime arrays

Coprime arrays have been recently proposed as effective sparse configurations suitable for radar beamforming and angle-of-arrival estimation applications. In this study, a new approach for passive beamforming using coprime arrays is presented. In particular, a new detection strategy is proposed, which outperforms the coprime processors presently available in the literature, both in terms of peak sidelobe ratio and integrated sidelobe ratio, without giving rise to ‘ghost’ targets in presence of multiple interferers. The advantage of the proposed detector is demonstrated through the simulation of appropriate array scanned responses and receiver operating characteristic curves.

Sequential quasi‐convex‐based algorithm for waveform design in colocated multiple‐input multiple‐output radars

This study considers the problem of waveform design for colocated multiple-input multiple-output (MIMO) radars for multiple targets in the presence of multiple interferences in white Gaussian noise. Here, the authors jointly design the transmit waveform and receive beamforming by a sequential algorithm. The proposed sequential algorithm maximises the minimum signal-to-interference-plus-noise ratio (SINR) to design both continuous and finite alphabet phase waveforms. In the case of continuous phase, all phases can be chosen in the waveform space, while in finite alphabet case, phases are only chosen from a confine set. Two important practical constraints of ‘constant envelope’ and ‘similarity’ are considered as well. The authors also have converted the waveform design problem into a quasi-convex optimisation problem which can be effectively solved by using convex optimisation toolbox (CVX). They have evaluated the performance of the matched filter output, beampattern and peak-to-average power ratio via numerical simulations and shown that the proposed sequential method achieves better SINR performance compared with existing MIMO radar transmit waveform design methods, for both single and multiple target scenarios.

SER for Optimal Combining in the Presence of Multiple Correlated Co-Channel Interferers

Symbol error rate (SER) performance has been analyzed for a receive diversity system in the presence of multiple interferers and noise over fading channels. Both unequal power interferers and correlated interferers have been considered. The derived approximate SER expressions are easy to evaluate and are applicable to any QAM constellation and arbitrary number of receive antennas and interferers. Further, the impact of correlation between interferer channels is studied and it is shown that correlation behaves like partial interference alignment.

Intelligent bearing fault signature extraction via iterative oscillatory behavior based signal decomposition (IOBSD)

A typical vibration signal from a defective bearing is composed of fault-induced transients (i.e., fault signature), resonance, multiple vibration interferences and background noise. Extracting the fault-induced transients from such signals is the primary goal for bearing fault diagnosis. This paper proposes an intelligent oscillatory behavior based signal decomposition (OBSD) method for this purpose. The OBSD technique exploits both the signal separation capability of morphological component analysis (MCA) and the basis creation potential of tunable Q-factor wavelet transform (TQWT). To generate proper bases for each individual signal component, the Q-factor determination and tuning strategies for the TQWT are developed in this study. In the presence of multiple interferences, one-time OBSD may not be sufficient to extract fault feature successfully. As such, an iterative OBSD (IOBSD) procedure is proposed. With the proposed method, a vibration signal can be decomposed into three signal components, i.e., low-oscillation component (fault signature presenting non-oscillation), high-oscillation component (interferences manifesting sustained oscillation) and residual (noise), according to their oscillatory behaviors. Bearing faults can then be reliably detected. The main features of the proposed method include: (1) it can remove in-band interference and noise that cannot be removed by the widely used frequency-based approaches, as it is frequency-independent in nature, (2) it can extract fault signatures from heavily interference-obscured signals without filtering the signals, and (3) it does not require the prior information of the signals. With these features, the IOBSD method can substantially reduce human involvement and facilitate its implementation in a fault detection expert system, particularly in an environment with various interferences. The IOBSD method has been favorably compared with one of the popular filtering techniques, i.e., SK method. The effectiveness of the proposed method has also been tested by simulation and experiments.

Outage Probability of Dual-Hop Selective AF With Randomly Distributed and Fixed Interferers

The outage probability performance of a dual-hop amplify-and-forward selective relaying system with global relay selection is analyzed for Nakagami-$m$ fading channels in the presence of multiple interferers at both the relays and the destination. Two different cases are considered. In the first case, the interferers are assumed to have random number and locations. Outage probability using the generalized Gamma approximation (GGA) in the form of one-dimensional integral is derived. In the second case, the interferers are assumed to have fixed number and locations. Exact outage probability in the form of one-dimensional integral is derived. For both cases, closed-form expressions of lower bounds and asymptotic expressions for high signal-to-interference-plus-noise ratio are also provided. Simplified closed-form expressions of outage probability for special cases (e.g., dominant interferences, i.i.d. interferers, Rayleigh distributed signals) are studied. Numerical results are presented to show the accuracy of our analysis by examining the effects of the number and locations of interferers on the outage performances of both AF systems with random and fixed interferers.

