Pub Date : 2003-04-22DOI: 10.1109/VETECS.2003.1208863
Manyuan Shen, Huaning Niu, Hui Liu
In this paper we develop a novel approach for joint iterative channel estimation and LDPC decoding, based on the factor graph representation and sum-product algorithm. The fast flat fading channel is modeled as an AR process in order to characterize its temporal variation. By approximating the feedback message from the channel decoder as a Gaussian pdf, we show that Kalman smoothing can be employed for channel estimation. We further derive a new bit metric calculation method which consider both channel noise and channel estimation variance. Simulations confirm the effectiveness of our approach.
{"title":"Iterative receiver design in Rayleigh fading using factor graph","authors":"Manyuan Shen, Huaning Niu, Hui Liu","doi":"10.1109/VETECS.2003.1208863","DOIUrl":"https://doi.org/10.1109/VETECS.2003.1208863","url":null,"abstract":"In this paper we develop a novel approach for joint iterative channel estimation and LDPC decoding, based on the factor graph representation and sum-product algorithm. The fast flat fading channel is modeled as an AR process in order to characterize its temporal variation. By approximating the feedback message from the channel decoder as a Gaussian pdf, we show that Kalman smoothing can be employed for channel estimation. We further derive a new bit metric calculation method which consider both channel noise and channel estimation variance. Simulations confirm the effectiveness of our approach.","PeriodicalId":272763,"journal":{"name":"The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124401258","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 : 2003-04-22DOI: 10.1109/VETECS.2003.1207741
K. Hwang, K. Lee
Multiple transmit (Tx) and multiple receive (Rx) antenna systems, referred to as multiple input multiple output (MIMO) systems, have been proposed to achieve higher data rates in wireless communication systems. In this paper, we investigate joint optimization of transmitter and receiver for MIMO system when the channel information is available at both transmitter and receiver. We discuss the problem of designing Tx and Rx filter based on minimum bit error probability criterion. We first derive the optimum Tx and Rx filters for the special case of two input data symbols. Based on this optimum filter, we propose a Tx and Rx filter optimization for the general case of input data symbols. The performance of the proposed Tx and Rx filters is compared with that of the conventional minimum mean-squared error (MMSE) filter. Performance analysis shows that the proposed filter provides significant improvement over the MMSE filter in bit error probability.
{"title":"Joint transmitter-receiver optimization for multiple input multiple output (MIMO) systems","authors":"K. Hwang, K. Lee","doi":"10.1109/VETECS.2003.1207741","DOIUrl":"https://doi.org/10.1109/VETECS.2003.1207741","url":null,"abstract":"Multiple transmit (Tx) and multiple receive (Rx) antenna systems, referred to as multiple input multiple output (MIMO) systems, have been proposed to achieve higher data rates in wireless communication systems. In this paper, we investigate joint optimization of transmitter and receiver for MIMO system when the channel information is available at both transmitter and receiver. We discuss the problem of designing Tx and Rx filter based on minimum bit error probability criterion. We first derive the optimum Tx and Rx filters for the special case of two input data symbols. Based on this optimum filter, we propose a Tx and Rx filter optimization for the general case of input data symbols. The performance of the proposed Tx and Rx filters is compared with that of the conventional minimum mean-squared error (MMSE) filter. Performance analysis shows that the proposed filter provides significant improvement over the MMSE filter in bit error probability.","PeriodicalId":272763,"journal":{"name":"The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.","volume":"446 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115014345","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 : 2003-04-22DOI: 10.1109/VETECS.2003.1207151
Y. Kim, K. S. Kim, Sang Hyun Lee, K. Chang
A suboptimal iterative demodulation and decoding receiver is presented for an LDPC coded spatial multiplexing OFDMA system. The proposed receiver is based on spatial demultiplexing at the first iteration and the interference cancellation with soft decoding outputs at the following iterations. It is shown that the proposed receiver can reduce the complexity of the optimal iterative demodulation and decoding with slight performance degradation. Moreover, we can achieve a performance gain over the non-iterative receivers if more latency is acceptable at the receiver.
