Pub Date : 2000-12-17DOI: 10.1109/ICPWC.2000.905845
S. Sengodan, D. Smith, M. Abou-Rizk
With the convergence of the Internet protocol (IP) and wireless technologies such as Bluetooth and the wireless application protocol (WAP), a study on end-to-end security issues has become important. Differences in security algorithms and protocols between these technologies needs to be clearly understood in order to understand the impact on end-to-end security. This paper describes some of these aspects in the context of Bluetooth and WAP interfacing with IP networks. Various security services - key generation, authentication and confidentiality - are considered and compared.
{"title":"On end-to-end security for Bluetooth/WAP and TCP/IP networks","authors":"S. Sengodan, D. Smith, M. Abou-Rizk","doi":"10.1109/ICPWC.2000.905845","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905845","url":null,"abstract":"With the convergence of the Internet protocol (IP) and wireless technologies such as Bluetooth and the wireless application protocol (WAP), a study on end-to-end security issues has become important. Differences in security algorithms and protocols between these technologies needs to be clearly understood in order to understand the impact on end-to-end security. This paper describes some of these aspects in the context of Bluetooth and WAP interfacing with IP networks. Various security services - key generation, authentication and confidentiality - are considered and compared.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130394622","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905788
R. van der Hofstad, M. J. Klok
For a direct-sequence code division multiple access system with hard decision parallel interference cancellation (DS-CDMA with HD-PIC), we derive analytical results concerning the probability of a bit error. More precisely, we investigate the exponential rate H/sub k//sup (s)/ of a CDMA system with s stages of HD-PIC, with k users and processing gain equal to n, as n/spl rarr//spl infin/. The rate is a good measure of performance and allows us to compare the performance after applying several stages of HD-PIC. Furthermore, we derive results for the asymptotic behaviour of the exponential rates H/sub k//sup (s)/ as k/spl rarr//spl infin/. Finally, we investigate what happens when, for k fixed, we perform many stages of HD-PIC. These results can be used to guarantee a small BEP by applying a number of HD-PIC stages that depends on the number of users. The results show analytically that HD-PIC significantly improves performance. This conference paper is based upon and extends results and techniques of Van der Hofstad et al. (2000), that we briefly discuss.
针对硬决策并行干扰消除的直接序列码分多址系统(DS-CDMA + HD-PIC)，给出了误码概率的分析结果。更准确地说，我们研究了具有5级HD-PIC、k个用户、处理增益等于n的CDMA系统的指数速率H/sub / k/ sup (s)/为n/spl rarr//spl infin/。速率是性能的一个很好的衡量标准，允许我们在应用HD-PIC的几个阶段后比较性能。进一步，我们得到了指数速率H/sub k//sup (s)/和k/spl rarr//spl infin/的渐近行为的结果。最后，我们研究了当k固定时，我们执行HD-PIC的许多阶段时会发生什么。这些结果可用于通过根据用户数量应用若干HD-PIC阶段来保证较小的BEP。分析结果表明，HD-PIC显著提高了性能。这篇会议论文是基于并扩展了Van der Hofstad et al.(2000)的结果和技术，我们将简要讨论。
{"title":"Performance analysis for DS-CDMA systems with multistage HD-PIC","authors":"R. van der Hofstad, M. J. Klok","doi":"10.1109/ICPWC.2000.905788","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905788","url":null,"abstract":"For a direct-sequence code division multiple access system with hard decision parallel interference cancellation (DS-CDMA with HD-PIC), we derive analytical results concerning the probability of a bit error. More precisely, we investigate the exponential rate H/sub k//sup (s)/ of a CDMA system with s stages of HD-PIC, with k users and processing gain equal to n, as n/spl rarr//spl infin/. The rate is a good measure of performance and allows us to compare the performance after applying several stages of HD-PIC. Furthermore, we derive results for the asymptotic behaviour of the exponential rates H/sub k//sup (s)/ as k/spl rarr//spl infin/. Finally, we investigate what happens when, for k fixed, we perform many stages of HD-PIC. These results can be used to guarantee a small BEP by applying a number of HD-PIC stages that depends on the number of users. The results show analytically that HD-PIC significantly improves performance. This conference paper is based upon and extends results and techniques of Van der Hofstad et al. (2000), that we briefly discuss.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114503271","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905839
A. Kumar
The 7 kHz audio bandwidth is increasingly being considered for natural quality communications, especially for binaural, hands-free listening situations such as in teleconferencing and digital AM broadcasting. Based on detailed performance comparisons of several alternative designs, we shortlisted an ACELP-based 7 kHz coder design for performance optimization. This paper presents several low-complexity design strategies which significantly reduce the computational complexity of the encoder and decoder while not compromising on the reconstructed signal quality. These include: (a) open-loop pitch estimation and reduced search adaptive codebook; (b) open-loop pitch estimation based on pre-search in downsampled signal domain; (c) LSF quantization using a combination of scalar and vector quantization; (d) a novel reduced complexity search of algebraic codebook; and (e) efficient postfiltering in the decoder. The computational complexity of the encoder and decoder modules of three ACELP coders with different bit allocations are compared.
