This paper proposes using adaptive puncturing for rate-adaptive OFDMA systems utilizing turbo codes. The scheme is based on adaptively puncturing a Single Code Word (SCW) and hence adaptively changing the rate within the codeword. We compare the SCW against the Multiple Code-Words (MCWs) scheme where different rates are obtained by separate encoding, puncturing, and interleaving on a per-tile basis. Noticeable gains are obtained over the MCW scheme due to the use of larger turbo block sizes and hence larger interleavers. The SCW has around 1dB gain in goodput compared to MCWs, with much improved BER performance. We also propose a novel rate selection scheme for the SCW which we call Recursive Mutual Information Effective SNR mapping (R-MIESM) and compare it against the conventional MIESM scheme. The R-MIESM provides further goodput performance gains for the SCW compared to the MIESM method.
{"title":"Adaptive Puncturing and Rate Selection in Single-Codeword Turbo-Coded OFDMA","authors":"Mai Abdelhakim, M. Nafie, A. Shalash, A. Elezabi","doi":"10.1109/MWS.2009.31","DOIUrl":"https://doi.org/10.1109/MWS.2009.31","url":null,"abstract":"This paper proposes using adaptive puncturing for rate-adaptive OFDMA systems utilizing turbo codes. The scheme is based on adaptively puncturing a Single Code Word (SCW) and hence adaptively changing the rate within the codeword. We compare the SCW against the Multiple Code-Words (MCWs) scheme where different rates are obtained by separate encoding, puncturing, and interleaving on a per-tile basis. Noticeable gains are obtained over the MCW scheme due to the use of larger turbo block sizes and hence larger interleavers. The SCW has around 1dB gain in goodput compared to MCWs, with much improved BER performance. We also propose a novel rate selection scheme for the SCW which we call Recursive Mutual Information Effective SNR mapping (R-MIESM) and compare it against the conventional MIESM scheme. The R-MIESM provides further goodput performance gains for the SCW compared to the MIESM method.","PeriodicalId":192563,"journal":{"name":"2009 IEEE Mobile WiMAX Symposium","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123900186","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}
With the IEEE 802.16e standard for MobileWiMAX the course for new 4G mobile radio communication systems is set. It offers significantly higher data rates than GSM orWCDMA/UMTS and supports different handover mechanismsand QoS features in contrast to WiFi (IEEE 802.11g) on theOSI-layer 2 (L2). Since WiMAX-devices are hardly availabletoday and protocol optimizations are strongly restricted with commercially available devices, a simulation model is not far to seek. Thus, we developed and implemented a simulation in OMNeT++ based on the INET framework in order to investigate and evaluate the performance of the new Mobile WiMAX protocol. In this paper we particularly focus on the handover performance on OSI-Layer 2 (L2) for noise affected channels. Beyond the standardized handover we propose a sliding window mechanism for the channel measurements the handover decision is based on. Ultimately a performance evaluation demonstrates the reductionof handover delay for certain noise levels by introducing acontinuous scanning process.
