Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.679122
M. Zatman
The "narrowband" or zero-bandwidth assumption is often made in the analysis of array signal processing algorithms. This paper provides both a definition and expression which precisely define the notion of narrowband The expression accurately predicts the point when the "narrowband" assumption fails for some superresolution algorithms, the Cramer Rao bound on angle estimation and the signal-to-interference-plus-noise performance of adaptive beamformers. Hence it is a useful design point for many types of sensor array systems.
{"title":"How narrow is narrowband? [adaptive array signal processing]","authors":"M. Zatman","doi":"10.1109/ACSSC.1997.679122","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.679122","url":null,"abstract":"The \"narrowband\" or zero-bandwidth assumption is often made in the analysis of array signal processing algorithms. This paper provides both a definition and expression which precisely define the notion of narrowband The expression accurately predicts the point when the \"narrowband\" assumption fails for some superresolution algorithms, the Cramer Rao bound on angle estimation and the signal-to-interference-plus-noise performance of adaptive beamformers. Hence it is a useful design point for many types of sensor array systems.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115991192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.679131
A. Duel-Hallen, S. Andrijic
This paper addresses multiuser detection and diversity combining for frequency selective fading code-division multiple access (CDMA) channels. It is well known that the decorrelating detector is an effective technique for separating signals of different users in bandwidth-efficient CDMA. For a general asynchronous CDMA channel, the output of the decorrelator for each user can be characterized by an equivalent single-user system with multiuser (MAI)-induced intersymbol interference (ISI). We investigate diversity combining techniques for this equivalent single-user channel using differential phase shift keying (DPSK) detection. This method does not require tracking of rapidly changing fading parameters. To improve the performance of the DPSK combiner, it can be beneficial to weigh the signals associated with different paths. We consider several criteria for choosing these weights. For the synchronous (ISI-free) channel, we show that the bit error rate (BER) of the optimal combiner can be closely approximated by a combination of two decorrelating detectors (with either noise whitening or signal whitening filters). We also discuss this "hybrid" approach for asynchronous channels with MAI-induced ISI. Finally, a minimum mean square error (MMSE) combiner is analyzed and compared to other techniques.
{"title":"DPSK diversity combining for CDMA frequency selective fading channels","authors":"A. Duel-Hallen, S. Andrijic","doi":"10.1109/ACSSC.1997.679131","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.679131","url":null,"abstract":"This paper addresses multiuser detection and diversity combining for frequency selective fading code-division multiple access (CDMA) channels. It is well known that the decorrelating detector is an effective technique for separating signals of different users in bandwidth-efficient CDMA. For a general asynchronous CDMA channel, the output of the decorrelator for each user can be characterized by an equivalent single-user system with multiuser (MAI)-induced intersymbol interference (ISI). We investigate diversity combining techniques for this equivalent single-user channel using differential phase shift keying (DPSK) detection. This method does not require tracking of rapidly changing fading parameters. To improve the performance of the DPSK combiner, it can be beneficial to weigh the signals associated with different paths. We consider several criteria for choosing these weights. For the synchronous (ISI-free) channel, we show that the bit error rate (BER) of the optimal combiner can be closely approximated by a combination of two decorrelating detectors (with either noise whitening or signal whitening filters). We also discuss this \"hybrid\" approach for asynchronous channels with MAI-induced ISI. Finally, a minimum mean square error (MMSE) combiner is analyzed and compared to other techniques.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115576862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.679082
L. Sellami, S.K. Singh, R. Newcomb, A. Rasmussen, M. Zaghloul
A previous CMOS bilateral linear resistor is modified into two different configurations of floating resistors using the structure of a two-transistor CMOS bilateral linear resistor in the first configuration and two two-transistor CMOS bilateral linear resistors and current mirrors in the second configuration. Simulation results using parameters of MOSIS transistors are presented to verify the theory. These floating resistors can be used for coupling weights in VLSI neural-type cell arrays.
