Pub Date : 2007-12-04DOI: 10.1093/ietcom/e91-b.10.3281
Kihong Park, Hong-Chuan Yang, Young-Chai Ko
There are usually rate loss and power spreading effects associated with transmit diversity systems based on orthogonal space-time block coding (OSTBC). Proper antenna selection scheme can help more effectively utilize the transmit antenna and transmission power in such systems. In this paper, we propose a new antenna selection scheme for such systems based on the idea of antenna switching. In particular, targeting at reducing the number of pilot channels and RF chains, the transmitter now replaces the antennas with the lowest received SNR with unused ones if the output SNR of space time decoder at the receiver is below a certain threshold. With this new scheme, not only the number of pilot channels and RF chains to be implemented is decreased, the average amount of information feedback is also reduced. To analyze the performance of this scheme, we derive the exact integral form expression for the probability density function (PDF) of the received SNR. We show through numerical examples that the proposed scheme offers better performance than traditional OSTBC systems using all available transmitting antenna, with a small amount of information feedback. We also examine the effect of different antenna configuration and feedback delay.
{"title":"Performance Analysis of Transmit Diversity Systems with Multiple Antenna Replacement","authors":"Kihong Park, Hong-Chuan Yang, Young-Chai Ko","doi":"10.1093/ietcom/e91-b.10.3281","DOIUrl":"https://doi.org/10.1093/ietcom/e91-b.10.3281","url":null,"abstract":"There are usually rate loss and power spreading effects associated with transmit diversity systems based on orthogonal space-time block coding (OSTBC). Proper antenna selection scheme can help more effectively utilize the transmit antenna and transmission power in such systems. In this paper, we propose a new antenna selection scheme for such systems based on the idea of antenna switching. In particular, targeting at reducing the number of pilot channels and RF chains, the transmitter now replaces the antennas with the lowest received SNR with unused ones if the output SNR of space time decoder at the receiver is below a certain threshold. With this new scheme, not only the number of pilot channels and RF chains to be implemented is decreased, the average amount of information feedback is also reduced. To analyze the performance of this scheme, we derive the exact integral form expression for the probability density function (PDF) of the received SNR. We show through numerical examples that the proposed scheme offers better performance than traditional OSTBC systems using all available transmitting antenna, with a small amount of information feedback. We also examine the effect of different antenna configuration and feedback delay.","PeriodicalId":261480,"journal":{"name":"2007 4th International Symposium on Wireless Communication Systems","volume":"102 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128576987","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 : 2007-12-04DOI: 10.1109/ISWCS.2007.4392344
A. Gjendemsjø, Hong-Chuan Yang, Mohamed-Slim Alouini, G. E. ien
We consider the joint application of power control, adaptive modulation and diversity combining in the uplink of a two-cell wireless network. The goal is to derive a practical low-complexity, bandwidth-efficient, and battery-power efficient transmission scheme addressing the particular challenges of uplink transmission. Employing dynamic spectral reuse, we allow for coordination of the transmit power levels to minimize the sum transmit power, and thus implicitly the interference to co-existing systems and cells. Based on assumed transmitter knowledge of the channel fading, the proposed schemes adaptively select the signal constellation. We show that the novel scheme provides significant average transmit power reductions, yielding a substantial increase of battery lifetime, and decreased interference, while maintaining high average spectral efficiency, and compliance with bit error rate constraints.
