1、中文 7130 字 第一章 Development of Wireless Communication 1.1 Introduction Nowadays, our world is full of wireless products. Such as Wi-Fi, cell phone, GPS and so forth are all over the world, which make our life much more convenient. However, most people only know nothing about wireless communication exc
2、ept for cellphone. Whats more, they also have no idea about the history of wireless communication, though they serve for our national defense as well as daily life. In fact, it costs a long period of time in history to gain such achievements in wireless communication. Several talented scientists pus
3、h this field forwards step by step and their names and work deserve to be remembered by us. In history, the first and the most fundamental discovery that was related to wireless communication was Maxwells equations, which were put forward by Maxwell. Buy solving those equations, he predicted that el
4、ectromagnetic wave exist in the universe, further, he demonstrated light also is a kind of electromagnetic wave. The next great scientist is Hertz. He found electromagnetic wave in experiment, who also strongly demonstrated Maxwells prediction. The discoveries above are the most important and essent
5、ial events in the history of wireless development. Also, photophone, radio, 3G are all the essential steps in the wireless progress. Whats more, like other industry, wireless communication industry also experienced its own golden and bleak age. 1.2 Classification There are lots of methods to connect
6、 two or more points to send information. One of them is to connect those points by wireless networks, which is what scientific community and current society call wireless communication. Thats to say anything that sends information without by using wire, cable or cord can be regarded as wireless comm
7、unication. However, according to the kind of media by which information is sent, wireless communication can be roughly classified into infrared wave, laser and radio wireless communication. Of course, there are also some other kinds of wireless communication that seldom are used. A common example of
8、 infrared wireless communication is television remote. Its infrared rather than electromagnetic wave, as what most people think, that is used in it. Laser wireless communication often is used for military purpose. Radio wireless communication is 1 the most common method of wireless communication for
9、 the reason that the cellphone, Wi-Fi and so forth that people often contact belong to radio wireless communication. such as television remote, Bluetooth, laser communication are all parts of wireless communication. 1.3 Advantage of the wireless network Currently and in the future, wireless communic
10、ation must replace wire network. The important and the only factor that drives this tendency is advantages of wireless network. As a book named Bluetooth Operation and Use said: It is, of course, obvious that a wired network requires installing lots of cable because each node in the network must hav
11、e physical access to the cable from its particular location. This can cause big headaches when the walls, floors, and ceilings of an existing building must be torn open for cable installation. The second reason is that wireless network gives us more mobility. Thus, people can use wireless devices, e
12、specially, cellphone, Wi-Fi, within a more much area. Television remote also can serve as a example to illustrate it. People can control television anywhere in the room as long as holding a television remote. Compared with wire communication, motility is the biggest advantage of wireless communicati
13、on, because mobility makes our life more convenient. Thirdly, wireless plan also can be economical. If everything is connected with each other by cable or wire, the world would be messed up. What s more, the qualified cable also needs valuable resource and much money. As a result, it becomes less ec
14、onomical than wireless communication. Because of these advantages, wireless communication is a extremely vibrate field in this world. 1.4 The prehistory of wireless communication Like many other industries or research field, wireless communication has a long history. There were lots of talented scie
15、ntists and engineers who contribute to it. Their names and work are both immortal. 1.4.1 Maxwell equations During 19th century, Maxwell, a great physical scientist of the UK, put forward a group of equations that consists of 4 equations and 4 variables. 2 Through these equations, he stated that elec
16、tromagnetic wave exists in our universe. Also, it is demonstrated that light is also a kind of electromagnetic wave. Because of this discovery, Maxwell is regarded as the pioneer of electromagnetism. 1.4.2 The discovery of electromagnetic wave by Hertz Hertz, a great Germanic physical scientists, he
17、 demonstrated that electromagnetic wave indeed exist in this universe in 1888, which, at the same time, also find evidence for Maxwell s theory. Scientific community use Hertz (Hz) as the unit of frequency of electromagnetic wave. 1.4.3Photophone Unexpectedly, the first invention that was related to
18、 wireless communication was through light beams rather than radio signals (which are widely used now). According to Byte Net and I paraphrase, in 1880, a telephone that conducted audio conversations wirelessly over modulated light beams was invented by Alexander Graham Bell. In the distant era when
19、had no electricity or laser, this invention had no practical applications. Besides, the availability of sunlight, good weather, clear line of sight between transmitter and receiver all highly limited the development of this invention. However, based on the discovery of laser, this invention become f
20、iber-optic communication, which replaced electric cable communication. What s more, after improved, photophone also is used in military communication. 1.5 Invention of cellphone It s the invention of cellphone denotes a new age mobile age. It developed extremely rapidly. In 1902, a person named Nath
21、an Stubblefield, lived in Kentucky State, invented a device that can be using to communicate and there was no need to connect with any cable or wire. Then in 1938， the Bell experiment invented the “ first cellphone” in the world for American military. What s the most important, according to Byte Net, Martin Cooper, a famous engineer served for Motorola Company,
