Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.679119
A.K. Wang, J. Leary
This paper considers the problem of co-channel interference suppression in a TDMA communication system. To improve the reception of the signal of interest (SOI) and null interfering signals, the sample matrix inversion (SMI) algorithm uses a known training sequence in each TDMA burst to tune the weights of an antenna array. However, when the interfering burst overlaps the SOI data but not the SOI training sequence, SMI performance is degraded. To overcome this problem, the constant modulus algorithm (CMA), updated over the entire SOI burst, is used to enhance the SMI array weights. Simulations of a co-channel interference scenario demonstrate that SMI-CMA achieves higher output SINR than the SMI-zero forcing and SMI-adjacent burst algorithms for a large range of burst overlap cases.
{"title":"SMI based beamforming algorithms for TDMA signals","authors":"A.K. Wang, J. Leary","doi":"10.1109/ACSSC.1997.679119","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.679119","url":null,"abstract":"This paper considers the problem of co-channel interference suppression in a TDMA communication system. To improve the reception of the signal of interest (SOI) and null interfering signals, the sample matrix inversion (SMI) algorithm uses a known training sequence in each TDMA burst to tune the weights of an antenna array. However, when the interfering burst overlaps the SOI data but not the SOI training sequence, SMI performance is degraded. To overcome this problem, the constant modulus algorithm (CMA), updated over the entire SOI burst, is used to enhance the SMI array weights. Simulations of a co-channel interference scenario demonstrate that SMI-CMA achieves higher output SINR than the SMI-zero forcing and SMI-adjacent burst algorithms for a large range of burst overlap cases.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"154 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134013394","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}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.680055
J. Perrin, S. Buljore, J. Zeidler, L. Milstein
For the next generation mobile systems, the design of high speed reliable wireless communications supporting data, image and voice transmission is of primary interest. Current cellular DS-CDMA systems have been designed to operate at low- or medium-bit rate transmission, of 9.6 or 14.4 kbits/s, but proposals to increase this data rate to 64 kbits/s, 384 kbits/s and 2 Mbits/s are currently being evaluated by the standard committees such as the Universal Mobile Telecommunications Service (UMTS or IMT-2000). We investigate the performance achievable by an asynchronous DS-CDMA system operating at data rates of up to 8 Mbits/s in conjunction with either QPSK or 16-QAM modulation and space-path diversity techniques in a frequency selective channel.
{"title":"Performance evaluation of space-path diversity and higher alphabet size for CDMA","authors":"J. Perrin, S. Buljore, J. Zeidler, L. Milstein","doi":"10.1109/ACSSC.1997.680055","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.680055","url":null,"abstract":"For the next generation mobile systems, the design of high speed reliable wireless communications supporting data, image and voice transmission is of primary interest. Current cellular DS-CDMA systems have been designed to operate at low- or medium-bit rate transmission, of 9.6 or 14.4 kbits/s, but proposals to increase this data rate to 64 kbits/s, 384 kbits/s and 2 Mbits/s are currently being evaluated by the standard committees such as the Universal Mobile Telecommunications Service (UMTS or IMT-2000). We investigate the performance achievable by an asynchronous DS-CDMA system operating at data rates of up to 8 Mbits/s in conjunction with either QPSK or 16-QAM modulation and space-path diversity techniques in a frequency selective channel.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131153034","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}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.680526
S. Hemami
Sensitivity to uniform quantization noise in wavelet subbands within an image was evaluated psychovisually with an uncontrolled survey and a controlled test. Quantizer step sizes for a single band were varied while the other bands were not quantized, allowing spatial masking to occur. The results of the survey are incorporated into a quantization strategy using standard Lagrangian bit allocation to provide images at a range of compression ratios that exhibit similar visual characteristics and are suitable for general-population use on the Web. The results of the second test suggest that quantizer step sizes causing just-noticeable-distortion are proportional to the square root of the standard deviations of the subbands rather than to the standard deviations themselves, as commonly used.
