The development of wireless communication technology so far can be basically summarized into five stages.
The first stage: early stage of dedicated mobile communications. It was the first to develop a dedicated mobile communication system in the shortwave frequency band. Its most representative application is the vehicle-mounted radio system used by the Detroit police in the United States. The original version of the system used a frequency of 2MHz. Since this system appeared in the early stages of wireless communication technology, research and application are not very mature, so it is generally dedicated and characterized by a low operating frequency.
The second stage: public mobile communication services began to come out. During this period, public mobile communication services began to develop. The most representative technology used is the technology of Bell Labs in the United States. In 1946, this technology was used to establish the world’s first “urban system” public car telephone network in St. Louis. This system uses three channels, each channel is spaced 120KHz apart, and only uses simplex communication. This system is obviously upgraded from a dedicated system to a public system, using manual connection. The communication capacity of the entire network is small, but this is an improvement in the entire wireless communication technology.
The third stage: the stage of improvement and perfection of the mobile communication system. The most representative technology is the improved mobile phone system launched in the United States, which can automatically select wireless channels and realize automatic connection on the public telephone network. The contribution of this stage is to realize the improvement of mobile communication system from manual to automatic.
The fourth stage: the stage of sustained and rapid development of mobile communications. At the end of 1978, Bell Labs in the United States developed the Advanced Mobile Phone System (AMPS) using a cell system and built a cellular mobile communication network, thereby greatly increasing the system capacity. The main feature of this stage is that cellular mobile communication networks have entered the practical application stage and are developing rapidly around the world.
The fifth stage: Mobile communication technology enters the stage of maturity and rapid development. Mobile communication technology at this stage has developed very maturely and can be said to have developed like a fast-moving train. The first generation of mobile communication analog methods appeared in 1995, and the user’s voice was transmitted in the form of analog signals. The main representatives of this technology are AMPS in the United States and TACS in the United Kingdom.
Only two years after the first generation system appeared, the second generation of mobile communications immediately appeared using digital technologies such as Global System for Mobile Communications (GSM) and Code Division Multiple Access Cellular Mobile Communications System (CDMA), allowing mobile phones to access the Internet. Then the third generation of mobile communications appeared. This generation of mobile communications can connect us to the Internet, enable seamless roaming around the world, enable users to use mobile phones to process music, images, and videos, browse web pages, and achieve open-ended The degree of telephone conferencing facilitates the development of e-commerce activities. Taking a cursory look at the development history of mobile communications, we will find that starting from the commercialization of the first generation of analog mobile communications in the early 1980s, a new generation of mobile communications technology has appeared basically every 10 years, and the old generation of technology has retired. It took about 15 to 20 years. At present, the first generation mobile communication system has long withdrawn from the stage of history, and the second generation mobile communication system occupies the mainstream of the market. However, as users have higher and higher requirements for services, this will inevitably lead to the development of mobile communication systems in the direction of the Internet and the Internet of Things. This will make 3G technology more and more mature, and the fourth generation mobile communication technology will develop faster. , and standards for 5G mobile communication technology have even begun to emerge.
Keywords: Wireless DTU module