Pub Date : 2010-04-29DOI: 10.1109/WSA.2010.5456397
G. Adamiuk, C. Heine, W. Wiesbeck, T. Zwick
This article describes a design of an UWB-Monopulse Antenna. A creation of the sum and difference beams is achieved over the large bandwidth from 3 GHz till 11 GHz. The distribution of the peak value of the impulse response over the angle around the antenna is calculated from the measurements. This information serves as an input data for the creation of the look-up table, which assigns the processed amplitudes and phases at both ports of the antenna to the certain angle. This allows for a sensing with very high range resolution with simultaneous determination of the angular direction of the target. The combination of UWB and Monopulse-Technique offers a solution for a precise target localization, where no antenna movement or beam steering technique must be applied.
{"title":"Vivaldi-based UWB Monopulse-Antenna","authors":"G. Adamiuk, C. Heine, W. Wiesbeck, T. Zwick","doi":"10.1109/WSA.2010.5456397","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456397","url":null,"abstract":"This article describes a design of an UWB-Monopulse Antenna. A creation of the sum and difference beams is achieved over the large bandwidth from 3 GHz till 11 GHz. The distribution of the peak value of the impulse response over the angle around the antenna is calculated from the measurements. This information serves as an input data for the creation of the look-up table, which assigns the processed amplitudes and phases at both ports of the antenna to the certain angle. This allows for a sensing with very high range resolution with simultaneous determination of the angular direction of the target. The combination of UWB and Monopulse-Technique offers a solution for a precise target localization, where no antenna movement or beam steering technique must be applied.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121168780","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 : 2010-04-29DOI: 10.1109/WSA.2010.5456447
C. Guthy, W. Utschick, M. Honig
Analytical expressions for the average sum rate of signal processing algorithms which require full Channel State Information at the transmitter are hard to obtain in practice. In the large system limit, where at least two system parameters go to infinity at a finite fixed ratio, analytical expressions can often be obtained, which also serve as a good approximation in systems with finite parameters. In this paper we present a large system analysis of the Successive Encoding Successive Allocation Method (SESAM) with Minimum Mean Square Error (MMSE) filters, which can almost achieve the optimum sum capacity at drastically reduced complexity. An analytical approximation of the asymptotic sum rate for Rayleigh fading channels is derived and compared with simulations in finite systems.
{"title":"Large system analysis of the Successive Encoding Successive Allocation Method for the MIMO BC","authors":"C. Guthy, W. Utschick, M. Honig","doi":"10.1109/WSA.2010.5456447","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456447","url":null,"abstract":"Analytical expressions for the average sum rate of signal processing algorithms which require full Channel State Information at the transmitter are hard to obtain in practice. In the large system limit, where at least two system parameters go to infinity at a finite fixed ratio, analytical expressions can often be obtained, which also serve as a good approximation in systems with finite parameters. In this paper we present a large system analysis of the Successive Encoding Successive Allocation Method (SESAM) with Minimum Mean Square Error (MMSE) filters, which can almost achieve the optimum sum capacity at drastically reduced complexity. An analytical approximation of the asymptotic sum rate for Rayleigh fading channels is derived and compared with simulations in finite systems.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116256668","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 : 2010-04-29DOI: 10.1109/WSA.2010.5456457
R. Fritzsche, J. Voigt, C. Jandura, G. Fettweis
Multiple-Input Multiple-Output (MIMO) technology is ready for deployment in commercial cellular networks in the very near future. Thus, the need of incorporating this technology into radio network planning and optimization rises dramatically for network operators. The main question to answer is how accurate MIMO channel models reflect the real MIMO channel. In this contribution we verify a detailed ray tracing channel simulator with channel sounding measurements in the 2.53 GHz range by comparing simulated and measured eigenvalue characteristics for various Single-User (SU) downlink scenarios in a Coordinated Multi-Point (CoMP) environment. From our comparison we can conclude that carefully performed Geometrical Optics based ray tracing simulations are an adequate prediction model to reflect main characteristics of SU-MIMO channels even in a CoMP scenario.
