报告人简介： Mohsen Kavehrad现任美国宾夕法尼亚州立大学电子工程系教授（W. L. Weiss Endowed Chair Professor），通信技术研究中心主任，美国IEEE学会会士（Fellow）。Kavehrad教授毕业于美国纽约大学理工学院（Polytechnic Institute of New York University）。曾先后工作于美国仙童工业公司（Fairchild Industries）、通用电话电子公司（GTE）、贝尔实验室（Bell Laboratories）。1989年3 月进入加拿大渥太华大学电子工程系工作，并担任教授职位。1997进入美国宾夕法尼亚州立大学电子工程系，并于1997-1998年兼任美国Tele-Beam 公司首席技术官和副总裁。Kavehrad博士还一直担任着日本电话电报公司（NTT）、加拿大北方电信公司（Nortel）、美国电话电报公司（AT&T）等知名企业与政府机构的高级顾问。Mohsen Kavehrad教授还曾是美国自然科学基金评审委员会成员，IEEE Communications Magazine 杂志、IEEE Magazine of Light-wave Telecommunications Systems杂志技术编委（Technical Editor），目前是International Journal of Wireless Information Networks杂志编委会成员。Mohsen Kavehrad教授还曾是IEEE许多学术会议、论坛的大会主席。Kavehrad教授一直从事卫星通信、点到点微波通信、便携式微波通信、大气激光通信、以及光纤通信等领域的研究与开发工作。共发表学术论文及会议报告400余篇，出版学术论著2本，拥有美国发明专利13项。
Biography: Dr. Kavehrad joined Penn State in January 1997 as the W. L. Weiss Endowed Chair Professor. He is the founding director of Center for Information and Communications Technology Research. His prior work experience includes working for Fairchild Industries, GTE (Satellite Corp. and Labs.) and Bell Laboratories before joining the Department of Electrical Engineering at University of Ottawa in March 1989 as a Professor and Director of Photonic Networks and Systems Thrust in the Communications and Information Technology Ontario (CITO). During 1997-1998 he was also the CTO and a Vice President at Tele-Beam Inc., State College, PA. He has been a senior consultant to NTT, Nortel and AT&T Shannon Research Labs and consultant to a score of other major corporations and government agencies. He is a Fellow of the IEEE. His works have been published in close to 400 refereed journal and conference papers, several books and book chapters, and he holds several key issued patents in his work areas.
报告摘要： 简单的介绍完滨州大学/佐治亚大学/自然基金委联合研究中心在光无线技术方面的研究进展后，我们将集中讨论在云层、大气湍流状态下的自由空间光通信技术（FSO）的发展状况。FSO是全球地面节点与空间节点建立通信链路的唯一可行技术。卫星与地面站间的海量数据传输无法通过传统的微波通信实现。而FSO具有非常大的带宽。另外，激光束优良的方向性也使这种通信方式更加保密。但是这种可观的传输速率仅能在非常好的天气条件下才能表现出来，在诸如多云、有雾、大气湍流等天气条件下，FSO就显得无能为力了。阴霾、雾会使脉冲在时间和空间上展宽，大气湍流会使信号闪烁和衰减。因此研究FSO在各种天气条件下的最佳工作方式就必须着眼于对发射、接收装置的设计。更具体来说，具有将湍流引起的畸变与雾霾散射引起的信号衰减、展宽补偿回来的复合发射、接收装置将是解决问题的一个方向。本次报告中将对FSO系统中Multiple-Input Multiple-Output (MIMO)发射、接收装置进行详细的介绍。
Abstract: After a brief overview on Penn-State/Georgia-Tech NSF Industry-University-Cooperative-Research Center on Optical Wireless Applications (COWA), we will focus on free space optical communications (FSO) through clouds and turbulent atmosphere. FSO communications is the only viable solution for creating a three-dimensional global communications grid of inter-connected ground and airborne nodes. The huge amount of data exchange between satellites and ground stations demands enormous capacity that cannot be provided by strictly regulated, scarce resources of the Radio Frequency (RF) spectrum. FSO communications, on the other hand, has the potential of providing virtually unlimited bandwidth. Furthermore, due to the spatial confinement of laser beams, such links are very secure. In other words, security is guaranteed at the physical layer. However, the promised enormous data rates are only available under clear weather conditions, and atmospheric phenomena such as clouds, fog, and even turbulence can degrade the performance, dramatically. While turbid media such as clouds and aerosols cause pulse broadening in space and time, turbulence presents itself as scintillation and fading. Hence, to exploit the great potentials of FSO at its best under all weather conditions, prudent measures must be taken in the design of transmitter and receiver. More specifically, multiple transmitters and receivers can be used to combat the turbulence-induced fading and to compensate for pulse attenuation and broadening caused by scattering. In this presentation, Multiple-Input Multiple-Output (MIMO) transmitter and receiver designs for FSO communications are investigated and the achievable performance improvements are discussed. |
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