Output Signal-to-interference Ratio Research Articles

MIMO radar waveform design for target detection in the presence of interference

The interference from clutter and active electromagnetic equipment deteriorates target detection performance greatly. In this paper, we design a MIMO radar transmit matrix to improve target detection performance in the presence of interference. To this end, we model the design problem by maximizing the signal to interference ratio (SIR) with the constraints of spectrum compatibility and constant modulus. To solve the resulting complicated optimization problem, the hierarchical approach is employed to convert the original problem into two subproblems, i.e., transmit design for sidelobe interference suppression and signal design for target detection under mainlobe interference. The first subproblem is solved by a novel anti-sidelobe-interference algorithm named as hybrid beampattern synthesizing (HBS) which can achieve lower nulling levels than the well-known beampattern synthesizing methods. The second subproblem is solved by two steps composed of energy spectrum density (ESD) design and signal design via the proposed hybrid ESD matching (HEM) algorithm which can balance the matching loss and the spectrum compatibility more flexibly than the existing ESD matching methods. Numerical examples verify the advantages of the proposed algorithms and that the designed MIMO radar transmit waveform can achieve higher output SIR than the traditional waveform.

Performance Analysis of a Selection Combining System That Uses the Minimal Interference Algorithm

In this paper, a new combining algorithm for selection combining (SC) receiver based on selection of diversity branch with the lowest interference is proposed. The system used for analysis consists of dual-branch SC diversity that operates over correlated Weibull fading channels. Closed-form expressions for joint probability density function (PDF) of desired signal and interference at the output and PDF of instantaneous signal-to-interference ratio (SIR) at the output are obtained and used to investigate important system performance indicators. System performance is analyzed using outage probability, average bit error probability (ABEP) and average output SIR. The obtained results are compared with the previously published for the SIR algorithm employed by the same system.

Performance analysis of dual-branch selection diversity system using novel mathematical approach

In this paper, novel mathematical approach for evaluation of probability density function (PDF) of instantaneous signal-to-interference ratio (SIR) at the receiver output in interference-limited environment is proposed. Dual-branch selection combining (SC) receiver operating over correlated Weibull fading channels applying SIR algorithm is considered. Analytical expression for joint PDF of desired signal and interference at the receiver output is derived and used for evaluation of PDF of instantaneous SIR. The expression for PDF of SIR is used for system performance analysis via outage probability, average bit error probability (ABEP) and average output SIR as system performance measures. Numerical results are graphically presented showing the effects of fading severity, average SIR at the input and level of correlation on the diversity receiver performance. In addition, results obtained for the PDF of instantaneous SIR in this paper, are compared to the results when the PDF of instantaneous SIR is directly calculated.

Power line interference attenuation in multi-channel sEMG signals: Algorithms and analysis.

Electromyogram (EMG) recordings are often corrupted by power line interference (PLI) even though the skin is prepared and well-designed instruments are used. This study focuses on the analysis of some of the recent and classical existing digital signal processing approaches have been used to attenuate, if not eliminate, the power line interference from EMG signals. A comparison of the signal to interference ratio (SIR) of the output signals is presented, for four methods: classical notch filter, spectral interpolation, adaptive noise canceller with phase locked loop (ANC-PLL) and adaptive filter, applied to simulated multichannel monopolar EMG signals with different SIR. The effect of each method on the shape of the EMG signals is also analyzed. The results show that ANC-PLL method gives the best output SIR and lowest shape distortion compared to the other methods. Classical notch filtering is the simplest method but some information might be lost as it removes both the interference and the EMG signals. Thus, it is obvious that notch filter has the lowest performance and it introduces distortion into the resulting signals.

Multiple Co-Channel Interferers Influence on Selection Combining over Correlated Weibull Fading Channels

In this paper, we provide performance analysis of signal-to-interference ratio (SIR) based selection combining (SC) receiver, operating over correlated Weibull fading channels, with an arbitrary number of correlated co-channel interferers, over each branch. Assuming this multibranch diversity technique, infinite series expressions were derived for PDF (probability density function) and CDF (cumulative distribution function) of the output SIR. The proposed analysis was used for evaluating outage probability (OP). The effects of various system parameters, such as number of multiple interferers, correlation level and fading severity on the OP, are graphically presented. Another important system performance measure, average bit error probability (ABER) is efficiently evaluated for modulation schemes such as binary frequency-shift keying (BFSK) and binary differentially phase-shift keying (BDPSK).

