What Is a Radiotelephone?

Mobile communication technology can be said to have been born since the invention of radio communication. In 1897, MG Marconi's wireless communication test was conducted between a fixed station and a tugboat at a distance of 18 nautical miles. The development of modern mobile communication technology began in the 1920s, and roughly experienced five development stages. 35 years ago, no one could imagine a day when everyone had a phone connected to this world. Nowadays, people can communicate through mobile phones, and smartphones are more like a small computer that they carry with them. After wireless network access through mobile communication networks such as 3G, personal information management and stock, news, weather, and transportation can be conveniently accessed , Product information, application downloads, music image downloads, etc.

Radiotelephone Phase I

From the 1920s to the 1940s, it was an early stage of development.

During this period, a dedicated mobile communication system was first developed in several short-wave frequency bands, the representative of which is the on-board radio system used by the Detroit police in the United States. The operating frequency of this system is 2MHz, and it will be increased to 30-40MHz by the 1940s. It can be considered that this stage is the initial stage of modern mobile communication, which is characterized by the development of dedicated systems and lower operating frequencies.

In October 1946, Bell Telephone Company launched a car radio telephone service

Radiotelephone Phase II

From the mid 1940s to the early 1960s.

During this period, public mobile communication services began to come out. In 1946, under the plan of the Federal Communications Commission (FCC), Bell System established the world's first public car telephone network in St. Louis, called the "Urban System." At that time, three channels were used, with an interval of 120 kHz, and the communication method was simplex. Subsequently, countries such as West Germany (1950), France (1956), and the United Kingdom (1959) successively developed public mobile phone systems. Bell Labs in the United States completed the continuation of the manual exchange system. This stage is characterized by the transition from a private mobile network to a public mobile network. The connection method is manual and the capacity of the network is small.

Radiotelephone Phase III

From the mid-1960s to the mid-1970s.

During this period, the United States introduced the Improved Mobile Phone System (IMTS), which uses the 150MHz and 450MHz frequency bands, adopts a large-area system, and has a small and medium capacity. It has automatically selected wireless channels and can automatically connect to the public telephone network. Germany has also launched the B network with the same technical level. It can be said that this stage is a stage of improvement and improvement of the mobile communication system, which is characterized by the use of large-area system, small and medium capacity, and the use of 450MHz frequency band to achieve automatic frequency selection and automatic connection.

Radiotelephone Phase 4

From the mid-1970s to the mid-1980s. This is a period of booming mobile communications.

At the end of 1978, Bell Labs in the United States successfully developed an advanced mobile phone system (AMPS) and built a cellular mobile communication network, which greatly increased the system capacity. This phase is called 1G (the first generation of mobile communication technology), and it mainly uses analog technology and frequency division multiple access (FDMA) technology. Nordic Mobile Phone (NMT) is one such standard used in Nordic countries, Eastern Europe, and Russia. Others include the Advanced Mobile Phone System (AMPS) in the United States, the Total Access Communication System (TACS) in the United Kingdom, and JTAGS in Japan, C-Netz in West Germany, Radiocom 2000 in France, and RTMI in Italy.

This stage is characterized by the cellular mobile communication network becoming a practical system and rapidly developing around the world. The main reason for the great development of mobile communications is that, in addition to the rapid increase in user requirements, there are several conditions for technological progress. First of all, microelectronic technology has made great progress in this period, which has made it possible to miniaturize and miniaturize communication equipment, and various portable radios have been continuously introduced. Secondly, a new mobile communication system was proposed and formed. With the increase in the number of users, the capacity provided by the district system is quickly saturated, which requires the exploration of a new system. The most important breakthrough in this regard is the concept of the cellular network proposed by Bell Labs in the 1970s, which resolved the contradiction between the large capacity of public mobile communication systems and the limited frequency resources. The third aspect is that with the development of large-scale integrated circuits, the microprocessor technology has become increasingly mature and the computer technology has developed rapidly, thus providing technical means for the management and control of large-scale communication networks. Although the first-generation mobile communication analog cellular network represented by AMPS and TACS has achieved great success, it also exposed some problems, such as limited capacity, too many formats, incompatible with each other, low voice quality, and inability to provide data services. , Can not provide automatic roaming, low spectrum utilization, complex mobile devices, expensive, and easy to eavesdrop on calls, etc., the main problem is that its capacity can no longer meet the growing needs of mobile users.

