High resolution methods such as MUSIC fail to separate closely spaced sources in difficult contexts (low SNR, short sample size,...). Halder et al.(1997) have applied an interleaving technique to improve the resolution as well as the performances in the case of frequency estimation. Here we extend this work and deal with the application of this technique to array processing. We aim to estimate closely spaced DOAs. After a first estimation with MUSIC, a second step of the algorithm consists in refining the angle resolution using downsampled covariance matrices together with a joint estimation strategy (JES) similar to that proposed by Gershman et al. (1996). This method improves MUSIC performances especially for low SNRs. Simulations examples are provided to illustrate the performance of the proposed method referred to as two step-MUSIC (TS-MUSIC).
{"title":"Two-step MUSIC algorithm for improved array resolution","authors":"R. Chavanne, Karim Abed-Meraim, D. Medynski","doi":"10.1109/SSP.2001.955335","DOIUrl":"https://doi.org/10.1109/SSP.2001.955335","url":null,"abstract":"High resolution methods such as MUSIC fail to separate closely spaced sources in difficult contexts (low SNR, short sample size,...). Halder et al.(1997) have applied an interleaving technique to improve the resolution as well as the performances in the case of frequency estimation. Here we extend this work and deal with the application of this technique to array processing. We aim to estimate closely spaced DOAs. After a first estimation with MUSIC, a second step of the algorithm consists in refining the angle resolution using downsampled covariance matrices together with a joint estimation strategy (JES) similar to that proposed by Gershman et al. (1996). This method improves MUSIC performances especially for low SNRs. Simulations examples are provided to illustrate the performance of the proposed method referred to as two step-MUSIC (TS-MUSIC).","PeriodicalId":70952,"journal":{"name":"信号处理","volume":"218 1","pages":"512-515"},"PeriodicalIF":0.0,"publicationDate":"2001-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78006412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a closed-form solution for obtaining the optimal coefficients of variable FIR filters with continuously adjustable fractional-delay (FD) response. The design is formulated as a weighted-least-squares (WLS) approximation problem without discretizing the frequency and fractional-delay parameters. Compared with the existing WLS method, the discretization-free one can yield a closed-form optimal solution with considerably reduced computational complexity.
{"title":"Optimal design of variable fractional-delay digital filters","authors":"T. Deng","doi":"10.1109/SSP.2001.955295","DOIUrl":"https://doi.org/10.1109/SSP.2001.955295","url":null,"abstract":"This paper presents a closed-form solution for obtaining the optimal coefficients of variable FIR filters with continuously adjustable fractional-delay (FD) response. The design is formulated as a weighted-least-squares (WLS) approximation problem without discretizing the frequency and fractional-delay parameters. Compared with the existing WLS method, the discretization-free one can yield a closed-form optimal solution with considerably reduced computational complexity.","PeriodicalId":70952,"journal":{"name":"信号处理","volume":"28 1","pages":"353-356"},"PeriodicalIF":0.0,"publicationDate":"2001-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90638916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A novel CDMA receiver with adaptive multiple access interference (MAI) and narrowband interference (NBI) suppression is proposed for reverse link signal reception over multipath channels. The design of the receiver involves the following procedure. First, adaptive correlators are constructed based on the generalized sidelobe canceller (GSC) scheme to collect the multipath signals and suppress strong MAI and time-varying NBI. In particular, partial adaptivity is incorporated into the GSC for reduced complexity processing. A simple combiner with channel estimation then gives the symbol decisions. In order to enhance the performance of the adaptive correlators, a decision aided scheme is introduced which subtracts the reconstructed signal from the input data of the GSC, leading to improved output SINR and convergence. The proposed CDMA receiver is evaluated through simulations, and the results show that it can outperform the conventional MMSE receiver designed for time-invariant interference.