{"title":"CMOS bilateral linear floating resistors for neural-type cell arrays","authors":"L. Sellami, S.K. Singh, R. Newcomb, A. Rasmussen, M. Zaghloul","doi":"10.1109/ACSSC.1997.679082","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.679082","url":null,"abstract":"A previous CMOS bilateral linear resistor is modified into two different configurations of floating resistors using the structure of a two-transistor CMOS bilateral linear resistor in the first configuration and two two-transistor CMOS bilateral linear resistors and current mirrors in the second configuration. Simulation results using parameters of MOSIS transistors are presented to verify the theory. These floating resistors can be used for coupling weights in VLSI neural-type cell arrays.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115234555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.680580
X. Xia
Ambiguity resistant (AR) precoding has been proposed in intersymbol interference (ISI) and multipath cancellation, where the ISI/multipath channel may have frequency-selective fading characteristics and its knowledge is not necessarily known. With the AR precoding, no diversity is necessary at the receiver. In the precoding, the AR property of the precoder plays an important role. We introduce the concepts of precoder distance and optimal precoders, and characterize and construct all optimal systematic AR precoders, when additive channel random noise is considered. A necessary and sufficient condition for an AR precoder to be optimal is given, which is easy to check. With the optimal precoders, numerical simulations are presented to show the improved performance over the known AR precoders in ISI cancellation applications.
{"title":"Ambiguity resistant precoders in ISI/multipath cancellation: distance and optimality","authors":"X. Xia","doi":"10.1109/ACSSC.1997.680580","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.680580","url":null,"abstract":"Ambiguity resistant (AR) precoding has been proposed in intersymbol interference (ISI) and multipath cancellation, where the ISI/multipath channel may have frequency-selective fading characteristics and its knowledge is not necessarily known. With the AR precoding, no diversity is necessary at the receiver. In the precoding, the AR property of the precoder plays an important role. We introduce the concepts of precoder distance and optimal precoders, and characterize and construct all optimal systematic AR precoders, when additive channel random noise is considered. A necessary and sufficient condition for an AR precoder to be optimal is given, which is easy to check. With the optimal precoders, numerical simulations are presented to show the improved performance over the known AR precoders in ISI cancellation applications.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115466664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.680241
B. Girod, N. Farber, U. Horn
The heterogeneous structure of the Internet is a great obstacle for establishing real-time video services. Scalable video codecs, generating bit-streams decodable at different rates, have been proposed to address the heterogeneity problem. In this paper, we review standard-compliant and non-compliant codec architectures for Internet video-on-demand. For compression based on the H.263 standard, we have developed a compatible architecture that allows to switch between pre-encoded bit-streamers of different bitrates. This architecture provides excellent streaming performance for point-to-point communication scenarios that offer a low delay feedback channel. Then we present a non-compliant fully scalable video codec based on a spatiotemporal resolution pyramid. This approach can encode embedded lower bit-rate layers at the same overall hit-rate as needed by H.263 single-layer coding and can also support multicasting. The complexity of both schemes is sufficiently low to allow software-only implementations of Internet video services. This is demonstrated by means of an implemented World Wide Web video server application.
{"title":"Scalable codec architectures for Internet video-on-demand","authors":"B. Girod, N. Farber, U. Horn","doi":"10.1109/ACSSC.1997.680241","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.680241","url":null,"abstract":"The heterogeneous structure of the Internet is a great obstacle for establishing real-time video services. Scalable video codecs, generating bit-streams decodable at different rates, have been proposed to address the heterogeneity problem. In this paper, we review standard-compliant and non-compliant codec architectures for Internet video-on-demand. For compression based on the H.263 standard, we have developed a compatible architecture that allows to switch between pre-encoded bit-streamers of different bitrates. This architecture provides excellent streaming performance for point-to-point communication scenarios that offer a low delay feedback channel. Then we present a non-compliant fully scalable video codec based on a spatiotemporal resolution pyramid. This approach can encode embedded lower bit-rate layers at the same overall hit-rate as needed by H.263 single-layer coding and can also support multicasting. The complexity of both schemes is sufficiently low to allow software-only implementations of Internet video services. This is demonstrated by means of an implemented World Wide Web video server application.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"421 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116229992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.679178
H. A. Çırpan, M. Tsatsanis
A blind stochastic maximum likelihood channel equalization algorithm is adapted to incorporate a known training sequence as part of the transmitted frame. A hidden Markov model formulation of the problem is introduced and the Baum-Welch (1970) algorithm is modified to provide a computationally efficient solution to the resulting optimization problem. The proposed method provides a unified framework for semi-blind channel estimation, which exploits information from both the training and the blind part of the received data record. The performance of the maximum likelihood estimator is studied, based on the evaluation of Cramer-Rao bounds. Finally, some simulation results are presented.
