Pub Date : 2001-03-20DOI: 10.1109/SPAWC.2001.923837
M. Valkama, M. Renfors, V. Koivunen
To achieve satisfactory performance in analog I/Q (inphase/quadrature) processing-based wireless receivers, the matching of amplitudes and phases of the I and Q branches becomes vital. In practice, there is always some imbalance and the image attenuation produced by the analog processing remains finite. Especially in wideband receivers, where the existence of strong image band signals makes the attenuation requirements extremely stringent, analog processing is incapable of providing adequate image rejection. We derive a general frequency-dependent signal model for an imbalanced analog front-end and present two alternative methods utilizing digital processing to enhance the analog front-end image rejection. Based on the obtained results, the proposed methods provide adequate image signal rejection with very few assumptions, even in the difficult cases of frequency-selective and/or time-varying imbalances.
{"title":"Compensation of frequency-selective I/Q imbalances in wideband receivers: models and algorithms","authors":"M. Valkama, M. Renfors, V. Koivunen","doi":"10.1109/SPAWC.2001.923837","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923837","url":null,"abstract":"To achieve satisfactory performance in analog I/Q (inphase/quadrature) processing-based wireless receivers, the matching of amplitudes and phases of the I and Q branches becomes vital. In practice, there is always some imbalance and the image attenuation produced by the analog processing remains finite. Especially in wideband receivers, where the existence of strong image band signals makes the attenuation requirements extremely stringent, analog processing is incapable of providing adequate image rejection. We derive a general frequency-dependent signal model for an imbalanced analog front-end and present two alternative methods utilizing digital processing to enhance the analog front-end image rejection. Based on the obtained results, the proposed methods provide adequate image signal rejection with very few assumptions, even in the difficult cases of frequency-selective and/or time-varying imbalances.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130796212","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 : 2001-03-20DOI: 10.1109/SPAWC.2001.923862
R. Pacheco, D. Hatzinakos
We propose a novel strategy for semi-blind spatio-temporal equalization and multiuser detection for short-burst asynchronous DS-CDMA systems. The technique is based on first performing semi-blind subspace-based channel identification and then semi-blind equalization via the constant modulus algorithm (CMA). In this way we are able to improve upon the traditional training-based least squares (LS) estimator by adding the constant modulus and cyclostationary properties of communication signals. Simulation results indicate a significant reduction in the required number of training symbols (for a short burst of data) compared with regularized LS estimators (both training-based and semi-blind). Application is in the reverse link of third-generation DS-CDMA systems.
{"title":"Semi-blind spatio-temporal equalization and multiuser detection for DS-CDMA systems","authors":"R. Pacheco, D. Hatzinakos","doi":"10.1109/SPAWC.2001.923862","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923862","url":null,"abstract":"We propose a novel strategy for semi-blind spatio-temporal equalization and multiuser detection for short-burst asynchronous DS-CDMA systems. The technique is based on first performing semi-blind subspace-based channel identification and then semi-blind equalization via the constant modulus algorithm (CMA). In this way we are able to improve upon the traditional training-based least squares (LS) estimator by adding the constant modulus and cyclostationary properties of communication signals. Simulation results indicate a significant reduction in the required number of training symbols (for a short burst of data) compared with regularized LS estimators (both training-based and semi-blind). Application is in the reverse link of third-generation DS-CDMA systems.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124274179","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 : 2001-03-20DOI: 10.1109/SPAWC.2001.923868
Bor‐Sen Chen, Chang-Lan Tsai
The orthogonal frequency division multiplexing (OFDM) system has recently attracted increasing interest for its robustness of frequency selective fading, and is believed to be an important technique for future high-speed wireline and wireless communications, including cellular mobile communication systems. However, a well-known problem of such a multi-carrier modulation is its vulnerability to synchronization errors. The frequency offset, which results from a Doppler shift, due to mobile movement, as well as the inherent instability of the transmit and the receive reference, causes a loss of orthogonality between the subcarriers, and hence, produces intercarrier interference (ICI). To solve this problem, we trade on the correlation of the samples at the output of the discrete Fourier transform (DFT) to estimate the frequency offset by using the extended Kalman filter (EKF), which blindly tracks the frequency offset via a recursive procedure. Simulation results are given to illustrate the tracking performance of this algorithm.
