Pub Date : 2008-12-08DOI: 10.1109/PIMRC.2008.4699777
M. Trivellato, F. Boccardi, Howard C. Huang
We consider a multiuser MIMO downlink system with multiple antenna mobile terminals where channel state information at the base station is provided through limited uplink feedback. In a multi-cell environment we compare two transceiver architectures based on zero forcing and unitary beamforming respectively. For both schemes we show how the additional degrees of freedom provided by multiple receive antennas can be exploited to improve system performance, by a proper design of the receive combiner. We propose channel quantization solutions that adapt to the transceiver architectures and exploit MIMO channel statistic. Numerical simulations validate the effectiveness of the proposals in a multi-cell environment where long-term proportional fairness is guaranteed among the users in the network.
{"title":"Zero-forcing vs unitary beamforming in multiuser MIMO systems with limited feedback","authors":"M. Trivellato, F. Boccardi, Howard C. Huang","doi":"10.1109/PIMRC.2008.4699777","DOIUrl":"https://doi.org/10.1109/PIMRC.2008.4699777","url":null,"abstract":"We consider a multiuser MIMO downlink system with multiple antenna mobile terminals where channel state information at the base station is provided through limited uplink feedback. In a multi-cell environment we compare two transceiver architectures based on zero forcing and unitary beamforming respectively. For both schemes we show how the additional degrees of freedom provided by multiple receive antennas can be exploited to improve system performance, by a proper design of the receive combiner. We propose channel quantization solutions that adapt to the transceiver architectures and exploit MIMO channel statistic. Numerical simulations validate the effectiveness of the proposals in a multi-cell environment where long-term proportional fairness is guaranteed among the users in the network.","PeriodicalId":125554,"journal":{"name":"2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications","volume":"210 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115769184","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 : 2008-12-08DOI: 10.1109/PIMRC.2008.4699970
O. Drögehorn, Sian Lun Lau, Niklas Klein, I. König, J. Porras
The current computing and communication services are driven by various technologies. The creation of such services is however not an easy task. The different platforms lack openness that simplifies interoperability. Service development is still mainly technical oriented, where service creation tools are meant for serving and assisting the professional developers. Service creation is not seen as a task for end users right now. In this paper we will discuss how end users could be enabled to create new services, shown on the example within a mobile context-aware service platform. This is achieved by introducing the concept of the technology agnostic approach into the process. We present the conceptual architecture and explain the idea of end-user driven service creation that can provide a solution. Several tools were designed and implemented to prove that the concepts work. With the help of semantic service description, the end users can express their service wishes and create services using a graphical interface technology agnostically. The idea was implemented in two European projects and we have identified the next steps to improve the prototypes as well as the idea. Based on several tools and an underlying platform the ideas have been tested in a development environment for mobile context-aware services. Here end-users are able to design their own services or combine existing services, which can be shared and used by other users later on.
{"title":"Service creation for end-users","authors":"O. Drögehorn, Sian Lun Lau, Niklas Klein, I. König, J. Porras","doi":"10.1109/PIMRC.2008.4699970","DOIUrl":"https://doi.org/10.1109/PIMRC.2008.4699970","url":null,"abstract":"The current computing and communication services are driven by various technologies. The creation of such services is however not an easy task. The different platforms lack openness that simplifies interoperability. Service development is still mainly technical oriented, where service creation tools are meant for serving and assisting the professional developers. Service creation is not seen as a task for end users right now. In this paper we will discuss how end users could be enabled to create new services, shown on the example within a mobile context-aware service platform. This is achieved by introducing the concept of the technology agnostic approach into the process. We present the conceptual architecture and explain the idea of end-user driven service creation that can provide a solution. Several tools were designed and implemented to prove that the concepts work. With the help of semantic service description, the end users can express their service wishes and create services using a graphical interface technology agnostically. The idea was implemented in two European projects and we have identified the next steps to improve the prototypes as well as the idea. Based on several tools and an underlying platform the ideas have been tested in a development environment for mobile context-aware services. Here end-users are able to design their own services or combine existing services, which can be shared and used by other users later on.","PeriodicalId":125554,"journal":{"name":"2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications","volume":"123 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114362022","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 : 2008-12-08DOI: 10.1109/PIMRC.2008.4699553
Wei-Cheng Zeng, G. Bi
Sensing the weak signals of primary users by cognitive UWB devices greatly challenges the capability of energy detector under noise uncertainty. This paper presents a simple and robust statistic for detecting the primary signals of OFDM type. The statistic, constructed from the auto-correlation function of the received signal, is unsusceptible to the noise uncertainty since it avoids estimating the noise level. The detection and false alarm probabilities are then calculated. The comparison with energy detection demonstrates its superiority to the energy detector in case of low SNR and noise uncertainty.