{"title":"Low complexity ACELP coding of 7 kHz speech and audio at 16 kbps","authors":"A. Kumar","doi":"10.1109/ICPWC.2000.905839","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905839","url":null,"abstract":"The 7 kHz audio bandwidth is increasingly being considered for natural quality communications, especially for binaural, hands-free listening situations such as in teleconferencing and digital AM broadcasting. Based on detailed performance comparisons of several alternative designs, we shortlisted an ACELP-based 7 kHz coder design for performance optimization. This paper presents several low-complexity design strategies which significantly reduce the computational complexity of the encoder and decoder while not compromising on the reconstructed signal quality. These include: (a) open-loop pitch estimation and reduced search adaptive codebook; (b) open-loop pitch estimation based on pre-search in downsampled signal domain; (c) LSF quantization using a combination of scalar and vector quantization; (d) a novel reduced complexity search of algebraic codebook; and (e) efficient postfiltering in the decoder. The computational complexity of the encoder and decoder modules of three ACELP coders with different bit allocations are compared.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"173 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116060503","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905813
S. Kundu, S. Chakrabarti
Probability of outage is an important parameter for capacity evaluation of a cellular CDMA system. A mathematical formulation with closed form expression for outage probability for integrated voice and data services has been proposed. The correlation between signal and interference is also considered in evaluating the outage. It is observed that considering the correlation a significant reduction in outage probability is obtained compared to the model of Ayyagari et al., 1999.
{"title":"Outage analysis of cellular CDMA for integrated voice and data services with correlated signal and interference","authors":"S. Kundu, S. Chakrabarti","doi":"10.1109/ICPWC.2000.905813","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905813","url":null,"abstract":"Probability of outage is an important parameter for capacity evaluation of a cellular CDMA system. A mathematical formulation with closed form expression for outage probability for integrated voice and data services has been proposed. The correlation between signal and interference is also considered in evaluating the outage. It is observed that considering the correlation a significant reduction in outage probability is obtained compared to the model of Ayyagari et al., 1999.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124823309","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905904
Ma Yu-chu, Gu Xuemai, Zhang Nai-tong
A nonzero intermediate frequency (IF) likelihood acquisition scheme for PN codes is introduced in this paper. The received signal is first downconverted to IF, and then direct sampled in IF using a 1-bit A/D converter. After the digitalization, the sampled data is detected using a hybrid likelihood acquisition scheme. Using this structure, problems, due to large noise figure of the analog mixer or active filters or due to amplitude and phase imbalance between low-frequency in-phase and quadrature-phase channels, can be avoided. An algorithm which allows easy implementation of the acquisition scheme is also derived. The performance and algorithm are verified by computer simulation.
