Pub Date : 2003-12-01DOI: 10.1109/GLOCOM.2003.1258508
P. Papadimitriou, C. Georghiades
In this paper, we study the binary code design problem for the fading channel with noncoherent maximum-likelihood detection. The /spl rho/-spectrum (i.e. all possible pairwise absolute cross-correlations) provides a way to define the optimal codes, based on the union bound on the error probability, as the codes achieving the optimal /spl rho/-spectrum for some code rate. We introduce some limited search methods based on the /spl rho/-spectrum, including a nested search, which for some code rates yields optimal codes. With our nested search, good codes were obtained easily up to code rate 12/n, n/spl les/4096. The codes developed offer good performance in the fading channel and can be used in place of the Hadamard-Walsh codes in synchronous CDMA systems to increase system capacity.
{"title":"On binary code design for the noncoherent block fading channel","authors":"P. Papadimitriou, C. Georghiades","doi":"10.1109/GLOCOM.2003.1258508","DOIUrl":"https://doi.org/10.1109/GLOCOM.2003.1258508","url":null,"abstract":"In this paper, we study the binary code design problem for the fading channel with noncoherent maximum-likelihood detection. The /spl rho/-spectrum (i.e. all possible pairwise absolute cross-correlations) provides a way to define the optimal codes, based on the union bound on the error probability, as the codes achieving the optimal /spl rho/-spectrum for some code rate. We introduce some limited search methods based on the /spl rho/-spectrum, including a nested search, which for some code rates yields optimal codes. With our nested search, good codes were obtained easily up to code rate 12/n, n/spl les/4096. The codes developed offer good performance in the fading channel and can be used in place of the Hadamard-Walsh codes in synchronous CDMA systems to increase system capacity.","PeriodicalId":301154,"journal":{"name":"GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125867327","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 : 2003-12-01DOI: 10.1109/GLOCOM.2003.1258730
Hajime Nakamura, H. Yokoyama, S. Nomoto
The basic concept of a novel architecture called statistical lambda multiplexing network (SLAMNet) was proposed to provide a pair of routers with multiple transparent wavelength paths in a dense wavelength division multiplexing (DWDM) network. The architecture achieves statistical multiplex gain in use of limited wavelength resources by dynamically adjusting the number of wavelength paths according to the volume of traffic on a best-effort basis. The most striking feature of the architecture is to switch the wavelength paths without signaling between nodes operated asynchronously. Fundamental performance of the architecture was verified on an experimental system. The basic concept assumes a single hop network of switched wavelength paths, and the assumption limits flexibility and efficiency of network operation. In this paper, the basic concept is extended in order to apply SLAMNet to a multihop network of switched wavelength paths. Based on the extended concept, circuit-based and burst-based wavelength path assignment methods are discussed as implementation scenarios of the architecture.
{"title":"Extended concept of statistical lambda multiplexing network (SLAMNet)","authors":"Hajime Nakamura, H. Yokoyama, S. Nomoto","doi":"10.1109/GLOCOM.2003.1258730","DOIUrl":"https://doi.org/10.1109/GLOCOM.2003.1258730","url":null,"abstract":"The basic concept of a novel architecture called statistical lambda multiplexing network (SLAMNet) was proposed to provide a pair of routers with multiple transparent wavelength paths in a dense wavelength division multiplexing (DWDM) network. The architecture achieves statistical multiplex gain in use of limited wavelength resources by dynamically adjusting the number of wavelength paths according to the volume of traffic on a best-effort basis. The most striking feature of the architecture is to switch the wavelength paths without signaling between nodes operated asynchronously. Fundamental performance of the architecture was verified on an experimental system. The basic concept assumes a single hop network of switched wavelength paths, and the assumption limits flexibility and efficiency of network operation. In this paper, the basic concept is extended in order to apply SLAMNet to a multihop network of switched wavelength paths. Based on the extended concept, circuit-based and burst-based wavelength path assignment methods are discussed as implementation scenarios of the architecture.","PeriodicalId":301154,"journal":{"name":"GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125978562","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 : 2003-12-01DOI: 10.1109/GLOCOM.2003.1258515
Nourddine Azzaoui, L. Clavier, R. Sabre
In this work we give a statistical model of the paths' arrival time in the 60 GHz wide band channel. This model is based on the class of stable distributions, we show its accurateness on modeling real data. We also give a theoretical justification of its compatibility.