{"title":"Visual sensitivity considerations for subband coding","authors":"S. Hemami","doi":"10.1109/ACSSC.1997.680526","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.680526","url":null,"abstract":"Sensitivity to uniform quantization noise in wavelet subbands within an image was evaluated psychovisually with an uncontrolled survey and a controlled test. Quantizer step sizes for a single band were varied while the other bands were not quantized, allowing spatial masking to occur. The results of the survey are incorporated into a quantization strategy using standard Lagrangian bit allocation to provide images at a range of compression ratios that exhibit similar visual characteristics and are suitable for general-population use on the Web. The results of the second test suggest that quantizer step sizes causing just-noticeable-distortion are proportional to the square root of the standard deviations of the subbands rather than to the standard deviations themselves, as commonly used.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130967080","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}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.680244
G. Davis, S. Chawla
A number of embedded transform coders, including Shapiro's (1993) EZW coder, Said and Pearlman's (1996) SPIHT coder, and Xiong et al.'s (1996) EZDCT coder employ a common algorithm called significance tree quantization (STQ). Each of these coders have been selected from a large family of significance tree quantizers based on empirical work and a priori knowledge about transform coefficient behavior. We describe an algorithm for selecting a particular form of STQ that is optimized for a given class of images. We apply our optimization procedure to the task of quantizing 8/spl times/8 DCT blocks. Our algorithm yields a fully embedded, low-complexity coder with PSNRs up to 2.0 dB better than baseline JPEG for standard test images.
{"title":"Embedded image coding using optimized significance tree quantization","authors":"G. Davis, S. Chawla","doi":"10.1109/ACSSC.1997.680244","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.680244","url":null,"abstract":"A number of embedded transform coders, including Shapiro's (1993) EZW coder, Said and Pearlman's (1996) SPIHT coder, and Xiong et al.'s (1996) EZDCT coder employ a common algorithm called significance tree quantization (STQ). Each of these coders have been selected from a large family of significance tree quantizers based on empirical work and a priori knowledge about transform coefficient behavior. We describe an algorithm for selecting a particular form of STQ that is optimized for a given class of images. We apply our optimization procedure to the task of quantizing 8/spl times/8 DCT blocks. Our algorithm yields a fully embedded, low-complexity coder with PSNRs up to 2.0 dB better than baseline JPEG for standard test images.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133645805","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}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.680536
J. L. Sullivan, J.W. Adams
This paper presents the peak-constrained least-squares (PCLS) approach to designing IIR filters. The PCLS IIR digital and analog filters are introduced that meet simultaneous specifications on the frequency response magnitude and phase related quantities.
{"title":"PCLS IIR filters with simultaneous frequency response magnitude and phase related specifications","authors":"J. L. Sullivan, J.W. Adams","doi":"10.1109/ACSSC.1997.680536","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.680536","url":null,"abstract":"This paper presents the peak-constrained least-squares (PCLS) approach to designing IIR filters. The PCLS IIR digital and analog filters are introduced that meet simultaneous specifications on the frequency response magnitude and phase related quantities.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132646481","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}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.680436
M. Amin, X. Ouyang, A. Lindsey
We use recursive short-time Fourier transforms (STFT) for interference excision in PN spread spectrum communication systems. The proposed excision method is based on the attractive localization properties of the impulse responses of the multiple pole filters. These impulse responses have Gaussian-like shapes and decrease in bandwidth with higher pole multiplicities. When used as a data window before Fourier transformation, they result in a large class of computationally efficient STFTs. Localization measures can be applied to determine the proper window (impulse response), which maximally concentrates the jammer in the time-frequency domain. Interference mitigation is then achieved by applying a binary excision to the STFT employing the optimum window for each data bit. We show that this method permits both data-dependent windowing and filtering, and leads to improved BER performance of the DS/SS system.