{"title":"A nonzero intermediate frequency likelihood acquisition scheme for CDMA system","authors":"Ma Yu-chu, Gu Xuemai, Zhang Nai-tong","doi":"10.1109/ICPWC.2000.905904","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905904","url":null,"abstract":"A nonzero intermediate frequency (IF) likelihood acquisition scheme for PN codes is introduced in this paper. The received signal is first downconverted to IF, and then direct sampled in IF using a 1-bit A/D converter. After the digitalization, the sampled data is detected using a hybrid likelihood acquisition scheme. Using this structure, problems, due to large noise figure of the analog mixer or active filters or due to amplitude and phase imbalance between low-frequency in-phase and quadrature-phase channels, can be avoided. An algorithm which allows easy implementation of the acquisition scheme is also derived. The performance and algorithm are verified by computer simulation.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122972958","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905853
D. Anvekar, M. Kapoor
In this paper, we present a scheme for combating the problem of interference in frequency hopping indoor wireless communication systems such as Bluetooth. Other methods in reported literature involve adapting the hopping sequence to avoid bad frequencies but they are unsuitable for Bluetooth which has a fixed hopping sequence for a picocell. The proposed scheme is based on the concept of frequency look-ahead and maintaining link state history (LSH) as a table. Look-ahead is employed to know a priori the frequencies that might be used for transmission in the near future. LSH is used to predict the probability of future interference. The paper gives two methods of recording LSH, the first based on the receipt of ACKs and NAKs from the slave and the second based on slave side monitoring of the channel. Before transmitting, the master checks the LSH table to select the slave and the packet size to transmit, such that both the transmissions to and from that slave have a low probability of error. By choosing the right packet size, the master is able to mask bad frequencies and does not need to change the hopping sequence in any way.
{"title":"Frequency look-ahead and link state history based interference avoidance in wireless picocellular networks","authors":"D. Anvekar, M. Kapoor","doi":"10.1109/ICPWC.2000.905853","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905853","url":null,"abstract":"In this paper, we present a scheme for combating the problem of interference in frequency hopping indoor wireless communication systems such as Bluetooth. Other methods in reported literature involve adapting the hopping sequence to avoid bad frequencies but they are unsuitable for Bluetooth which has a fixed hopping sequence for a picocell. The proposed scheme is based on the concept of frequency look-ahead and maintaining link state history (LSH) as a table. Look-ahead is employed to know a priori the frequencies that might be used for transmission in the near future. LSH is used to predict the probability of future interference. The paper gives two methods of recording LSH, the first based on the receipt of ACKs and NAKs from the slave and the second based on slave side monitoring of the channel. Before transmitting, the master checks the LSH table to select the slave and the packet size to transmit, such that both the transmissions to and from that slave have a low probability of error. By choosing the right packet size, the master is able to mask bad frequencies and does not need to change the hopping sequence in any way.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114972457","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905805
K. Soyjaudah, G. Ramsawock
We design and implement the partitioned convolutional code (PCC) and the parallel-concatenated nonrecursive convolutional code (PCNCC). A comparison of the two codes is then carried out based on the following aspects: BER, encoder and decoder complexity, effective code rate, and throughput. It is shown that the PCNCC has identical error performance to the PCC but with less hardware complexity and a slightly higher effective code rate. Also, puncturing is used to increase the code rate of the PCNCC and computer simulation results show that the best PCNCC are those in which the component encoders are derived from the basic encoder.
{"title":"Comparative study of partitioned and parallel concatenated convolutional codes with puncturing","authors":"K. Soyjaudah, G. Ramsawock","doi":"10.1109/ICPWC.2000.905805","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905805","url":null,"abstract":"We design and implement the partitioned convolutional code (PCC) and the parallel-concatenated nonrecursive convolutional code (PCNCC). A comparison of the two codes is then carried out based on the following aspects: BER, encoder and decoder complexity, effective code rate, and throughput. It is shown that the PCNCC has identical error performance to the PCC but with less hardware complexity and a slightly higher effective code rate. Also, puncturing is used to increase the code rate of the PCNCC and computer simulation results show that the best PCNCC are those in which the component encoders are derived from the basic encoder.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126180865","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905764
S. Nagaraj, Yih-Fang Huang
A recently introduced method for closed-loop transmit diversity (see Nagaraj, S. and Huang, Y.F., Asilomar Conference on Signals, Systems and Computers, 2000) is further analyzed in this paper. Specifically, the amount of power saving possible due to the inherent feature of selective feedback is quantified via a capacity analysis. An optimal adaptive algorithm for channel estimation, in the sense of maximum likelihood, is derived to provide robustness against feedback errors, which arise due to incorrect detection at the mobile.