{"title":"Joint Adaptive Modulation, Diversity Combining, and Power Control for Uplink Transmission in Two-cell Wireless Networks","authors":"A. Gjendemsjø, Hong-Chuan Yang, Mohamed-Slim Alouini, G. E. ien","doi":"10.1109/ISWCS.2007.4392344","DOIUrl":"https://doi.org/10.1109/ISWCS.2007.4392344","url":null,"abstract":"We consider the joint application of power control, adaptive modulation and diversity combining in the uplink of a two-cell wireless network. The goal is to derive a practical low-complexity, bandwidth-efficient, and battery-power efficient transmission scheme addressing the particular challenges of uplink transmission. Employing dynamic spectral reuse, we allow for coordination of the transmit power levels to minimize the sum transmit power, and thus implicitly the interference to co-existing systems and cells. Based on assumed transmitter knowledge of the channel fading, the proposed schemes adaptively select the signal constellation. We show that the novel scheme provides significant average transmit power reductions, yielding a substantial increase of battery lifetime, and decreased interference, while maintaining high average spectral efficiency, and compliance with bit error rate constraints.","PeriodicalId":261480,"journal":{"name":"2007 4th International Symposium on Wireless Communication Systems","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133071234","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 : 2007-12-04DOI: 10.1109/ISWCS.2007.4392335
A. Paier, J. Karedal, N. Czink, H. Hofstetter, C. Dumard, T. Zemen, F. Tufvesson, A. Molisch, C. Mecklenbräuker
We carried out a car-to-infrastructure (C2I) and car-to-car (C2C) 4x4 multiple-input multiple-output (MIMO) radio channel measurement campaign at 5.2 GHz in Lund, Sweden. This paper presents first results on pathloss, power-delay profiles, and delay-Doppler spectra in a C2C highway scenario, where both cars were traveling in opposite directions. A pathloss coefficient of 1.8 yields the best fit with our measurement results in the mean square sense. The measured Doppler shift of the line of sight path matches exactly with theoretical calculations. Selected paths are investigated in the delay and Doppler domain. The avererage delay spread is 250 ns; Doppler shifts of more than 1000 Hz are observed.
{"title":"Car-to-car radio channel measurements at 5 GHz: Pathloss, power-delay profile, and delay-Doppler spectrum","authors":"A. Paier, J. Karedal, N. Czink, H. Hofstetter, C. Dumard, T. Zemen, F. Tufvesson, A. Molisch, C. Mecklenbräuker","doi":"10.1109/ISWCS.2007.4392335","DOIUrl":"https://doi.org/10.1109/ISWCS.2007.4392335","url":null,"abstract":"We carried out a car-to-infrastructure (C2I) and car-to-car (C2C) 4x4 multiple-input multiple-output (MIMO) radio channel measurement campaign at 5.2 GHz in Lund, Sweden. This paper presents first results on pathloss, power-delay profiles, and delay-Doppler spectra in a C2C highway scenario, where both cars were traveling in opposite directions. A pathloss coefficient of 1.8 yields the best fit with our measurement results in the mean square sense. The measured Doppler shift of the line of sight path matches exactly with theoretical calculations. Selected paths are investigated in the delay and Doppler domain. The avererage delay spread is 250 ns; Doppler shifts of more than 1000 Hz are observed.","PeriodicalId":261480,"journal":{"name":"2007 4th International Symposium on Wireless Communication Systems","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133267260","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 : 2007-12-04DOI: 10.1109/ISWCS.2007.4392314
D. Laselva, Jens Steiner, F. Khokhar, T. Kolding, J. Wigard
This paper illustrates the optimization of design parameters for quality-of-service (QoS) aware packet schedulers in multi-service environments with WCDMA/HSDPA. The optimization sets the objective of maximizing the cell throughput while meeting certain minimum QoS criteria and focuses on two variants of the proportional fair with barrier function (PF-B) family of schedulers and on the proportional fair with required activity detection. The assessment on the sensitivity of the scheduler parameters to the traffic load and mixture is evaluated in scenarios with both real-time (streaming) and non real-time type of users (web browsing). This study shows that the PF-B schedulers require a per scenario dedicated optimization, while PF-RAD is quite insensitive and robust to support a general traffic mix. Overall, PF-RAD significantly outperforms PF-barrier schedulers in the investigated scenarios, providing up to 100% streaming cell throughput gain.
