Pub Date : 1900-01-01DOI: 10.1109/SPAWC.2001.923878
Wing-Kin Ma, T. Davidson, K. Wong, Z. Luo, P. Ching
In the standard scenario of multiuser detection, the maximum-likelihood (ML) detector is optimum in the sense of minimum error probability. Unfortunately, ML detection requires the solution of a difficult optimization problem for which it is unlikely that the optimal solution can be efficiently found. We consider an accurate and efficient quasi-ML detector which uses semi-definite relaxation (SDR) to approximate the ML detector. This SDR-ML detector was recently shown to be capable of achieving a bit error rate (BER) close to that of the true ML detector. Here, we show that several existing suboptimal detectors, such as the decorrelator, can be viewed as degenerate versions of the SDR-ML detector. Hence, it is expected that the SDR-ML detector should perform better than those detectors. This expectation is confirmed by simulations, where the BER performance of the SDR-ML detector is significantly better than that of other suboptimal detectors including the decorrelator and the linear-minimum-mean-square-error detector.
{"title":"An efficient quasi-maximum-likelihood multiuser detector using semi-definite relaxation","authors":"Wing-Kin Ma, T. Davidson, K. Wong, Z. Luo, P. Ching","doi":"10.1109/SPAWC.2001.923878","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923878","url":null,"abstract":"In the standard scenario of multiuser detection, the maximum-likelihood (ML) detector is optimum in the sense of minimum error probability. Unfortunately, ML detection requires the solution of a difficult optimization problem for which it is unlikely that the optimal solution can be efficiently found. We consider an accurate and efficient quasi-ML detector which uses semi-definite relaxation (SDR) to approximate the ML detector. This SDR-ML detector was recently shown to be capable of achieving a bit error rate (BER) close to that of the true ML detector. Here, we show that several existing suboptimal detectors, such as the decorrelator, can be viewed as degenerate versions of the SDR-ML detector. Hence, it is expected that the SDR-ML detector should perform better than those detectors. This expectation is confirmed by simulations, where the BER performance of the SDR-ML detector is significantly better than that of other suboptimal detectors including the decorrelator and the linear-minimum-mean-square-error detector.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116964199","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 : 1900-01-01DOI: 10.1109/SPAWC.2001.923913
J. Xin, H. Tsuji, H. Ohmori, A. Sano
By exploiting the cyclostationarity exhibited by most communication signals, we propose a computationally efficient method for estimating the directions-of-arrival (DOA) of coherent narrowband signals impinging on a uniform linear array without eigendecomposition and spatial smoothing processes. An online implementation of this method is proposed for tracking the DOA of moving signals in a multipath propagation environment. In the proposed algorithm, a combination of the cyclostationarity and a subarray scheme are used to decorrelate the signal coherency and to suppress the noise and interfering signals, while the noise subspace is estimated from the resulting cyclic correlation matrix through a linear operation. As a result, the proposed algorithm has the advantages of computational simplicity and robust detection capability.
{"title":"Directions-of-arrival tracking of coherent cyclostationary signals without eigendecomposition","authors":"J. Xin, H. Tsuji, H. Ohmori, A. Sano","doi":"10.1109/SPAWC.2001.923913","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923913","url":null,"abstract":"By exploiting the cyclostationarity exhibited by most communication signals, we propose a computationally efficient method for estimating the directions-of-arrival (DOA) of coherent narrowband signals impinging on a uniform linear array without eigendecomposition and spatial smoothing processes. An online implementation of this method is proposed for tracking the DOA of moving signals in a multipath propagation environment. In the proposed algorithm, a combination of the cyclostationarity and a subarray scheme are used to decorrelate the signal coherency and to suppress the noise and interfering signals, while the noise subspace is estimated from the resulting cyclic correlation matrix through a linear operation. As a result, the proposed algorithm has the advantages of computational simplicity and robust detection capability.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133789187","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 : 1900-01-01DOI: 10.1109/SPAWC.2001.923869
Juinn-Horng Deng, Ta-Sung Lee
A multistage multi-carrier CDMA (MSMC-CDMA) receiver with enhanced multiple access interference (MAI) suppression is proposed. MC-CDMA is based on a combination of CDMA and orthogonal frequency division multiplexing (OFDM) techniques. The design of the receiver involves the following procedure. First, a set of adaptive matched filters (MF) is constructed to collect multipath signals with different time delays. The tap weights of each MF are determined in accordance with the linearly constrained minimum variance (LCMV) criterion so that strong MAI can be effectively suppressed. Second, channel estimation and signal reconstruction are accomplished by exploiting pilot symbols, decision-directed symbols and the signal's signature. Finally, a decision-directed RAKE receiver gives the estimate of the signal, which is then subtracted from the data sent to the next stage. The proposed receiver can be used in a reverse link system with time-multiplexed pilot symbols, and achieves nearly the performance of the optimal maximum SINR (MSINR) receiver.
