[Show abstract][Hide abstract] ABSTRACT: The most commonly used spectrum sensing techniques in cognitive radio (CR) networks, such as the energy detector (ED), matched filter (MF), and others, suffer from the noise uncertainty and signal-to-noise ratio (SNR) wall phenomenon. These detectors cannot achieve the required signal detection performance regardless of the sensing time. In this paper, we explore a signal processing scheme, namely, the generalized detector (GD) constructed based on the generalized approach to signal processing (GASP) in noise, in spectrum sensing of CR network based on antenna array with the purpose to alleviate the SNR wall problem and improve the signal detection robustness under the low SNR. The simulation results confirm our theoretical issues and effectiveness of GD implementation in CR networks based on antenna array.
[Show abstract][Hide abstract] ABSTRACT: An adaptive detection threshold under employment of the generalised detector (GD) in radar sensor systems is defined. GD is constructed in accordance with the generalised approach to signal processing in noise. To define the GD adaptive threshold based on the observed noise samples, the authors apply an appropriate noise power estimation technique. This study deals with an adaptive GD detection threshold definition as a function of the estimated noise power. Under investigations, they use two noise power estimation procedures. The first is the sliding window technique with the reference cells. The second procedure is based on the adaptive noise power estimation. Comparative analysis of simulation results demonstrates superiority by detection performance in favour of GD implementation in comparison with the well-known constant false alarm rate (CFAR) detectors, namely, cell averaging CFAR and ordered statistics CFAR detectors.
IET Signal Processing 08/2014; 8(6):622-632. DOI:10.1049/iet-spr.2013.0235 · 0.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We derive the probability of false alarm and detection threshold under employment of the generalized detector (GD) in cognitive radio (CR) systems for two scenarios: firstly, the independent antenna array elements; the secondly, the correlated antenna array elements. The energy detector (ED) and GD spectrum sensing performances are compared under the same initial conditions. The simulation results show that implementation of the GD improves the spectrum sensing performance in CR systems both for independent and correlated antenna array elements.
International Journal of Antennas and Propagation 06/2013; 2013. DOI:10.1155/2013/853746 · 0.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The bit error rate (BER) performance of wireless communication system employing the generalized receiver (GR) under the binary phase shift keying (BPSK) modulation over Rayleigh fading channel with three common diversity combining techniques, namely, the selection combining, equal gain combining, and maximal ratio combining with the purpose to mitigate the effects of multipath fading is investigated. Simulation demonstrates a high performance gain under employment of GR in wireless communication system in comparison with modern approaches.
[Show abstract][Hide abstract] ABSTRACT: The parametric Rao test for multichannel adaptive signal detection by
the adaptive generalized detector (GD) constructed based on the
generalized approach to signal processing in noise is derived by
modeling the disturbance signal as a multichannel autoregressive
process. The parametric Rao test takes a form identical to that of
parametric GD for space-time adaptive processing in airborne
surveillance radar systems and other similar applications. The
equivalence offers new insights into the performance and implementation
of the GD. Specifically, the Rao/GD is asymptotically (in the case of
large samples) a parametric generalized likelihood ratio test
generalized detector (GLRT GD) due to an asymptotic equivalentce between
the Rao test and the GLRT/GD. The asymptotic distribution of the Rao/GD
test statistic is obtained in closed form, which follows an exponential
distribution under the null hypothesis (the target return signal is
absent) and, respectively, a non-central Chi-squared distribution with
two degrees of freedom under the alternative hypothesis (the target
return signal is present). The noncentrality parameter of the noncentral
Chi-squared distribution is determined by the output
signal-to-interference-plus-noise ratio of a temporal whitening filter.
Since the asymptotic distribution under the null hypothesis is
independent of the unknown parameters, the Rao/GD asymptotically
achieves constant false alarm rate (CFAR) GD. Numerical results show
that these results are superior in predicting the performance of the
parametric adaptive matched filter detector even with moderate data
Proceedings of SPIE - The International Society for Optical Engineering 05/2012; 8393:4-. DOI:10.1117/12.919843 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Probability of bit-error Per performance of asynchronous direct-sequence
code-division multiple-access (DS-CDMA) wireless communication systems
employing the generalized detector (GD) constructed based on the
generalized approach to signal processing in noise is analyzed. The
effects of pulse shaping, quadriphase or direct sequence quadriphase
shift keying (DS-QPSK) spreading, aperiodic spreading sequences are
considered in DS-CDMA based on GD and compared with the coherent
Neyman-Pearson receiver. An exact Per expression and several
approximations: one using the characterristic function method, a
simplified expression for the improved Gaussian approximation (IGA) and
the simplified improved Gaussian approximation are derived. Under
conditions typically satisfied in practice and even with a small number
of interferers, the standard Gaussian approximation (SGA) for the
multiple-access interference component of the GD statistic and Per
performance is shown to be accurate. Moreover, the IGA is shown to
reduce to the SGA for pulses with zero excess bandwidth. Second, the GD
Per performance of quadriphase DS-CDMA is shown to be superior to that
of bi-phase DS-CDMA. Numerical examples by Monte Carlo simulation are
presented to illustrate the GD Per performance for square-root
raised-cosine pulses and spreading factors of moderate to large values.