{"title":"Optimization of QoS-aware Packet Schedulers in Multi-Service Scenarios over HSDPA","authors":"D. Laselva, Jens Steiner, F. Khokhar, T. Kolding, J. Wigard","doi":"10.1109/ISWCS.2007.4392314","DOIUrl":"https://doi.org/10.1109/ISWCS.2007.4392314","url":null,"abstract":"This paper illustrates the optimization of design parameters for quality-of-service (QoS) aware packet schedulers in multi-service environments with WCDMA/HSDPA. The optimization sets the objective of maximizing the cell throughput while meeting certain minimum QoS criteria and focuses on two variants of the proportional fair with barrier function (PF-B) family of schedulers and on the proportional fair with required activity detection. The assessment on the sensitivity of the scheduler parameters to the traffic load and mixture is evaluated in scenarios with both real-time (streaming) and non real-time type of users (web browsing). This study shows that the PF-B schedulers require a per scenario dedicated optimization, while PF-RAD is quite insensitive and robust to support a general traffic mix. Overall, PF-RAD significantly outperforms PF-barrier schedulers in the investigated scenarios, providing up to 100% streaming cell throughput gain.","PeriodicalId":261480,"journal":{"name":"2007 4th International Symposium on Wireless Communication Systems","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116105491","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 : 2007-12-04DOI: 10.1109/ISWCS.2007.4392294
K. Aksoy, Ümit Aygölü
We propose a concatenated trellis code (TC) and coordinate interleaved differential space-time block code (STBC) for OFDM. The coordinate interleaver, provides signal space diversity and improves the codeword error rate (CER) performance of the system in wideband channels. Coordinate interleaved differential space-time block codes are proposed for the concatenated scheme. TC design criteria are derived, and the CER performances of the proposed system are compared with existing concatenated TC and differential STBC. The proposed scheme has superior diversity gain and improved CER performance compared to the existing differential schemes.
{"title":"Concatenated Trellis and Coordinate Interleaved Differential Space-Time Block Codes for OFDM","authors":"K. Aksoy, Ümit Aygölü","doi":"10.1109/ISWCS.2007.4392294","DOIUrl":"https://doi.org/10.1109/ISWCS.2007.4392294","url":null,"abstract":"We propose a concatenated trellis code (TC) and coordinate interleaved differential space-time block code (STBC) for OFDM. The coordinate interleaver, provides signal space diversity and improves the codeword error rate (CER) performance of the system in wideband channels. Coordinate interleaved differential space-time block codes are proposed for the concatenated scheme. TC design criteria are derived, and the CER performances of the proposed system are compared with existing concatenated TC and differential STBC. The proposed scheme has superior diversity gain and improved CER performance compared to the existing differential schemes.","PeriodicalId":261480,"journal":{"name":"2007 4th International Symposium on Wireless Communication Systems","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121689470","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 : 2007-12-04DOI: 10.1109/ISWCS.2007.4392304
I. Sarris, I. Er, P. Kong, C. Guguen
ASTRALS is a project funded by the FP6 1ST program which focuses on the in-home delivery, adaptation and processing of multiple audio/visual streams. One aspect of this project focuses on the wireless transmission of these streams using the IEEE 802.16 standard. A premium Quality of Service and IP based transmission scheme is employed in this project including MIMO and mesh extensions for increased throughput and robustness. The MIMO architecture is based on a novel technique which maximises the performance over both Line-of- Sight and non-line-of-sight conditions. On the other hand, mesh networking is responsible for multi-hopping transmission when a direct link is not available. This paper contains a number of simulation results which imply the possibility towards fully deterministic wireless audio/visual transmission in the home environment.