{"title":"Stochastic maximum likelihood methods for semi-blind channel equalization","authors":"H. A. Çırpan, M. Tsatsanis","doi":"10.1109/ACSSC.1997.679178","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.679178","url":null,"abstract":"A blind stochastic maximum likelihood channel equalization algorithm is adapted to incorporate a known training sequence as part of the transmitted frame. A hidden Markov model formulation of the problem is introduced and the Baum-Welch (1970) algorithm is modified to provide a computationally efficient solution to the resulting optimization problem. The proposed method provides a unified framework for semi-blind channel estimation, which exploits information from both the training and the blind part of the received data record. The performance of the maximum likelihood estimator is studied, based on the evaluation of Cramer-Rao bounds. Finally, some simulation results are presented.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"110 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116281957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.679142
G. Langdon, B. Mealy
We have studied some of the features incorporated into the baseline versions of the emerging standard called JPEG-LS. The baseline version had its genesis in response to the call for algorithm contributions submitted by Hewlett-Packard Company (Marcelo et al., 1995). A set of test images are used to evaluate various aspects of this very effective, yet relatively simple, lossless image compression algorithm.
我们已经研究了被合并到称为JPEG-LS的新兴标准的基线版本中的一些特性。基线版本的起源是为了响应惠普公司提交的算法贡献呼吁(Marcelo et al.， 1995)。使用一组测试图像来评估这种非常有效但相对简单的无损图像压缩算法的各个方面。
{"title":"On prediction error coding methods for lossless image compression","authors":"G. Langdon, B. Mealy","doi":"10.1109/ACSSC.1997.679142","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.679142","url":null,"abstract":"We have studied some of the features incorporated into the baseline versions of the emerging standard called JPEG-LS. The baseline version had its genesis in response to the call for algorithm contributions submitted by Hewlett-Packard Company (Marcelo et al., 1995). A set of test images are used to evaluate various aspects of this very effective, yet relatively simple, lossless image compression algorithm.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114433056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.679139
Xiaolin Wu, P. Bao
In this paper we report experimental work on L/sub /spl infin//-constrained high-fidelity image compression. In our experiments minimum-entropy pre-quantization and minimum-entropy trellis quantization did not lead to competitive L/sub /spl infin//-constrained near-lossless compression performance against our previous work of L/sub /spl infin//-constrained CALIC (Wu et al. 1997). But we were able to improve L/sub /spl infin//-constrained CALIC, the best L/sub /spl infin//-constrained image coder for error tolerance below 7 so far by a hybrid approach. First, an input image is wavelet transformed, the wavelet coefficients are quantized in an L/sub /spl infin// criterion and entropy coded. Then a wavelet approximation of the image is constructed by inverse transform based on the quantized wavelet coefficients. Finally, L/sub /spl infin//-constrained CALIC is used to compress the residue image between the wavelet approximation and the original.