A Novel Variable Index and Excision CFAR Based Ship Detection Method on SAR Imagery

When applying the constant false alarm rate (CFAR) detector to ship detection on synthetic aperture radar (SAR) imagery, multiple interferers such as upwelling, breaking waves, ambiguities, and neighboring ships in a dense traffic area will degrade the probability of detection. In this paper, we propose a novel variable index and excision CFAR (VIE-CFAR) based ship detection method to alleviate the masking effect of multiple interferers. Firstly, we improve the variable index (VI) CFAR with an excision procedure, which censors the multiple interferers from the reference cells. And then, the paper integrates the novel CFAR concept into a ship detection scheme on SAR imagery, which adopts the VIE-CFAR to screen reference cells and the distribution to derive detection threshold. Finally, we analyze the performances of the VIE-CFAR under different environments and validate the proposed method on both ENVISAT and TerraSAR-X SAR data. The results demonstrate that the proposed method outperforms other existing detectors, especially in the presence of multiple interferers.

Relay Selection of Cooperative Diversity Networks With Interference-Limited Destination

We study relay selection in both decode-and-forward (DF)-based and amplify-and-forward (AF)-based cooperative diversity networks consisting of a source, multiple relays, and a destination in the presence of multiple interferers, where each terminal has a single antenna and operates in half-duplex mode. In the network, it is assumed that the multiple interferers locate near the destination and far away from relays; thus, only the destination receives interfering signals, which is referred to as the interference-limited destination. Specifically, we first propose relay selection to maximize the mutual information on cooperative networks with the interference-limited destination. Then, for relay selection of DF-based networks, we derive the exact outage probability. Finally, for relay selection of AF-based networks, we derive the exact outage probability in integral form and its closed-form lower bound.

Three-dimensional multiple-source focalization in an uncertain ocean environment

This letter develops a Bayesian focalization approach for three-dimensional localization of an unknown number of sources in shallow water with uncertain environmental properties. The algorithm minimizes the Bayesian information criterion using adaptive hybrid optimization for environmental parameters, Metropolis sampling for source bearing, and Gibbs sampling for source ranges and depths. Maximum-likelihood expressions are used for unknown complex source strengths and noise variance, which allows these parameters to be sampled implicitly. An efficient scheme for adding/deleting sources is used during the optimization. A synthetic example considers localizing a quiet source in the presence of multiple interferers using a horizontal line array.

A non-parametric non-filtering approach to bearing fault detection in the presence of multiple interference

Reliable fault detection of bearing faults is crucial to avoid costly machine failures. To this end, many methods have been proposed over the years. However, most of them are dependent on properly selected parameters, such as the center frequency and the bandwidth of the bandpass filter for the pass band in the high-frequency resonance method. Such parameters may also have to be updated in a variable operating environment which may not always be possible without the involvement of domain experts. As such, we propose a new non-parametric and non-filtering method which can perform reasonably well in the presence of vibration interference and noise. This method is based on the derivation of amplitude demodulation of a signal to suppress unwanted periodic interference components in the acquired signal. It has been shown that the proposed method can boost the signal-to-interference ratio by up to 2–12 times compared with the energy operator approach and can handle signals tinted by both noise and multiple interference. It compares favorably with other non-parameter methods, such as the plain envelope method and energy operator method. Its effectiveness has further been demonstrated using both simulated and experimental data.

Analysis of MIMO Systems used in planning a 4G-WiMAX Network in Ghana

With the increasing demand for mobile data services, Broadband Wireless Access (BWA) is emerging as one of the fastest growing areas within mobile communications. Innovative wireless communication systems, such as WiMAX, are expected to offer highly reliable broadband radio access in order to meet the increasing demands of emerging high speed data and multimedia services. In Ghana, deployment of WiMAX technology has recently begun. Planning these high capacity networks in the presence of multiple interferences in order to achieve the aim of enabling users enjoy cheap and reliable internet services is a critical design issue. This paper has used a deterministic approach for simulating the Bit-Error-Rate (BER) of initial MIMO antenna configurations which were considered in deploying a high capacity 4G-WiMAX network in Ghana. The radiation pattern of the antenna used in the deploying the network has been simulated with Genex-Unet and NEC and results presented. An adaptive 4x4 MIMO antenna configuration with optimally suppressed sidelobes has been suggested for future network deployment since the adaptive 2x2 MIMO antenna configuration, which was used in the initial network deployment provides poor estimates for average BER performance as compared to 4x4 antenna configuration which seem less affected in the presence of multiple interferers.