The world's first mobile phone, the Motorola DynaTAC 8000X, weighs 2 pounds, talks for half an hour and sells for $ 3,995.

Radiotelephone Phase 5

Since the mid-1980s. This is a period of development and maturity of digital mobile communication systems. This stage can be further divided into 2G, 2.5G, 3G, 4G and so on.

2G :

2G is the abbreviation of the second generation mobile phone communication technical specifications, which are generally defined as digital voice transmission technology as the core, and cannot directly transmit information such as e-mail, software, etc .; it only has phone calls and some mobile phone communication technical specifications such as time and date transmission. However, short message service (SMS) can be implemented in some 2G specifications. The main use is digital time division multiple access (TDMA) technology and code division multiple access (CDMA) technology, which corresponds to the two main systems of the world are GSM and CDMA.

2.5G :

2.5G is a connecting technology that moves from 2G to 3G. Because 3G is a huge project, 2.5G mobile phones involve many layers and are complex. It is impossible to connect from 2G to 3G at once, so the introduction 2.5G between 2G and 3G. HSCSD, WAP, EDGE, Bluetooth, EPOC and other technologies are all 2.5G technologies. 2.5G function is usually related to GPRS technology, which is a transition technology based on GSM. The introduction of GPRS marks the most significant step in the development history of GSM. GPRS provides a connection between mobile users and data networks, and provides mobile users with high-speed wireless IP and X.25 packet data access services. . . Compared with 2G services, 2.5G wireless technology can provide higher speeds and more functions.

3G

3G is the abbreviation of 3Generation in English, which refers to the third generation mobile communication technology that supports high-speed data transmission. Compared with the first-generation and second-generation mobile communication technologies represented by analog technology in the past, 3G will have a wider bandwidth, with a minimum transmission speed of 384K, a maximum of 2M, and a bandwidth of more than 5MHz. Not only can transmit voice, but also data, so as to provide fast and convenient wireless applications, such as wireless access to the Internet. The ability to achieve high-speed data transmission and broadband multimedia services is another major feature of third-generation mobile communications. There are four standards for the first 3G: CDMA2000, WCDMA, TD-SCDMA, and WiMAX. The third generation mobile communication network can combine high-speed mobile access and Internet Protocol-based services to improve the efficiency of wireless frequency utilization. Provide global coverage, including satellites, and enable seamless connectivity for wired and wireless, and services between different wireless networks. Meet the requirements of multimedia services, so as to provide users with more economical and richer wireless communication services.

3G smartphone

Compared with the first generation of analog mobile phones (1G) and the second generation of digital mobile phones (2G) such as GSM and TDMA, the third generation of mobile phones generally refers to a new generation of mobile communication systems combining wireless communications with multimedia communications such as the Internet . It is a terminal device based on mobile Internet technology. The 3G mobile phone is a product of the integration of the communications industry and the calculator industry. Compared with previous mobile phones, the difference is too great, so more and more people are beginning to call this new Mobile communication products are "personal communication terminals". Even the most layman in the communication industry can easily judge whether a mobile phone is a "third generation" from the appearance: the third generation mobile phone has a large color display and is often touch-based. 3G mobile phones can perform high-quality daily communications, as well as multimedia communications. Users can write, draw directly on the touch display of a 3G phone and transfer it to another phone, which may take less than a second. Of course, you can also transfer this information to a computer, or download some information from the computer; users can use the 3G mobile phone to directly access the Internet, check email or browse the web; there will be many models of 3G mobile phones with cameras, which Will allow users to use their mobile phones for computer meetings and even replace digital cameras.

