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1、,Wireless Communication Fundamentals,Dr. Jiang Zhu, Professor,Department of Military Communication Engineering,School of Electronic Science and Engineering,Wired Vs. Wireless Communication,Wired Vs. Wireless Communication,Wired Vs. Wireless Communication,How does signal propagate ? How much attenuat
2、ion take place ? How does signal look like at the receiver ? How does signals using the same propag- ation channel ?,Wired Vs. Wireless Communication,Provide comprehensive understanding of fundamental principles underlying wireless communications and networking Principles include: Characteristics an
3、d performance limits of wireless systems Techniques to overcome the difficulties,Goal of This Course,Outline,Outline,Email: jiangzhugfkd.mtn Phone: 74477 13787179473 Office: 103 room, 4th Departments General Building,Course information,Instructor Information,Course information,Text Wireless Communi
4、cations and Networking by Jon W.Mark and Weihua Zhuang Reference Modern Wireless Communications by Simon Haykin and Michael Moher Lecture Notes by Dr. Jiang Zhu,Course Material,Course information,Some basic knowledge of communication Some basic knowledge of signals and systems Some basic knowledge o
5、f probability and statistics,Prerequisites,Course information,Class Time: 18 Lectures (36 credit hours) Labs: 4 credit hours Final exam : ?,Time & schedule,Course information,Experiment 15% Homeworks & Class Participation 5% Final Exam 80%,Grading,Outline,Introduction to main topics,Introduction to
6、main topics,Introduction to main topics,Introduction to main topics,Introduction to main topics,Outline,1.1 Definition of Wireless communication,Transmitting voice and data using electromagnetic waves in open space Electromagnetic waves Travel at speed of light (c = 3x108 m/s) Has a frequency (f ) a
7、nd wavelength (l) c = f l,What is wireless communication?,1.1 Definition of Wireless communication,Propagation characteristics are different in each frequency band,AM radio,S/W radio,FM radio,TV,TV,cellular,What is wireless communication?,1.1 Definition of Wireless communication,Ground Wave,Sky wave
8、,Space wave,What is wireless communication?,1.1 Definition of Wireless communication,Provides mobility A user can send or receive a message no matter where he or she is located Added convenience/reduced cost Enables communication without installing an expensive infrastructure,1.1 Definition of Wirel
9、ess communication,Why use wireless comm?,1.1 Definition of Wireless communication,The wireless channel Wireless channels are a difficult and capacity limited broadcast communications medium Modulation、coding、equalization、diversity etc. User mobility Traffic patterns, user locations, and network cond
10、itions are constantly changing Handoff and Location management,Challenges of wireless comm,1.1 Definition of Wireless communication,The fundamental physical resource in wireless systems is the radio spectrum. The development of wireless communications has often a search for more efficient ways of us
11、ing the radio spectrum.,Challenges of wireless comm,1.1 Definition of Wireless communication,OSI Model,This layer provides the physical mechanism for transmitting bits between any pair of nodes.,One purpose of the data-link layer is to perform error correction of detection, this layer is also respon
12、sible for the way in which different users share the transmission medium.,This layer has several functions, one of which is to determine the routing of the information. A second function is flow control, to ensure that the network does not become congested.,1.2 History of wireless communication,1864
13、 - Maxwell predicts existence of electro-magnetic (EM) waves 1887 - Hertz proves existence of EM waves; first spark transmitter generates a spark in a receiver several meters away 1890 - Branly develops coherer for detecting radio waves 1896 - Marconi demonstrates wireless telegraph to English teleg
14、raph office,Before the “Birth of Radio”, 1864-1896,1.2 History of wireless communication,莫尔斯电报和贝尔电话都是有线通信，当时人们认为电只能沿导线传输。可当时的英国科学家麦克斯韦尔不这样认为，早在1864年麦克斯韦尔就从理论上预言了电磁波的存在，他认为电能可以在空间以电磁波的形式存在，1864年麦克斯韦尔在英国皇家学院发表了他的第三篇著名论文电磁场力学的理论，在这篇论文中，麦克斯韦尔严格推导出完善的电磁波方程（麦克斯韦尔方程）并得出电磁波的传播速度等于光速（30万公里/秒）的重要结论。1887年德国物理学
15、家赫兹用实验证实了电磁波的存在证明了麦克斯韦尔预见的正确性。,1895年，意大利的马可尼和俄国的波波夫把电磁波应用到无线电报通信中，但当时电波的传送距离较近（20300公里），而且声音很微弱，只能用耳机收听，距离远了就听不见。直到1906年，26岁的美国青年，业余无线电爱好者德福雷斯特发明了具有放大能力的真空三极管后，通信技术有了突飞猛进的发展，先后出现了无线电广播，电视，无线电话，并发展到今天的计算机通信、卫星通信，光纤通信，网络通信，移动通信等。,1.2 History of wireless communication,“The Birth of Radio”,1897 - Marcon
16、i awarded patent for wireless telegraph 1897 - First “Marconi station” established on Needles island to communicate with English coast 1898 - Marconi awarded English patent for tuned communication 1898 - Wireless telegraphic connection between England and France established,1901 - Marconi successfully transmits radio signal across Atlantic Ocean from Cornwall to Newfoundland 1902 - First bidirectional communication across Atlantic 1909 - Marconi awarded Nobel prize for physics,