{"title":"Recursive Fourier transform for interference suppression in PN spread spectrum communications","authors":"M. Amin, X. Ouyang, A. Lindsey","doi":"10.1109/ACSSC.1997.680436","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.680436","url":null,"abstract":"We use recursive short-time Fourier transforms (STFT) for interference excision in PN spread spectrum communication systems. The proposed excision method is based on the attractive localization properties of the impulse responses of the multiple pole filters. These impulse responses have Gaussian-like shapes and decrease in bandwidth with higher pole multiplicities. When used as a data window before Fourier transformation, they result in a large class of computationally efficient STFTs. Localization measures can be applied to determine the proper window (impulse response), which maximally concentrates the jammer in the time-frequency domain. Interference mitigation is then achieved by applying a binary excision to the STFT employing the optimum window for each data bit. We show that this method permits both data-dependent windowing and filtering, and leads to improved BER performance of the DS/SS system.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132755452","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}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.679147
L. Scharf, B. Friedlander, C. Mullis
The quadratic time-frequency representations (TFRs) that may be called time-varying spectrum estimators are derived from first principles. They turn out to be time-varying multiwindow spectrum estimators. In special cases they are time-varying spectrograms that may be written as Fourier transforms of lag-windowed, time-varying correlation sequences or as spectrally smoothed time-varying periodograms. These are not ad-hoc variations on stationary ideas to accommodate time variation. Rather they are the only variations one can obtain for time-varying spectrum analysis.
{"title":"Time-varying spectrum estimators","authors":"L. Scharf, B. Friedlander, C. Mullis","doi":"10.1109/ACSSC.1997.679147","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.679147","url":null,"abstract":"The quadratic time-frequency representations (TFRs) that may be called time-varying spectrum estimators are derived from first principles. They turn out to be time-varying multiwindow spectrum estimators. In special cases they are time-varying spectrograms that may be written as Fourier transforms of lag-windowed, time-varying correlation sequences or as spectrally smoothed time-varying periodograms. These are not ad-hoc variations on stationary ideas to accommodate time variation. Rather they are the only variations one can obtain for time-varying spectrum analysis.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"155-156 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133803160","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}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.679076
G.T. Zhou, R.W. Schafer, W. Schafer
The Poisson random process is widely used to describe experiments involving discrete arrival data. However, for creating models of egg-laying behavior in recent neural biology studies on the nematode Caenorhabditis elegans, the authors have found that homogeneous Poisson processes are inadequate to capture the measured temporal patterns. They present here a novel three-state model that effectively represents the measured temporal patterns and that correlates well with the cellular and molecular mechanisms that are known to be responsible for the measured behavior. Although the model involves a combination of two Poisson processes, it is surprisingly tractable. The authors derive closed-form expressions for the probabilistic and statistical properties of the model and present several parameter estimation procedures including a maximum likelihood algorithm. Both simulated and experimental results are illustrated. The experiments with measured data show that the egg-laying patterns fit the three-state model very well. The model also may be applicable in quantifying the link between other neural processes and behavior or in other situations where discrete events occur in clusters.