Also, a superiority of GD employment in CDMA systems over the
Neyman-Pearson receiver is demonstrated
Proceedings of SPIE - The International Society for Optical Engineering 05/2012; 8404:14-. DOI:10.1117/12.920351 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We consider a problem of detecting a random spatially distributed signal
source by an array of sensors based on the generalized approach to
signal processing in noise. We derive some generalized detector (GD)
structures under several assumptions on the available statistics. The GD
performance is evaluated and the effect of source angular spread is
investigated. We notice the degrees of freedom of detection statistic
distributions depend on both the signal angular spread and the number of
data snapshots. At high signal-to-noise ratio and with small degrees of
freedom, an increase of angular spread improves the detection
performance. With large degrees of freedom the increase of angular
spread reduces the detection performance. A comparison between GD and
conventional beamformer is carried out by computer simulations. The
results indicate a superiority of GD as the angular spread becomes large
over the conventional beamformer detector.
Proceedings of SPIE - The International Society for Optical Engineering 05/2012; 8361:193-. DOI:10.1117/12.919579 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The noise power estimation process is a vital factor to adaptively define a threshold of target return signal in radar sensor systems and controller area networks (CAN) that are employed to design safety driving applications, collision avoidance systems, and target vehicle tracking systems. This research derives the required detection threshold under implementation of the generalized detector (GD) in frequency modulation continuous wave (FMCW) radar sensor systems for safety driving and tracking applications, for example, under closing vehicle detection. In this paper we propose an appropriate adaptive noise power estimation technique to define the GD threshold based on locally observed noise samples. The improvement in the detection performance reflects an effectiveness of the proposed solution.
[Show abstract][Hide abstract] ABSTRACT: Radar sensors are an attractive technology for different kinds of applications, especially, in the case of safety driving systems. This research deals with designing the target return signal detection algorithm for radar sensors using the generalized detector (GD) with adaptive detection threshold based on a sliding window technique to estimate the noise power. The general GD structure is introduced, and the proposed method to define the adaptive detection threshold is assumed to be employed by 24 GHz frequency modulation continuous wave (FMCW) radar sensor and the simulation results show the better detection performance in comparison with the cell averaging constant false alarm rate (CA-CFAR) detector one which is widely used by radar sensor systems for car applications.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we investigate a generalized receiver (GR) constructed on the basis of the generalized approach to signal processing (GASP) in noise employing by direct-sequence code-division multiple access (DS-CDMA) downlink wireless communication system with multipath fading. Transmitted signaling technique is based on using the orthogonal unified complex Hadamard transform spreading sequences. The use of GR allows us to maintain the orthogonality between users and reduce the multipath fading effect and interference from other users. A general multipath-fading model is assumed. Bit-error rate (BER) performance of system is evaluated by means of the signal-to-interference-plus-noise ratio (SINR) at the output of GR employed by DS-CDMA downlink wireless communication system. Using the orthogonal unified complex Hadamard transform spreading sequences as the transmitted signaling technique, we obtain that SINR at the GR output is independent of the phase offsets between different paths. If the Walsh–Hadamard (WH) spreading sequences are used as the transmitted signaling technique, the SINR at the output of GR employed by the same system is a function of squared cosine of path phase offsets. As a result, the BER performance of the last DS-CDMA downlink wireless communication system is worse in comparison with that of the first system. Comparative analysis between the BER performance of DS-CDMA downlink wireless communication systems employing both the GR and the Rake receiver, which consists of a bank of correlation receivers, with each individual receiver correlating with a different arriving multipath component, shows us a superiority of the first system over the second one both at high and low SINRs.
Digital Signal Processing 12/2011; 21(6):725-733. DOI:10.1016/j.dsp.2011.07.005 · 1.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The generalized receiver (GR) based on a generalized approach to signal processing (GASP) in noise is investigated in a direct-sequence
code-division multiple access (DS-CDMA) wireless communication system with frequency-selective channels. We consider four
avenues: linear equalization with finite impulse response (FIR) beamforming filters; channel estimation and spatially correlation;
optimal combining; and partial cancellation. We investigate the GR with simple linear equalization and FIR beamforming filters.