{"title":"Robust detection of OFDM signals for cognitive UWB in low SNR with noise uncertainty","authors":"Wei-Cheng Zeng, G. Bi","doi":"10.1109/PIMRC.2008.4699553","DOIUrl":"https://doi.org/10.1109/PIMRC.2008.4699553","url":null,"abstract":"Sensing the weak signals of primary users by cognitive UWB devices greatly challenges the capability of energy detector under noise uncertainty. This paper presents a simple and robust statistic for detecting the primary signals of OFDM type. The statistic, constructed from the auto-correlation function of the received signal, is unsusceptible to the noise uncertainty since it avoids estimating the noise level. The detection and false alarm probabilities are then calculated. The comparison with energy detection demonstrates its superiority to the energy detector in case of low SNR and noise uncertainty.","PeriodicalId":125554,"journal":{"name":"2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114519455","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 : 2008-12-08DOI: 10.1109/PIMRC.2008.4699485
M. García-Lozano, S. Ruiz-Boqué, J. Pérez-Romero, O. Sallent
This paper concentrates on the dynamic tuning of radio resource management parameters in the context of HSDPA systems coexisting with UMTS Relpsila99. In particular, an automatic tuning system is proposed taking into account the close interdependence between the cell throughput and the users channel quality indicators. From these, appropriate performance indicators are derived and a mid-term allocation mechanism is designed to maximize cell throughput while guaranteeing blocking and dropping criteria.
{"title":"Performance improvement of HSDPA/UMTS networks through dynamic code tuning","authors":"M. García-Lozano, S. Ruiz-Boqué, J. Pérez-Romero, O. Sallent","doi":"10.1109/PIMRC.2008.4699485","DOIUrl":"https://doi.org/10.1109/PIMRC.2008.4699485","url":null,"abstract":"This paper concentrates on the dynamic tuning of radio resource management parameters in the context of HSDPA systems coexisting with UMTS Relpsila99. In particular, an automatic tuning system is proposed taking into account the close interdependence between the cell throughput and the users channel quality indicators. From these, appropriate performance indicators are derived and a mid-term allocation mechanism is designed to maximize cell throughput while guaranteeing blocking and dropping criteria.","PeriodicalId":125554,"journal":{"name":"2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123497570","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 : 2008-12-08DOI: 10.1109/PIMRC.2008.4699966
L. Sørensen, K. Skouby
When it comes to discussing the future of electronic communication, social networking is the buzzword. The Internet has become a platform where new social networks emerge and the Internet it itself support the more traditional computer supported communication. The way users build and verifies different online networks for communities of people who share interests or individuals who presents themselves through user produced content is what makes up the social networking of today. The purpose of this paper is to discuss perceived user requirements to the next generation social networks. The paper is based on a survey of users working within the ICT field as well as user requirement categorizations developed within the WWRF.
{"title":"Next generation social networks - elicitation of user requirements","authors":"L. Sørensen, K. Skouby","doi":"10.1109/PIMRC.2008.4699966","DOIUrl":"https://doi.org/10.1109/PIMRC.2008.4699966","url":null,"abstract":"When it comes to discussing the future of electronic communication, social networking is the buzzword. The Internet has become a platform where new social networks emerge and the Internet it itself support the more traditional computer supported communication. The way users build and verifies different online networks for communities of people who share interests or individuals who presents themselves through user produced content is what makes up the social networking of today. The purpose of this paper is to discuss perceived user requirements to the next generation social networks. The paper is based on a survey of users working within the ICT field as well as user requirement categorizations developed within the WWRF.","PeriodicalId":125554,"journal":{"name":"2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications","volume":"152 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123643214","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 : 2008-12-08DOI: 10.1109/PIMRC.2008.4699503
Shih-Chang Huang, Chien Chen, R. Jan, C. Hsieh
This paper proposes an energy-efficient traffic scheduling approach for 802.16e broadband wireless networks. Instead of considering a single Mobile Subscriber Station (MSS) as most of the current researchers do, multiple MSSs are considered in our work. The constant bit rate traffic with QoS delay constraint is considered in this paper. The proposed approach considers both energy efficiency and bandwidth utilization. First, we derive a minimum wakeup time for each MSS to achieve the maximum power saving by waking up the minimum number of time slots. After then, we interleave the traffic of multiple MSSs by taking advantage of feasible slot allocation. In order to support the maximum number of MSSs, our scheduling problem can be transformed into a maximum bipartite matching problem. We use the Ford-Fulkerson maximum flow algorithm to obtain a feasible schedule for multiple MSSs. Simulation results show that our proposed approach has better bandwidth utilization and achieves maximum energy saving.