Closed-Form Expressions for Selection Combining System Statistics over Correlated Generalized-K Fading Channels in the Presence of Interference

This paper considers the effects of simultaneous correlated multipath fading and shadowing on the performances of a signal-to-interference ratio (SIR)-based dual-branch selection combining (SC) diversity receiver. This analysis includes the presence of cochannel interference. A generalized fading/shadowing channel model in an interference-limited correlated fading environment is modeled by generalized-K distribution. Closed-form expressions are obtained for probability density function and cumulative distribution function of the SC output SIR, as well as for the outage probability. Based on this, the influence of various fading and shadowing parameter values and the correlation level on the outage probability is examined.

Performance analysis of dual switched diversity over correlated Weibull fading channels with co‐channel interference

AbstractThis paper studies the performance of switch and stay combining (SSC) diversity in the presence of co‐channel interference over correlated Weibull fading channels. SSC diversity based on signal‐to‐interference ratio (SIR) is a low‐complexity and a very efficient technique that reduces fading and co‐channel interference influence. New closed‐form expressions for the probability density function and cumulative distribution function of the output SIR's are derived. These formulas are used in a detailed analysis of the average output SIR and outage probability. The influence of fading severity and correlation coefficient on the optimum switching threshold and system performance is investigated. Monte Carlo simulations are performed to verify obtained theoretical results and determine average bit error rate in detecting binary phase‐shift keying (BPSK), differential BPSK and quadrature amplitude modulation signals. Copyright © 2011 John Wiley & Sons, Ltd.

Generalised approach for performance analysis of SIR‐based multiple selection diversity over constant correlated α – µ fading channels

AbstractSelection combining (SC) is commonly used space‐diversity technique in wireless communication systems to alleviate effects of channel fading and interference influence. In this paper, we analyse the performance of multibranch signal‐to‐interference‐ratio (SIR)‐based SC diversity over correlated α – µ fading channels with arbitrary parameters. The novel formulae for the probability density function (pdf) and cumulative distribution function (cdf) of output SIR are derived. Some numerical and simulation results are obtained pointing out the effects of fading severity, level of correlation, input SIR unbalance and diversity order to the outage probability. Also, the average error probability for several modulation schemes is numerically evaluated. Copyright © 2010 John Wiley & Sons, Ltd.

Performance analysis of system with triple selection combining over correlated Weibull fading channel in the presence of cochannel interference

In this paper, closed-form expressions for probability density function (PDF) and cumulative distribution function (CDF) of the signal-to-interference ratio (SIR) at the output of the triple selection combining (SC) receiver over correlated Weibull fading channels in the presence of correlated cochannel interference (CCI) are derived. These expressions are used to study wireless system performance criteria, such as outage probability, average bit error probability and average output SIR. .

TOD Performance Model for Staring Thermal Imager with Machine Vision

A triangle orientation discrimination threshold(TOD) performance theoretical model is derived for the staring thermal imager based on machine vision. Specifically, how to obtain the TOD curve based on machine vision is briefly described. The spatial frequency distribution of the triangle test pattern is first determined. The transform and response characteristics of the non-periodic triangle pattern and its background clutter through machine vision-based thermal imager are analyzed. The three-dimensional matched filter is adopted to characterize quantitatively the spatial and temporal integration of image enhancement algorithms to the output triangle pattern signal, various noise components and background clutter, and the signal-to-interference ratio (SIR) of the triangle pattern output image is derived for the staring thermal imager based on machine vision. Then, the TOD performance theoretical model is established by assuming that the output SIR is equal to the threshold SIR75% determined by the discrimination criteria of machine vision. Preliminary simulation and experimental results show that this theoretical model can give reasonable prediction of the TOD performance curve for staring thermal imagers based on machine vision.