{"title":"Frequency offset estimation in an OFDM system","authors":"Bor‐Sen Chen, Chang-Lan Tsai","doi":"10.1109/SPAWC.2001.923868","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923868","url":null,"abstract":"The orthogonal frequency division multiplexing (OFDM) system has recently attracted increasing interest for its robustness of frequency selective fading, and is believed to be an important technique for future high-speed wireline and wireless communications, including cellular mobile communication systems. However, a well-known problem of such a multi-carrier modulation is its vulnerability to synchronization errors. The frequency offset, which results from a Doppler shift, due to mobile movement, as well as the inherent instability of the transmit and the receive reference, causes a loss of orthogonality between the subcarriers, and hence, produces intercarrier interference (ICI). To solve this problem, we trade on the correlation of the samples at the output of the discrete Fourier transform (DFT) to estimate the frequency offset by using the extended Kalman filter (EKF), which blindly tracks the frequency offset via a recursive procedure. Simulation results are given to illustrate the tracking performance of this algorithm.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115891359","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 : 2001-03-20DOI: 10.1109/SPAWC.2001.923886
S. Attallah, K. Abed-Meraim
We present two normalized versions of the Oja (1992) algorithm (NOja and NOOja) which can be used for the estimation of minor (noise) and principal (signal) subspaces of a vector sequence. The new algorithms offer, as compared to Oja, a faster convergence, a better orthogonality and numerical stability with a slight increase in computational complexity. These algorithms can find many applications, in particular, in wireless communications.
{"title":"Subspace estimation and tracking using enhanced versions of Oja's algorithm","authors":"S. Attallah, K. Abed-Meraim","doi":"10.1109/SPAWC.2001.923886","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923886","url":null,"abstract":"We present two normalized versions of the Oja (1992) algorithm (NOja and NOOja) which can be used for the estimation of minor (noise) and principal (signal) subspaces of a vector sequence. The new algorithms offer, as compared to Oja, a faster convergence, a better orthogonality and numerical stability with a slight increase in computational complexity. These algorithms can find many applications, in particular, in wireless communications.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123757280","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 : 2001-03-20DOI: 10.1109/SPAWC.2001.923890
R. Punchalard, C. Benjangkaprasert, N. Anantrasirichai, K. Janchitrapongvej
The best adaptive algorithm requires fast convergence speed, low variance, unbias and low steady-state mean square error (MSE) in both low and high signal-to-noise ratio (SNR) situations. We have proposed a robust variable step-size LMS-like algorithm (VS-LMS-L) for a second-order adaptive IIR notch filter for frequency detection in radar, sonar and communication systems. This algorithm is compared with the conventional LMS-like algorithm called the plain gradient algorithm (PG). The time-varying step-size /spl mu/(n) is adjusted by using the square of the time-averaged estimate of autocorrelation of the present output signal y(n) and the past one y(n-1). This technique can reject the effect of the uncorrelated noise sequence on the step-size update, resulting in a small MSE due to the small final /spl mu/(n). Moreover, this algorithm can also improve the convergence speed by comparison with the PG at the same MSE value.
{"title":"A robust variable step-size LMS-like algorithm for a second-order adaptive IIR notch filter for frequency detection","authors":"R. Punchalard, C. Benjangkaprasert, N. Anantrasirichai, K. Janchitrapongvej","doi":"10.1109/SPAWC.2001.923890","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923890","url":null,"abstract":"The best adaptive algorithm requires fast convergence speed, low variance, unbias and low steady-state mean square error (MSE) in both low and high signal-to-noise ratio (SNR) situations. We have proposed a robust variable step-size LMS-like algorithm (VS-LMS-L) for a second-order adaptive IIR notch filter for frequency detection in radar, sonar and communication systems. This algorithm is compared with the conventional LMS-like algorithm called the plain gradient algorithm (PG). The time-varying step-size /spl mu/(n) is adjusted by using the square of the time-averaged estimate of autocorrelation of the present output signal y(n) and the past one y(n-1). This technique can reject the effect of the uncorrelated noise sequence on the step-size update, resulting in a small MSE due to the small final /spl mu/(n). Moreover, this algorithm can also improve the convergence speed by comparison with the PG at the same MSE value.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"310 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122783842","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 : 2001-03-20DOI: 10.1109/SPAWC.2001.923931
Chii-Jen Chung, Wenyu Chen
A low-complexity voice recognition method in a car environment is proposed. Models of noise in the car environment are adaptable in an easy way. Power computation and memory storage for the proposed method are very low. Some real world tests are conducted and show that the proposed voice recognition method has potential for application to car cellular telephones.
{"title":"Low complexity voice recognition in car environment","authors":"Chii-Jen Chung, Wenyu Chen","doi":"10.1109/SPAWC.2001.923931","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923931","url":null,"abstract":"A low-complexity voice recognition method in a car environment is proposed. Models of noise in the car environment are adaptable in an easy way. Power computation and memory storage for the proposed method are very low. Some real world tests are conducted and show that the proposed voice recognition method has potential for application to car cellular telephones.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121400876","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 : 2001-03-20DOI: 10.1109/SPAWC.2001.923829
L. Harju, M. Kuulusa, J. Nurmi
This paper presents a novel RAKE receiver architecture for WCDMA FDD downlink reception in mobile terminals. In contrast to the conventional RAKE finger approach, the proposed FlexRake architecture performs signal reception with a single correlator engine and a buffer which stores the entire delay spread of the baseband I/Q samples. This allows each of the tracked multipaths to be despread sequentially with codes that are exactly in the same phase. The main benefits of the proposed receiver architecture are flexible multipath allocation, symbol-synchronous operation, and straightforward receiver control.
