Pub Date : 2010-04-29DOI: 10.1109/WSA.2010.5456427
R. Sharma, J. Wallace
Accurate and efficient spectrum sensing is a critical component of cognitive radio, which is a technology poised to improve dynamic resource management in future wireless networks. Autocorrelation exploitation has been shown to provide improvements in sensing performance over simple methods like energy detection. A new upper bound on the performance of autocorrelation-based detectors based on an NP test under the assumption of correlation distribution information (CDI) is presented, where random parameters of the signal autocorrelation are not known, but their distribution is assumed to be known. Not only does this reveal how close existing ad-hoc autocorrelation-based detectors are to optimal performance, but also it indicates how much performance improvement over energy detection is theoretically possible.
{"title":"Improved autocorrelation-based sensing using correlation distribution information","authors":"R. Sharma, J. Wallace","doi":"10.1109/WSA.2010.5456427","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456427","url":null,"abstract":"Accurate and efficient spectrum sensing is a critical component of cognitive radio, which is a technology poised to improve dynamic resource management in future wireless networks. Autocorrelation exploitation has been shown to provide improvements in sensing performance over simple methods like energy detection. A new upper bound on the performance of autocorrelation-based detectors based on an NP test under the assumption of correlation distribution information (CDI) is presented, where random parameters of the signal autocorrelation are not known, but their distribution is assumed to be known. Not only does this reveal how close existing ad-hoc autocorrelation-based detectors are to optimal performance, but also it indicates how much performance improvement over energy detection is theoretically possible.","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":"133616686","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.2010.5456398
Sabrina Gerbracht, A. Wolf, Eduard Axel Jorswieck
Secrecy on the physical layer receives increased research interest. Especially in the wireless communication scenarios, the interest in confidentiality of messages increases. In this paper, we discuss the effectiveness of the beamforming strategies maximum ratio transmission (MRT), zero forcing (ZF), and an optimized beamforming (BF) strategy for the transmission under secrecy constraints. The applied channel model is the flat-fading MISO (multiple-input singleoutput) wiretap channel, where the channel to the eavesdropper is only partly known at the transmitter. The scenario with perfect and no channel information to the eavesdropper are included as special cases. We show that under certain conditions the achievable secrecy rates for the transmission with optimized beam-forming can be increased by transmitting artificial noise (AN) in the null space of the channel to the intended receiver, which produces additional interference only at the eavesdropper. We provide a characterization of the optimal beamforming and artificial noise beamforming and analyze the optimal power allocation for asymptotic cases (low and high SNR as well as no and perfect channel information). Numerical simulations illustrate the results.
{"title":"Beamforming for fading wiretap channels with partial channel information","authors":"Sabrina Gerbracht, A. Wolf, Eduard Axel Jorswieck","doi":"10.1109/WSA.2010.5456398","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456398","url":null,"abstract":"Secrecy on the physical layer receives increased research interest. Especially in the wireless communication scenarios, the interest in confidentiality of messages increases. In this paper, we discuss the effectiveness of the beamforming strategies maximum ratio transmission (MRT), zero forcing (ZF), and an optimized beamforming (BF) strategy for the transmission under secrecy constraints. The applied channel model is the flat-fading MISO (multiple-input singleoutput) wiretap channel, where the channel to the eavesdropper is only partly known at the transmitter. The scenario with perfect and no channel information to the eavesdropper are included as special cases. We show that under certain conditions the achievable secrecy rates for the transmission with optimized beam-forming can be increased by transmitting artificial noise (AN) in the null space of the channel to the intended receiver, which produces additional interference only at the eavesdropper. We provide a characterization of the optimal beamforming and artificial noise beamforming and analyze the optimal power allocation for asymptotic cases (low and high SNR as well as no and perfect channel information). Numerical simulations illustrate the results.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"9 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":"121890423","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.2010.5456444
C. Siegl, R. Fischer
In order to reduce the peak-to-average power ratio (PAR) of multi-antenna orthogonal frequency-division multiplexing (MIMO OFDM) systems selected mapping (SLM) and its MIMO extensions are considered. With SLM the transmission of some side information is necessary. In this paper, we focus on the approach of embedding the side information into the OFDM frame using combinations of unrotated and π/4 rotated QAM constellations, known for single-antenna systems, and extend it to the MIMO scenario. Moreover, we analyze the detection and estimation of the side information at the receiver. We analyze soft decision for the side information and derive strategies for joint estimation (within one MIMO OFDM frame) of the embedded side information. Numerical results show that the PAR reduction performance behaves conversely to the side information error performance. For instance, directed SLM exhibits the best PAR reduction performance of the SLM variants discussed in this paper but is slightly more prone to transmission errors. However, applying the schemes mentioned above is beneficial to the side information error performance of directed SLM.
