The first stage, from 1920s to 1940s, is an early development stage. During this period, firstly, a special mobile communication system was developed in several short-wave frequency bands, and its representative was the car radio system used by Detroit police in the United States. The working frequency of the system is 2MHz, which was increased to 30 ~ 40 MHz in 1940s. It can be considered that this stage is the primary stage of modern mobile communication, characterized by the development of dedicated systems and low working frequency.
The second stage is from the mid-1940s to the early 1960s. During this period, public mobile communication services began to come out. From 65438 to 0946, according to the plan of the Federal Communications Commission (FCC), Bell System established the world's first bus telephone network in St. Louis, which was called "urban system". At that time, three channels were used with an interval of 120kHz, and the communication mode was simplex. Subsequently, West Germany (1950), France (1956), Britain (1959) and other countries successively developed public mobile phone systems. Bell Laboratories completed the connection of the manual exchange system. This stage is characterized by the transition from private mobile network to public mobile network, and the connection mode is manual, so the network capacity is small.
The third stage is from the mid-1960s to the mid-1970s. During this period, the United States introduced an improved mobile phone system (1MTS), which used 150MHz and 450MHz frequency bands, adopted a large-area system and small and medium capacity, and realized automatic selection of wireless channels and automatic connection with public telephone networks. Germany has also launched the B-net with the same technical level. It can be said that this stage is the improvement and perfection stage of mobile communication system, which is characterized by adopting large-area system, medium and small capacity and using 450MHz frequency band to realize automatic frequency selection and automatic connection.
The fourth stage is from the middle of 1970s to the middle of 1980s. This is a period of vigorous development of mobile communication. At the end of 1978, Bell Laboratories successfully developed the Advanced Mobile Phone System (AMPS) and built a cellular mobile communication network, which greatly improved the system capacity. 1983, first put into commercial use in Chicago. In February of the same year, it was also opened in Washington. After that, the service area in the United States gradually expanded. By March 1985, it has expanded to 47 regions, with about 654.38+million mobile users. Other industrialized countries have also developed cellular public mobile communication networks. 1979, Japan introduced the 800MHz car telephone system (HAMTS) and put it into commercial use in Tokyo, Dajiao and Kobe. West Germany completed the C network at 1984, with a frequency band of 450MHz. 1985, Britain developed the full address communication system (TACS), which was first put into use in London and then covered the whole country, with a frequency band of 900MHz. France developed the 450 system. Canada introduced the 450MHz mobile phone system MTS, 1980, and Sweden and other four Nordic countries developed and put into use the NMT—450 mobile communication network with a frequency band of 450MHz.
The characteristic of this stage is that the cellular mobile communication network has become a practical system and developed rapidly in the world. The reason for the rapid development of mobile communication is not only the main driving force for the rapid growth of user demand, but also the conditions provided by several aspects of technological progress. First of all, great progress has been made in microelectronics technology during this period, which makes it possible to miniaturize and miniaturize communication equipment, and various portable radios are constantly introduced. Secondly, a new mobile communication system is proposed and formed. With the increase of the number of users, the capacity provided by the regional system will soon be saturated, so it is necessary to explore new systems. The most important breakthrough in this respect is the concept of cellular network put forward by Bell Laboratories in 1970s. Cellular network, the so-called cell system, greatly improves the system capacity because of frequency reuse. It can be said that the concept of cellular really solves the contradiction between large capacity and limited frequency resources required by public mobile communication systems. The third progress is that with the development of large-scale integrated circuits, the maturity of microprocessor technology and the rapid development of computer technology, it provides technical means for the management and control of large-scale communication networks.
The fifth stage began in the mid-1980s. This is the development and maturity of digital mobile communication system.
The first generation cellular mobile communication network represented by AMPS and TACS is an analog system. Although the analog cellular network has achieved great success, it also exposes some problems. For example, the spectrum utilization rate is low, the mobile equipment is complex, the cost is expensive, the service type is limited, and the call is easy to be eavesdropped. The main problem is that its capacity can no longer meet the growing demand of mobile users. The solution to these problems is to develop a new generation of digital cellular mobile communication system. Digital wireless transmission has high spectrum utilization rate, which can greatly improve the system capacity. In addition, digital networks can provide voice and data services and are compatible with ISDN. In fact, as early as the late 1970s, when analog cellular systems were still in the development stage, some developed countries began to study digital cellular mobile communication systems. By the mid-1980s, the Pan-European Digital Mobile Communication Network (GSM) system was first introduced in Europe. Subsequently, the United States and Japan also developed their own digital mobile communication systems. The pan-European network GSM was put into commercial use in July, and it is expected that 199 1995 will cover major European cities, airports and highways. It can be said that digital cellular mobile communication will be in a period of great development in the next decade, and it may become the main system of land public mobile communication.
Like the development of other modern technologies, the development of mobile communication technology is also accelerating. At the moment when digital cellular network has just entered the practical stage and is in the ascendant, the discussion about future mobile communication has been like a vegetable field. Various schemes have been introduced, the most popular of which is the so-called personal mobile communication network. There are different explanations about the concept and structure of this system. But one thing is certain, that is, the future mobile communication system will provide global quality services and truly realize the highest goal of mobile communication, that is, to provide communication services to anyone at any time and any place.