{"title":"A flexible RAKE receiver architecture for WCDMA mobile terminals","authors":"L. Harju, M. Kuulusa, J. Nurmi","doi":"10.1109/SPAWC.2001.923829","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923829","url":null,"abstract":"This paper presents a novel RAKE receiver architecture for WCDMA FDD downlink reception in mobile terminals. In contrast to the conventional RAKE finger approach, the proposed FlexRake architecture performs signal reception with a single correlator engine and a buffer which stores the entire delay spread of the baseband I/Q samples. This allows each of the tracked multipaths to be despread sequentially with codes that are exactly in the same phase. The main benefits of the proposed receiver architecture are flexible multipath allocation, symbol-synchronous operation, and straightforward receiver control.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114690898","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 : 2001-03-20DOI: 10.1109/SPAWC.2001.923893
Chong-Yung Chi, Ching-Yung Chen
Ding and Nguyen's (2000) kurtosis maximization algorithm (KMA) for blind signal separation and antenna beamforming assumes the absence of multipath channels. This paper proposes a multistage source separation (MSS) algorithm assuming that source signals are independent identically distributed (iid) non-Gaussian and received in the presence of multiple paths (as practically happens in wireless communications). The proposed MSS algorithm includes extraction and blind maximum ratio combing (BMRC) of a source signal from different paths using a fast KMA (FKMA), besides signal classification, time delay estimation, and cancellation of the contribution of the extracted source signal from the received signal at each stage. The proposed MSS algorithm with no need of prior information about the array configuration and direction of arrival (DOA) is supported through computer simulation.
{"title":"Blind beamforming and maximum ratio combining by kurtosis maximization for source separation in multipath","authors":"Chong-Yung Chi, Ching-Yung Chen","doi":"10.1109/SPAWC.2001.923893","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923893","url":null,"abstract":"Ding and Nguyen's (2000) kurtosis maximization algorithm (KMA) for blind signal separation and antenna beamforming assumes the absence of multipath channels. This paper proposes a multistage source separation (MSS) algorithm assuming that source signals are independent identically distributed (iid) non-Gaussian and received in the presence of multiple paths (as practically happens in wireless communications). The proposed MSS algorithm includes extraction and blind maximum ratio combing (BMRC) of a source signal from different paths using a fast KMA (FKMA), besides signal classification, time delay estimation, and cancellation of the contribution of the extracted source signal from the received signal at each stage. The proposed MSS algorithm with no need of prior information about the array configuration and direction of arrival (DOA) is supported through computer simulation.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131195331","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 : 2001-03-20DOI: 10.1109/SPAWC.2001.923923
Hsien-Tsai Wu, Jui-Yuan Chang, Chun-Bo Tseng, Chia-Hao Kao, W. Hung
This project comes from the inconvenience of the traditional message-board for a visitor when the host is not at home. Besides the written message, a visitor can also leave a voice message, can telephone his host immediately, and also include a simple security checking in our board system. When the visitor pushes a special key, the telephone system autodials the preset telephone number by the host. To reduce the system cost, the compressed voice message is stored in the internal and external memory space of the DSP chip instead of the voice IC.
{"title":"Active DSP message-board","authors":"Hsien-Tsai Wu, Jui-Yuan Chang, Chun-Bo Tseng, Chia-Hao Kao, W. Hung","doi":"10.1109/SPAWC.2001.923923","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923923","url":null,"abstract":"This project comes from the inconvenience of the traditional message-board for a visitor when the host is not at home. Besides the written message, a visitor can also leave a voice message, can telephone his host immediately, and also include a simple security checking in our board system. When the visitor pushes a special key, the telephone system autodials the preset telephone number by the host. To reduce the system cost, the compressed voice message is stored in the internal and external memory space of the DSP chip instead of the voice IC.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130661260","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 : 2001-03-20DOI: 10.1109/SPAWC.2001.923875
BuiLong Thanh, V. Krishnamurthy, R. Evans
This paper develops a sequential composite hypotheses test for detecting failure of a decision directed recursive least squares (RLS) multiuser detector (MUD) and convergence of a blind RLS MUD when used in the downlink of a DS-CDMA system. Simulations demonstrate the effectiveness of the test and characterize the SIR improvement achievable in a dynamic environment.
{"title":"Detection aided recursive least squares multiuser detection in the downlink of DS/CDMA mobile systems","authors":"BuiLong Thanh, V. Krishnamurthy, R. Evans","doi":"10.1109/SPAWC.2001.923875","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923875","url":null,"abstract":"This paper develops a sequential composite hypotheses test for detecting failure of a decision directed recursive least squares (RLS) multiuser detector (MUD) and convergence of a blind RLS MUD when used in the downlink of a DS-CDMA system. Simulations demonstrate the effectiveness of the test and characterize the SIR improvement achievable in a dynamic environment.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130724509","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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