{"title":"An LDPC-coded spatial multiplexing OFDMA system with iterative demodulation and decoding","authors":"Y. Kim, K. S. Kim, Sang Hyun Lee, K. Chang","doi":"10.1109/VETECS.2003.1207151","DOIUrl":"https://doi.org/10.1109/VETECS.2003.1207151","url":null,"abstract":"A suboptimal iterative demodulation and decoding receiver is presented for an LDPC coded spatial multiplexing OFDMA system. The proposed receiver is based on spatial demultiplexing at the first iteration and the interference cancellation with soft decoding outputs at the following iterations. It is shown that the proposed receiver can reduce the complexity of the optimal iterative demodulation and decoding with slight performance degradation. Moreover, we can achieve a performance gain over the non-iterative receivers if more latency is acceptable at the receiver.","PeriodicalId":272763,"journal":{"name":"The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114651636","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 : 2003-04-22DOI: 10.1109/VETECS.2003.1207850
Yukihiro Sasazaki, T. Ohtsuki
In this paper, we propose new design criteria based on the distance spectrum for the coding gain of space-frequency and trellis codes (SFTCs) with interleaver over quasi-static frequency selective fading channels. Moreover, we propose new 4-PSK, 4 state and 8-PSK, 8 state SFTCs that achieve a good frame error rate (FER) with interleaver by computer search based on the proposed design criteria. By computer simulation, we show that the proposed design criteria are useful for SFTCs with interleaver over quasi-static frequency selective fading channels. We also show that the proposed SFTCs achieve a better FER than the conventional SFTCs with interleaver over quasi-static frequency selective fading channels.
{"title":"Improved design criteria and new codes for space-frequency trellis coding with interleaver over frequency selective fading channels","authors":"Yukihiro Sasazaki, T. Ohtsuki","doi":"10.1109/VETECS.2003.1207850","DOIUrl":"https://doi.org/10.1109/VETECS.2003.1207850","url":null,"abstract":"In this paper, we propose new design criteria based on the distance spectrum for the coding gain of space-frequency and trellis codes (SFTCs) with interleaver over quasi-static frequency selective fading channels. Moreover, we propose new 4-PSK, 4 state and 8-PSK, 8 state SFTCs that achieve a good frame error rate (FER) with interleaver by computer search based on the proposed design criteria. By computer simulation, we show that the proposed design criteria are useful for SFTCs with interleaver over quasi-static frequency selective fading channels. We also show that the proposed SFTCs achieve a better FER than the conventional SFTCs with interleaver over quasi-static frequency selective fading channels.","PeriodicalId":272763,"journal":{"name":"The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117148867","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 : 2003-04-22DOI: 10.1109/VETECS.2003.1207098
Lei-Liang Yang, L. Hanzo
In this contribution a novel sequential estimation method is proposed for the acquisition of m-sequences. This sequential estimation method exploits the principle of iterative soft-in-soft-out (SISO) decoding for enhancing the acquisition performance, and that of differential pre-processing for the sake of achieving an enhanced acquisition performance, when communicating over various propagation environments. Hence the advocated acquisition arrangement is referred to as the differential recursive soft sequential estimation (DRSSE) acquisition scheme. The DRSSE acquisition scheme exhibits a low complexity, which is similar to that of an m-sequence generator, while achieving an acquisition time that is linearly dependent on the number of stages in the m-sequence generator. Owing to these attractive characteristics, the DRSSE acquisition scheme constitutes a promising initial synchronization scheme, in particular, when acquiring long m-sequences transmitted over various propagation environments.
{"title":"Iterative soft sequential estimation aided differential acquisition of m-sequences","authors":"Lei-Liang Yang, L. Hanzo","doi":"10.1109/VETECS.2003.1207098","DOIUrl":"https://doi.org/10.1109/VETECS.2003.1207098","url":null,"abstract":"In this contribution a novel sequential estimation method is proposed for the acquisition of m-sequences. This sequential estimation method exploits the principle of iterative soft-in-soft-out (SISO) decoding for enhancing the acquisition performance, and that of differential pre-processing for the sake of achieving an enhanced acquisition performance, when communicating over various propagation environments. Hence the advocated acquisition arrangement is referred to as the differential recursive soft sequential estimation (DRSSE) acquisition scheme. The DRSSE acquisition scheme exhibits a low complexity, which is similar to that of an m-sequence generator, while achieving an acquisition time that is linearly dependent on the number of stages in the m-sequence generator. Owing to these attractive characteristics, the DRSSE acquisition scheme constitutes a promising initial synchronization scheme, in particular, when acquiring long m-sequences transmitted over various propagation environments.","PeriodicalId":272763,"journal":{"name":"The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.","volume":"520 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116192028","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 : 2003-04-22DOI: 10.1109/VETECS.2003.1207610
Wonil Roh, A. Paulraj
Performance of the proposed generalized distributed antenna system (GDAS) [W. Roh et.al. (2002)] in a multi-cell network is presented. A multi-cell signal model for GDAS is introduced and a framework for obtaining the output SINR of optimum and sub-optimum combiners for GDAS is discussed. The actual Monte Carlo simulation is performed first with the simplified signal model to investigate the interaction among parameters on performance without dealing with path loss variation, and later with the original model in cellular geometry to draw a conclusion in realistic conditions. The outage and BER performance of various combining techniques are obtained from the observed SINR statistics, and the decision for best scheme is made based on the network condition such as the number of interferers (J), GDAS parameters N and L, SIR and SNR.