{"title":"Performance Evaluation for Mobile WiMAX Handover with a Continuous Scanning Algorithm","authors":"K. Daniel, S. Rohde, S. Subik, C. Wietfeld","doi":"10.1109/MWS.2009.30","DOIUrl":"https://doi.org/10.1109/MWS.2009.30","url":null,"abstract":"With the IEEE 802.16e standard for MobileWiMAX the course for new 4G mobile radio communication systems is set. It offers significantly higher data rates than GSM orWCDMA/UMTS and supports different handover mechanismsand QoS features in contrast to WiFi (IEEE 802.11g) on theOSI-layer 2 (L2). Since WiMAX-devices are hardly availabletoday and protocol optimizations are strongly restricted with commercially available devices, a simulation model is not far to seek. Thus, we developed and implemented a simulation in OMNeT++ based on the INET framework in order to investigate and evaluate the performance of the new Mobile WiMAX protocol. In this paper we particularly focus on the handover performance on OSI-Layer 2 (L2) for noise affected channels. Beyond the standardized handover we propose a sliding window mechanism for the channel measurements the handover decision is based on. Ultimately a performance evaluation demonstrates the reductionof handover delay for certain noise levels by introducing acontinuous scanning process.","PeriodicalId":192563,"journal":{"name":"2009 IEEE Mobile WiMAX Symposium","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128230210","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}
In this paper, a location service algorithm using swarm intelligence techniques, called SLS has been developed to provide location service to all MANET (Mobile Ad Hoc Network) routing protocols. MANET is a network with mobile nodes without internet like infrastructure where every mobile node acts as a router. The location service is intended to solve the existing problems in MANET due to frequent movements of nodes. A node can know its location using GPS or triangulation based on radio signal characteristics or hardcoded location information if it is a stationary node. There are some location services available for MANET, however, to the best of our knowledge, SLS is the only technique to learn the location of other nodes intelligently and efficiently using swarm concept. SLS has been applied to the Swarm Autonomous Routing Algorithm (SARA) protocol and simulation is performed in QualNet The simulation results have showed better network performance using SLS than without using it.
{"title":"A Distributed Location Service for MANET Using Swarm Intelligence","authors":"S. Gajurel, Mark Heiferling","doi":"10.1109/MWS.2009.10","DOIUrl":"https://doi.org/10.1109/MWS.2009.10","url":null,"abstract":"In this paper, a location service algorithm using swarm intelligence techniques, called SLS has been developed to provide location service to all MANET (Mobile Ad Hoc Network) routing protocols. MANET is a network with mobile nodes without internet like infrastructure where every mobile node acts as a router. The location service is intended to solve the existing problems in MANET due to frequent movements of nodes. A node can know its location using GPS or triangulation based on radio signal characteristics or hardcoded location information if it is a stationary node. There are some location services available for MANET, however, to the best of our knowledge, SLS is the only technique to learn the location of other nodes intelligently and efficiently using swarm concept. SLS has been applied to the Swarm Autonomous Routing Algorithm (SARA) protocol and simulation is performed in QualNet The simulation results have showed better network performance using SLS than without using it.","PeriodicalId":192563,"journal":{"name":"2009 IEEE Mobile WiMAX Symposium","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130208385","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}
This paper proposes a high capacity carrier interferometry/multicarrier code division multiple access (CI/MCCDMA)system through the simultaneous support of highand low data rate transmission. High data rate users transmitdata through all sub-carriers while alternate odd andeven subcarriers are shared by the low data rate users.The usage of alternate sub-carriers suggests to split CIcodes in odd and even parts leading to an increase incapacity. The cross-correlations among the code patternsare reduced through the phase shift of even (odd) CI codeusing odd (even) sub-carriers by an amount of π/2 andodd (even) CI code using odd (even) sub-carriers by -π/2,all measured with respect to orthogonal codes assigned tosupport high data rate transmission. Performance in termof BER (bit error rate) is then analyzed by carrying outsimulation on frequency selective Rayleigh fading channel.The MAI (multiple access interference) effect is subtractedat the subcarrier projection domain leading to the reductionin high computation cost inherent in parallel interferencecancelation. Performance improvement for different combinationsof low and high data rate users are shown comparedto the conventional CI/MC-CDMA system as well as blockPIC scheme.