{"title":"Audio-Visual Wireless Streaming Platform for the Residential Environment Employing Mesh and MIMO Extensions","authors":"I. Sarris, I. Er, P. Kong, C. Guguen","doi":"10.1109/ISWCS.2007.4392304","DOIUrl":"https://doi.org/10.1109/ISWCS.2007.4392304","url":null,"abstract":"ASTRALS is a project funded by the FP6 1ST program which focuses on the in-home delivery, adaptation and processing of multiple audio/visual streams. One aspect of this project focuses on the wireless transmission of these streams using the IEEE 802.16 standard. A premium Quality of Service and IP based transmission scheme is employed in this project including MIMO and mesh extensions for increased throughput and robustness. The MIMO architecture is based on a novel technique which maximises the performance over both Line-of- Sight and non-line-of-sight conditions. On the other hand, mesh networking is responsible for multi-hopping transmission when a direct link is not available. This paper contains a number of simulation results which imply the possibility towards fully deterministic wireless audio/visual transmission in the home environment.","PeriodicalId":261480,"journal":{"name":"2007 4th International Symposium on Wireless Communication Systems","volume":"258 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124236543","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 : 2007-12-04DOI: 10.1109/ISWCS.2007.4392377
Chengchen Hu, Kai X. Miao, J. Vicente, S. Rungta, M. Ye
Multi-radio wireless mesh network (MWMN) has been recognized as a significant direction for the next generation wireless network. This paper presents a performance problem due to transmission oscillation that occurs in multi-radio wireless mesh network, which has not been reported by anyone in the research community. Such transmission oscillation introduces reduced throughput, greater network delay and unacceptable delay variations, which have all been identified in our experiments on a multi-radio test-bed. In this paper, to overcome this oscillation problem, we propose a mechanism which we call channel and radio interface switching (CHRIS). In operation, CHRIS first carries out a metric comparison and then employs a two-phase switching process. This mechanism has been evaluated on a multi-radio test-bed and the results show that CHRIS is not only able to improve average performance, but also smoothes out variations in specific performance characteristics.
{"title":"CHRIS: CHannel and Radio Interface Switching for Multi-Radio Wireless Mesh Network","authors":"Chengchen Hu, Kai X. Miao, J. Vicente, S. Rungta, M. Ye","doi":"10.1109/ISWCS.2007.4392377","DOIUrl":"https://doi.org/10.1109/ISWCS.2007.4392377","url":null,"abstract":"Multi-radio wireless mesh network (MWMN) has been recognized as a significant direction for the next generation wireless network. This paper presents a performance problem due to transmission oscillation that occurs in multi-radio wireless mesh network, which has not been reported by anyone in the research community. Such transmission oscillation introduces reduced throughput, greater network delay and unacceptable delay variations, which have all been identified in our experiments on a multi-radio test-bed. In this paper, to overcome this oscillation problem, we propose a mechanism which we call channel and radio interface switching (CHRIS). In operation, CHRIS first carries out a metric comparison and then employs a two-phase switching process. This mechanism has been evaluated on a multi-radio test-bed and the results show that CHRIS is not only able to improve average performance, but also smoothes out variations in specific performance characteristics.","PeriodicalId":261480,"journal":{"name":"2007 4th International Symposium on Wireless Communication Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129937605","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 : 2007-12-04DOI: 10.1109/ISWCS.2007.4392393
Yi Xian, Chin-Tser Huang
Voice over Internet Protocol (VoIP) service has been a very popular and important application over the Internet. Wireless VoIP also becomes more and more popular due to its features of low cost and convenience. Recently, wireless mesh network has been considered as a good solution for VoIP services since it is easy to deploy and provides a larger area coverage. However, the security and performance are the main challenges. In this work, we focus on the security issues and present a new protocol for securing the voice traffic over the wireless mesh network, including the client authentication, intermediate mesh nodes authentication to ensure secure multi-hop communication, voice traffic confidentiality and secure optimal routing selection by using the probing packets.