{"title":"Performance of the distributed antenna systems in a multi-cell environment","authors":"Wonil Roh, A. Paulraj","doi":"10.1109/VETECS.2003.1207610","DOIUrl":"https://doi.org/10.1109/VETECS.2003.1207610","url":null,"abstract":"Performance of the proposed generalized distributed antenna system (GDAS) [W. Roh et.al. (2002)] in a multi-cell network is presented. A multi-cell signal model for GDAS is introduced and a framework for obtaining the output SINR of optimum and sub-optimum combiners for GDAS is discussed. The actual Monte Carlo simulation is performed first with the simplified signal model to investigate the interaction among parameters on performance without dealing with path loss variation, and later with the original model in cellular geometry to draw a conclusion in realistic conditions. The outage and BER performance of various combining techniques are obtained from the observed SINR statistics, and the decision for best scheme is made based on the network condition such as the number of interferers (J), GDAS parameters N and L, SIR and SNR.","PeriodicalId":272763,"journal":{"name":"The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116436360","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 : 2003-04-22DOI: 10.1109/VETECS.2003.1207585
Dongwoo Kim, D. Kwon, S. K. Kim
A minimum rate supporting scheduler (MRSS) is proposed in this paper. MRSS guides the user selection in order to provide, if any, a prespecified minimum rate for each user. The minimum rate, however, is not always guaranteed especially when the traffic offered in downlink is heavy or excessive. In this case, additional call admission control is necessary, which falls outside the scope of the present paper. MRSS is numerically evaluated to show to what extent of the offered traffic the scheduler could provide the minimum rate. A main advantage of MRSS is its simplicity. MRSS causes little attendant increase in complexity compared to proportional fairness rate scheduler (PFRS) that is currently implemented in cdma2000 1xEV. Thus, MRSS is also implementable. Numerical evaluation of the performance for MRSS is done under UTRA/TDD HSDPA environments. The results show that it support to keep the minimum rate up to fairly high traffic load where existing methods fail and achieves better throughput than PFRS. Therefore, MRSS is a simple, minimum rate supporting and performance-enhanced scheduler that is possibly used in practical 3G mobile system.
{"title":"A simple minimum rate supporting scheduler for UTRA/TDD high speed downlink packet access","authors":"Dongwoo Kim, D. Kwon, S. K. Kim","doi":"10.1109/VETECS.2003.1207585","DOIUrl":"https://doi.org/10.1109/VETECS.2003.1207585","url":null,"abstract":"A minimum rate supporting scheduler (MRSS) is proposed in this paper. MRSS guides the user selection in order to provide, if any, a prespecified minimum rate for each user. The minimum rate, however, is not always guaranteed especially when the traffic offered in downlink is heavy or excessive. In this case, additional call admission control is necessary, which falls outside the scope of the present paper. MRSS is numerically evaluated to show to what extent of the offered traffic the scheduler could provide the minimum rate. A main advantage of MRSS is its simplicity. MRSS causes little attendant increase in complexity compared to proportional fairness rate scheduler (PFRS) that is currently implemented in cdma2000 1xEV. Thus, MRSS is also implementable. Numerical evaluation of the performance for MRSS is done under UTRA/TDD HSDPA environments. The results show that it support to keep the minimum rate up to fairly high traffic load where existing methods fail and achieves better throughput than PFRS. Therefore, MRSS is a simple, minimum rate supporting and performance-enhanced scheduler that is possibly used in practical 3G mobile system.","PeriodicalId":272763,"journal":{"name":"The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121924951","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 : 2003-04-22DOI: 10.1109/VETECS.2003.1207801
Lu Zhao, J. Huber
A new power efficient concatenated space-time block-code (STBC) consisting of a simple 4-states rate 1/2 convolutional code and an orthogonal STBC (oSTBC) with suitable labeling of 16QAM symbols over Rayleigh fading channel with two transmit and one receive antenna is proposed by means of extrinsic information transfer (EXIT) chart analysis. This scheme can achieve a bit error ratio (BER) below 10/sup -4/ for E/sub b//N/sub o/ = 4.4 dB at a transmission rate of 2 bits per channel use, which seems to be highly efficient w.r.t. simplicity and power efficiency.