Numerical results and simulation show that the GR with FIR beamforming filters surpasses in performance the optimum infinite
impulse response beamforming filters with conventional receivers, and can closely approach the performance of GR with infinite
impulse response beamforming filters. Channel estimation errors are taken into consideration so that DS-CDMA wireless communication
system performance will not be degraded under practical channel estimation. GR takes an estimation error of a maximum likelihood
(ML) multiple-input multiple-output (MIMO) channel estimation and GR spatially correlation into account in computation of
minimum mean square error (MMSE) and log-likelihood ratio (LLR) of each coded bit. The symbol error rate (SER) performance
of DS-CDMA employing GR with a quadrature sub-branch hybrid selection/maximal-ratio combining (HS/MRC) scheme for 1-D modulations
in Rayleigh fading is obtained and compared with that of conventional HS/MRC receivers. Procedure of selecting a partial cancelation
factor (PCF) for the first stage of a hard-decision partial parallel interference cancellation (PPIC) of the GR employed in
DS-CDMA wireless communication system is proposed. A range of optimal PCFs is derived based on the Price’s theorem. Computer
simulation results show superiority in bit error rate (BER) performance that is very close to that potentially achieved and
surpasses the BER performance of the real PCF for DS-CDMA systems discussed in literature.
KeywordsDirect-sequence code-division multiple access (DS-CDMA)–Generalized receiver (GR)–Frequency-selective fading–Signal-to-interference-plus-noise ratio (SINR)–Bit-error rate (BER) performance–Additive white Gaussian noise (AWGN)–Rake receiver–Symbol error rate (SER) performance
Circuits Systems and Signal Processing 12/2011; 30(6):1197-1230. DOI:10.1007/s00034-011-9273-1 · 1.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper, we consider the problem of M-ary signal detection based on the generalized approach to signal processing (GASP) in noise over a single-input multiple-output (SIMO) channel affected by frequency-dispersive Rayleigh distributed fading and corrupted by additive non-Gaussian noise modeled as spherically invariant random process. We derive both the optimum generalized detector (GD) structure based on GASP and a suboptimal reduced-complexity GD applying the low energy coherence approach jointly with the GASP in noise. Both GD structures are independent of the actual noise statistics. We also carry out a performance analysis of both GDs and compare with the conventional receivers. The performance analysis is carried out with reference to the case that the channel is affected by a frequency-selective fading and for a binary frequency-shift keying (BFSK) signaling format. The results obtained through both a Chernoff-bounding technique and Monte Carlo simulations reveal that the adoption of diversity also represents a suitable means to restore performance in the presence of dispersive fading and impulsive non-Gaussian noise. It is also shown that the suboptimal GD incurs a limited loss with respect to the optimum GD and this loss is less in comparison with the conventional receiver.
Proceedings of SPIE - The International Society for Optical Engineering 05/2011; 8050. DOI:10.1117/12.883763 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper, we address an adaptive detection of range-spread targets or targets embedded in Gaussian noise with unknown covariance matrix by the generalized detector (GD) based on the generalized approach to signal processing (GASP) in noise. We assume that cells or secondary data that are free of signal components are available. Those secondary data are supposed to process either the same covariance matrix or the same structure of the covariance matrix of the cells under test. In this context, under designing GD we use a two-step procedure. The criteria lead to receivers ensuring the constant false alarm rate (CFAR) property with respect to unknown quantities. A thorough performance assessment of the proposed detection strategies highlights that the two-step design procedure of decision-making rule in accordance with GASP is to be preferred with respect to the plain one. In fact, the proposed design procedure leads to GD that achieves significant improvement in detection performance under several situation of practical interest. For estimation purposes, we resort to a set of secondary data. In addition to the classical homogeneous scenario, we consider the case wherein the power value of primary and secondary data vectors is not the same. The design of adaptive detection algorithms based on GASP in the case of mismatch is a problem of primary concern for radar applications. We demonstrate that two-step design procedure based on GASP ensures minimal loss.
Proceedings of SPIE - The International Society for Optical Engineering 05/2011; 8021. DOI:10.1117/12.883759 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The frequency modulation continuous wave (FMCW) technique is widely used in radar sensor systems with the purpose to prevent vehicle collisions and in other safety driving systems. In this paper, we consider the signal detection algorithm based on linear FMCW (LFMCW) technique to define the relative velocity of the target vehicle. Additionally, we define the distance between the subject and target vehicles. We present simulation results for LFMCW radar sensor system.
