Pub Date : 2001-03-20DOI: 10.1109/SPAWC.2001.923854
H. Artes, F. Hlawatsch
We propose two methods for deterministic blind equalization of linear time-varying (LTV) channels with multiple users. Our approach is based on an LTI (linear time invariant) multichannel representation of LTV channels. With the first method, the multiuser channel is equalized up to an instantaneous mixture that is subsequently resolved by means of a POCS (projections onto convex sets) algorithm. The second method performs the entire equalization (including resolution of the instantaneous mixture) by means of a POCS algorithm. Simulation results demonstrate the good performance of our methods.
{"title":"Blind multiuser equalization for time-varying channels","authors":"H. Artes, F. Hlawatsch","doi":"10.1109/SPAWC.2001.923854","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923854","url":null,"abstract":"We propose two methods for deterministic blind equalization of linear time-varying (LTV) channels with multiple users. Our approach is based on an LTI (linear time invariant) multichannel representation of LTV channels. With the first method, the multiuser channel is equalized up to an instantaneous mixture that is subsequently resolved by means of a POCS (projections onto convex sets) algorithm. The second method performs the entire equalization (including resolution of the instantaneous mixture) by means of a POCS algorithm. Simulation results demonstrate the good performance of our methods.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"395 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":"126753004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to overcome the MAI and ISI problems in time-varying multipath fading channels, a novel H/sub /spl infin//-subweight algorithm for the decision feedback equalizer (DFE) in a DS-CDMA system is presented. The subweight technique can reduce the computational load of the H/sub /spl infin// algorithm, but dynamic estimation error in subweight partition may degrade performance. The advantage of insensitivity to modeling error of the H/sub /spl infin// algorithm just can mitigate the degradation of the subweight technique. Therefore, the individual advantages of the H/sub /spl infin// algorithm and subweight technique can be successfully integrated. The H/sub /spl infin//-subweight algorithm owns the advantages of low complexity and robustness against modeling error caused by the time-varying multipath channels as well as subweight partition. On the other hand, the RLS-subweight algorithm seriously suffers from the drawback of dynamic estimation error. The reduction of computational complexity by subweight partition is analyzed. Simulation results show that the H/sub /spl infin//-subweight DPE outperforms the RLS-subweight DFE in suppressing equalization error.
{"title":"Adaptive H/sub /spl infin//-subweight equalizer for DS-CDMA communication system in time-varying multipath channels","authors":"Ching-Tai Chiang, Chian-Chung Chen, Yuan-Hwang Chen","doi":"10.1109/SPAWC.2001.923858","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923858","url":null,"abstract":"In order to overcome the MAI and ISI problems in time-varying multipath fading channels, a novel H/sub /spl infin//-subweight algorithm for the decision feedback equalizer (DFE) in a DS-CDMA system is presented. The subweight technique can reduce the computational load of the H/sub /spl infin// algorithm, but dynamic estimation error in subweight partition may degrade performance. The advantage of insensitivity to modeling error of the H/sub /spl infin// algorithm just can mitigate the degradation of the subweight technique. Therefore, the individual advantages of the H/sub /spl infin// algorithm and subweight technique can be successfully integrated. The H/sub /spl infin//-subweight algorithm owns the advantages of low complexity and robustness against modeling error caused by the time-varying multipath channels as well as subweight partition. On the other hand, the RLS-subweight algorithm seriously suffers from the drawback of dynamic estimation error. The reduction of computational complexity by subweight partition is analyzed. Simulation results show that the H/sub /spl infin//-subweight DPE outperforms the RLS-subweight DFE in suppressing equalization error.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"178 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":"128165653","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.2001.923863
K. Yang, T. Ohira
Electronically steerable passive array radiator (ESPAR) antennas are capable of spatially forming a beam toward the desired signal with the lowest cost, and are suitable to be employed in ad hoc wireless network systems. We propose a cascaded scheme for ESPAR antenna-based signal processing, where the beam toward the desired user terminal is formed in advance, and the equalizer for direct-sequence code division multiple access (DS-CDMA) signal waveforms is followed. According to the scheme, cochannel user-terminal signals and intersymbol interference signals are respectively suppressed by spatial filtering of the desired beam and the waveform-based adaptive equalization. The steady state and convergence performance of the proposed scheme is illustrated numerically by simulations.