{"title":"A multistage multi-carrier CDMA receiver with enhanced interference suppression","authors":"Juinn-Horng Deng, Ta-Sung Lee","doi":"10.1109/SPAWC.2001.923869","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923869","url":null,"abstract":"A multistage multi-carrier CDMA (MSMC-CDMA) receiver with enhanced multiple access interference (MAI) suppression is proposed. MC-CDMA is based on a combination of CDMA and orthogonal frequency division multiplexing (OFDM) techniques. The design of the receiver involves the following procedure. First, a set of adaptive matched filters (MF) is constructed to collect multipath signals with different time delays. The tap weights of each MF are determined in accordance with the linearly constrained minimum variance (LCMV) criterion so that strong MAI can be effectively suppressed. Second, channel estimation and signal reconstruction are accomplished by exploiting pilot symbols, decision-directed symbols and the signal's signature. Finally, a decision-directed RAKE receiver gives the estimate of the signal, which is then subtracted from the data sent to the next stage. The proposed receiver can be used in a reverse link system with time-multiplexed pilot symbols, and achieves nearly the performance of the optimal maximum SINR (MSINR) receiver.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122106419","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 : 1900-01-01DOI: 10.1109/SPAWC.2001.923831
Lu-Ming Chang, Y. Su, Li-Der Jeng
Conventional narrowband interference (NBI) rejection algorithms often assume perfect pseudo-noise (PN) code synchronization and coherent detection. The functions of NBI rejection, data detection and code tracking are performed separately and independently by an adaptive detector and a code tracking loop, respectively. This paper presents three new noncoherent receiver structures for differential phase shift keying (DPSK), direct sequence spread spectrum (DS/SS) signals. Our receivers are designed to suppress NBI, mitigate multipath interference and minimize code tracking jitter at the same time. We first propose a generic receiver structure and evaluate the signal-to-interference ratio (SIR) for its detection decision variable. Optimal interference suppression and code tracking algorithms that maximize SIR are then derived. Other algorithms that use different criteria are also given. Numerical results using both analysis and computer simulation are presented to compare performance of various receiver structures.
{"title":"Noncoherent anti-interference receivers for DS/SS signals","authors":"Lu-Ming Chang, Y. Su, Li-Der Jeng","doi":"10.1109/SPAWC.2001.923831","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923831","url":null,"abstract":"Conventional narrowband interference (NBI) rejection algorithms often assume perfect pseudo-noise (PN) code synchronization and coherent detection. The functions of NBI rejection, data detection and code tracking are performed separately and independently by an adaptive detector and a code tracking loop, respectively. This paper presents three new noncoherent receiver structures for differential phase shift keying (DPSK), direct sequence spread spectrum (DS/SS) signals. Our receivers are designed to suppress NBI, mitigate multipath interference and minimize code tracking jitter at the same time. We first propose a generic receiver structure and evaluate the signal-to-interference ratio (SIR) for its detection decision variable. Optimal interference suppression and code tracking algorithms that maximize SIR are then derived. Other algorithms that use different criteria are also given. Numerical results using both analysis and computer simulation are presented to compare performance of various receiver structures.","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":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130182034","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 : 1900-01-01DOI: 10.1109/SPAWC.2001.923833
Wen-Jye Huang, J. Doherty
Space division multiple access (SDMA) is a technique that can be superimposed on traditional multiple access schemes such as frequency division multiple access (FDMA), time division multiple access (TDMA) or code division multiple access (CDMA) to increase the system capacity. Several different studies have shown the effectiveness of SDMA in a mobile communication environment. This paper derives a modified formulation for SDMA blocking probability from Galvan-Tejada and Gardiner's (1999) derivation and the cellular traffic theory (Lee and Miller, 1998). A simulation is also presented to verify our derivation.