{"title":"A decision feedback CDMA receiver with partially adaptive interference suppression","authors":"Gau-Joe Lin, Ta-Sung Lee, Chan-Choo Tan","doi":"10.1109/SSP.2001.955234","DOIUrl":"https://doi.org/10.1109/SSP.2001.955234","url":null,"abstract":"A novel CDMA receiver with adaptive multiple access interference (MAI) and narrowband interference (NBI) suppression is proposed for reverse link signal reception over multipath channels. The design of the receiver involves the following procedure. First, adaptive correlators are constructed based on the generalized sidelobe canceller (GSC) scheme to collect the multipath signals and suppress strong MAI and time-varying NBI. In particular, partial adaptivity is incorporated into the GSC for reduced complexity processing. A simple combiner with channel estimation then gives the symbol decisions. In order to enhance the performance of the adaptive correlators, a decision aided scheme is introduced which subtracts the reconstructed signal from the input data of the GSC, leading to improved output SINR and convergence. The proposed CDMA receiver is evaluated through simulations, and the results show that it can outperform the conventional MMSE receiver designed for time-invariant interference.","PeriodicalId":70952,"journal":{"name":"信号处理","volume":"133 1","pages":"110-113"},"PeriodicalIF":0.0,"publicationDate":"2001-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84924201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The windowed linear local polynomial approximation (LPA) of the time-varying direction-of-arrival (DOA) is developed for nonparametric high-resolution estimation of multiple moving sources. The method gives the estimates of instantaneous values of the directions as well as their first derivatives. The asymptotic variance and bias of these estimates are derived and used for the optimal window size selection. Marginal beamformers are proposed for estimation and sources visualization. These marginal beamformers are able to localize and track every source individually nulling signals from all other moving sources. Recursive implementation of estimation algorithms are developed for two different tasks: estimation of DOAs with varying number of sources and multiple source tracking in time.
{"title":"Array signal processing for recursive tracking of multiple moving sources based on LPA beamforming","authors":"V. Katkovnik, Yong-Hoon Kim","doi":"10.1109/SSP.2001.955340","DOIUrl":"https://doi.org/10.1109/SSP.2001.955340","url":null,"abstract":"The windowed linear local polynomial approximation (LPA) of the time-varying direction-of-arrival (DOA) is developed for nonparametric high-resolution estimation of multiple moving sources. The method gives the estimates of instantaneous values of the directions as well as their first derivatives. The asymptotic variance and bias of these estimates are derived and used for the optimal window size selection. Marginal beamformers are proposed for estimation and sources visualization. These marginal beamformers are able to localize and track every source individually nulling signals from all other moving sources. Recursive implementation of estimation algorithms are developed for two different tasks: estimation of DOAs with varying number of sources and multiple source tracking in time.","PeriodicalId":70952,"journal":{"name":"信号处理","volume":"1 1","pages":"532-535"},"PeriodicalIF":0.0,"publicationDate":"2001-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83511569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a technique for simulating time-varying mobile radio channels. This technique is specifically suited to the small relative Doppler bandwidths of wideband channels encountered in CDMA and OFDM communications. A "subsampled" ARMA innovations filter and multistage interpolation are used to achieve an accurate and computationally efficient approximation of specified or measured Doppler spectra (scattering functions). We discuss the calculation of the ARMA coefficients and the optimal design of the multistage interpolator. Simulation results demonstrate the excellent performance of the proposed channel simulator.
{"title":"Simulation of wideband mobile radio channels using subsampled ARMA models and multistage interpolation","authors":"D. Schafhuber, G. Matz, F. Hlawatsch","doi":"10.1109/SSP.2001.955351","DOIUrl":"https://doi.org/10.1109/SSP.2001.955351","url":null,"abstract":"We present a technique for simulating time-varying mobile radio channels. This technique is specifically suited to the small relative Doppler bandwidths of wideband channels encountered in CDMA and OFDM communications. A \"subsampled\" ARMA innovations filter and multistage interpolation are used to achieve an accurate and computationally efficient approximation of specified or measured Doppler spectra (scattering functions). We discuss the calculation of the ARMA coefficients and the optimal design of the multistage interpolator. Simulation results demonstrate the excellent performance of the proposed channel simulator.","PeriodicalId":70952,"journal":{"name":"信号处理","volume":"56 7 1","pages":"571-574"},"PeriodicalIF":0.0,"publicationDate":"2001-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83382268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we discuss the application of sequential importance sampling (SIS) to joint channel estimation and decoding of space-time trellis codes (STTC). First, we present the dynamic state space model (DSSM) of the system, and then we briefly review the theory of SIS. A special case of SIS, a combination of SIS and Kalman filtering, is shown through simulations to be a viable approach to the problem which addresses time-varying flat-fading environments. Our solution is admissible if phase ambiguity can be avoided. We show that the phase ambiguity can be reduced by carefully designing the STTC modulation constellations.