{"title":"Verifying ray tracing based CoMP-MIMO predictions with channel sounding measurements","authors":"R. Fritzsche, J. Voigt, C. Jandura, G. Fettweis","doi":"10.1109/WSA.2010.5456457","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456457","url":null,"abstract":"Multiple-Input Multiple-Output (MIMO) technology is ready for deployment in commercial cellular networks in the very near future. Thus, the need of incorporating this technology into radio network planning and optimization rises dramatically for network operators. The main question to answer is how accurate MIMO channel models reflect the real MIMO channel. In this contribution we verify a detailed ray tracing channel simulator with channel sounding measurements in the 2.53 GHz range by comparing simulated and measured eigenvalue characteristics for various Single-User (SU) downlink scenarios in a Coordinated Multi-Point (CoMP) environment. From our comparison we can conclude that carefully performed Geometrical Optics based ray tracing simulations are an adequate prediction model to reflect main characteristics of SU-MIMO channels even in a CoMP scenario.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125210562","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 : 2010-04-29DOI: 10.1109/WSA.2010.5456448
G. D. Menghwar, C. Mecklenbräuker
With the increasing demand of reliable communications on move, cooperative communications has proved to be an efficient solution to reduce the effects of unreliable nature of wireless channel. In this paper, we study the Space-Time (ST) cooperative communications aided by a fixed relay, forwarding network coded bits to the destination. We present the performance analysis in terms of outage probability. With analytical results, we show that the investigated scheme outperforms the cooperative transmission based on ST codes only. To be specific, the analytical results show that ST codes with the help of dedicated relay forwarding network coding can achieve diversity order of 3 while ST codes based cooperative communications, without use of network coding, only offers diversity order of 2.
{"title":"Outage analysis of cooperative Space-Time codes with network coding","authors":"G. D. Menghwar, C. Mecklenbräuker","doi":"10.1109/WSA.2010.5456448","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456448","url":null,"abstract":"With the increasing demand of reliable communications on move, cooperative communications has proved to be an efficient solution to reduce the effects of unreliable nature of wireless channel. In this paper, we study the Space-Time (ST) cooperative communications aided by a fixed relay, forwarding network coded bits to the destination. We present the performance analysis in terms of outage probability. With analytical results, we show that the investigated scheme outperforms the cooperative transmission based on ST codes only. To be specific, the analytical results show that ST codes with the help of dedicated relay forwarding network coding can achieve diversity order of 3 while ST codes based cooperative communications, without use of network coding, only offers diversity order of 2.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131326425","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 : 2010-04-29DOI: 10.1109/WSA.2010.5456451
Mark Petermann, M. Niemiec, D. Wübben, K. Kammeyer, M. Stefer, Martin Schneider
Currently evolving communication standards, especially those using multi-antenna (MIMO) multicarrier modulation techniques, are based on the exploitation of channel state information (CSI) at the transmitter. The utilization of adaptive transmission schemes comes with a more sensitive behavior with respect to front-end imperfections. Direct-conversion architectures in turn allow for low-cost transceiver solutions but introduce higher imbalances of the in-phase (I) and quadrature (Q) branches. For adaptive systems with high data rates severe performance losses are observed with respect to bit error rates (BER). In this paper the influence of transmitter side I/Q imbalances is investigated with respect to a MIMO hardware demonstrator, which applies adaptive Orthogonal Frequency Division Multiplexing (OFDM) strategies. An enhanced algorithm for blind online pre-compensation is presented. Comparable single-tone low-IF measurement results indicate an improved image signal suppression and higher convergence robustness while the system shows decreased downlink BER after compensation.
{"title":"Iterative pre-compensation of I/Q imbalances in an adaptive 2.4 GHz MIMO-OFDM system","authors":"Mark Petermann, M. Niemiec, D. Wübben, K. Kammeyer, M. Stefer, Martin Schneider","doi":"10.1109/WSA.2010.5456451","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456451","url":null,"abstract":"Currently evolving communication standards, especially those using multi-antenna (MIMO) multicarrier modulation techniques, are based on the exploitation of channel state information (CSI) at the transmitter. The utilization of adaptive transmission schemes comes with a more sensitive behavior with respect to front-end imperfections. Direct-conversion architectures in turn allow for low-cost transceiver solutions but introduce higher imbalances of the in-phase (I) and quadrature (Q) branches. For adaptive systems with high data rates severe performance losses are observed with respect to bit error rates (BER). In this paper the influence of transmitter side I/Q imbalances is investigated with respect to a MIMO hardware demonstrator, which applies adaptive Orthogonal Frequency Division Multiplexing (OFDM) strategies. An enhanced algorithm for blind online pre-compensation is presented. Comparable single-tone low-IF measurement results indicate an improved image signal suppression and higher convergence robustness while the system shows decreased downlink BER after compensation.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126952227","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 : 2010-04-29DOI: 10.1109/WSA.2010.5456433
Holger Degenhardt, Dirk Czepluch, F. Demmel, A. Klein
A precise knowledge of the electromagnetic receiving characteristics of the antenna is mandatory for a precise determination of the directions of the impinging signals. For circular arrays the phase-mode description is an effective way of approximating the receiving characteristics of the antenna elements. For antenna elements, which are mounted in front of a cone-shaped reflector, angular ranges are defined to reduce the coupling and scattering influences. In these angular ranges, the receiving characteristics are more robust towards changes in the antenna structure and can be well approximated by a small number of phase-modes. The limitation of the angular range per element leads to the sector concept for DOA estimation. Especially the combination of the Virtual Array concept with the sector concept increases the robustness of the DOA estimation approaches against array imperfections.
