Pub Date : 2003-10-15DOI: 10.1109/WCT.2003.1321446
J. Kim, Wan Choi
Summary form only given. A decorrelating detector is a suboptimal multiuser detector that has attracted much attention due to its inherent merits (Zvonar, Z. and Brady, D., 1995). The decorrelating detector provides substantial performance gains over the conventional detector under various conditions. The multicarrier DS/CDMA system is regarded as a viable alternative to the classical single carrier DS/CDMA system in that an available bandwidth is decomposed into a set of subbands. In each subband, the fading has non-selectivity. That is, path diversity is converted to frequency diversity. A new multiuser detector combining decorrelating detector and multicarrier schemes is proposed and analyzed in a frequency-selective Rayleigh fading channel. From numerical results, it is shown that the proposed detector achieves better BER performance and lower computational complexity than the conventional decorrelating detector. It is also shown that the proposed detector is robust to partial narrowband interference.
只提供摘要形式。去相关检测器是一种次优多用户检测器，由于其固有的优点而引起了广泛的关注(Zvonar, Z. and Brady, D.， 1995)。在各种条件下，与传统检测器相比，去相关检测器提供了实质性的性能增益。多载波DS/CDMA系统是传统单载波DS/CDMA系统的可行替代方案，它将可用带宽分解为一组子带。在每个子带内，衰落具有非选择性。即路径分集转换为频率分集。提出了一种结合去相关检测器和多载波方案的多用户检测器，并对其在频率选择性瑞利衰落信道中的应用进行了分析。数值结果表明，与传统的去相关检测器相比，该检测器具有更好的误码率性能和更低的计算复杂度。实验还表明，该检测器对部分窄带干扰具有较强的鲁棒性。
{"title":"Multiuser detector combining multicarrier transmission and decorrelating detector in a Rayleigh fading channel","authors":"J. Kim, Wan Choi","doi":"10.1109/WCT.2003.1321446","DOIUrl":"https://doi.org/10.1109/WCT.2003.1321446","url":null,"abstract":"Summary form only given. A decorrelating detector is a suboptimal multiuser detector that has attracted much attention due to its inherent merits (Zvonar, Z. and Brady, D., 1995). The decorrelating detector provides substantial performance gains over the conventional detector under various conditions. The multicarrier DS/CDMA system is regarded as a viable alternative to the classical single carrier DS/CDMA system in that an available bandwidth is decomposed into a set of subbands. In each subband, the fading has non-selectivity. That is, path diversity is converted to frequency diversity. A new multiuser detector combining decorrelating detector and multicarrier schemes is proposed and analyzed in a frequency-selective Rayleigh fading channel. From numerical results, it is shown that the proposed detector achieves better BER performance and lower computational complexity than the conventional decorrelating detector. It is also shown that the proposed detector is robust to partial narrowband interference.","PeriodicalId":6305,"journal":{"name":"2003 IEEE Topical Conference on Wireless Communication Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79031517","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 : 2003-10-15DOI: 10.1109/WCT.2003.1321486
T. Fujino, A. Hirata, T. Shiozawa
We evaluated the induced SAR in an inhomogeneous model of the human body for exposure to EM waves from a dipole antenna at 400 MHz. In particular, we compared the results for the homogeneous and inhomogeneous models. For the main result, a large difference in the SAR distributions was observed. Additionally, the peak SAR averaged over 1g or 10g of tissue obtained in the homogeneous model are overestimated as compared with those in the inhomogeneous model, only when the antenna-model distance is small.
{"title":"Evaluation of induced SAR in the human body due to EM waves emitted from a dipole antenna at 400 MHz band","authors":"T. Fujino, A. Hirata, T. Shiozawa","doi":"10.1109/WCT.2003.1321486","DOIUrl":"https://doi.org/10.1109/WCT.2003.1321486","url":null,"abstract":"We evaluated the induced SAR in an inhomogeneous model of the human body for exposure to EM waves from a dipole antenna at 400 MHz. In particular, we compared the results for the homogeneous and inhomogeneous models. For the main result, a large difference in the SAR distributions was observed. Additionally, the peak SAR averaged over 1g or 10g of tissue obtained in the homogeneous model are overestimated as compared with those in the inhomogeneous model, only when the antenna-model distance is small.","PeriodicalId":6305,"journal":{"name":"2003 IEEE Topical Conference on Wireless Communication Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79185265","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 : 2003-10-15DOI: 10.1109/WCT.2003.1321491
C. Dermawan, A. Sugiura
IP telephones using wireless LAN only communicate with other terminal through IP addresses on one's area network or access point area (cell). When a terminal moves from a certain cell to another cell, handover occurs because the terminal can not use the same IP address. On the other hand, by using Bluetooth, communication between terminals can be performed through IP address and Bluetooth addresses. Even if a terminal moves to another cell, the Bluetooth address can be used without a break in the communication.