{"title":"Transmission and detection of side information for selected mapping in MIMO OFDM","authors":"C. Siegl, R. Fischer","doi":"10.1109/WSA.2010.5456444","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456444","url":null,"abstract":"In order to reduce the peak-to-average power ratio (PAR) of multi-antenna orthogonal frequency-division multiplexing (MIMO OFDM) systems selected mapping (SLM) and its MIMO extensions are considered. With SLM the transmission of some side information is necessary. In this paper, we focus on the approach of embedding the side information into the OFDM frame using combinations of unrotated and π/4 rotated QAM constellations, known for single-antenna systems, and extend it to the MIMO scenario. Moreover, we analyze the detection and estimation of the side information at the receiver. We analyze soft decision for the side information and derive strategies for joint estimation (within one MIMO OFDM frame) of the embedded side information. Numerical results show that the PAR reduction performance behaves conversely to the side information error performance. For instance, directed SLM exhibits the best PAR reduction performance of the SLM variants discussed in this paper but is slightly more prone to transmission errors. However, applying the schemes mentioned above is beneficial to the side information error performance of directed SLM.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"31 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":"127423378","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.2010.5456463
A. Chaaban, A. Sezgin
We consider the interference channel with two transmit-receive pairs when there is a delay in receiving the desired message compared to interference. We study this channel in the weak interference regime (noisy interference), and show that delay does not affect the capacity of the interference channel in this region. This also holds for an interference channel with a more general delay, where receiving the desired message is delayed compared to the interference, or vice versa. This result is then applied to a previous results on the interference MIMO relay channel where a scheme is used to transform it to an interference channel with delay. We show that using a relay can be helpful when interference is treated as noise in the interference relay channel.
{"title":"Interference channel with delay: Noisy interference","authors":"A. Chaaban, A. Sezgin","doi":"10.1109/WSA.2010.5456463","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456463","url":null,"abstract":"We consider the interference channel with two transmit-receive pairs when there is a delay in receiving the desired message compared to interference. We study this channel in the weak interference regime (noisy interference), and show that delay does not affect the capacity of the interference channel in this region. This also holds for an interference channel with a more general delay, where receiving the desired message is delayed compared to the interference, or vice versa. This result is then applied to a previous results on the interference MIMO relay channel where a scheme is used to transform it to an interference channel with delay. We show that using a relay can be helpful when interference is treated as noise in the interference relay channel.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"23 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":"129739497","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.2010.5456452
Carolina Reyes, Thibault Hilaire, S. Paul, C. Mecklenbräuker
In previous work, we developed and investigated a distributed Projection Approximation Subspace Tracking Algorithm (PAST-Consensus) based on Consensus Propagation for wireless sensor networks. Preliminary simulation results showing a good tracking capability and still reduced complexity, have motivated us to evaluate the performance of the aforementioned algorithm. In this work, some simulation results will be presented comparing the root mean square error for several signal to noise ratios, as well as the error in the signal subspace given by its angle difference.
{"title":"Evaluation of the root mean square error performance of the PAST-Consensus algorithm","authors":"Carolina Reyes, Thibault Hilaire, S. Paul, C. Mecklenbräuker","doi":"10.1109/WSA.2010.5456452","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456452","url":null,"abstract":"In previous work, we developed and investigated a distributed Projection Approximation Subspace Tracking Algorithm (PAST-Consensus) based on Consensus Propagation for wireless sensor networks. Preliminary simulation results showing a good tracking capability and still reduced complexity, have motivated us to evaluate the performance of the aforementioned algorithm. In this work, some simulation results will be presented comparing the root mean square error for several signal to noise ratios, as well as the error in the signal subspace given by its angle difference.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"27 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":"127896559","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.2010.5456393
Bin Song, F. Roemer, M. Haardt
We propose a Flexible Coordinated Beamforming (FlexCoBF) algorithm for the Multi-User MIMO downlink in the case where the total number of receive antennas exceeds the number of transmit antennas at the base station. This case is relevant for many scenarios that have been discussed recently. For instance, for coordinated multipoint (CoMP) transmissions, which play a significant role in LTE to achieve the IMT-Advanced requirements [1], we have to consider users across cell borders jointly and hence a large total number of receive antennas is present. FlexCoBF is significantly more flexible compared to previous approaches, since the linear transmit as well as receive strategies can be chosen arbitrarily. Moreover, we achieve the same sum rate as the best known coordinated beamforming (CBF) algorithm with significantly fewer iterations.