{"title":"Joint channel estimation and decoding of space-time trellis codes","authors":"Jianqiu Zhang, P. Djuric","doi":"10.1109/SSP.2001.955348","DOIUrl":"https://doi.org/10.1109/SSP.2001.955348","url":null,"abstract":"In this paper, we discuss the application of sequential importance sampling (SIS) to joint channel estimation and decoding of space-time trellis codes (STTC). First, we present the dynamic state space model (DSSM) of the system, and then we briefly review the theory of SIS. A special case of SIS, a combination of SIS and Kalman filtering, is shown through simulations to be a viable approach to the problem which addresses time-varying flat-fading environments. Our solution is admissible if phase ambiguity can be avoided. We show that the phase ambiguity can be reduced by carefully designing the STTC modulation constellations.","PeriodicalId":70952,"journal":{"name":"信号处理","volume":"13 1","pages":"559-562"},"PeriodicalIF":0.0,"publicationDate":"2001-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75252838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In radio telescope arrays, the complex receiver gains and sensor noise powers are initially unknown and have to be calibrated. Gain calibration enhances the quality of astronomical sky images and moreover, improves the effectiveness of certain radio telescope phased-array data processing techniques, such as radio interference (RFI) mitigation and beamforming. We present several closed form and iterative complex gain estimation methods. These methods are analyzed and compared to the Cramer-Rao lower bound for the variance of the estimated gain. The models are tested both on simulated data and on observed telescope data.
{"title":"Gain decomposition methods for radio telescope arrays","authors":"A. Boonstra, A. van der Veen","doi":"10.1109/SSP.2001.955298","DOIUrl":"https://doi.org/10.1109/SSP.2001.955298","url":null,"abstract":"In radio telescope arrays, the complex receiver gains and sensor noise powers are initially unknown and have to be calibrated. Gain calibration enhances the quality of astronomical sky images and moreover, improves the effectiveness of certain radio telescope phased-array data processing techniques, such as radio interference (RFI) mitigation and beamforming. We present several closed form and iterative complex gain estimation methods. These methods are analyzed and compared to the Cramer-Rao lower bound for the variance of the estimated gain. The models are tested both on simulated data and on observed telescope data.","PeriodicalId":70952,"journal":{"name":"信号处理","volume":"37 1","pages":"365-368"},"PeriodicalIF":0.0,"publicationDate":"2001-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78354990","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Variable structure multiple model (VSMM) is one of the most powerful algorithms for effectively tracking a single maneuvering target. Although VSMM is developed specifically to improve the interactive multiple model (MM) method focused to reducing computational cost and improving tracking performance, it presents an inherent limitation in the form of the presence of mode set jump delay (MJD). MJD as an undesirable phenomenon in VSMM is described and analyzed. In order to eliminate the MJD, a neural network based VSMM that automatically selects the optimal mode set as achieved by supervised training is proposed. Through representative simulations we show the proposed algorithm outperforming over the conventional digraph switching VSMM in terms of tracking error.
