Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.737000
M. Bingle, J. Cloete, D. Davidson
A theoretical and experimental study is conducted to investigate the role of chirality in synthetic microwave absorbers. Three closely related anisotropic unit cells of thin wire objects, one chiral, one racemic and one non-chiral, are studied around resonance in a rectangular waveguide. Conducting thin wire chiral and non-chiral objects, embedded in an absorbing dielectric host and positioned in a rectangular waveguide, are numerically analysed with the finite difference time domain method. Measured and predicted results for the scattering parameters are presented.
{"title":"Microwave absorption by chiral, racemic and non-chiral unit cells: the role of chirality in absorbing materials","authors":"M. Bingle, J. Cloete, D. Davidson","doi":"10.1109/COMSIG.1998.737000","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.737000","url":null,"abstract":"A theoretical and experimental study is conducted to investigate the role of chirality in synthetic microwave absorbers. Three closely related anisotropic unit cells of thin wire objects, one chiral, one racemic and one non-chiral, are studied around resonance in a rectangular waveguide. Conducting thin wire chiral and non-chiral objects, embedded in an absorbing dielectric host and positioned in a rectangular waveguide, are numerically analysed with the finite difference time domain method. Measured and predicted results for the scattering parameters are presented.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126883245","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736915
W. Wilson, M. Winter, C. Nohr, F. Aghdasi
Fast Fourier transformation (FFT) of the auditory brainstem response (ABR) has proven useful in improving this tests sensitivity and specificity as a diagnostic assessment tool, but has suffered from poor control of pre-FFT windowing procedures. This study compared the clinical significance, as versus the obvious mathematical significance, of using no Blackman, and modified Blackman window techniques for FFT analysis of ABRs in normal subjects. Windowing was shown to statistically reduce ABR FFT magnitudes with the differences between window results all being clinically significant. These findings warn against the clinical comparison of ABR FFT results obtained using different windows and reinforces the need to state specifically the FFT procedures used when conducting clinical ABR frequency analysis.
{"title":"Signal processing of the auditory brainstem response: clinical effects of variations in fast Fourier transform analysis","authors":"W. Wilson, M. Winter, C. Nohr, F. Aghdasi","doi":"10.1109/COMSIG.1998.736915","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736915","url":null,"abstract":"Fast Fourier transformation (FFT) of the auditory brainstem response (ABR) has proven useful in improving this tests sensitivity and specificity as a diagnostic assessment tool, but has suffered from poor control of pre-FFT windowing procedures. This study compared the clinical significance, as versus the obvious mathematical significance, of using no Blackman, and modified Blackman window techniques for FFT analysis of ABRs in normal subjects. Windowing was shown to statistically reduce ABR FFT magnitudes with the differences between window results all being clinically significant. These findings warn against the clinical comparison of ABR FFT results obtained using different windows and reinforces the need to state specifically the FFT procedures used when conducting clinical ABR frequency analysis.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114232290","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736940
R. Majoor, F. Takawira
Several MAC protocols for wireless ATM have been described in the literature; TDMA and FDMA combinations making up the bulk of these. Very little has appeared on MAC protocols for ATM over CDMA channels. This paper introduces a protocol for carrying ATM cells over a wireless CDMA channel between a mobile and a base station. The paper considers CBR, VBR and ABR traffic. QoS is guaranteed in the CAC scheme, and implemented using a power control mechanism. The protocol makes use of a movable boundary mechanism to partition the bandwidth in proportion to traffic demand. The soft capacity nature of CDMA is exploited by allowing CBR and VBR traffic to 'steal' bandwidth from ABR traffic. Simulation results show that this leads to a greater throughput than would be achieved without this mechanism.
{"title":"A MAC protocol for wireless ATM over CDMA","authors":"R. Majoor, F. Takawira","doi":"10.1109/COMSIG.1998.736940","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736940","url":null,"abstract":"Several MAC protocols for wireless ATM have been described in the literature; TDMA and FDMA combinations making up the bulk of these. Very little has appeared on MAC protocols for ATM over CDMA channels. This paper introduces a protocol for carrying ATM cells over a wireless CDMA channel between a mobile and a base station. The paper considers CBR, VBR and ABR traffic. QoS is guaranteed in the CAC scheme, and implemented using a power control mechanism. The protocol makes use of a movable boundary mechanism to partition the bandwidth in proportion to traffic demand. The soft capacity nature of CDMA is exploited by allowing CBR and VBR traffic to 'steal' bandwidth from ABR traffic. Simulation results show that this leads to a greater throughput than would be achieved without this mechanism.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129065645","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736917
D. Saban, R. Braun
A multicarrier direct sequence code division multiple access (MC-DS-CDMA) technique is proposed for point-to-multipoint communication systems. Time delays and related interference phenomenon are discussed and multicarrier techniques for mitigating multipath effects are highlighted. An independent two-ray multipath model is used for determining the major channel effects that influence multicarrier DS-CDMA. In particular, time dispersion and frequency distortion are examined in terms of their effect on multicarrier modulation schemes. Empirical simulated analysis is presented for additive white Gaussian and multipath channels in order to highlight the bandwidth efficiency, interference generation and the bit error rate (BER) of multicarrier DS-CDMA under selected multipath configurations. Coding strategies are discussed for mitigating multipath induced error and their expense on the bandwidth efficiency is emphasized.