{"title":"A point process model for biological events involving activation","authors":"G.T. Zhou, R.W. Schafer, W. Schafer","doi":"10.1109/ACSSC.1997.679076","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.679076","url":null,"abstract":"The Poisson random process is widely used to describe experiments involving discrete arrival data. However, for creating models of egg-laying behavior in recent neural biology studies on the nematode Caenorhabditis elegans, the authors have found that homogeneous Poisson processes are inadequate to capture the measured temporal patterns. They present here a novel three-state model that effectively represents the measured temporal patterns and that correlates well with the cellular and molecular mechanisms that are known to be responsible for the measured behavior. Although the model involves a combination of two Poisson processes, it is surprisingly tractable. The authors derive closed-form expressions for the probabilistic and statistical properties of the model and present several parameter estimation procedures including a maximum likelihood algorithm. Both simulated and experimental results are illustrated. The experiments with measured data show that the egg-laying patterns fit the three-state model very well. The model also may be applicable in quantifying the link between other neural processes and behavior or in other situations where discrete events occur in clusters.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115425954","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}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.680189
R. Hardesty, W. Brewer, B. J. Rye
Doppler lidar offers a method of remotely measuring wind speeds in optically clear air. A laser source directs a pulse of narrowband optical radiation into the atmosphere. As the pulse propagates, it irradiates small aerosol particles, which scatter radiation back toward the lidar system. Because the aerosol particles are small enough to be borne by the wind, the frequency of the scattered radiation is Doppler shifted as a result of motion toward or away from the lidar. Measurement of this Doppler shift provides an estimate of the radial wind component, while computation of the power in the backscattered radiation gives insight into the atmospheric turbidity, presence of aerosol layers or clouds, and attenuation. Pulsed Doppler lidar systems have been used in a number of meteorological applications. Deployment of a Doppler lidar on an Earth-orbiting satellite has been proposed to remotely measure tropospheric winds on a global scale. In a large number of these applications, lidar system performance, impact, and maximum range is limited by weak backscattered signals present at the lidar receiver. Because potential methods of improving signal-to-noise ratio can be technically infeasible and/or very expensive, optimizing signal processing of the lidar return to improve performance at very low signal levels has received significant attention. In the remainder of this paper, we describe techniques for processing Doppler lidar returns from weak and fluctuating signals, and discuss system design tradeoffs to obtain maximum performance.
{"title":"Estimation of wind velocity and backscatter signal intensity from Doppler lidar returns","authors":"R. Hardesty, W. Brewer, B. J. Rye","doi":"10.1109/ACSSC.1997.680189","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.680189","url":null,"abstract":"Doppler lidar offers a method of remotely measuring wind speeds in optically clear air. A laser source directs a pulse of narrowband optical radiation into the atmosphere. As the pulse propagates, it irradiates small aerosol particles, which scatter radiation back toward the lidar system. Because the aerosol particles are small enough to be borne by the wind, the frequency of the scattered radiation is Doppler shifted as a result of motion toward or away from the lidar. Measurement of this Doppler shift provides an estimate of the radial wind component, while computation of the power in the backscattered radiation gives insight into the atmospheric turbidity, presence of aerosol layers or clouds, and attenuation. Pulsed Doppler lidar systems have been used in a number of meteorological applications. Deployment of a Doppler lidar on an Earth-orbiting satellite has been proposed to remotely measure tropospheric winds on a global scale. In a large number of these applications, lidar system performance, impact, and maximum range is limited by weak backscattered signals present at the lidar receiver. Because potential methods of improving signal-to-noise ratio can be technically infeasible and/or very expensive, optimizing signal processing of the lidar return to improve performance at very low signal levels has received significant attention. In the remainder of this paper, we describe techniques for processing Doppler lidar returns from weak and fluctuating signals, and discuss system design tradeoffs to obtain maximum performance.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"45 7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115560921","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}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.680439
M. Webster, R. Roberts
Discrete multitone modulation (DMT) is a useful waveform in the communication systems engineer's toolbox. For certain applications, DMT produces designs which are easier to implement than a single-carrier-based design, while attaining higher performance. An important component in the asymmetric digital subscriber loop (ADSL) the DMT system is the finite-length equalizer which truncates the channel impulse response, greatly reducing the requisite FFT size. This paper argues that the preferred channel-truncating equalizer is one which whitens the composite error sequence. A white error sequence tends to achieve information-transmission optimality.
{"title":"Finite length equalization for FFT-based multicarrier systems-an error-whitening viewpoint","authors":"M. Webster, R. Roberts","doi":"10.1109/ACSSC.1997.680439","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.680439","url":null,"abstract":"Discrete multitone modulation (DMT) is a useful waveform in the communication systems engineer's toolbox. For certain applications, DMT produces designs which are easier to implement than a single-carrier-based design, while attaining higher performance. An important component in the asymmetric digital subscriber loop (ADSL) the DMT system is the finite-length equalizer which truncates the channel impulse response, greatly reducing the requisite FFT size. This paper argues that the preferred channel-truncating equalizer is one which whitens the composite error sequence. A white error sequence tends to achieve information-transmission optimality.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114305377","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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