1, development of wireless communication technology
Looking back at the history of communication development, we found a very interesting process: 1832, Morse invented the telegraph, and the information it transmitted was composed of the well-known dot-and-dash code, that is, the earliest communication of human beings was carried out in a digital way. Later, Bell invented the telephone and started the telecommunications industry. For more than a century, the telecommunications industry, which mainly focuses on telephone business, has taken a successful road and made great progress. However, with the development of human society, the telecommunications business has also developed from the early telegraph and telephone to the coexistence of various services today, and the communication scale has also undergone earth-shaking changes. With the development of science and technology, modern communication has entered the digital age. In the 1990s, the wave of information revolution, the clarion call for building an information superhighway, the explosive growth of information and knowledge, especially the rapid development after the commercialization of the Internet, made the traditional telecommunications industry suffer a huge impact. The enlightenment is that the core of the problem lies in "information". In the era when information and knowledge have become the strategic resources and basic elements of social and economic development, people need to obtain information anytime and anywhere, and the original point-to-point fixed telephone communication mode is far from meeting the demand. Humans need broadband wireless communication technology to meet the multimedia, popular, diversified, global and personalized information exchange. Wireless communication refers to the communication mode that uses electromagnetic waves to transmit information. As early as 1897, Marconi conducted the world's first transatlantic wireless communication experiment from Britain to Newfoundland, North America, using 800KHZ medium wave signals, which initiated a new era of human wireless communication. In the early days of wireless communication, due to the limitation of technical conditions, people used long wave and medium wave for communication. Shortwave communication was discovered in the early 1920s. Until the rise of satellite communication in the 1960s, it has been an important means of long-distance international communication, and it still has certain practical value for emergency communication and military communication.
In the 1940s and 1950s, microwave communication with wide transmission bandwidth and stable performance appeared, which became an important means of long-distance and large-capacity ground trunk wireless transmission. Analog FM transmission capacity is as high as 2700 channels, and it can also transmit high-quality color TV signals at the same time; Er gradually enters the digital microwave transmission from medium capacity to large capacity. Since the mid-1980s, with the discovery of the influence of frequency-selective dispersion fading on digital microwave transmission interruption, and the development of a series of adaptive fading countermeasures and high-state modulation detection technology, digital microwave transmission has undergone revolutionary changes. In particular, a set of high-speed polymorphic adaptive coding modulation and demodulation technology, information signal processing and signal detection technology developed from 1980s to 1990s have played an important role in signal design, signal processing and application in many fields such as satellite communication, mobile communication, all-digital HDTV transmission, universal high-speed wired/wireless access, and even high-quality magnetic recording. With the informationization of national economic and social development, people should innovate working methods, management methods, business methods, financial methods, ideas exchange methods, cultural and educational methods, medical and health care methods and consumption and lifestyle through informationization. Wireless communication has also developed from fixed mode to mobile mode, and the development of mobile communication has gone through about five stages so far;
The first stage, from the early 1920s to the early 1950s, was mainly used in ships and military equipment, using short-wave frequency and electron tube technology. At the end of this stage, the VHF simplex public mobile phone system MTS with 150MHZ appeared.
The second stage is from 1950s to 1960s. At this time, the frequency band has been extended to UHF450MHZ, and the device technology has been transferred to semiconductors, mostly dedicated systems in mobile environment, and the connection problem between mobile phones and public telephone networks has been solved.
In the third stage, from the early 1970s to the early 1980s, the frequency band was extended to 800MHZ. In the late 1970s, Bell Institute of America put forward the concept of cellular system, and carried out AMPS test.
The fourth stage, from the early 1980s to the mid-1990s, is the rise and great development stage of the second generation digital mobile communication, and gradually moves towards personal communication services. At this time, various systems and services, such as D-AMPS, TACS, ETACS, GSM/DCS, cdmaOne, PDC, PHS, DECT, PACS, PCS, etc. Appeared, the frequency band expanded to 900MHZ~ 1.9GHZ, in addition to public cellular telephone communication systems, there are wireless paging systems, cordless telephone systems, trunking systems, centerless multi-channel mobile communication systems and other types.
The fifth stage is from the mid-1990s to the present. With the development of data communication and multimedia services, the third-generation mobile communication, which meets the needs of mobile data, mobile computing and mobile multimedia services, is emerging, and its global standardization and corresponding integration work, prototype development and field testing work are advancing rapidly, including the smooth transition from the second generation to the third generation mobile communication. For the third generation mobile TMT-2000, they have participated in the formulation of standards. After many integration efforts, five types of RTT technical standards were held in Helsinki, Finland from1October 25th1999 10 to1October 5th10titu-rtg8/1. China's TD-SCDMA scheme has also become one of them. It should be pointed out that the corresponding prototype of UTRAWCDMA DS and TIA cdma2000MC has been born, including the second generation semi-transition equipment (G)EDGE based on GSM and csmaOne backward compatibility, cdma IS-95B HDR(2.4Mbit/s peak rate, 64QAM modulation) and cdma2000- 1X, etc.