Central limit theorem for signal-to-interference ratio of reduced rank linear receiver

Let $\mathbf{s}_{k}=\frac{1}{\sqrt{N}}(v_{1k},\ldots,v_{Nk})^{T}$, with {vik, i, k=1, …} independent and identically distributed complex random variables. Write Sk=(s1, …, sk−1, sk+1, …, sK), Pk=diag(p1, …, pk−1, pk+1, …, pK), Rk=(SkPkSk*+σ2I) and Akm=[sk, Rksk, …, Rkm−1sk]. Define βkm=pksk*Akm(Akm*×RkAkm)−1Akm*sk, referred to as the signal-to-interference ratio (SIR) of user k under the multistage Wiener (MSW) receiver in a wireless communication system. It is proved that the output SIR under the MSW and the mutual information statistic under the matched filter (MF) are both asymptotic Gaussian when N/K→c>0. Moreover, we provide a central limit theorem for linear spectral statistics of eigenvalues and eigenvectors of sample covariance matrices, which is a supplement of Theorem 2 in Bai, Miao and Pan [Ann. Probab. 35 (2007) 1532–1572]. And we also improve Theorem 1.1 in Bai and Silverstein [Ann. Probab. 32 (2004) 553–605].

Performance analysis of system with selection combining over correlated Weibull fading channels in the presence of cochannel interference

Selection diversity based on the signal to interference ratio (SIR) is a very efficient technique that reduces fading and channel interference influence. In this paper, system performances of selection combining and correlated Weibull channels are analyzed. Fading between the diversity branches and between interferers is correlated and Weibull distributed. Very useful closed-form expressions are obtained for the output SIR's probability density function (PDF) and cumulative distribution function which is main contribution of this paper. Outage probability, the average output SIR, and the average error probability for coherent, noncoherent modulation are derived. Numerical results presented in this paper point out the effects of fading severity and correlation on the system performances.

Effects of Spatial Correlation on MIMO Adaptive Antenna System With Optimum Combining

In this paper, we investigate the effects of the spatial fading correlation on the performance of a multiple-input multiple-output (MIMO) adaptive antenna system with optimum combining (OC) in the presence of multiple cochannel interferers over a correlated Rayleigh fading channel. Based on the Khatri's distribution functions of quadratic forms in complex Gaussian random matrices, we develop a unified determinant representation of those joint eigenvalue distributions. Taking into account the spatial correlation among the antenna elements at the transmitter or receiver, we derive the closed-form formulas for the probability density function and outage probability of the maximum output signal-to-interference ratio (SIR) in an interference-limited MIMO-OC system. Furthermore, the average output SIR and error probability are also investigated. From numerical examples, we show that a new theoretical approach gives a simple and accurate way to assess the performance of the MIMO-OC system over arbitrarily correlated fading channels

Decoupled Beamforming and Noise Cancellation

The enhancement of noise-corrupted speech acquired by microphones is indispensable to the functioning of a wide variety of digital signal processing algorithms. Many existing products are equipped with steerable, stand-alone fixed beamformers which provide moderate levels of directivity. Moreover, many applications have long employed the classical adaptive noise canceller configuration with a reference sensor near the noise source to cancel unwanted noise. In this paper, the cascading of stand-alone beamformers with back-end adaptive noise cancellers is studied. A decoupled model for signal enhancement using front-end beamformers and cascaded noise cancellers is presented. The inter-operation of the beamforming and noise canceling units is studied by defining the signal-to-interference ratio (SIR) gain, directivity index, and white noise gain offered by the beamforming and noise cancelling components. The performance of decoupled beamformer-noise canceller structures is evaluated using experimental measurements. An experimental procedure for evaluating output SIR is presented. Results reveal SIR improvements of up to 27 dB, and are compared to those stemming from conventional adaptive beamformers

Performance analysis of SIR-based dual selection diversity over correlated Nakagami-m fading channels

Signal-to-interference-ratio (SIR)-based selection diversity is an efficient technique to mitigate fading and cochannel interference in wireless communications systems. An approach to the performance analysis of dual SIR-based selection diversity over correlated Nakagami-m fading channels with arbitrary parameters is presented. Useful formulae for the outage probability, the average output SIR, and the average error probability for coherent, noncoherent, and multilevel modulation schemes are derived. The main contribution of the paper is that, for the first time, the proposed analysis is carried out assuming correlated Nakagami-m fading with arbitrary parameters for both the desired signals and the cochannel interferers, which is the real scenario in practical dual selection diversity systems with insufficient antenna spacing. It is shown that the presented general results reduce to the specific ones for the independent fading case, previously published. Numerical and simulation results are also presented to show the effects of various parameters, such as the fading severity, input SIR unbalance, and level of correlation, to the system's performance.