{"title":"An energy-efficient scheduling for multiple MSSs in IEEE 802.16e broadband wireless","authors":"Shih-Chang Huang, Chien Chen, R. Jan, C. Hsieh","doi":"10.1109/PIMRC.2008.4699503","DOIUrl":"https://doi.org/10.1109/PIMRC.2008.4699503","url":null,"abstract":"This paper proposes an energy-efficient traffic scheduling approach for 802.16e broadband wireless networks. Instead of considering a single Mobile Subscriber Station (MSS) as most of the current researchers do, multiple MSSs are considered in our work. The constant bit rate traffic with QoS delay constraint is considered in this paper. The proposed approach considers both energy efficiency and bandwidth utilization. First, we derive a minimum wakeup time for each MSS to achieve the maximum power saving by waking up the minimum number of time slots. After then, we interleave the traffic of multiple MSSs by taking advantage of feasible slot allocation. In order to support the maximum number of MSSs, our scheduling problem can be transformed into a maximum bipartite matching problem. We use the Ford-Fulkerson maximum flow algorithm to obtain a feasible schedule for multiple MSSs. Simulation results show that our proposed approach has better bandwidth utilization and achieves maximum energy saving.","PeriodicalId":125554,"journal":{"name":"2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124047493","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 : 2008-12-08DOI: 10.1109/PIMRC.2008.4699436
Patrick Hosein, Tao Wu
Orthogonal frequency division multiple access (OFDMA) transmission has been chosen for the next generation of wireless networks. Multiple input multiple output (MIMO) techniques are well suited for OFDMA and will be used for increased transmission efficiency for both downlink and uplink. In this paper we focus on space division multiple access (SDMA) techniques for the uplink of such a network. In particular, we consider the problem of scheduling uplink users so as to maximize the uplink resources while satisfying the QoS requirements of each userpsilas flows. We do this by assigning suitable utility functions to user flows that are designed to maintain the specified QoS constraints. Since multiple users can be simultaneously scheduled, the scheduling problem becomes multi-dimensional and, in general, its computational complexity grows non-linearly with the number of users. In addition to choosing the users to be scheduled one must also determine the optimal transmission power for each scheduled user. For the case of two users per frame we show that the optimal power allocation scheme is such that either both users transmit with full power or only one transmits with full power. We then propose a coordinate ascent algorithm for solving the utility-based scheduling problem. Simulations are then used to show that the solution produced by this approach is close to optimal and is quite robust.
{"title":"Coordinate ascent scheduler for the multi-user MIMO uplink channel","authors":"Patrick Hosein, Tao Wu","doi":"10.1109/PIMRC.2008.4699436","DOIUrl":"https://doi.org/10.1109/PIMRC.2008.4699436","url":null,"abstract":"Orthogonal frequency division multiple access (OFDMA) transmission has been chosen for the next generation of wireless networks. Multiple input multiple output (MIMO) techniques are well suited for OFDMA and will be used for increased transmission efficiency for both downlink and uplink. In this paper we focus on space division multiple access (SDMA) techniques for the uplink of such a network. In particular, we consider the problem of scheduling uplink users so as to maximize the uplink resources while satisfying the QoS requirements of each userpsilas flows. We do this by assigning suitable utility functions to user flows that are designed to maintain the specified QoS constraints. Since multiple users can be simultaneously scheduled, the scheduling problem becomes multi-dimensional and, in general, its computational complexity grows non-linearly with the number of users. In addition to choosing the users to be scheduled one must also determine the optimal transmission power for each scheduled user. For the case of two users per frame we show that the optimal power allocation scheme is such that either both users transmit with full power or only one transmits with full power. We then propose a coordinate ascent algorithm for solving the utility-based scheduling problem. Simulations are then used to show that the solution produced by this approach is close to optimal and is quite robust.","PeriodicalId":125554,"journal":{"name":"2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124125248","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 : 2008-12-08DOI: 10.1109/PIMRC.2008.4699658
J. P. Nair, Ratnam V. Raja Kumar
In this work an iterative time domain least squares (LS) based channel estimation method using superimposed training (ST) for an orthogonal frequency division multiplexing (OFDM) system over frequency selective fading channels is proposed. The performance of the channel estimator is analyzed in terms of the mean square estimation error (MSEE) and its impact on the uncoded bit error rate (BER) of the OFDM system is studied. The selection criterion for the training sequences is proposed by jointly optimizing the MSEE and the BER of the OFDM system. A chirp based sequence satisfying the selection criterion is proposed and compared with the other sequences found in the literature. The sequence is generalized to incorporate the use of guard subcarriers in the OFDM based system. The proposed sequence offers fairness through providing equal interference in all the data carriers unlike earlier proposals. Experimental studies are carried to study the performance of the proposed scheme and also its comparison with the existing schemes is presented. Also, the proposed scheme is applied to the IEEE 802.16e OFDM standard, its suitability is examined and a case is made with the required design of the sequence.