In addition, wireless application protocol (WAP) and wireless connection technology (Bluetooth) have been generated to connect Internet mobile browsing applications. From the network point of view, access networks can be divided into wired access networks and wireless access networks. Coaxial hybrid access networks include optical cable, copper cable, twisted pair, telephone (usually copper wire) access networks and so on. Wireless access technology is a new technical field that has developed rapidly in recent years. It has made a great leap in concept, that is, it does not need wired physical transmission medium, but uses wireless transmission means to replace part or even all of the access network, thus achieving the purpose of reducing costs, improving flexibility and extending transmission distance. There are many kinds of wireless access networks, such as mobile medical system, cellular mobile communication system, trunking communication system, point-to-multipoint microwave communication system and microwave cellular wireless local access system (PHS, PAS, PACS, DECT). The short-range access technologies mainly include Bluetooth, infrared, DECT, IEEE802. 1 1 and * * * SWAP)/HomeRF system. After wide Area Network (WAN, Wind, Area Network or MAN) and local area network (LAN), people recently put forward "WPAN". This new concept promotes small-scale application to the height of network theory. In a short time, WPAN has become a new hot spot, attracting people's attention. The WPAN research group was established less than 1, and it has evolved into IEEE802.5 (WPAN working group, established in March 1999), which shows its importance.
Comparatively speaking, Bluetooth system is more representative, which is developed according to the concept of WPAN. In fact, the concepts of Bluetooth and WPAN are complementary, and Bluetooth is the prototype of WPAN. Since Ericsson, IBM, Inter, Nokia and Toshiba were the original sponsors for the first time, they have attracted nearly 2,000 internationally influential companies to participate in it for more than 1 year. At the end of 1999, three American companies, Lucent, Microsoft and Motorola, like the above five companies, were the initiating organizations of Bluetooth, which made them stand out 3COM the competition with SWAP, IEEE802. 1 1 and other similar application standards, and their development prospects became clearer. In order to promote the development of Bluetooth, the standard of Bluetooth is non-patented. Bluetooth has become a new hotspot in the field of communication, and it is expected to become an international standard for small-scale wireless multimedia communication in the near future. In a word, wireless communication technology has a bright future.
2. Development of wireless communication technology in China.
At present, China is the focus of communication technology operators and equipment manufacturers all over the world, and everyone wants to occupy their own development space and market share in the China market. The development of mobile communication in China is very rapid, and the development trend of mobile communication in China has been concerned by the world. 1987165438+10, the first TACS analog cellular mobile communication system was officially opened in Guangdong, China, realizing the breakthrough of "zero" for mobile phone users. At the end of 1994, Guangdong took the lead in opening the GSM digital cellular mobile communication system. By 1995, five provinces and cities across the country had also opened the GSM mobile communication network. Up to now, GSM networks have been built in all provinces, autonomous regions and municipalities directly under the Central Government, realizing automatic temperature survey at home and abroad. At present, China is actively preparing for the commercial test of the third generation mobile communication in 2 1 early century.
Since 1987, the number of mobile phone users in China has increased rapidly, especially the GSM network is developing at an unexpected speed. This is mainly because GSM system has greater advantages than TACS system in technology and economy, and more importantly, China has introduced competition mechanism in the field of GSM operation, which has promoted the development of GSM network. China has more than 80 million mobile communication users, ranking second in the world.
In the past 10 years, China has also made gratifying progress in scientific research and equipment production in the field of mobile communication. Domestic switching systems, base stations, mobile phones and other mobile communication equipment have been put into production and put on the market one after another, and the development and research of the third generation mobile communication system is also in sync with the world. Thus, China wireless communication has achieved the first stage of success in operation and manufacturing.
3. Future trend of wireless communication technology.
Telecommunications technology in the 2 1 century is entering a critical turning point, and the next decade will be the most active period of technological development. The arrival of information society and the rise of IP technology are profoundly changing the face of telecommunication network and the development trend of future technology. The main development trends of wireless communication technology in the future are broadband, grouping, integration and personalization. The main features are as follows:
(1) Broadband is one of the important development directions of communication and information technology. With the further development of optical fiber transmission technology and high-permeability network nodes, the broadband of wired networks is being carried out worldwide, and the wireless communication technology is also evolving towards the broadband of wireless access. The wireless transmission rate will develop from 9.6Kbit/s in the second generation system to the highest rate of 2Mbit/s in the third generation mobile communication system.
(2) Convergence of core networks and diversification of access networks. In the future, the structural mode of information network will change to core network/access network. The grouping and broadband of the network make it possible to transmit all kinds of business information on the same core network. The integration of networks, the gradual opening of regulation and the need of market competition will further promote the integration of traditional telecommunication networks and emerging computer networks. Access network is the most potential part of communication information network. In the future, the network can access the core network through different access devices such as fixed access, mobile cellular access and wireless local loop access, so as to realize various services required by users. The technical integration of different services such as fixed communication and mobile communication, especially the advent of wireless application protocol (WAP), will greatly promote the development of wireless data services and further promote the integration of mobile services and IP services.