{"title":"Wireless IP phone using Bluetooth for ITS application","authors":"C. Dermawan, A. Sugiura","doi":"10.1109/WCT.2003.1321491","DOIUrl":"https://doi.org/10.1109/WCT.2003.1321491","url":null,"abstract":"IP telephones using wireless LAN only communicate with other terminal through IP addresses on one's area network or access point area (cell). When a terminal moves from a certain cell to another cell, handover occurs because the terminal can not use the same IP address. On the other hand, by using Bluetooth, communication between terminals can be performed through IP address and Bluetooth addresses. Even if a terminal moves to another cell, the Bluetooth address can be used without a break in the communication.","PeriodicalId":6305,"journal":{"name":"2003 IEEE Topical Conference on Wireless Communication Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75139310","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 : 2003-10-15DOI: 10.1109/WCT.2003.1321445
J. Kim, Hoon Huh
Summary form only given. In a code division multiple access (CDMA) system, multiple access interference (MAI) coupled with the near-far problem is one of the major factors limiting system performance. To overcome these issues, various multiuser detection schemes have been proposed. The complexity of the multiuser detection schemes is important, especially when they are adopted in a multicarrier DS/CDMA system which employs lots of subcarriers. Successive interference cancellation (SIC) is relatively simpler than other multiuser detection schemes when used in a multicarrier CDMA system because it does not require separate channel estimation for each of the subcarriers. A SIC scheme based on order statistics is proposed and analyzed for a multicarrier CDMA system over a Rayleigh fading channel. The SIC scheme is employed for each subcarrier, and the subcarrier signals, after interference cancellation, are combined through maximal-ratio or equal-gain combining techniques. The effect of imperfect interference cancellation is also investigated. From the numerical results, it is shown that the proposed system achieves significant performance improvement over a conventional multicarrier CDMA system. The proposed system is robust to MAI and the near-far problem, which translates to a significant increase in system capacity.
{"title":"MAI mitigation by SIC for a multicarrier CDMA system","authors":"J. Kim, Hoon Huh","doi":"10.1109/WCT.2003.1321445","DOIUrl":"https://doi.org/10.1109/WCT.2003.1321445","url":null,"abstract":"Summary form only given. In a code division multiple access (CDMA) system, multiple access interference (MAI) coupled with the near-far problem is one of the major factors limiting system performance. To overcome these issues, various multiuser detection schemes have been proposed. The complexity of the multiuser detection schemes is important, especially when they are adopted in a multicarrier DS/CDMA system which employs lots of subcarriers. Successive interference cancellation (SIC) is relatively simpler than other multiuser detection schemes when used in a multicarrier CDMA system because it does not require separate channel estimation for each of the subcarriers. A SIC scheme based on order statistics is proposed and analyzed for a multicarrier CDMA system over a Rayleigh fading channel. The SIC scheme is employed for each subcarrier, and the subcarrier signals, after interference cancellation, are combined through maximal-ratio or equal-gain combining techniques. The effect of imperfect interference cancellation is also investigated. From the numerical results, it is shown that the proposed system achieves significant performance improvement over a conventional multicarrier CDMA system. The proposed system is robust to MAI and the near-far problem, which translates to a significant increase in system capacity.","PeriodicalId":6305,"journal":{"name":"2003 IEEE Topical Conference on Wireless Communication Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75198903","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 : 2003-10-15DOI: 10.1109/WCT.2003.1321480
H. Bertoni
Because communication systems operate at many locations over a wide range of building environments, the description of the parameters are necessarily statistical in nature. This view of the channel is complementary with the ray description of propagation, which is appropriate at frequencies in the UHF band and above. The results obtained from ray tracing need only be processed to achieve the manifestation appropriate to the communication system. Statistical variations of the channel parameters may be obtained from Monte Carlo simulations for ray results at many receiver locations.
{"title":"Theoretical prediction of radio channel statistics","authors":"H. Bertoni","doi":"10.1109/WCT.2003.1321480","DOIUrl":"https://doi.org/10.1109/WCT.2003.1321480","url":null,"abstract":"Because communication systems operate at many locations over a wide range of building environments, the description of the parameters are necessarily statistical in nature. This view of the channel is complementary with the ray description of propagation, which is appropriate at frequencies in the UHF band and above. The results obtained from ray tracing need only be processed to achieve the manifestation appropriate to the communication system. Statistical variations of the channel parameters may be obtained from Monte Carlo simulations for ray results at many receiver locations.","PeriodicalId":6305,"journal":{"name":"2003 IEEE Topical Conference on Wireless Communication Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75425090","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 : 2003-10-15DOI: 10.1109/WCT.2003.1321602
Hitoshi Ishida, Kiyomichi Araki
To realize a band pass filter (BPF) in ultra-wide band (UWB) communications, a device using a ring resonator with a stub is investigated. A new proposal is made to control the frequency of the attenuation poles using both the ring and the stub impedance. A five stage wide-band BPF is fabricated in this manner. Its center frequency and bandwidth are calculated based on the ring resonator model. The circuit conditions for obtaining two attenuation poles at either side of the pass band are given, together with a method for controlling them.