{"title":"Near-lossless image compression by combining wavelets and CALIC","authors":"Xiaolin Wu, P. Bao","doi":"10.1109/ACSSC.1997.679139","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.679139","url":null,"abstract":"In this paper we report experimental work on L/sub /spl infin//-constrained high-fidelity image compression. In our experiments minimum-entropy pre-quantization and minimum-entropy trellis quantization did not lead to competitive L/sub /spl infin//-constrained near-lossless compression performance against our previous work of L/sub /spl infin//-constrained CALIC (Wu et al. 1997). But we were able to improve L/sub /spl infin//-constrained CALIC, the best L/sub /spl infin//-constrained image coder for error tolerance below 7 so far by a hybrid approach. First, an input image is wavelet transformed, the wavelet coefficients are quantized in an L/sub /spl infin// criterion and entropy coded. Then a wavelet approximation of the image is constructed by inverse transform based on the quantized wavelet coefficients. Finally, L/sub /spl infin//-constrained CALIC is used to compress the residue image between the wavelet approximation and the original.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125380071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.680372
C. Tontiruttananon, Jitendra Tugnait
The problem of closed-loop system identification given noisy input-output measurements is considered. The closed-loop system operates under an external cyclostationary input which is not measured. Noisy measurements of the (direct) input and output of the plant are assumed to be available. The various disturbances affecting the system are either stationary or cyclostationary with cycle frequencies different from the input cycle frequencies. The closed-loop system must be stable but it is allowed to be unstable in open-loop. A frequency-domain parametric solution is proposed and analyzed using an equation error formulation, and cyclic spectrum and cross-spectrum of the input-output measurements. The parameter estimator is shown to be consistent. A simulation example using an unstable open-loop system is presented to illustrate the proposed approach.
{"title":"Equation-error closed-loop system identification using cyclic spectral analysis","authors":"C. Tontiruttananon, Jitendra Tugnait","doi":"10.1109/ACSSC.1997.680372","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.680372","url":null,"abstract":"The problem of closed-loop system identification given noisy input-output measurements is considered. The closed-loop system operates under an external cyclostationary input which is not measured. Noisy measurements of the (direct) input and output of the plant are assumed to be available. The various disturbances affecting the system are either stationary or cyclostationary with cycle frequencies different from the input cycle frequencies. The closed-loop system must be stable but it is allowed to be unstable in open-loop. A frequency-domain parametric solution is proposed and analyzed using an equation error formulation, and cyclic spectrum and cross-spectrum of the input-output measurements. The parameter estimator is shown to be consistent. A simulation example using an unstable open-loop system is presented to illustrate the proposed approach.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126644272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-11-02DOI: 10.1109/ACSSC.1997.680147
P. Subramanian, D. Blasiak, Jiandong Shen, W. Chan
In a motion-compensated discrete-cosine-transform (MC/DCT) coding framework similar to the H.263-standard video coder, we explore the performance gain furnished by rate-distortion (R-D) optimization. We show that exact global R-D optimization is a very complex task. We seek good performance-complexity tradeoffs instead. We explore an encoding scheme that has several complexity reduction features: noniterative Lagrangian motion estimation, optimized table-based estimators of DCT coding bit rate and distortion performance, and bottom-up propagation of block matching results. Our scheme is compared with the advanced prediction mode (APM) of H.263, as instrumented by the popular Telenor test model. For typical QCIF video test sequences, our scheme furnishes PSNR gains ranging from 0.35 to 1.1 dB. Visual quality improvement is highly palpable. The complexity of our scheme is roughly 30% higher than the Telenor implementation.
{"title":"Encoder optimization in an extended H.263 framework","authors":"P. Subramanian, D. Blasiak, Jiandong Shen, W. Chan","doi":"10.1109/ACSSC.1997.680147","DOIUrl":"https://doi.org/10.1109/ACSSC.1997.680147","url":null,"abstract":"In a motion-compensated discrete-cosine-transform (MC/DCT) coding framework similar to the H.263-standard video coder, we explore the performance gain furnished by rate-distortion (R-D) optimization. We show that exact global R-D optimization is a very complex task. We seek good performance-complexity tradeoffs instead. We explore an encoding scheme that has several complexity reduction features: noniterative Lagrangian motion estimation, optimized table-based estimators of DCT coding bit rate and distortion performance, and bottom-up propagation of block matching results. Our scheme is compared with the advanced prediction mode (APM) of H.263, as instrumented by the popular Telenor test model. For typical QCIF video test sequences, our scheme furnishes PSNR gains ranging from 0.35 to 1.1 dB. Visual quality improvement is highly palpable. The complexity of our scheme is roughly 30% higher than the Telenor implementation.","PeriodicalId":240431,"journal":{"name":"Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136)","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126686590","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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