{"title":"Subcarrier PIC Scheme for High Capacity CI/MC-CDMA System with Variable Data Rates","authors":"S. Maity, M. Mukherjee","doi":"10.1109/MWS.2009.19","DOIUrl":"https://doi.org/10.1109/MWS.2009.19","url":null,"abstract":"This paper proposes a high capacity carrier interferometry/multicarrier code division multiple access (CI/MCCDMA)system through the simultaneous support of highand low data rate transmission. High data rate users transmitdata through all sub-carriers while alternate odd andeven subcarriers are shared by the low data rate users.The usage of alternate sub-carriers suggests to split CIcodes in odd and even parts leading to an increase incapacity. The cross-correlations among the code patternsare reduced through the phase shift of even (odd) CI codeusing odd (even) sub-carriers by an amount of π/2 andodd (even) CI code using odd (even) sub-carriers by -π/2,all measured with respect to orthogonal codes assigned tosupport high data rate transmission. Performance in termof BER (bit error rate) is then analyzed by carrying outsimulation on frequency selective Rayleigh fading channel.The MAI (multiple access interference) effect is subtractedat the subcarrier projection domain leading to the reductionin high computation cost inherent in parallel interferencecancelation. Performance improvement for different combinationsof low and high data rate users are shown comparedto the conventional CI/MC-CDMA system as well as blockPIC scheme.","PeriodicalId":192563,"journal":{"name":"2009 IEEE Mobile WiMAX Symposium","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117022277","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}
This paper describes the design and deployment of the University of Maryland MAXWell Laboratory, a WiMAX Forum Applications Laboratory. In an effort to increase research and development of WiMAX-specific applications, the WiMAX Forum established a program for endorsing testbeds located at vendor-neutral locations as venues for research and collaboration into new "killer apps" for WiMAX.The MAXWell Lab is one such venue, and this paper describes the basic design, architecture, and deployment of this campus-wide testbed. Additionally, we describe possible directions in applications research, and the MyeVyu system currently under development at the University of Maryland.
{"title":"MAXWell Lab: Building a WiMAX Forum Applications Laboratory","authors":"T. Clancy, Andy Burnette, A. Agrawala","doi":"10.1109/MWS.2009.11","DOIUrl":"https://doi.org/10.1109/MWS.2009.11","url":null,"abstract":"This paper describes the design and deployment of the University of Maryland MAXWell Laboratory, a WiMAX Forum Applications Laboratory. In an effort to increase research and development of WiMAX-specific applications, the WiMAX Forum established a program for endorsing testbeds located at vendor-neutral locations as venues for research and collaboration into new \"killer apps\" for WiMAX.The MAXWell Lab is one such venue, and this paper describes the basic design, architecture, and deployment of this campus-wide testbed. Additionally, we describe possible directions in applications research, and the MyeVyu system currently under development at the University of Maryland.","PeriodicalId":192563,"journal":{"name":"2009 IEEE Mobile WiMAX Symposium","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117290318","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}
In this paper, we present our design and development of a compact, light weight, high gain smart antenna for WiMAX radio systems. The antenna head is an 8-monopole uniform circular array placed on a ground plane with ground skirt. The operation frequency is 5.8GHz. The array is connected to an 8-channel beamforming board via low-loss coax. The 8-channel signal combines through a power splitter/combiner which directs the signal to/from the WiMAX radio. An FPGA chip is on board to control the digital phase shifters, attenuators and switches for T/R synchronization, signal searching, beamforming, and tracking. The test results show that the smart antenna is capable of tracking mobile targets, communicating directionally with desired users, suppressing interference and jamming, and enabling a long range with high throughput and reliable connection.
{"title":"A Compact Smart Antenna for WiMAX Radio","authors":"Yikun Huang, W. Tidd, A. Olson, R. Wolff","doi":"10.1109/MWS.2009.37","DOIUrl":"https://doi.org/10.1109/MWS.2009.37","url":null,"abstract":"In this paper, we present our design and development of a compact, light weight, high gain smart antenna for WiMAX radio systems. The antenna head is an 8-monopole uniform circular array placed on a ground plane with ground skirt. The operation frequency is 5.8GHz. The array is connected to an 8-channel beamforming board via low-loss coax. The 8-channel signal combines through a power splitter/combiner which directs the signal to/from the WiMAX radio. An FPGA chip is on board to control the digital phase shifters, attenuators and switches for T/R synchronization, signal searching, beamforming, and tracking. The test results show that the smart antenna is capable of tracking mobile targets, communicating directionally with desired users, suppressing interference and jamming, and enabling a long range with high throughput and reliable connection.","PeriodicalId":192563,"journal":{"name":"2009 IEEE Mobile WiMAX Symposium","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122833981","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}
A novel multi-band internal antenna configuration has been developed for WiMax-capable cellular phones. The new antenna configuration covers all the WiMax bands with other applications in multi-standard multifunction handsets. It consists of three new wideband antennas, which together can cover the whole band from 470 MHz to 6 GHz. The three antennas may have to be used together or only one or two of them may be required depending on the allocated frequencies of WiMax and the other applications in the handset. Each of the three new antennas has a bandwidth of more than 65%. They are low-cost multi-polarized unbalanced resonant antennas that do not need matching circuits or baluns. Their overall sizes are very small and they have high efficiencies and high peak gains. The performance of the new internal antenna is superior in Multi-Input Multi-Output (MIMO) techniques. Two or more similar internal antennas having the same frequency band can be embedded inside the handset for MIMO. The locations and orientations of MOMO antennas are optimized for both space and polarization diversity with minimum coupling between them.