{"title":"Multi-carrier direct sequence CDMA in fading situations","authors":"D. Saban, R. Braun","doi":"10.1109/COMSIG.1998.736917","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736917","url":null,"abstract":"A multicarrier direct sequence code division multiple access (MC-DS-CDMA) technique is proposed for point-to-multipoint communication systems. Time delays and related interference phenomenon are discussed and multicarrier techniques for mitigating multipath effects are highlighted. An independent two-ray multipath model is used for determining the major channel effects that influence multicarrier DS-CDMA. In particular, time dispersion and frequency distortion are examined in terms of their effect on multicarrier modulation schemes. Empirical simulated analysis is presented for additive white Gaussian and multipath channels in order to highlight the bandwidth efficiency, interference generation and the bit error rate (BER) of multicarrier DS-CDMA under selected multipath configurations. Coding strategies are discussed for mitigating multipath induced error and their expense on the bandwidth efficiency is emphasized.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"100 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127175888","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736914
W. Wilson, M. Winter, G. Kerr, F. Aghdasi
Multiresolutional wavelet analysis of the auditory brainstem response (ABR) in the time frequency domain (TFD) has immense potential for improving this test's sensitivity and specificity as a diagnostic assessment tool, but the choice of wavelet remains a problem. This study compared the clinical significance, as versus the obvious mathematical significance, of using Daubechies 5, symlet 4, and biorthogonal 3.5 wavelet techniques to obtain ABR TFD results in normal subjects. The wavelet techniques showed multiple statistical differences between their TFD results, with a significant number being clinically significant, particularly for TFD component amplitudes. These findings warn against the clinical comparison of TFD ABR results obtained using different wavelets and reinforces the need to state specifically the wavelet procedures used when conducting clinical ABR multiresolutional wavelet analysis.
{"title":"Signal processing of the auditory brainstem response: investigation into the use of discrete wavelet analysis","authors":"W. Wilson, M. Winter, G. Kerr, F. Aghdasi","doi":"10.1109/COMSIG.1998.736914","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736914","url":null,"abstract":"Multiresolutional wavelet analysis of the auditory brainstem response (ABR) in the time frequency domain (TFD) has immense potential for improving this test's sensitivity and specificity as a diagnostic assessment tool, but the choice of wavelet remains a problem. This study compared the clinical significance, as versus the obvious mathematical significance, of using Daubechies 5, symlet 4, and biorthogonal 3.5 wavelet techniques to obtain ABR TFD results in normal subjects. The wavelet techniques showed multiple statistical differences between their TFD results, with a significant number being clinically significant, particularly for TFD component amplitudes. These findings warn against the clinical comparison of TFD ABR results obtained using different wavelets and reinforces the need to state specifically the wavelet procedures used when conducting clinical ABR multiresolutional wavelet analysis.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":" 39","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132074545","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736944
W. Penzhorn
The linear complexity of a binary sequences is an important attribute in applications such as secure communications. In this article we introduce the concept of quadratic complexity of a binary sequences. It is shown that this complexity measure is closely linked to the theory of primitive Reed-Muller codes. Making use of the parity-check polynomial h(x) of a Reed-Muller code, a new algorithm for the computation of the quadratic complexity profile of a sequence is developed. Experimental results confirm the close resemblance between expected theoretical and practical behaviour.
{"title":"Quadratic complexity of binary sequences","authors":"W. Penzhorn","doi":"10.1109/COMSIG.1998.736944","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736944","url":null,"abstract":"The linear complexity of a binary sequences is an important attribute in applications such as secure communications. In this article we introduce the concept of quadratic complexity of a binary sequences. It is shown that this complexity measure is closely linked to the theory of primitive Reed-Muller codes. Making use of the parity-check polynomial h(x) of a Reed-Muller code, a new algorithm for the computation of the quadratic complexity profile of a sequence is developed. Experimental results confirm the close resemblance between expected theoretical and practical behaviour.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121285615","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736926
N. van der Merwe, A. Hoffman
The selection and preprocessing of features are crucial to the success of a classifier for pattern recognition applications. The preprocessing often involves filters, transformations and non-linear processing of the raw data. Since the training data required is an exponential function of the number of features, a reduction or transformation of the features is essential. While it is frequently possible to heuristically select reasonable values pertaining to the selection of these parameters, an automated approach could be of great value in different application areas. Various factors relating to the optimization process are described and the results of continuous wavelet based optimization on seismic buffer recognition are described.