本文进一步分析了最近引入的闭环传输分集方法(见Nagaraj, S.和Huang, Y.F, Asilomar Conference on Signals, Systems and Computers, 2000)。具体地说，由于选择性反馈的固有特性，可能节省的电量是通过容量分析量化的。在最大似然的意义上，导出了信道估计的最优自适应算法，以提供对反馈误差的鲁棒性，这些误差是由于移动设备的不正确检测引起的。
{"title":"Downlink transmit diversity: feedback efficiency and robustness","authors":"S. Nagaraj, Yih-Fang Huang","doi":"10.1109/ICPWC.2000.905764","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905764","url":null,"abstract":"A recently introduced method for closed-loop transmit diversity (see Nagaraj, S. and Huang, Y.F., Asilomar Conference on Signals, Systems and Computers, 2000) is further analyzed in this paper. Specifically, the amount of power saving possible due to the inherent feature of selective feedback is quantified via a capacity analysis. An optimal adaptive algorithm for channel estimation, in the sense of maximum likelihood, is derived to provide robustness against feedback errors, which arise due to incorrect detection at the mobile.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130588419","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905774
P. Venkataram, S. Laxman, R. Rajavelsamy
In this paper, a new data transfer control scheme is proposed to provide a high degree of data transfer during handoffs for multimedia traffic carried in microcellular, picocellular, and high speed wireless networks. The method performs efficient buffering of the data at the base station using toggled buffers. The method has been tested on in-house wired/wireless networks. The results have shown enormous improvement in the continuity of data transfer during multiple handoffs while running multimedia applications such as video-on-demand (VoD) and audio-on-demand (AoD).
{"title":"A method of data transfer control during handoffs in mobile multimedia networks","authors":"P. Venkataram, S. Laxman, R. Rajavelsamy","doi":"10.1109/ICPWC.2000.905774","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905774","url":null,"abstract":"In this paper, a new data transfer control scheme is proposed to provide a high degree of data transfer during handoffs for multimedia traffic carried in microcellular, picocellular, and high speed wireless networks. The method performs efficient buffering of the data at the base station using toggled buffers. The method has been tested on in-house wired/wireless networks. The results have shown enormous improvement in the continuity of data transfer during multiple handoffs while running multimedia applications such as video-on-demand (VoD) and audio-on-demand (AoD).","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"3 S1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120851488","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905835
M. Sugano, T. Araki, M. Murata, T. Hatauchi, Y. Hosooka
In an ad hoc wireless network system, wireless terminals can autonomously construct a network and directly communicate with each other without using a wired network. A flexible radio network is one of the ad hoc wireless network systems which has been operational in recent years. In the flexible radio network, an original communication protocol is implemented to obtain reliability of communication. We evaluate the performance by means of simulations for the data-link protocol and routing protocol of the flexible radio network. We first show the performance when system parameters are changed to examine how these parameters affect the system performance. Furthermore, we investigate the performance improvement by changing the network configuration.
{"title":"Performance evaluation of a wireless ad hoc network: flexible radio network (FRN)","authors":"M. Sugano, T. Araki, M. Murata, T. Hatauchi, Y. Hosooka","doi":"10.1109/ICPWC.2000.905835","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905835","url":null,"abstract":"In an ad hoc wireless network system, wireless terminals can autonomously construct a network and directly communicate with each other without using a wired network. A flexible radio network is one of the ad hoc wireless network systems which has been operational in recent years. In the flexible radio network, an original communication protocol is implemented to obtain reliability of communication. We evaluate the performance by means of simulations for the data-link protocol and routing protocol of the flexible radio network. We first show the performance when system parameters are changed to examine how these parameters affect the system performance. Furthermore, we investigate the performance improvement by changing the network configuration.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"07 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127195801","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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