{"title":"ESPAR antennas-based signal processing for DS-CDMA signal waveforms in ad hoc network systems","authors":"K. Yang, T. Ohira","doi":"10.1109/SPAWC.2001.923863","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923863","url":null,"abstract":"Electronically steerable passive array radiator (ESPAR) antennas are capable of spatially forming a beam toward the desired signal with the lowest cost, and are suitable to be employed in ad hoc wireless network systems. We propose a cascaded scheme for ESPAR antenna-based signal processing, where the beam toward the desired user terminal is formed in advance, and the equalizer for direct-sequence code division multiple access (DS-CDMA) signal waveforms is followed. According to the scheme, cochannel user-terminal signals and intersymbol interference signals are respectively suppressed by spatial filtering of the desired beam and the waveform-based adaptive equalization. The steady state and convergence performance of the proposed scheme is illustrated numerically by simulations.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"284 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":"114452307","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.2001.923827
Tongtong Li, Jitendra Tugnait
A code-constrained constant-modulus approach (CMA) was presented recently in Li et al., (2000) for blind detection of asynchronous short-code DS-CDMA (direct sequence code division multiple access) signals in multipath channels. Only the spreading code of the desired user is assumed to be known; its transmission delay may be unknown. The equalizer was determined by minimizing the Godard/CMA cost function of the equalizer output with respect to the equalizer coefficients subject to the fact that the equalizer lies in a subspace associated with the desired user's code sequence. We analyze the identifiability properties of this approach. Global minima and some of the local minima of the cost function are investigated. These aspects were not discussed in Li. More extensive simulation comparisons with existing approaches are also provided.
{"title":"New results on blind asynchronous CDMA receivers using code-constrained CMA","authors":"Tongtong Li, Jitendra Tugnait","doi":"10.1109/SPAWC.2001.923827","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923827","url":null,"abstract":"A code-constrained constant-modulus approach (CMA) was presented recently in Li et al., (2000) for blind detection of asynchronous short-code DS-CDMA (direct sequence code division multiple access) signals in multipath channels. Only the spreading code of the desired user is assumed to be known; its transmission delay may be unknown. The equalizer was determined by minimizing the Godard/CMA cost function of the equalizer output with respect to the equalizer coefficients subject to the fact that the equalizer lies in a subspace associated with the desired user's code sequence. We analyze the identifiability properties of this approach. Global minima and some of the local minima of the cost function are investigated. These aspects were not discussed in Li. More extensive simulation comparisons with existing approaches are also provided.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"3 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":"114534609","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.2001.923859
Chong-Yung Chi, Chii-Horng Chen
Tugnait's multi-input multi-output inverse filter criteria (MIMO-IFC) using either second- and third-order or second- and fourth-order cumulants for blind deconvolution are extended to those using second- and higher-order (/spl ges/ 3) cumulants. Next, a blind maximum ratio combining (BMRC) method using the MIMO-IFC is proposed. Then a blind equalization algorithm for multiuser DS/CDMA systems in multipath channels is proposed using the proposed BMRC method and MIMO-IFC. Finally, some simulation results are provided to support the proposed algorithm.