{"title":"Path delay model based on /spl alpha/-stable distribution for the 60 GHz indoor channel","authors":"Nourddine Azzaoui, L. Clavier, R. Sabre","doi":"10.1109/GLOCOM.2003.1258515","DOIUrl":"https://doi.org/10.1109/GLOCOM.2003.1258515","url":null,"abstract":"In this work we give a statistical model of the paths' arrival time in the 60 GHz wide band channel. This model is based on the class of stable distributions, we show its accurateness on modeling real data. We also give a theoretical justification of its compatibility.","PeriodicalId":301154,"journal":{"name":"GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489)","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126191544","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 : 2003-12-01DOI: 10.1109/GLOCOM.2003.1258670
Shiou-Hong Chen, Way-Hong He, Hou-Shin Chen, Yumin Lee
A baseband receiver for DVB-T OFDM with variable number of subcarriers is presented in this paper. The proposed receiver consists of a blind mode detector, time and frequency synchronizer, and channel estimator. The blind mode detector uses a novel algorithm to detect the number of OFDM subcarriers in the received signal. Time and frequency synchronization is performed after the transmission mode is detected. Finally, channel estimation is performed using ID or 2D interpolation. Simulation results show that the proposed mode detection and synchronization algorithms are close to ideal, and good overall performance is achievable.
{"title":"Mode detection, synchronization, and channel estimation for DVB-T OFDM receiver","authors":"Shiou-Hong Chen, Way-Hong He, Hou-Shin Chen, Yumin Lee","doi":"10.1109/GLOCOM.2003.1258670","DOIUrl":"https://doi.org/10.1109/GLOCOM.2003.1258670","url":null,"abstract":"A baseband receiver for DVB-T OFDM with variable number of subcarriers is presented in this paper. The proposed receiver consists of a blind mode detector, time and frequency synchronizer, and channel estimator. The blind mode detector uses a novel algorithm to detect the number of OFDM subcarriers in the received signal. Time and frequency synchronization is performed after the transmission mode is detected. Finally, channel estimation is performed using ID or 2D interpolation. Simulation results show that the proposed mode detection and synchronization algorithms are close to ideal, and good overall performance is achievable.","PeriodicalId":301154,"journal":{"name":"GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489)","volume":"302 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129425985","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 : 2003-12-01DOI: 10.1109/GLOCOM.2003.1259013
R. Piechocki, C. Kasparis, A. Nix, P. Fletcher, J. McGeehan
The paper reports on a new class of equalisation/detection for wideband multiple input-multiple output (MIMO) communications systems. The proposed scheme is somewhat akin to a multi-carrier MIMO system, and more precisely, builds upon a single carrier frequency domain equalised (SCFDE) MIMO system. At the core of our system lies a novel concept of iterative self-reused equalisation/detection (bootstrapping) combined with semi-hard decision making. The bootstrapping concept is derived from a new formulation of Tikhonov regularisation. The proposed scheme achieves a remarkable performance/complexity trade-off. In particular we show that our system approaches the performance of ML-MIMO-OFDM while being only slightly more complex than MMSE-MIMO-OFDM. The coded version achieves virtually the same performance as turbo MIMO-OFDM at a fraction of the complexity. The resulting system is termed zero tailed bootstrap frequency equalised (ZTBFE) MIMO system.
{"title":"Bootstrap frequency equalisation for MIMO wireless systems","authors":"R. Piechocki, C. Kasparis, A. Nix, P. Fletcher, J. McGeehan","doi":"10.1109/GLOCOM.2003.1259013","DOIUrl":"https://doi.org/10.1109/GLOCOM.2003.1259013","url":null,"abstract":"The paper reports on a new class of equalisation/detection for wideband multiple input-multiple output (MIMO) communications systems. The proposed scheme is somewhat akin to a multi-carrier MIMO system, and more precisely, builds upon a single carrier frequency domain equalised (SCFDE) MIMO system. At the core of our system lies a novel concept of iterative self-reused equalisation/detection (bootstrapping) combined with semi-hard decision making. The bootstrapping concept is derived from a new formulation of Tikhonov regularisation. The proposed scheme achieves a remarkable performance/complexity trade-off. In particular we show that our system approaches the performance of ML-MIMO-OFDM while being only slightly more complex than MMSE-MIMO-OFDM. The coded version achieves virtually the same performance as turbo MIMO-OFDM at a fraction of the complexity. The resulting system is termed zero tailed bootstrap frequency equalised (ZTBFE) MIMO system.","PeriodicalId":301154,"journal":{"name":"GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129452210","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 : 2003-12-01DOI: 10.1109/GLOCOM.2003.1258827
Guansong Zhang, H. J. Chao, Jinoo Joung
Packet classification plays an important role in next-generation Internet routers in providing various services such as packet filtering, policy routing, traffic policing, and load balancing. In this paper, we propose an original field-level trie classification (FLTC) scheme that accommodates classifier (rule database) with multiple fields specified in different forms (prefix and range). The FLTC achieves a high classification speed with reasonable storage. It is also highly scalable regarding the size and the number of fields of classifiers.