(3) Individualization of information is one of the main directions for the further development of information industry at the beginning of the next century. Mobile IP is an important technical means to realize information personalization in the future, and the realization of various IP applications and mobile IP technologies on mobile phones is gradually becoming one of the focuses of people's attention. The combination of mobile intelligent network technology and IP technology will further promote the global personal communication trend.
(4) The structure of mobile communication network is undergoing profound changes. With the formation of the dominant position of data services in the network, the trend of transition from the existing circuit-switched network to IP network is unstoppable. IP technology will become the core technology of the future network, and IP protocol will become the dominant communication protocol of telecommunication network. With the introduction of General Packet Radio Service (GPRS), users will send and receive data by end-to-end packet transmission, breaking the traditional data access connection. Based on IP networking, mobile backbone network began the practice of IP application.
4. The application of wireless communication technology in digital community.
The development of wireless communication technology provides a strong guarantee for the realization of digital community, and digital community provides a strong guarantee. Digital community is characterized by extensive and convenient information exchange. Whether in the laboratory, office or home, the application of computers and their peripherals is becoming more and more popular, and the equipment in the community is also controlled by computers. If the communication between them is still wired, it will bring great inconvenience to use. Bluetooth technology has established a wireless working environment and living environment for us. Bluetooth standard has established interface protocols with computers, Internet, PSTN, ISDN (Integrated Services Digital Network), LAN, WAN and xDSL(xDSL), and its goal is to establish connections with many international standards with a single Bluetooth standard. At present, the speed of 1mB/s can completely overcome these tasks. In the future, according to the development plan of IEEE802. 15, the speed can be increased to more than 20mB/s ... We can connect electronic equipment in the office and at home with wireless cables, even keyboards, mice and so on. We have a wireless service package, represented by portable computers and handheld computers, which are connected to other devices or networks in a wireless way, so that we have a mobile office.
With the rapid development of Internet and mobile communication, people's demand for various data sources and network services other than computers is increasing. Digital cameras, digital video cameras and other devices are equipped with Bluetooth system, which can not only avoid the inconvenience of using cables, but also avoid the trouble of memory overflow. Photographed photos or images can be sent back to the designated computer anytime and anywhere through mobile phones or other devices equipped with Bluetooth system. After PDA (Personal Digital Assistant) is equipped with Bluetooth system, it will be more convenient to receive, send e-mails and even browse the web by wireless means. The hardware circuit of Bluetooth can be miniaturized, which is very suitable for headphones. Headphones equipped with Bluetooth system can be wirelessly connected with mobile phones, and people can walk around and listen to music freely in a small area and hold conference calls in a large area. The characteristics of miniaturization, low power consumption and low cost have opened up almost unlimited space for the application of Bluetooth in people's daily life. For example, the radio electronic lock composed of Bluetooth has higher security and applicability than other non-contact electronic locks or ic locks, and various radio remote controllers (especially car anti-theft and remote control) have more powerful functions than infrared remote controllers, so it is more convenient to wirelessly transmit menus in two directions or call a waiter to provide specified services (such as adding tea and drinks) when dining in a restaurant. The sensor made of Bluetooth can monitor the change of refrigerator inventory at home at any time, so as to reflect the items needed by users at any time. If you connect to the internet again, you can realize online shopping.
The future information appliance will be based on Internet and home network, and realize two-way transmission through wireless connection. It is an information product with certain intelligence and 3C (computer, communication and consumer) integration. Digital mobile phones, home and office phones, small PBX and other telephone systems designed by Bluetooth technology have realized real personal communication. Bluetooth provides low-cost and low-power wireless access, which conforms to the development trend of modern communication technology and application and has great development potential in the fields of information appliances and mobile communication. Bluetooth technology has been popular all over the world in just two years since it was put forward. According to market research and forecast, the global sales of 1999 Bluetooth products are almost zero, and will soar to $36.7 million in 2000, $654.38+26 million in 2006 and $699 million in 2006. In 2002, the number of computer peripherals using Bluetooth technology will reach 65.438+0.5 billion, and the number of notebook computers using Bluetooth technology will reach 25 million. In 2003, more than 90% of the world's notebook computers will adopt Bluetooth technology, and in 2006, 670 million information appliances with Bluetooth technology will be launched worldwide.
Looking back on the development of wireless communication, the demand for mobility of personal communication and seamless coverage of multimedia integrated services will become more and more prominent. The electromagnetic "wireless fiber" whose frequency spectrum extends to millimeter wave and submillimeter wave, and even the wireless communication in the fields of laser and particle communication will have an increasingly broad activity stage and bright development prospects. The market is the driving force of development. Despite the rapid development of mobile communication and Internet in China, the penetration rate of mobile phone and Internet users in China is still very low. With a population of 654.38+0.2 billion in China, China has great development space in terms of network scale and capacity. At the same time, the formation of competitive situation urges operating enterprises to actively expand new businesses and applications, provide users with rich choices and meet users' diverse and multi-level needs. Therefore, the application development in mobile communication and Internet also has great development potential. Actively promote scientific and technological progress and technological innovation in the wireless field, and make positive contributions to realizing the strategy of rejuvenating the country through science and education, enhancing the comprehensive national strength of the Chinese nation and the development of the international community and all mankind under the environment of global informationization and economic globalization.