{"title":"MIMO inverse filter criteria and blind maximum ratio combining using HOS for equalization of DS/CDMA systems in multipath","authors":"Chong-Yung Chi, Chii-Horng Chen","doi":"10.1109/SPAWC.2001.923859","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923859","url":null,"abstract":"Tugnait's multi-input multi-output inverse filter criteria (MIMO-IFC) using either second- and third-order or second- and fourth-order cumulants for blind deconvolution are extended to those using second- and higher-order (/spl ges/ 3) cumulants. Next, a blind maximum ratio combining (BMRC) method using the MIMO-IFC is proposed. Then a blind equalization algorithm for multiuser DS/CDMA systems in multipath channels is proposed using the proposed BMRC method and MIMO-IFC. Finally, some simulation results are provided to support the proposed algorithm.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"113 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":"133850307","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.2001.923912
B. Banister, J. Zeidler
It is generally accepted that the downlink of next generation cellular systems will require greater capacity than the uplink, due to the asymmetry of data traffic patterns. The use of transmit adaptive antenna arrays at the base station is a promising area for downlink capacity improvement. This paper describes a gradient algorithm utilizing mobile to base feedback in order to achieve some of those possible gains. A simple algorithm for adaptation of the complex baseband weights of a transmit antenna array utilizing feedback from the receiving unit is presented. A dedicated pilot signal is transmitted from the transmitting unit with a pair of perturbed test weights; a feedback bit is transmitted from the receiving unit indicating which weight vector provided the larger power; the transmitting unit adjusts a base weight to this selection and continues the process. This approach is shown to be a coarse stochastic gradient algorithm. The settling time and steady state characteristics of the algorithm are investigated analytically and verified by simulation, and the algorithm is shown to converge to those weights which maximize the power delivered to the receiver.
{"title":"A stochastic gradient algorithm for transmit antenna weight adaptation with feedback","authors":"B. Banister, J. Zeidler","doi":"10.1109/SPAWC.2001.923912","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923912","url":null,"abstract":"It is generally accepted that the downlink of next generation cellular systems will require greater capacity than the uplink, due to the asymmetry of data traffic patterns. The use of transmit adaptive antenna arrays at the base station is a promising area for downlink capacity improvement. This paper describes a gradient algorithm utilizing mobile to base feedback in order to achieve some of those possible gains. A simple algorithm for adaptation of the complex baseband weights of a transmit antenna array utilizing feedback from the receiving unit is presented. A dedicated pilot signal is transmitted from the transmitting unit with a pair of perturbed test weights; a feedback bit is transmitted from the receiving unit indicating which weight vector provided the larger power; the transmitting unit adjusts a base weight to this selection and continues the process. This approach is shown to be a coarse stochastic gradient algorithm. The settling time and steady state characteristics of the algorithm are investigated analytically and verified by simulation, and the algorithm is shown to converge to those weights which maximize the power delivered to the receiver.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"36 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":"127145944","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.2001.923864
P. Nanan, M. Nakagawa
This paper studies the performance of the uplink synchronous multi-carrier code division multiple access. The synchronization in uplink transmission can be maintained by using signaling to control it. The performance is evaluated compared with the asynchronous system. Numerical results show that our synchronous transmission technique can offer better performance than conventional asynchronous transmission, especially for an exponentially decaying multipath intensity profile.
{"title":"Performance of uplink synchronous multi-carrier CDMA in wireless communications","authors":"P. Nanan, M. Nakagawa","doi":"10.1109/SPAWC.2001.923864","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923864","url":null,"abstract":"This paper studies the performance of the uplink synchronous multi-carrier code division multiple access. The synchronization in uplink transmission can be maintained by using signaling to control it. The performance is evaluated compared with the asynchronous system. Numerical results show that our synchronous transmission technique can offer better performance than conventional asynchronous transmission, especially for an exponentially decaying multipath intensity profile.","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":"2001-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127703269","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.2001.923871
W. Sheen, M. Chang, Cheng-Shong Wu
The non-coherent second-order digital delay locked loop with Doppler shift present is analyzed. The analysis is unique on two counts. First, the effects of the loop A/D quantization on the loop performance, which have been neglected previously, are examined. Second, MTLL (mean time to lose lock) and MSE (mean square error) are evaluated more accurately than by previous methods. Numerical results show that: (1) the number of quantization levels significantly alters the loop behavior, including the lock-in range, transient responses, MTLL and MSE; and (2) the traditional analysis based on Gaussian approximation may result in a large error in performance evaluation when the A/D quantization is taken into account.