{"title":"Fast packet classification using field-level trie","authors":"Guansong Zhang, H. J. Chao, Jinoo Joung","doi":"10.1109/GLOCOM.2003.1258827","DOIUrl":"https://doi.org/10.1109/GLOCOM.2003.1258827","url":null,"abstract":"Packet classification plays an important role in next-generation Internet routers in providing various services such as packet filtering, policy routing, traffic policing, and load balancing. In this paper, we propose an original field-level trie classification (FLTC) scheme that accommodates classifier (rule database) with multiple fields specified in different forms (prefix and range). The FLTC achieves a high classification speed with reasonable storage. It is also highly scalable regarding the size and the number of fields of classifiers.","PeriodicalId":301154,"journal":{"name":"GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128357548","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 : 2003-12-01DOI: 10.1109/GLOCOM.2003.1258230
Yong Peng, Shiduan Cheng, Yu Lin
Numerous researches have shown that the original DCF access mode of IEEE 802.11 has low performance in case of heavy traffic environment. Based on the analysis of previous IEEE 802.11 DCF, we have proposed a parameter that closely relative to the traffic load of the current wireless LAN and formed a new DCF-based protocol with the name of NSAD (new self-adapt DCF-based protocol). NSAD is proved effective in the error-free environment. In this paper, we proposed some new mechanisms to further enhance the performance of NSAD and formed a new MAC mechanism RSAD (robust self-adapt DCF-based protocol). We have done simulation in a more real environment than we do in NSAD. The simulation results have shown that the proposed RSAD can achieve better performance when compared with the original NSAD algorithm in an error-prone environment (e.g. better property in goodput and window tuning accuracy).
大量研究表明，IEEE 802.11原有的DCF接入方式在大流量环境下性能较差。在分析前人IEEE 802.11 DCF的基础上，我们提出了一个与当前无线局域网的流量负荷密切相关的参数，并形成了一个新的基于DCF的协议，命名为NSAD (new self- adaptive DCF- Based protocol)。NSAD在无差错环境下被证明是有效的。在本文中，我们提出了一些新的机制来进一步提高NSAD的性能，形成了一个新的MAC机制RSAD(鲁棒自适应DCF-based protocol)。我们在一个比NSAD更真实的环境中做了模拟。仿真结果表明，在易出错的环境下，与原有的NSAD算法相比，本文提出的RSAD算法可以获得更好的性能(例如，更好的good - put性能和窗口调优精度)。
{"title":"Design of a robust self-adapt DCF-based protocol","authors":"Yong Peng, Shiduan Cheng, Yu Lin","doi":"10.1109/GLOCOM.2003.1258230","DOIUrl":"https://doi.org/10.1109/GLOCOM.2003.1258230","url":null,"abstract":"Numerous researches have shown that the original DCF access mode of IEEE 802.11 has low performance in case of heavy traffic environment. Based on the analysis of previous IEEE 802.11 DCF, we have proposed a parameter that closely relative to the traffic load of the current wireless LAN and formed a new DCF-based protocol with the name of NSAD (new self-adapt DCF-based protocol). NSAD is proved effective in the error-free environment. In this paper, we proposed some new mechanisms to further enhance the performance of NSAD and formed a new MAC mechanism RSAD (robust self-adapt DCF-based protocol). We have done simulation in a more real environment than we do in NSAD. The simulation results have shown that the proposed RSAD can achieve better performance when compared with the original NSAD algorithm in an error-prone environment (e.g. better property in goodput and window tuning accuracy).","PeriodicalId":301154,"journal":{"name":"GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489)","volume":"31 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128649011","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 : 2003-12-01DOI: 10.1109/GLOCOM.2003.1258627
Chih-Ming Fu, W. Hwang, Chung-Lin Huang
The acquisition problem in wavelet-based modulation is very important. We discuss the problem of the ML-based method proposed by M. Luise et al. (see IEEE Trans. Commun., vol.48, p.1047-54, 2000) for timing acquisition and then we develop a novel acquisition algorithm. Our method uses the properties of the scaling function in the derivation of the acquisition function. We also show that the S-curve of our acquisition algorithm is smooth and has a unique zero during the signaling interval. Thus, we can acquire the correct symbol timing without ambiguity. The performance of our acquisition algorithm is evaluated by Monto-Carlo simulation using the Meyer wavelet.