{"title":"Closed loop optimization of features for neural classifiers","authors":"N. van der Merwe, A. Hoffman","doi":"10.1109/COMSIG.1998.736926","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736926","url":null,"abstract":"The selection and preprocessing of features are crucial to the success of a classifier for pattern recognition applications. The preprocessing often involves filters, transformations and non-linear processing of the raw data. Since the training data required is an exponential function of the number of features, a reduction or transformation of the features is essential. While it is frequently possible to heuristically select reasonable values pertaining to the selection of these parameters, an automated approach could be of great value in different application areas. Various factors relating to the optimization process are described and the results of continuous wavelet based optimization on seismic buffer recognition are described.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"85 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121236343","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736916
G. Venayagamoorthy, V. Moonasar, K. Sandrasegaran
One solution to the crime and illegal immigration problem in South Africa may be the use of biometric techniques and technology. Biometrics are methods for recognizing a user based on unique physiological and/or behavioural characteristics of the user. This paper presents the results of ongoing work into using neural networks for voice recognition.
{"title":"Voice recognition using neural networks","authors":"G. Venayagamoorthy, V. Moonasar, K. Sandrasegaran","doi":"10.1109/COMSIG.1998.736916","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736916","url":null,"abstract":"One solution to the crime and illegal immigration problem in South Africa may be the use of biometric techniques and technology. Biometrics are methods for recognizing a user based on unique physiological and/or behavioural characteristics of the user. This paper presents the results of ongoing work into using neural networks for voice recognition.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129231456","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736935
B.A. Alaylioglu, F. Aghdasi
The presence of microcalcification clusters (MCCs) is a primary sign of breast cancer. Thus, the successful detection of microcalcifications during mammographic examination is vital for the early diagnosis of the cancer. Computer-based detection methods aim to ameliorate the diagnostic process by providing the radiologist with a second opinion. An automatic detection scheme making use of a neural network classifier, with input feature vectors containing spatial and spectral image attributes, is investigated. A wavelet-based image enhancement technique is employed to improve the detection. The detection scheme is tested and preliminary results are reported.
{"title":"An artificial neural network for detecting microcalcifications in wavelet-enhanced digitised mammograms","authors":"B.A. Alaylioglu, F. Aghdasi","doi":"10.1109/COMSIG.1998.736935","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736935","url":null,"abstract":"The presence of microcalcification clusters (MCCs) is a primary sign of breast cancer. Thus, the successful detection of microcalcifications during mammographic examination is vital for the early diagnosis of the cancer. Computer-based detection methods aim to ameliorate the diagnostic process by providing the radiologist with a second opinion. An automatic detection scheme making use of a neural network classifier, with input feature vectors containing spatial and spectral image attributes, is investigated. A wavelet-based image enhancement technique is employed to improve the detection. The detection scheme is tested and preliminary results are reported.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125122113","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736934
Dani Kramer, F. Aghdasi
We present a multiscale statistical approach to texture analysis. These techniques are used to classify microcalcifications in digitised mammograms as benign or malignant. In this study we extract the proposed multiscale statistical texture signatures, based on the co-occurrence matrix, as well as wavelet-based texture signatures from the regions of interest containing the microcalcifications. The discriminatory ability of these texture signatures is demonstrated by their ability to successfully distinguish between benign and malignant cases. Classification is performed by means of a k-nearest neighbour classifier. One hundred percent correct classification is achieved when using a combination of the multiscale statistical texture signatures and the wavelet-based texture signatures. A database with a small number of samples was used, and further analysis with a larger database will give these results greater statistical significance.
{"title":"Classification of microcalcifications in digitised mammograms using multiscale statistical texture analysis","authors":"Dani Kramer, F. Aghdasi","doi":"10.1109/COMSIG.1998.736934","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736934","url":null,"abstract":"We present a multiscale statistical approach to texture analysis. These techniques are used to classify microcalcifications in digitised mammograms as benign or malignant. In this study we extract the proposed multiscale statistical texture signatures, based on the co-occurrence matrix, as well as wavelet-based texture signatures from the regions of interest containing the microcalcifications. The discriminatory ability of these texture signatures is demonstrated by their ability to successfully distinguish between benign and malignant cases. Classification is performed by means of a k-nearest neighbour classifier. One hundred percent correct classification is achieved when using a combination of the multiscale statistical texture signatures and the wavelet-based texture signatures. A database with a small number of samples was used, and further analysis with a larger database will give these results greater statistical significance.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125670212","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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