通过外部信息传输(EXIT)图分析，在瑞利衰落信道上，提出了一种由简单的4态速率1/2卷积码和适合标记16QAM码的正交空时分组码(oSTBC)组成的低功耗串联空时分组码(STBC)。在E/sub / b/ N/sub / o = 4.4 dB的情况下，该方案可以在每个信道使用2比特的传输速率下实现低于10/sup -4/的误码率(BER)，这似乎是高效的w.r.t.简单性和功耗效率。
{"title":"A new high power efficient bit-interleaved concatenated STBC","authors":"Lu Zhao, J. Huber","doi":"10.1109/VETECS.2003.1207801","DOIUrl":"https://doi.org/10.1109/VETECS.2003.1207801","url":null,"abstract":"A new power efficient concatenated space-time block-code (STBC) consisting of a simple 4-states rate 1/2 convolutional code and an orthogonal STBC (oSTBC) with suitable labeling of 16QAM symbols over Rayleigh fading channel with two transmit and one receive antenna is proposed by means of extrinsic information transfer (EXIT) chart analysis. This scheme can achieve a bit error ratio (BER) below 10/sup -4/ for E/sub b//N/sub o/ = 4.4 dB at a transmission rate of 2 bits per channel use, which seems to be highly efficient w.r.t. simplicity and power efficiency.","PeriodicalId":272763,"journal":{"name":"The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122093927","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 : 2003-04-22DOI: 10.1109/VETECS.2003.1207752
S. Hamalainen, T. Henttonen, J. Numminen, J. Vikstedt
The compressed mode (CM) functionality has been discussed from the beginning of 3GPP standardization work [http://www.3gpp.org], in research projects focusing to 3/sup rd/ generation access technologies. In those days it was identified that existing CDMA systems are lacking of well defined inter-frequency measurement capabilities. Based on this a discontinuous reception and transmission ideas were introduced.
{"title":"Network effects of WCDMA compressed mode","authors":"S. Hamalainen, T. Henttonen, J. Numminen, J. Vikstedt","doi":"10.1109/VETECS.2003.1207752","DOIUrl":"https://doi.org/10.1109/VETECS.2003.1207752","url":null,"abstract":"The compressed mode (CM) functionality has been discussed from the beginning of 3GPP standardization work [http://www.3gpp.org], in research projects focusing to 3/sup rd/ generation access technologies. In those days it was identified that existing CDMA systems are lacking of well defined inter-frequency measurement capabilities. Based on this a discontinuous reception and transmission ideas were introduced.","PeriodicalId":272763,"journal":{"name":"The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.","volume":"36 10","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120875498","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 : 2003-04-22DOI: 10.1109/VETECS.2003.1207596
Jung-Tae Kim, D. Han
This paper presents a fast direction of arrival (DOA) estimation algorithm that can rapidly estimate the incidence angles of signals using a pseudo covariance matrix even under coherent signal conditions. The conventional multiple signal classification (MUSIC) algorithm requires hundreds of snapshots to produce a covariance matrix of signals, as such, it cannot perform a DOA estimation while acquiring this covariance matrix. In addition, the MUSIC algorithm cannot be used under rapidly changing or correlated signal conditions. In contrast, the proposed algorithm obtains the bearing response and directional spectrum after acquiring a pseudo covariance matrix for each snapshot. The incidence angles can then be exactly estimated by combining the bearing response and directional spectrum. Accordingly, unlike the MUSIC algorithm, since the proposed algorithm only uses a single snapshot to obtain the pseudo covariance matrix. It can rapidly estimate the DOAs of signals even when they are correlated.
{"title":"Fast DOA estimation algorithm using pseudo covariance matrix","authors":"Jung-Tae Kim, D. Han","doi":"10.1109/VETECS.2003.1207596","DOIUrl":"https://doi.org/10.1109/VETECS.2003.1207596","url":null,"abstract":"This paper presents a fast direction of arrival (DOA) estimation algorithm that can rapidly estimate the incidence angles of signals using a pseudo covariance matrix even under coherent signal conditions. The conventional multiple signal classification (MUSIC) algorithm requires hundreds of snapshots to produce a covariance matrix of signals, as such, it cannot perform a DOA estimation while acquiring this covariance matrix. In addition, the MUSIC algorithm cannot be used under rapidly changing or correlated signal conditions. In contrast, the proposed algorithm obtains the bearing response and directional spectrum after acquiring a pseudo covariance matrix for each snapshot. The incidence angles can then be exactly estimated by combining the bearing response and directional spectrum. Accordingly, unlike the MUSIC algorithm, since the proposed algorithm only uses a single snapshot to obtain the pseudo covariance matrix. It can rapidly estimate the DOAs of signals even when they are correlated.","PeriodicalId":272763,"journal":{"name":"The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123978206","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：