{"title":"Consideration of sectors for direction of arrival estimation with circular arrays","authors":"Holger Degenhardt, Dirk Czepluch, F. Demmel, A. Klein","doi":"10.1109/WSA.2010.5456433","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456433","url":null,"abstract":"A precise knowledge of the electromagnetic receiving characteristics of the antenna is mandatory for a precise determination of the directions of the impinging signals. For circular arrays the phase-mode description is an effective way of approximating the receiving characteristics of the antenna elements. For antenna elements, which are mounted in front of a cone-shaped reflector, angular ranges are defined to reduce the coupling and scattering influences. In these angular ranges, the receiving characteristics are more robust towards changes in the antenna structure and can be well approximated by a small number of phase-modes. The limitation of the angular range per element leads to the sector concept for DOA estimation. Especially the combination of the Virtual Array concept with the sector concept increases the robustness of the DOA estimation approaches against array imperfections.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127560279","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 : 2010-04-29DOI: 10.1109/WSA.2010.5456432
J. Ser, I. Olabarrieta, S. Gil-Lopez, P. Crespo
Recent contributions have shown that, by switching frequency bands at intermediate relay nodes, enhanced diversity can be attained in two-user wireless frequency division relay networks at a minimum computational cost. This paper elaborates on the design of frequency-switching patterns for more involved relay scenarios. We conclude that in general, the optimum set of frequency-switching patterns is based on the subset of derangement permutations of {f1, ..., fN}, i.e. of the N frequency bands utilized in the setup. In order to illustrate our approach, our work focuses on the particular distributed data fusion scenario where the data generated by an information source is simultaneously sensed by N nodes and broadcasted, through a relay network, to N remote destinations. Simulation results made for several scenarios verify that the proposed derangement-based relaying scheme outperforms other frequency-switching relay approaches in terms of end-to-end fused Bit Error Rate (BER).
{"title":"On the design of frequency-switching patterns for distributed data fusion over relay networks","authors":"J. Ser, I. Olabarrieta, S. Gil-Lopez, P. Crespo","doi":"10.1109/WSA.2010.5456432","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456432","url":null,"abstract":"Recent contributions have shown that, by switching frequency bands at intermediate relay nodes, enhanced diversity can be attained in two-user wireless frequency division relay networks at a minimum computational cost. This paper elaborates on the design of frequency-switching patterns for more involved relay scenarios. We conclude that in general, the optimum set of frequency-switching patterns is based on the subset of derangement permutations of {f1, ..., fN}, i.e. of the N frequency bands utilized in the setup. In order to illustrate our approach, our work focuses on the particular distributed data fusion scenario where the data generated by an information source is simultaneously sensed by N nodes and broadcasted, through a relay network, to N remote destinations. Simulation results made for several scenarios verify that the proposed derangement-based relaying scheme outperforms other frequency-switching relay approaches in terms of end-to-end fused Bit Error Rate (BER).","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132783417","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 : 2010-04-29DOI: 10.1109/WSA.2010.5456435
S. Seydnejad, Sadegh Akhzari
To suppress co-channel interferences in OFDM systems two main schemes namely, the pre-FFT and the post-FFT schemes have been proposed. While pre-FFT is a timedomain beamforming method, post-FFT uses beamforming in frequency domain to suppress directional interferences. It is generally believed that the post-FFT scheme is superior in performance than the pre-FFT method. In this study we first compare these two schemes in pilot-assisted OFDM systems under different channel and system conditions. It is shown that each of these methods shows better performance in a different condition. To take advantage of the strategy of each method, a combined time-frequency method is proposed which produces better results than each of the individual methods while its computational complexity is not much increased compared to the post-FFT scheme. The simple structure of the combined method makes it a suitable choice for interference suppression in the receiver of OFDM systems in practice.