{"title":"A Multi-band Antenna Configuration for MIMO WiMax in Multi-standard Multifunction Handsets","authors":"M. Sanad, N. Hassan, N. Hassan","doi":"10.1109/MWS.2009.14","DOIUrl":"https://doi.org/10.1109/MWS.2009.14","url":null,"abstract":"A novel multi-band internal antenna configuration has been developed for WiMax-capable cellular phones. The new antenna configuration covers all the WiMax bands with other applications in multi-standard multifunction handsets. It consists of three new wideband antennas, which together can cover the whole band from 470 MHz to 6 GHz. The three antennas may have to be used together or only one or two of them may be required depending on the allocated frequencies of WiMax and the other applications in the handset. Each of the three new antennas has a bandwidth of more than 65%. They are low-cost multi-polarized unbalanced resonant antennas that do not need matching circuits or baluns. Their overall sizes are very small and they have high efficiencies and high peak gains. The performance of the new internal antenna is superior in Multi-Input Multi-Output (MIMO) techniques. Two or more similar internal antennas having the same frequency band can be embedded inside the handset for MIMO. The locations and orientations of MOMO antennas are optimized for both space and polarization diversity with minimum coupling between them.","PeriodicalId":192563,"journal":{"name":"2009 IEEE Mobile WiMAX Symposium","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126535346","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}
In this paper, we consider channel estimation for the reception of OFDM signal in spatially correlated multi-antenna environments. To improve the accuracy of channel estimation, we exploit the characteristics in three dimensions; time, frequency and spatial domain. The channel information is first estimated from pilot signal by means of a conventional least squared method in the frequency domain. Then the estimated signal is transformed into the time domain by means of inverse discrete Fourier transform (DFT) and further transformed into the spatial domain by exploiting the spatial covariance matrix of the channel. To reduce the effect of channel noise on the estimation performance, we only utilize signal components having enough power strength for the channel estimation to minimize the mean squared error. Finally, the analytic results are verified by computer simulation. Numerical results show that the proposed channel estimation scheme is quite effective in spatially correlated environments.