{"title":"Design and analysis of UWB band pass filter","authors":"Hitoshi Ishida, Kiyomichi Araki","doi":"10.1109/WCT.2003.1321602","DOIUrl":"https://doi.org/10.1109/WCT.2003.1321602","url":null,"abstract":"To realize a band pass filter (BPF) in ultra-wide band (UWB) communications, a device using a ring resonator with a stub is investigated. A new proposal is made to control the frequency of the attenuation poles using both the ring and the stub impedance. A five stage wide-band BPF is fabricated in this manner. Its center frequency and bandwidth are calculated based on the ring resonator model. The circuit conditions for obtaining two attenuation poles at either side of the pass band are given, together with a method for controlling them.","PeriodicalId":6305,"journal":{"name":"2003 IEEE Topical Conference on Wireless Communication Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74667554","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 : 2003-10-15DOI: 10.1109/WCT.2003.1321580
K. Ghanem, T. Denidni
The conventional generalized on-off algorithm (Choi et al. (2002)) requires many bit durations to converge. In order to reduce the processing time, a new algorithm, called the variable on-off (VOO), is proposed. This algorithm carries out the updating for chip duration instead of the bit duration, and performs the adaptation for the different paths at the same time. The latter operation allows us to reduce the processing time by L, where L is the number of paths. When the channel is subject to rapid variations or under high mobility, the angles of arrival change significantly over some symbol intervals. To overcome these problems, the variable step size of the VOO algorithm, which follows power gradient variation, allows the tracking of such an adverse environment, while simultaneously tracking the maximum power.
传统的广义开关算法(Choi et al.(2002))需要许多位持续时间才能收敛。为了缩短处理时间，提出了一种新的算法——可变开-关算法。该算法对芯片持续时间进行更新，而不是对比特持续时间进行更新，同时对不同的路径进行自适应。后一种操作允许我们将处理时间减少L，其中L是路径的数量。当信道受到快速变化或高流动性的影响时，到达角在某些符号间隔内发生显著变化。为了克服这些问题，遵循功率梯度变化的VOO算法的可变步长允许在跟踪最大功率的同时跟踪这种不利环境。
{"title":"Improved on-off algorithm for adaptive antenna arrays in CDMA mobile communication systems","authors":"K. Ghanem, T. Denidni","doi":"10.1109/WCT.2003.1321580","DOIUrl":"https://doi.org/10.1109/WCT.2003.1321580","url":null,"abstract":"The conventional generalized on-off algorithm (Choi et al. (2002)) requires many bit durations to converge. In order to reduce the processing time, a new algorithm, called the variable on-off (VOO), is proposed. This algorithm carries out the updating for chip duration instead of the bit duration, and performs the adaptation for the different paths at the same time. The latter operation allows us to reduce the processing time by L, where L is the number of paths. When the channel is subject to rapid variations or under high mobility, the angles of arrival change significantly over some symbol intervals. To overcome these problems, the variable step size of the VOO algorithm, which follows power gradient variation, allows the tracking of such an adverse environment, while simultaneously tracking the maximum power.","PeriodicalId":6305,"journal":{"name":"2003 IEEE Topical Conference on Wireless Communication Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75594341","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 : 2003-10-15DOI: 10.1109/WCT.2003.1321530
Y. Nakaya, T. Toda, S. Hara, J. Takada, Y. Oishi
We propose the incorporation of an RF-adaptive array antenna (RF-AAA) into each receive branch on multiple-input multiple output (MIMO) systems. The RF-AAA consists of multiple antenna elements where a variable-gained low-noise amplifier (VG-LNA) and a 360/spl deg/- continuously adjustable phase shifter are inserted in each antenna element and an adder for the array output is connected into the RF front-end of each receive branch. The phase shifters are adaptively controlled to increase the total channel capacity of MIMO systems. Computer simulations showed that the capacity of a 2-element-receive-RF-AAA incorporated 2 /spl times/ 2 MIMO system is higher than that of a conventional 3 /spl times/ 3 MIMO system (without RF-AAA) under average transmit power constraints.