{"title":"Flexible Coordinated Beamforming (FlexCoBF) algorithm for the downlink of multi-user MIMO systems","authors":"Bin Song, F. Roemer, M. Haardt","doi":"10.1109/WSA.2010.5456393","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456393","url":null,"abstract":"We propose a Flexible Coordinated Beamforming (FlexCoBF) algorithm for the Multi-User MIMO downlink in the case where the total number of receive antennas exceeds the number of transmit antennas at the base station. This case is relevant for many scenarios that have been discussed recently. For instance, for coordinated multipoint (CoMP) transmissions, which play a significant role in LTE to achieve the IMT-Advanced requirements [1], we have to consider users across cell borders jointly and hence a large total number of receive antennas is present. FlexCoBF is significantly more flexible compared to previous approaches, since the linear transmit as well as receive strategies can be chosen arbitrarily. Moreover, we achieve the same sum rate as the best known coordinated beamforming (CBF) algorithm with significantly fewer iterations.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"21 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":"121132415","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.2010.5456418
Andreas Dotzler, D. Schmidt, G. Dietl, W. Utschick
We regard a MIMO network with two transmitters and two receivers, in which each transmitter sends information to both of the receivers, a scenario known as the MIMO X channel. For such a system, the recently proposed interference alignment technique is proven to achieve the maximum degrees of freedom, which cannot be reached by conventional zero-forcing. In contrast to other scenarios, for the MIMO X channel algebraic expressions to obtain interference alignment can be easily found. Additionally, the set of parameters for possible alignments is a continuous manifold rather than a discrete set, which directly raises the question of how to find the best alignment when aiming at maximizing a utility of the transmission rates. Due to the non-convexity of the problem, finding the global optimally solution is numerically exhaustive and we are willing to accept a locally optimal solution. In this work we show an efficient parametrization of the problem which allows to apply a projected gradient approach that guarantees an aligned solution. In numerical simulations we show the superiority of our method compared to existing algorithms.
{"title":"Gradient projection based interference alignment for the MIMO X channel","authors":"Andreas Dotzler, D. Schmidt, G. Dietl, W. Utschick","doi":"10.1109/WSA.2010.5456418","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456418","url":null,"abstract":"We regard a MIMO network with two transmitters and two receivers, in which each transmitter sends information to both of the receivers, a scenario known as the MIMO X channel. For such a system, the recently proposed interference alignment technique is proven to achieve the maximum degrees of freedom, which cannot be reached by conventional zero-forcing. In contrast to other scenarios, for the MIMO X channel algebraic expressions to obtain interference alignment can be easily found. Additionally, the set of parameters for possible alignments is a continuous manifold rather than a discrete set, which directly raises the question of how to find the best alignment when aiming at maximizing a utility of the transmission rates. Due to the non-convexity of the problem, finding the global optimally solution is numerically exhaustive and we are willing to accept a locally optimal solution. In this work we show an efficient parametrization of the problem which allows to apply a projected gradient approach that guarantees an aligned solution. In numerical simulations we show the superiority of our method compared to existing algorithms.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"17 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":"121472006","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.2010.5456454
A. Mezghani, F. Antreich, J. Nossek
We present a general problem formulation for optimal parameter estimation based on quantized observations, with application to antenna array communication and processing (channel estimation, time-of-arrival (TOA) and direction-of-arrival (DOA) estimation). The work is of interest in the case when low resolution A/D-converters (ADCs) have to be used to enable higher sampling rate and to simplify the hardware. An Expectation-Maximization (EM) based algorithm is proposed for solving this problem in a general setting. Besides, we derive the Cramér-Rao Bound (CRB) and discuss the effects of quantization and the optimal choice of the ADC characteristic. Numerical and analytical analysis reveals that reliable estimation may still be possible even when the quantization is very coarse.