{"title":"An optimal superimposed training sequence for channel estimation in OFDM systems","authors":"J. P. Nair, Ratnam V. Raja Kumar","doi":"10.1109/PIMRC.2008.4699658","DOIUrl":"https://doi.org/10.1109/PIMRC.2008.4699658","url":null,"abstract":"In this work an iterative time domain least squares (LS) based channel estimation method using superimposed training (ST) for an orthogonal frequency division multiplexing (OFDM) system over frequency selective fading channels is proposed. The performance of the channel estimator is analyzed in terms of the mean square estimation error (MSEE) and its impact on the uncoded bit error rate (BER) of the OFDM system is studied. The selection criterion for the training sequences is proposed by jointly optimizing the MSEE and the BER of the OFDM system. A chirp based sequence satisfying the selection criterion is proposed and compared with the other sequences found in the literature. The sequence is generalized to incorporate the use of guard subcarriers in the OFDM based system. The proposed sequence offers fairness through providing equal interference in all the data carriers unlike earlier proposals. Experimental studies are carried to study the performance of the proposed scheme and also its comparison with the existing schemes is presented. Also, the proposed scheme is applied to the IEEE 802.16e OFDM standard, its suitability is examined and a case is made with the required design of the sequence.","PeriodicalId":125554,"journal":{"name":"2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129913703","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 : 2008-12-08DOI: 10.1109/PIMRC.2008.4699434
Zhan Shi, Jianmin Zhou, H. Hayashi, T. Kubo
There are many digital baseband predistorters, which are used to overcome the nonlinearity and memory effect of power amplifier for wideband signals. Look-up table-based Hammerstein predistorter is one of them and has remarkable advantages comparing with the others. In this paper, an iterative algorithm is proposed for extracting the coefficients of the look-up table-based Hammerstein predistorter. An ADS simulation testbed is built to verify the predistorter and algorithm, and the simulation results demonstrate the good performance of our algorithm.
{"title":"A coefficients extraction algorithm for LUT-based Hammerstein predistorters","authors":"Zhan Shi, Jianmin Zhou, H. Hayashi, T. Kubo","doi":"10.1109/PIMRC.2008.4699434","DOIUrl":"https://doi.org/10.1109/PIMRC.2008.4699434","url":null,"abstract":"There are many digital baseband predistorters, which are used to overcome the nonlinearity and memory effect of power amplifier for wideband signals. Look-up table-based Hammerstein predistorter is one of them and has remarkable advantages comparing with the others. In this paper, an iterative algorithm is proposed for extracting the coefficients of the look-up table-based Hammerstein predistorter. An ADS simulation testbed is built to verify the predistorter and algorithm, and the simulation results demonstrate the good performance of our algorithm.","PeriodicalId":125554,"journal":{"name":"2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128927098","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 : 2008-12-08DOI: 10.1109/PIMRC.2008.4699500
S. S. Al-Samahi, S. L. Goff, B. Sharif, C. Tsimenidis
Selected mapping (SLM) is a technique used to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) systems. SLM requires the transmission of several side information bits for each data block, which results in some data rate loss. These bits must be channel-encoded because they are particularly critical to the error performance of the system. This increases the system complexity and transmission delay, and decreases the data rate even further. In this paper, we propose a novel SLM method for which no side information needs to be sent. By considering the example of several OFDM systems using either QPSK or 16-QAM modulation, we show that the proposed method performs very well in terms of bit error rate at the receiver output provided that the number of subcarriers is large enough.
{"title":"A novel OFDM PAPR reduction scheme using selected mapping without explicit side information","authors":"S. S. Al-Samahi, S. L. Goff, B. Sharif, C. Tsimenidis","doi":"10.1109/PIMRC.2008.4699500","DOIUrl":"https://doi.org/10.1109/PIMRC.2008.4699500","url":null,"abstract":"Selected mapping (SLM) is a technique used to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) systems. SLM requires the transmission of several side information bits for each data block, which results in some data rate loss. These bits must be channel-encoded because they are particularly critical to the error performance of the system. This increases the system complexity and transmission delay, and decreases the data rate even further. In this paper, we propose a novel SLM method for which no side information needs to be sent. By considering the example of several OFDM systems using either QPSK or 16-QAM modulation, we show that the proposed method performs very well in terms of bit error rate at the receiver output provided that the number of subcarriers is large enough.","PeriodicalId":125554,"journal":{"name":"2008 IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128979897","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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