{"title":"An improvement on blocking probability for SDMA","authors":"Wen-Jye Huang, J. Doherty","doi":"10.1109/SPAWC.2001.923833","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923833","url":null,"abstract":"Space division multiple access (SDMA) is a technique that can be superimposed on traditional multiple access schemes such as frequency division multiple access (FDMA), time division multiple access (TDMA) or code division multiple access (CDMA) to increase the system capacity. Several different studies have shown the effectiveness of SDMA in a mobile communication environment. This paper derives a modified formulation for SDMA blocking probability from Galvan-Tejada and Gardiner's (1999) derivation and the cellular traffic theory (Lee and Miller, 1998). A simulation is also presented to verify our derivation.","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":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125583922","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 : 1900-01-01DOI: 10.1109/SPAWC.2001.923860
Yih-Ming Tsuie, Wen-Rong Wu
It is very difficult to analyse the error probability of the adaptive decision feedback equalizer (DFE) when it is operated under a time-varying channel. A decision error not only propagates through the feedback filter affecting the future outputs, but also through the adaptive algorithm updating the tap weights towards a wrong direction. Most of the existing analysis works do not consider the error propagation effect in the adaptive algorithm. We specifically take this effect into account and analyze the error probability of the DFE under slowly fading channels. We consider the most widely used adaptive algorithm, namely, the least mean square (LMS) algorithm. Closed-form expressions are derived for the training mode as well as the decision-directed mode. Finally, the validity of the theoretical results are verified through computer simulations.
{"title":"Error probability analysis for adaptive decision feedback equalizers under slowly fading multipath channels","authors":"Yih-Ming Tsuie, Wen-Rong Wu","doi":"10.1109/SPAWC.2001.923860","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923860","url":null,"abstract":"It is very difficult to analyse the error probability of the adaptive decision feedback equalizer (DFE) when it is operated under a time-varying channel. A decision error not only propagates through the feedback filter affecting the future outputs, but also through the adaptive algorithm updating the tap weights towards a wrong direction. Most of the existing analysis works do not consider the error propagation effect in the adaptive algorithm. We specifically take this effect into account and analyze the error probability of the DFE under slowly fading channels. We consider the most widely used adaptive algorithm, namely, the least mean square (LMS) algorithm. Closed-form expressions are derived for the training mode as well as the decision-directed mode. Finally, the validity of the theoretical results are verified through computer simulations.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129383225","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 : 1900-01-01DOI: 10.1109/SPAWC.2001.923877
Wen-Rong Wu, Wenyan Su, Yu-Tao Hsieh
The partial parallel interference cancellation (PIC) detector is considered as an effective yet simple receiver for multiuser detection in code-division multiple access (CDMA) systems. It cancels the multiple access interference (MAI) of the received signal partially resulting from other users. However, the optimal cancellation level which is controlled by a partial cancellation factor (PCF) is usually determined by trial and error, since no theoretical values have been reported. We introduce a MMSE criterion for the two-stage partial PIC receiver to derive the optimal PCF. Simulations show that the performance of proposed methods is very close to that of empirically chosen PCF. We also demonstrate that the derived PCF is insensitive to the estimate bias of noise level and the interfering signal power.