[Show abstract][Hide abstract] ABSTRACT: Symbol error rate (SER) of quadrature subbranch hybrid selection/maximal- ratio combining (HS/MRC) scheme for 1-D modulations in Rayleigh fading under employment of the generalized receiver (GR), which is constructed based on the generalized approach to signal processing (GASP) in noise, is investigated. N diversity input branches are split into 2 N in-phase and quadrature subbranches. M -ary pulse amplitude modulation, including coherent binary phase-shift keying (BPSK), with quadrature subbranch HS/MRC is investigated. GR SER performance for quadrature HS/MRC and HS/MRC schemes is investigated and compared with the conventional HS/MRC receiver. Comparison shows that the GR with quadrature subbranch HS/MRC and HS/MRC schemes outperforms the traditional HS/MRC receiver. Procedure of partial cancellation factor (PCF) selection for the first stage of hard-decision partial parallel interference cancellation (PPIC) using GR employed by direct-sequence code-division multiple access (DS-CDMA) systems under multipath fading channel in the case of periodic code scenario is proposed. Optimal PCF range is derived based on Price's theorem. Simulation confirms that the bit error rate (BER) performance is very close to potentially achieved one and surpasses the BER performance of real PCF for DS-CDMA systems discussed in the literature.
Journal on Advances in Signal Processing 01/2011; 2011. DOI:10.1155/2011/913189 · 0.78 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We derive the closed-form expressions for the bit error rate (BER) performance of M-ary pulse am-plitude modulated (MPAM) signal constellations under implementation of the generalized detector (GR), which is constructed based on the generalized approach to signal processing in noise, as a function of the analog-to-di-gital converter (ADC) word length, the signal-to-noise ratio (SNR), and the fading distribution. These results allow us rapidly and accurately to evaluate the system performance when the ADC resolution is limited, as is generally the case in high sampling rate wireless communication systems, and thus provide a useful tool for wi-reless communication system design based on the generalized approach to signal processing in noise, analysis and optimization.
[Show abstract][Hide abstract] ABSTRACT: A multiuser detection scheme based on the generalized approach to signal processing in noise is proposed. It is shown that under this scheme, the generalized receiver can be designed blindly, i.e., it can be estimated from the received signal with the prior knowledge of only the signature waveform and timing of the user of interest. A blind adaptive implementation based on a signal subspace-tracking algorithm is also developed. It is seen that compared with the minimum-output-energy blind adaptive multiuser detector, the proposed subspace-based blind adaptive generalized receiver offers better performance but higher computational complexity.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we consider the problem of multiple-input multiple-output (MIMO) radars employing the generalized detector based on the generalized approach to signal processing in noise and using the space-time coding to achieve desired diversity. To that end, we derive a suitable generalized detector structure after briefly outlining the model of the received target return signal. The generalized detector performance is expressed in closed form as a function of the clutter statistical properties and of the space-time code matrix. We investigate a particular case when the generalized detector requires a priori knowledge of the clutter covariance, i.e., the decision statistics, under the null hypothesis of no target, is an ancillary statistic, in the sense that it depends on the actual clutter covariance matrix, but its probability density function (pdf) is functionally independent of such a matrix. Therefore, threshold setting is feasible with no a priori knowledge as to the clutter power spectrum. As to the detection performance, a general integral form of the detection probability is provided, holding independent of the target fluctuation model. The formula is not analytically manageable, nor does it appear to admit general approximate expressions, which allow giving an insightful look in the system behavior. We thus restrict our attention to the case of Rayleigh-distributed target attenuation (Swerling-1 model). To code construction we use an information-theoretic approach. This approach offers a methodological framework for space-time coding in MIMO radar systems, as well as simple and intuitive bounds for performance prediction.
Proceedings of SPIE - The International Society for Optical Engineering 04/2010; DOI:10.1117/12.850668 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We consider the problem of waveform design for multiple-input multiple-output (MIMO) radar systems employing the generalized detector that is constructed based on the generalized approach to signal processing in noise. We investigate the case of an extended target and without limiting ourselves to orthogonal waveforms. Instead, we develop a procedure to design the optimal waveform that maximizes the signal-to-interference plus-noise ratio (SINR) at the generalized detector output. The optimal waveform requires a knowledge of both target and clutter statistics. We also develop several suboptimal waveforms requiring knowledge of target statistics only, clutter statistics only, or both. Thus, the transmit waveforms are adjusted based on target and clutter statistics. A model for the radar returns that incorporates the transmit waveforms is developed. The target detection problem is formulated for that model. Optimal and suboptimal algorithms are derived for designing the transmit waveforms under different assumptions regarding the statistical information available to the generalized detector. The performance of these algorithms is illustrated by computer simulation.
Proceedings of SPIE - The International Society for Optical Engineering 04/2010; 7697. DOI:10.1117/12.850858 · 0.20 Impact Factor