{"title":"A combined time-frequency domain beamforming method for OFDM systems","authors":"S. Seydnejad, Sadegh Akhzari","doi":"10.1109/WSA.2010.5456435","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456435","url":null,"abstract":"To suppress co-channel interferences in OFDM systems two main schemes namely, the pre-FFT and the post-FFT schemes have been proposed. While pre-FFT is a timedomain beamforming method, post-FFT uses beamforming in frequency domain to suppress directional interferences. It is generally believed that the post-FFT scheme is superior in performance than the pre-FFT method. In this study we first compare these two schemes in pilot-assisted OFDM systems under different channel and system conditions. It is shown that each of these methods shows better performance in a different condition. To take advantage of the strategy of each method, a combined time-frequency method is proposed which produces better results than each of the individual methods while its computational complexity is not much increased compared to the post-FFT scheme. The simple structure of the combined method makes it a suitable choice for interference suppression in the receiver of OFDM systems in practice.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128345825","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 : 2010-04-29DOI: 10.1109/WSA.2010.5456394
Màrius Caus, A. Pérez-Neira
By including a cyclic prefix (CP), systems based on orthogonal frequency division multiplexing (OFDM) are capable of mitigating multipath with a single tap equalizer. Aiming at increasing the spectral efficiency, filter banks based multi carrier systems (FBMC) along with an offset quadrature amplitude modulation (OQAM) can be seen as a good alternative, although single tap equalizers may not provide enough robustness. In this regard we adapt to FBMC systems the structure consisting of a space-time processor together with a maximum likelihood sequence estimator (MLSE). Simulations show that in presence of large delay spreads the proposed scheme outperforms orthogonal frequency division multiplexing (OFDM) systems in terms of bit error rate (BER).
{"title":"Space-time receiver for filterbank based multicarrier systems","authors":"Màrius Caus, A. Pérez-Neira","doi":"10.1109/WSA.2010.5456394","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456394","url":null,"abstract":"By including a cyclic prefix (CP), systems based on orthogonal frequency division multiplexing (OFDM) are capable of mitigating multipath with a single tap equalizer. Aiming at increasing the spectral efficiency, filter banks based multi carrier systems (FBMC) along with an offset quadrature amplitude modulation (OQAM) can be seen as a good alternative, although single tap equalizers may not provide enough robustness. In this regard we adapt to FBMC systems the structure consisting of a space-time processor together with a maximum likelihood sequence estimator (MLSE). Simulations show that in presence of large delay spreads the proposed scheme outperforms orthogonal frequency division multiplexing (OFDM) systems in terms of bit error rate (BER).","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133130205","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 : 2010-04-29DOI: 10.1109/WSA.2010.5456389
M. Castañeda, I. Slim, A. Mezghani, J. Nossek
Multiple transmit antennas can be employed in a downlink channel to serve multiple users under the assumption of perfect channel state information (CSI) of all users at the base station. In practice, however, the channel knowledge available at the base station is not perfect. For instance, in case of a time division duplex (TDD) system, the transmit CSI is the estimated uplink channel. On the other hand, in a frequency division duplex (FDD) system, feedback from the users is required to obtain transmit CSI. In this case, we assume the transmit CSI consists of a quantized version of the normalized estimated channel vector and the statistics of the channel norm of each user. In this work we consider the transceiver design of the downlink of a multiuser MISO system based on the minimum mean square error (MMSE) criterion with imperfect CSI as discussed above.
{"title":"Transceiver design in multiuser MISO systems with imperfect transmit CSI","authors":"M. Castañeda, I. Slim, A. Mezghani, J. Nossek","doi":"10.1109/WSA.2010.5456389","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456389","url":null,"abstract":"Multiple transmit antennas can be employed in a downlink channel to serve multiple users under the assumption of perfect channel state information (CSI) of all users at the base station. In practice, however, the channel knowledge available at the base station is not perfect. For instance, in case of a time division duplex (TDD) system, the transmit CSI is the estimated uplink channel. On the other hand, in a frequency division duplex (FDD) system, feedback from the users is required to obtain transmit CSI. In this case, we assume the transmit CSI consists of a quantized version of the normalized estimated channel vector and the statistics of the channel norm of each user. In this work we consider the transceiver design of the downlink of a multiuser MISO system based on the minimum mean square error (MMSE) criterion with imperfect CSI as discussed above.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132006580","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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