{"title":"Multiple parameter estimation with quantized channel output","authors":"A. Mezghani, F. Antreich, J. Nossek","doi":"10.1109/WSA.2010.5456454","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456454","url":null,"abstract":"We present a general problem formulation for optimal parameter estimation based on quantized observations, with application to antenna array communication and processing (channel estimation, time-of-arrival (TOA) and direction-of-arrival (DOA) estimation). The work is of interest in the case when low resolution A/D-converters (ADCs) have to be used to enable higher sampling rate and to simplify the hardware. An Expectation-Maximization (EM) based algorithm is proposed for solving this problem in a general setting. Besides, we derive the Cramér-Rao Bound (CRB) and discuss the effects of quantization and the optimal choice of the ADC characteristic. Numerical and analytical analysis reveals that reliable estimation may still be possible even when the quantization is very coarse.","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":"115300078","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.2010.5456380
Marcus Grossmann, T. Matsumoto
We analyze the outage probability of frequency domain minimum mean squared error turbo equalization over frequency-selective Rayleigh fading channels with exponential delay power profile. A correlation chart analysis is used to evaluate the convergence property of the iterative system. Based on the convergence characteristic of the equalizer and decoder, we derive a closed form approximation to the outage probability of the turbo equalizer. Specifically, an upper bounding technique and a central limit theorem are used to show that the outage probability is well approximated by a sum of complementary Gaussian error functions. Numerical results of outage probability simulations of the turbo equalizer in channels with different delay power profiles are presented to demonstrate the accuracy of the proposed method.
{"title":"On the outage probability of MMSE turbo equalization in frequency-selective Rayleigh fading channels","authors":"Marcus Grossmann, T. Matsumoto","doi":"10.1109/WSA.2010.5456380","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456380","url":null,"abstract":"We analyze the outage probability of frequency domain minimum mean squared error turbo equalization over frequency-selective Rayleigh fading channels with exponential delay power profile. A correlation chart analysis is used to evaluate the convergence property of the iterative system. Based on the convergence characteristic of the equalizer and decoder, we derive a closed form approximation to the outage probability of the turbo equalizer. Specifically, an upper bounding technique and a central limit theorem are used to show that the outage probability is well approximated by a sum of complementary Gaussian error functions. Numerical results of outage probability simulations of the turbo equalizer in channels with different delay power profiles are presented to demonstrate the accuracy of the proposed method.","PeriodicalId":311394,"journal":{"name":"2010 International ITG Workshop on Smart Antennas (WSA)","volume":"5 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":"132574531","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.2010.5456429
M. Usman, R. Abd‐Alhameed, Y. A. Dama, P. Excell, D. Zhou, B. Ibrahim, E. Elkhazmi
A dual-polarisation dipole antenna is investigated, intended for use as one of three collocated orthogonal antennas in a polarisation-diversity Multiple-Input Multiple-Output (MIMO) communication system. The antenna actually consists of two overlaid dipoles, one electric and the other magnetic, such that their radiation patterns are nominally identical but they are cross-polarised and hence only interact minimally. Using Finite Difference Time Domain (FDTD) and HFSS simulations, it was found that the antenna performed broadly as expected, although the engineering to create a physical realisation would be challenging. In principle, however, a system using two of the triplicated antennas could, in a richly scattering environment, achieve a six-fold increase in channel capacity for the same bandwidth as a traditional line-of-sight link. Furthermore the channel capacity of the antennas has been investigated using various power azimuth spectrums.
{"title":"New compact dual polarised dipole antenna for MIMO communications","authors":"M. Usman, R. Abd‐Alhameed, Y. A. Dama, P. Excell, D. Zhou, B. Ibrahim, E. Elkhazmi","doi":"10.1109/WSA.2010.5456429","DOIUrl":"https://doi.org/10.1109/WSA.2010.5456429","url":null,"abstract":"A dual-polarisation dipole antenna is investigated, intended for use as one of three collocated orthogonal antennas in a polarisation-diversity Multiple-Input Multiple-Output (MIMO) communication system. The antenna actually consists of two overlaid dipoles, one electric and the other magnetic, such that their radiation patterns are nominally identical but they are cross-polarised and hence only interact minimally. Using Finite Difference Time Domain (FDTD) and HFSS simulations, it was found that the antenna performed broadly as expected, although the engineering to create a physical realisation would be challenging. In principle, however, a system using two of the triplicated antennas could, in a richly scattering environment, achieve a six-fold increase in channel capacity for the same bandwidth as a traditional line-of-sight link. Furthermore the channel capacity of the antennas has been investigated using various power azimuth spectrums.","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":"130993024","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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