{"title":"Channel Estimation Using Orthogonal Transformation in Spatially-Correlated Multi-antenna OFDM Systems","authors":"Soo-Kwan Kim, Yong-Hwan Lee","doi":"10.1109/MWS.2009.15","DOIUrl":"https://doi.org/10.1109/MWS.2009.15","url":null,"abstract":"In this paper, we consider channel estimation for the reception of OFDM signal in spatially correlated multi-antenna environments. To improve the accuracy of channel estimation, we exploit the characteristics in three dimensions; time, frequency and spatial domain. The channel information is first estimated from pilot signal by means of a conventional least squared method in the frequency domain. Then the estimated signal is transformed into the time domain by means of inverse discrete Fourier transform (DFT) and further transformed into the spatial domain by exploiting the spatial covariance matrix of the channel. To reduce the effect of channel noise on the estimation performance, we only utilize signal components having enough power strength for the channel estimation to minimize the mean squared error. Finally, the analytic results are verified by computer simulation. Numerical results show that the proposed channel estimation scheme is quite effective in spatially correlated environments.","PeriodicalId":192563,"journal":{"name":"2009 IEEE Mobile WiMAX Symposium","volume":"2013 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127434966","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}
In WiMAX Systems, orthogonal frequency division multiplexing (OFDM) is chosen as the modulation format. However, the main drawback of OFDM is the high peak to average power ratio (PAPR), which significantly limits the power efficiency of the operating power amplifier in order to avoid nonlinear distortions. Recently a PAPR reduction scheme called the metric based amplitude predistortion (MBAP) has been proposed with low complexity. In this paper, we further analyze our proposed phase reversal scheme which uses the same metric as in the MBAP scheme to reduce PAPR. The main advantage of our proposed scheme is to achieve PAPR reduction without increasing the input power and also the bit error rate (BER). Simulation results indicate that the proposed phase reversal scheme can effectively improve the performance of the MBAP in most scenarios.
{"title":"PAPR Reduction in OFDM via Phase Reversal","authors":"Li-Chung Chang, Yen-Yen Lin","doi":"10.1109/MWS.2009.24","DOIUrl":"https://doi.org/10.1109/MWS.2009.24","url":null,"abstract":"In WiMAX Systems, orthogonal frequency division multiplexing (OFDM) is chosen as the modulation format. However, the main drawback of OFDM is the high peak to average power ratio (PAPR), which significantly limits the power efficiency of the operating power amplifier in order to avoid nonlinear distortions. Recently a PAPR reduction scheme called the metric based amplitude predistortion (MBAP) has been proposed with low complexity. In this paper, we further analyze our proposed phase reversal scheme which uses the same metric as in the MBAP scheme to reduce PAPR. The main advantage of our proposed scheme is to achieve PAPR reduction without increasing the input power and also the bit error rate (BER). Simulation results indicate that the proposed phase reversal scheme can effectively improve the performance of the MBAP in most scenarios.","PeriodicalId":192563,"journal":{"name":"2009 IEEE Mobile WiMAX Symposium","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132634592","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}
Byoung Jun Lee, J. W. Kim, Byeong C. Kim, Joungcheol Kim, C. Kang
In this paper, we evaluate the system-level performance of MIMO-based Mobile WiMAX system, a.k.a. Wave-2 system, especially taking the spatially correlated channel characteristics and channel estimation error into account in the different radio environments and propagation scenarios. Our simulation framework carefully follows the standard evaluation methodology and channel models, especially provided by IEEE 802.16m task group. Our simulation results show that the Wave-2 system with 2x2 antennas improves the system throughput by more than 50% as compared with the SISO system in the typical network scenario, even if the performance gain depends on a loading factor of neighbor cells as well as the radio environments and mobile speed while channel estimation error reduces its performance by 10%-12% on the average under our simulation scenarios.
{"title":"System-Level Performance of MIMO-based Mobile WiMAX System","authors":"Byoung Jun Lee, J. W. Kim, Byeong C. Kim, Joungcheol Kim, C. Kang","doi":"10.1109/MWS.2009.43","DOIUrl":"https://doi.org/10.1109/MWS.2009.43","url":null,"abstract":"In this paper, we evaluate the system-level performance of MIMO-based Mobile WiMAX system, a.k.a. Wave-2 system, especially taking the spatially correlated channel characteristics and channel estimation error into account in the different radio environments and propagation scenarios. Our simulation framework carefully follows the standard evaluation methodology and channel models, especially provided by IEEE 802.16m task group. Our simulation results show that the Wave-2 system with 2x2 antennas improves the system throughput by more than 50% as compared with the SISO system in the typical network scenario, even if the performance gain depends on a loading factor of neighbor cells as well as the radio environments and mobile speed while channel estimation error reduces its performance by 10%-12% on the average under our simulation scenarios.","PeriodicalId":192563,"journal":{"name":"2009 IEEE Mobile WiMAX Symposium","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134013704","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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