{"title":"A two-stage MMSE partial PIC receiver for multiuser detection","authors":"Wen-Rong Wu, Wenyan Su, Yu-Tao Hsieh","doi":"10.1109/SPAWC.2001.923877","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923877","url":null,"abstract":"The partial parallel interference cancellation (PIC) detector is considered as an effective yet simple receiver for multiuser detection in code-division multiple access (CDMA) systems. It cancels the multiple access interference (MAI) of the received signal partially resulting from other users. However, the optimal cancellation level which is controlled by a partial cancellation factor (PCF) is usually determined by trial and error, since no theoretical values have been reported. We introduce a MMSE criterion for the two-stage partial PIC receiver to derive the optimal PCF. Simulations show that the performance of proposed methods is very close to that of empirically chosen PCF. We also demonstrate that the derived PCF is insensitive to the estimate bias of noise level and the interfering signal power.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115391525","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 : 1900-01-01DOI: 10.1109/SPAWC.2001.923867
Xiaoli Ma, C. Tepedelenlioğlu, G. Giannakis
The ability of orthogonal frequency division multiplexing systems to mitigate frequency-selective channels is impaired by the presence of carrier frequency offsets (CFO). We investigate identifiability issues involving high-resolution techniques that have been proposed for blind CFO estimation based on null subcarriers. We also propose new approaches that do not suffer from the lack of identifiability problems and channel-dependent performance.
{"title":"Consistent blind synchronization of OFDM transmissions using null sub-carriers with distinct spacings","authors":"Xiaoli Ma, C. Tepedelenlioğlu, G. Giannakis","doi":"10.1109/SPAWC.2001.923867","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923867","url":null,"abstract":"The ability of orthogonal frequency division multiplexing systems to mitigate frequency-selective channels is impaired by the presence of carrier frequency offsets (CFO). We investigate identifiability issues involving high-resolution techniques that have been proposed for blind CFO estimation based on null subcarriers. We also propose new approaches that do not suffer from the lack of identifiability problems and channel-dependent performance.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132498958","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 : 1900-01-01DOI: 10.1109/SPAWC.2001.923927
Fu-Kun Chen, J. Yang
For the purpose of low cost or low power consumption, a cost-effective solution with good trade-off between quality and complexity must be estimated for a small mobile device. We propose a condensed MP-MLQ algorithm to reduce the search computation required for G723.1. Simulation results show that the proposed method can reduce about 50/spl sim/82% the computational load for stochastic codebook search with perceptually intangible degradation. This reduction would be helpful to save power consumption and relax the CPU load for a mobile device in wireless communication, e.g., PALM, PDA.
{"title":"Candidate scheme for MP-MLQ search in G723.1","authors":"Fu-Kun Chen, J. Yang","doi":"10.1109/SPAWC.2001.923927","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923927","url":null,"abstract":"For the purpose of low cost or low power consumption, a cost-effective solution with good trade-off between quality and complexity must be estimated for a small mobile device. We propose a condensed MP-MLQ algorithm to reduce the search computation required for G723.1. Simulation results show that the proposed method can reduce about 50/spl sim/82% the computational load for stochastic codebook search with perceptually intangible degradation. This reduction would be helpful to save power consumption and relax the CPU load for a mobile device in wireless communication, e.g., PALM, PDA.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115415502","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 : 1900-01-01DOI: 10.1109/SPAWC.2001.923889
C. Tepedelenlioğlu, N. Sidiropoulos, G. B. Giannakis
In mobile communications, accurate power estimation is important for power control and handoff decisions. Power estimation algorithms aim to filter out the fast variation in the received power due to multipath fading, and should ideally exhibit very low complexity. For this reason, linear filtering (local mean) is almost exclusively used for power estimation in practice. We derive the maximum likelihood estimator in an idealized setting, and motivated by the statistical properties of the multipath signal, we also propose median filtering for power estimation. Simulations show promising results, indicating gains in RMSE and robustness to increased window size.
{"title":"Median filtering for power estimation in mobile communication systems","authors":"C. Tepedelenlioğlu, N. Sidiropoulos, G. B. Giannakis","doi":"10.1109/SPAWC.2001.923889","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923889","url":null,"abstract":"In mobile communications, accurate power estimation is important for power control and handoff decisions. Power estimation algorithms aim to filter out the fast variation in the received power due to multipath fading, and should ideally exhibit very low complexity. For this reason, linear filtering (local mean) is almost exclusively used for power estimation in practice. We derive the maximum likelihood estimator in an idealized setting, and motivated by the statistical properties of the multipath signal, we also propose median filtering for power estimation. Simulations show promising results, indicating gains in RMSE and robustness to increased window size.","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":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128571971","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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