{"title":"Timing acquisition for wavelet-based multirate transmissions","authors":"Chih-Ming Fu, W. Hwang, Chung-Lin Huang","doi":"10.1109/GLOCOM.2003.1258627","DOIUrl":"https://doi.org/10.1109/GLOCOM.2003.1258627","url":null,"abstract":"The acquisition problem in wavelet-based modulation is very important. We discuss the problem of the ML-based method proposed by M. Luise et al. (see IEEE Trans. Commun., vol.48, p.1047-54, 2000) for timing acquisition and then we develop a novel acquisition algorithm. Our method uses the properties of the scaling function in the derivation of the acquisition function. We also show that the S-curve of our acquisition algorithm is smooth and has a unique zero during the signaling interval. Thus, we can acquire the correct symbol timing without ambiguity. The performance of our acquisition algorithm is evaluated by Monto-Carlo simulation using the Meyer wavelet.","PeriodicalId":301154,"journal":{"name":"GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128676284","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 : 2003-12-01DOI: 10.1109/GLOCOM.2003.1258806
Jinsheng Sun, Guanrong Chen, K. Ko, Sammy Chan, M. Zukerman
This paper describes a proportional-differential (PD) control algorithm as a new active queue management (AQM) scheme for TCP/IP congestion control. From the viewpoint of the control theory, TCP congestion control system can be regarded as a feedback regulating system. In this paper, a robust AQM called PD-controller is proposed. The design principles of PD-controller are presented in details. Its performance is extensively evaluated by simulations. The results demonstrate that the PD-controller AQM is stable and robust against traffic load fluctuations, UDP and HTTP disturbances. Its superiority over other AQMs is also demonstrated.
{"title":"PD-controller: a new active queue management scheme","authors":"Jinsheng Sun, Guanrong Chen, K. Ko, Sammy Chan, M. Zukerman","doi":"10.1109/GLOCOM.2003.1258806","DOIUrl":"https://doi.org/10.1109/GLOCOM.2003.1258806","url":null,"abstract":"This paper describes a proportional-differential (PD) control algorithm as a new active queue management (AQM) scheme for TCP/IP congestion control. From the viewpoint of the control theory, TCP congestion control system can be regarded as a feedback regulating system. In this paper, a robust AQM called PD-controller is proposed. The design principles of PD-controller are presented in details. Its performance is extensively evaluated by simulations. The results demonstrate that the PD-controller AQM is stable and robust against traffic load fluctuations, UDP and HTTP disturbances. Its superiority over other AQMs is also demonstrated.","PeriodicalId":301154,"journal":{"name":"GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489)","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129673777","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 : 2003-12-01DOI: 10.1109/GLOCOM.2003.1258256
K. Nolan, P. Mackenzie, L. Doyle, D. Flood
In this paper, we present findings relating to frame synchronization algorithms for software radio based OFDM systems in addition to an overview of the design and implementation of an (OFDM) software radio based on a general-purpose processor (GPP) platform. The objectives of this work are to advance on existing research carried out in the area of reconfigurable wireless flexible architecture nodes, which are subject to multipath fading, Doppler effects, and adjacent channel interference and have low cost yet robust and reliable operation requirements. We also include findings dealing with bit error rate (BER) versus channel signal to noise ratio (SNR) for BPSK and QPSK modulation schemes, and also the effect of non real-time operating systems (OS) running on GPPs on the transmitter processing time.
{"title":"Flexible architecture software radio OFDM transceiver system and frame synchronization analysis","authors":"K. Nolan, P. Mackenzie, L. Doyle, D. Flood","doi":"10.1109/GLOCOM.2003.1258256","DOIUrl":"https://doi.org/10.1109/GLOCOM.2003.1258256","url":null,"abstract":"In this paper, we present findings relating to frame synchronization algorithms for software radio based OFDM systems in addition to an overview of the design and implementation of an (OFDM) software radio based on a general-purpose processor (GPP) platform. The objectives of this work are to advance on existing research carried out in the area of reconfigurable wireless flexible architecture nodes, which are subject to multipath fading, Doppler effects, and adjacent channel interference and have low cost yet robust and reliable operation requirements. We also include findings dealing with bit error rate (BER) versus channel signal to noise ratio (SNR) for BPSK and QPSK modulation schemes, and also the effect of non real-time operating systems (OS) running on GPPs on the transmitter processing time.","PeriodicalId":301154,"journal":{"name":"GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489)","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129740293","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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