{"title":"Neural net based variable structure multiple model reducing mode set jump delay","authors":"D. Choi, B. Ahn, Hanseok Ko","doi":"10.1109/SSP.2001.955242","DOIUrl":"https://doi.org/10.1109/SSP.2001.955242","url":null,"abstract":"Variable structure multiple model (VSMM) is one of the most powerful algorithms for effectively tracking a single maneuvering target. Although VSMM is developed specifically to improve the interactive multiple model (MM) method focused to reducing computational cost and improving tracking performance, it presents an inherent limitation in the form of the presence of mode set jump delay (MJD). MJD as an undesirable phenomenon in VSMM is described and analyzed. In order to eliminate the MJD, a neural network based VSMM that automatically selects the optimal mode set as achieved by supervised training is proposed. Through representative simulations we show the proposed algorithm outperforming over the conventional digraph switching VSMM in terms of tracking error.","PeriodicalId":70952,"journal":{"name":"信号处理","volume":"79 1","pages":"142-145"},"PeriodicalIF":0.0,"publicationDate":"2001-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74537784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Abrahamsson, E. Larsson, J. Li, J. Habersat, G. Maksymonko, M. Bradley
We address the problem of removing specular ground surface reflections and leakage/cross-talk from downward looking stepped frequency ground-penetrating radar (GPR) data. A new model for the ground-bounce and the leakage/cross-talk is introduced. An algorithm that jointly estimates these effects from collected data is presented. The algorithm has the sound foundation of a nonlinear least squares (LS) fit to the presented model. The minimization is performed in a cyclic manner where one step is a linear LS minimization and the other step is a non-linear LS minimization where the optimum can efficiently be found using, e.g., the chirp-transform algorithm. The results after applying the algorithm to measured GPR data, collected at a US army test range, are also shown.
{"title":"Elimination of leakage and ground-bounce effects in ground-penetrating radar data","authors":"R. Abrahamsson, E. Larsson, J. Li, J. Habersat, G. Maksymonko, M. Bradley","doi":"10.1109/SSP.2001.955244","DOIUrl":"https://doi.org/10.1109/SSP.2001.955244","url":null,"abstract":"We address the problem of removing specular ground surface reflections and leakage/cross-talk from downward looking stepped frequency ground-penetrating radar (GPR) data. A new model for the ground-bounce and the leakage/cross-talk is introduced. An algorithm that jointly estimates these effects from collected data is presented. The algorithm has the sound foundation of a nonlinear least squares (LS) fit to the presented model. The minimization is performed in a cyclic manner where one step is a linear LS minimization and the other step is a non-linear LS minimization where the optimum can efficiently be found using, e.g., the chirp-transform algorithm. The results after applying the algorithm to measured GPR data, collected at a US army test range, are also shown.","PeriodicalId":70952,"journal":{"name":"信号处理","volume":"116 1","pages":"150-153"},"PeriodicalIF":0.0,"publicationDate":"2001-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80879730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We analyze sonar recordings of various boats as well as ambient sea noise using nonlinear dynamical signal models. Specifically, we discuss the estimation of the parameters of nonlinear delay differential equations from data. Using the model parameters as classification features we implement a three class Bayesian minimum-error-rate classifier and demonstrate almost perfect classification of the data set considered. This indicates that classifiers based on nonlinear dynamical models can be useful in sonar applications.
{"title":"Passive signature characterization and classification by means of nonlinear dynamics","authors":"R. Lennartsson, J. Kadtke, A. Pentek","doi":"10.1109/SSP.2001.955253","DOIUrl":"https://doi.org/10.1109/SSP.2001.955253","url":null,"abstract":"We analyze sonar recordings of various boats as well as ambient sea noise using nonlinear dynamical signal models. Specifically, we discuss the estimation of the parameters of nonlinear delay differential equations from data. Using the model parameters as classification features we implement a three class Bayesian minimum-error-rate classifier and demonstrate almost perfect classification of the data set considered. This indicates that classifiers based on nonlinear dynamical models can be useful in sonar applications.","PeriodicalId":70952,"journal":{"name":"信号处理","volume":"36 1","pages":"186-189"},"PeriodicalIF":0.0,"publicationDate":"2001-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81240279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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