{"title":"Securing VoIP Services in Multi-Hop Wireless Mesh Networks","authors":"Yi Xian, Chin-Tser Huang","doi":"10.1109/ISWCS.2007.4392393","DOIUrl":"https://doi.org/10.1109/ISWCS.2007.4392393","url":null,"abstract":"Voice over Internet Protocol (VoIP) service has been a very popular and important application over the Internet. Wireless VoIP also becomes more and more popular due to its features of low cost and convenience. Recently, wireless mesh network has been considered as a good solution for VoIP services since it is easy to deploy and provides a larger area coverage. However, the security and performance are the main challenges. In this work, we focus on the security issues and present a new protocol for securing the voice traffic over the wireless mesh network, including the client authentication, intermediate mesh nodes authentication to ensure secure multi-hop communication, voice traffic confidentiality and secure optimal routing selection by using the probing packets.","PeriodicalId":261480,"journal":{"name":"2007 4th International Symposium on Wireless Communication Systems","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128849019","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 : 2007-12-04DOI: 10.1109/ISWCS.2007.4392331
N. Youssef, M. Pätzold, Kun Yang
In this paper, we derive two approximate solutions for the probability density function (PDF) of lognormal shadow fading intervals at deep fading levels. The first approximate solution is based on the Rice probability function, while the second one is deduced from the asymptotic behavior analysis of lognormal processes. Based on the latter approximate solution, expressions for the average as well as the variance of fading intervals are also provided. The validity of the analytical solutions is verified by computer simulations obtained for different propagation environments.
{"title":"Approximate Solutions to the Distribution of the Fading Intervals of Lognormal Processes","authors":"N. Youssef, M. Pätzold, Kun Yang","doi":"10.1109/ISWCS.2007.4392331","DOIUrl":"https://doi.org/10.1109/ISWCS.2007.4392331","url":null,"abstract":"In this paper, we derive two approximate solutions for the probability density function (PDF) of lognormal shadow fading intervals at deep fading levels. The first approximate solution is based on the Rice probability function, while the second one is deduced from the asymptotic behavior analysis of lognormal processes. Based on the latter approximate solution, expressions for the average as well as the variance of fading intervals are also provided. The validity of the analytical solutions is verified by computer simulations obtained for different propagation environments.","PeriodicalId":261480,"journal":{"name":"2007 4th International Symposium on Wireless Communication Systems","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126497528","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 : 2007-12-04DOI: 10.1109/ISWCS.2007.4392336
Dmitry Umansky, M. Pätzold
In this paper, we have proposed a new method of determining the parameters of measurement-based simulation models for wideband mobile radio channels. The method is grounded on fitting the temporal autocorrelation function (TACF) and the frequency correlation function (FCF) of the simulation model to those of measured channels. We have studied the possibility of exploiting the diversity in the frequency and time domains to improve the estimates of the TACF and FCF of the channel, obtained from the time-varying frequency response of the measured channel. The proposed method of determining the parameters of the channel simulator uses numerical optimization techniques and is called the iterative nonlinear least squares approximation (INLSA) algorithm. The simulation results show that the quality of the approximation of the TACF and FCF achieved by applying the INSLA algorithm is better than that attained by using the well-known subspace-alternating generalized expectation-maximization (SAGE) algorithm.
{"title":"Design of Measurement-Based Wideband Mobile Radio Channel Simulators","authors":"Dmitry Umansky, M. Pätzold","doi":"10.1109/ISWCS.2007.4392336","DOIUrl":"https://doi.org/10.1109/ISWCS.2007.4392336","url":null,"abstract":"In this paper, we have proposed a new method of determining the parameters of measurement-based simulation models for wideband mobile radio channels. The method is grounded on fitting the temporal autocorrelation function (TACF) and the frequency correlation function (FCF) of the simulation model to those of measured channels. We have studied the possibility of exploiting the diversity in the frequency and time domains to improve the estimates of the TACF and FCF of the channel, obtained from the time-varying frequency response of the measured channel. The proposed method of determining the parameters of the channel simulator uses numerical optimization techniques and is called the iterative nonlinear least squares approximation (INLSA) algorithm. The simulation results show that the quality of the approximation of the TACF and FCF achieved by applying the INSLA algorithm is better than that attained by using the well-known subspace-alternating generalized expectation-maximization (SAGE) algorithm.","PeriodicalId":261480,"journal":{"name":"2007 4th International Symposium on Wireless Communication Systems","volume":"02 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128943451","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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