{"title":"Performance analysis of digital second order delay locked loops for direct sequence spread spectrum systems with Doppler shift and A/D quantization","authors":"W. Sheen, M. Chang, Cheng-Shong Wu","doi":"10.1109/SPAWC.2001.923871","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923871","url":null,"abstract":"The non-coherent second-order digital delay locked loop with Doppler shift present is analyzed. The analysis is unique on two counts. First, the effects of the loop A/D quantization on the loop performance, which have been neglected previously, are examined. Second, MTLL (mean time to lose lock) and MSE (mean square error) are evaluated more accurately than by previous methods. Numerical results show that: (1) the number of quantization levels significantly alters the loop behavior, including the lock-in range, transient responses, MTLL and MSE; and (2) the traditional analysis based on Gaussian approximation may result in a large error in performance evaluation when the A/D quantization is taken into account.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"137 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":"116025324","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.2001.923843
A. Medles, T. Slock, E. Carvalho, Eurecom
The multichannel aspect has led to the development of a wealth of blind channel estimation techniques over the last decade. However, most of these blind techniques are not very robust and only allow us to estimate the channel up to a number of ambiguities, especially in the MIMO case. On the other hand, all current standardized communication systems employ some form of known inputs to allow channel estimation. The channel estimation performance in those cases can always be improved by a semi-blind approach which exploits both training and blind information. The purpose of this paper is to introduce semi-blind techniques of which the complexity is not immensely much higher than that of training-based techniques. The semi-blind criteria are quadratic and combine a training-based least-squares criterion with a blind criterion based on linear prediction. A variety of convenient linear prediction approaches are considered.
{"title":"Linear prediction based semi-blind estimation of MIMO FIR channels","authors":"A. Medles, T. Slock, E. Carvalho, Eurecom","doi":"10.1109/SPAWC.2001.923843","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923843","url":null,"abstract":"The multichannel aspect has led to the development of a wealth of blind channel estimation techniques over the last decade. However, most of these blind techniques are not very robust and only allow us to estimate the channel up to a number of ambiguities, especially in the MIMO case. On the other hand, all current standardized communication systems employ some form of known inputs to allow channel estimation. The channel estimation performance in those cases can always be improved by a semi-blind approach which exploits both training and blind information. The purpose of this paper is to introduce semi-blind techniques of which the complexity is not immensely much higher than that of training-based techniques. The semi-blind criteria are quadratic and combine a training-based least-squares criterion with a blind criterion based on linear prediction. A variety of convenient linear prediction approaches are considered.","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":"116270547","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.2001.923895
Yimin D. Zhang, M. Amin, A. Lindsey, K. Yang
Space-time coding and interference cancellation based on orthogonal projection are powerful techniques to improve the communication quality and capacity in downlink CDMA systems. The space-time encoder output stream is transmitted through the fading channel using multiple transmitter antennas, increasing communication reliability against multipath fading. On the other hand, orthogonal projection-based interference cancellation mitigates the multiuser interference. This is achieved by projecting the received signals to the orthogonal subspace of the interference signal subspace. We propose a method that combines these two techniques. The proposed method allows the downlink CDMA system to be robust against both channel fading and multiuser access interference. Simulation results are provided for both static and dynamic fading channel environments.
{"title":"Downlink CDMA systems with space-time codes and interference cancellation","authors":"Yimin D. Zhang, M. Amin, A. Lindsey, K. Yang","doi":"10.1109/SPAWC.2001.923895","DOIUrl":"https://doi.org/10.1109/SPAWC.2001.923895","url":null,"abstract":"Space-time coding and interference cancellation based on orthogonal projection are powerful techniques to improve the communication quality and capacity in downlink CDMA systems. The space-time encoder output stream is transmitted through the fading channel using multiple transmitter antennas, increasing communication reliability against multipath fading. On the other hand, orthogonal projection-based interference cancellation mitigates the multiuser interference. This is achieved by projecting the received signals to the orthogonal subspace of the interference signal subspace. We propose a method that combines these two techniques. The proposed method allows the downlink CDMA system to be robust against both channel fading and multiuser access interference. Simulation results are provided for both static and dynamic fading channel environments.","PeriodicalId":435867,"journal":{"name":"2001 IEEE Third Workshop on Signal Processing Advances in Wireless Communications (SPAWC'01). Workshop Proceedings (Cat. No.01EX471)","volume":"18 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":"122501863","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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