{"title":"Incorporation of RF-adaptive array antenna into MIMO receivers","authors":"Y. Nakaya, T. Toda, S. Hara, J. Takada, Y. Oishi","doi":"10.1109/WCT.2003.1321530","DOIUrl":"https://doi.org/10.1109/WCT.2003.1321530","url":null,"abstract":"We propose the incorporation of an RF-adaptive array antenna (RF-AAA) into each receive branch on multiple-input multiple output (MIMO) systems. The RF-AAA consists of multiple antenna elements where a variable-gained low-noise amplifier (VG-LNA) and a 360/spl deg/- continuously adjustable phase shifter are inserted in each antenna element and an adder for the array output is connected into the RF front-end of each receive branch. The phase shifters are adaptively controlled to increase the total channel capacity of MIMO systems. Computer simulations showed that the capacity of a 2-element-receive-RF-AAA incorporated 2 /spl times/ 2 MIMO system is higher than that of a conventional 3 /spl times/ 3 MIMO system (without RF-AAA) under average transmit power constraints.","PeriodicalId":6305,"journal":{"name":"2003 IEEE Topical Conference on Wireless Communication Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78385919","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 : 2003-10-15DOI: 10.1109/WCT.2003.1321449
D. Wenzel, J. Poklemba
As wireless technologies have evolved, the available radiofrequency spectrum has become an important commodity. The current crowding of the spectrum leads to the investigation of more efficient uses of allocated bandwidth. Quadrature-vestigial-sideband (QVSB) is a bandwidth-efficient modulation scheme that doubles the data capacity of conventional VSB. By superimposing two VSB-modulated, independent data streams, QVSB can achieve data rates equivalent to conventional, Nyquist-filtered, double-sideband (DSB) schemes, using half the bandwidth. Efficient, high-rate, turbo-product-codes (TPCs) are used in conjunction with QVSB modulation, to achieve a system which is both power and bandwidth efficient. In particular, capacity performance is about 4 to 5.5 dB from the Shannon bound, up to approximately 5 bits/s/Hz, the highest capacity simulated thus far.
{"title":"Bandwidth-efficient modulation for wireless communications","authors":"D. Wenzel, J. Poklemba","doi":"10.1109/WCT.2003.1321449","DOIUrl":"https://doi.org/10.1109/WCT.2003.1321449","url":null,"abstract":"As wireless technologies have evolved, the available radiofrequency spectrum has become an important commodity. The current crowding of the spectrum leads to the investigation of more efficient uses of allocated bandwidth. Quadrature-vestigial-sideband (QVSB) is a bandwidth-efficient modulation scheme that doubles the data capacity of conventional VSB. By superimposing two VSB-modulated, independent data streams, QVSB can achieve data rates equivalent to conventional, Nyquist-filtered, double-sideband (DSB) schemes, using half the bandwidth. Efficient, high-rate, turbo-product-codes (TPCs) are used in conjunction with QVSB modulation, to achieve a system which is both power and bandwidth efficient. In particular, capacity performance is about 4 to 5.5 dB from the Shannon bound, up to approximately 5 bits/s/Hz, the highest capacity simulated thus far.","PeriodicalId":6305,"journal":{"name":"2003 IEEE Topical Conference on Wireless Communication Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87761029","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 : 2003-10-15DOI: 10.1109/WCT.2003.1321502
R. Nevels, J. Jeong
As a signal travels through a waveguide or through the atmosphere, natural conditions such as inhomogeneity and dissipation can cause alterations in the signal quality. While generally we determine the received signal given the initial waveform along with its distribution in space and the conditions between the source and received points, here we attempt to solve the inverse problem. That is, given the received signal at a point in space, reconstruct the source signal. Naturally this can be accomplished by a number of methods given the field distribution over a cross section of a region in space, but here we only wish to consider the possibility of being provided with the material conditions of the space between the source and receiver and the actual signal received at a point in space. A scheme for restoring such distorted waves has been presented by Foong (1959), based on a generalized Kac method (1959). Our approach is similar in that it relies upon a Feyman path integral formulation, but in a form quite different from that of Kac.
{"title":"Signal reconstruction by path integral methods","authors":"R. Nevels, J. Jeong","doi":"10.1109/WCT.2003.1321502","DOIUrl":"https://doi.org/10.1109/WCT.2003.1321502","url":null,"abstract":"As a signal travels through a waveguide or through the atmosphere, natural conditions such as inhomogeneity and dissipation can cause alterations in the signal quality. While generally we determine the received signal given the initial waveform along with its distribution in space and the conditions between the source and received points, here we attempt to solve the inverse problem. That is, given the received signal at a point in space, reconstruct the source signal. Naturally this can be accomplished by a number of methods given the field distribution over a cross section of a region in space, but here we only wish to consider the possibility of being provided with the material conditions of the space between the source and receiver and the actual signal received at a point in space. A scheme for restoring such distorted waves has been presented by Foong (1959), based on a generalized Kac method (1959). Our approach is similar in that it relies upon a Feyman path integral formulation, but in a form quite different from that of Kac.","PeriodicalId":6305,"journal":{"name":"2003 IEEE Topical Conference on Wireless Communication Technology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2003-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83118739","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：