Convergence analysis of the least squares constant modulus algorithm in interference cancellation applications

The convergence behavior of the least squares constant modulus (CM) algorithm in an adaptive beamforming application is examined. It is assumed that the desired signal and the interference are uncorrelated. The improvement in output signal-to-interference ratio (SIR) with each iteration of the algorithm is predicted for several different signal environments. Deterministic results are presented for an environment containing two complete sinusoids. Probabilistic results are presented for a CM desired signal with a CM interferer and with a Gaussian interferer. The asymptotic improvement in output SIR as the output SIR becomes high is also derived. The results of Monte Carlo simulations using sinusoidal, frequency modulation, and quadrature phase-shift keying signals are included to support the derivations.

Fading effects on antenna arrays in cellular communications

In future application of antenna arrays to wireless communications, it is envisioned that known signal waveforms (e.g., synchronization data stream) will be used for estimating the array response for all the relevant links. Once the array response is known, it will be used for separation and reconstruction of the unknown data stream. Since the array response matrix is estimated with finite precision, we examine the error effects on the signal reconstruction errors. The results are presented in the form of output signal-to-interference ratio (SIR) and output signal-to-noise ratio (SNR) for uncorrelated signals. We obtain closed-form expressions for the average output SNR and SIR for Rayleigh, Ricean, and Nagakami fading. It is shown that in the presence of slowly fading channels, the diversity advantage of the array decreases as the number of signals (or interferers) increases.

Interference suppression by biased nonlinearities

It is shown that, when the input signal-to-interference ratio (SIR) is small, a biased nonlinearity that has a dead zone below some threshold value can provide a large enhancement in output SIR and signal-to-interference-plus-intermodulation ratio (SIIMR) if the threshold is set equal or close to the amplitude of the strong interference. In the absence of noise, the output SIR and SIIMIR are virtually independent of the input SIR, however low the latter may be. It Is shown that, for a dead-zone limiter, the output SIIMR in this case is -4.93 dB regardless of the input SIR. Under strong interference, any noise present in the input reduces the SIR and SIIMR improvement, but a biased nonlinearity can still provide an output SIR and SIIMR superior to the input SIR, i.e. an output SIIMR 6.35 dB below the input signal-to-noise ratio (SNR) instead of 6.02 dB below the input SIR as is the case with hard limiting. >

Maximum likelihood signal estimation for polarization sensitive arrays

The authors consider the problem of separating and estimating the waveforms of superimposed signals received by a polarization-sensitive array. Signal estimation is accomplished by a two-step maximum likelihood procedure: (i) The directions of arrival and polarization parameters of all the signals are estimated. (ii) The estimated signal is obtained as a linear combination of the array outputs, with weights which are computed from the estimated direction/polarization parameters. The objective of this study is to analyze the quality of the estimated signal in terms of the output signal-to-interference ratio (SIR) and output signal-to-noise ratio (SNR). Closed-form expressions are derived for the output SIR and SNR of a general diversely polarized array. By evaluating these expressions for selected test cases it is shown that polarization-sensitive arrays can provide significantly higher output SIR and SNR than uniformly polarized arrays. The performance improvement is especially significant for closed spaced sources with sufficiently different polarization characteristics. >

Analysis of a signal estimation algorithm for diversely polarized arrays

The problem of separating and estimating the waveforms of superimposed signals received by a diversely polarized array is considered. Signal estimation is accomplished by a two-step procedure: (1) The directions of arrival and polarization parameters of all the signals are estimated using an eigenstructure-based technique; (2) The estimated signal is obtained as a linear combination of the array outputs, with weights that are computed from the estimated direction/polarization parameters. The objective is to analyze the quality of the estimated signal in terms of the output signal-to-interference ratio (SIR) and output signal-to-noise ratio (SNR). Closed-form expressions are derived for the output SIR and SNR of a general diversely polarized array. By evaluating these expressions for selected test cases it is shown that polarization sensitive arrays can provide significantly higher output SIR and SNR than uniformly polarized arrays. The performance improvement is especially significant for closely spaced sources with sufficiently different polarization characteristics. >