4G

4G is an abbreviation for the fourth generation of mobile communication and its technology. It is a technology product that integrates 3G and WLAN and can transmit high-quality video images, and the image transmission quality is comparable to that of high-definition television. The 4G system can download at 100Mbps, which is 2,000 times faster than dial-up. The upload speed can also reach 20Mbps, and it can meet the requirements of almost all users for wireless services. In terms of prices that users are most concerned about, 4G is on par with fixed broadband networks in terms of price, and the billing method is more flexible, and users can fully determine the services they need based on their own needs. In addition, 4G can be deployed where DSL and cable modems are not covered, and then extended to the entire area. Obviously, 4G has incomparable advantages.

While LTE (Long Term Evolution) and WiMax are vigorously promoted in the global telecommunications industry, the former (LTE) is also the most powerful 4G mobile communication leading technology. IBM data shows that 67% of operators are considering using LTE because Their main source of future markets. The above news also confirmed this statement of IBM. Only 8% of operators are considering using WiMAX. Although WiMax can provide its customers with the fastest transmission network on the market, it is still not a competitor to LTE technology. The LTE (Long Term Evolution, Long Term Evolution) project is an evolution of 3G. It improves and enhances 3G's air access technology, and adopts OFDM and MIMO as its wireless network evolution standards. The main feature is that it can provide a peak rate of 100Mbit / s and 50Mbit / s in the uplink with a bandwidth of 20MHz. Compared with 3G networks, it greatly increases the capacity of the cell and greatly reduces the network delay. 5ms, the transition time of the control plane from the sleep state to the startup state is less than 50ms, and the transition time from the resident state to the startup state is less than 100ms.

4G is a combination of 3G and WLAN, and can transmit high-quality video images. Its image transmission quality is comparable to that of high-definition television. The 4G system can download at 100Mbps, which is 2,000 times faster than dial-up. The upload speed can also reach 20Mbps, and it can meet the requirements of almost all users for wireless services. In terms of prices that users are most concerned about, 4G is on par with fixed broadband networks in terms of price, and the billing method is more flexible, and users can fully determine the services they need based on their own needs. In addition, 4G can be deployed where DSL and cable modems are not covered, and then extended to the entire area. Obviously, 4G has incomparable advantages.

4G system network structure and its key technologies

The network structure of a 4G mobile system can be divided into three layers: a physical network layer, an intermediate environment layer, and an application network layer. The physical network layer provides access and routing functions, which are completed by a combination of wireless and core networks. The functions of the middle environment layer include QoS mapping, address translation, and integrity management. The interface between the physical network layer and the middle environment layer and its application environment is open. It makes it easier to develop and provide new applications and services, provides seamless high-data-rate wireless services, and runs on multiple frequency band. This service can adapt to multiple wireless standards and multi-mode terminal capabilities, and provides a wide range of services across multiple operators and services. The key technologies of mobile communication systems include channel transmission; high-speed anti-interference high-speed access technology, modulation, and information transmission technology; high-performance, miniaturized, and low-cost adaptive array smart antennas; large-capacity, low-cost wireless interfaces and optical Interfaces; system management resources; software radio, network structure protocols, etc. Mobile communication systems are mainly based on Orthogonal Frequency Division Multiplexing (OFDM). The characteristics of OFDM technology are highly scalable network structure, good anti-noise performance and anti-multichannel interference ability, can provide higher quality (higher speed, lower delay) services and better performance prices than previous wireless data technologies Than, can provide better solutions for 4G wireless networks. For example, wireless area loop (WLL), digital audio broadcasting (DAB), etc., will use OFDM technology. 4G mobile communications provide a technical response to the demands of accelerating growth of wideband wireless connections, guaranteeing seamless services to multiple wireless systems and networks that span the public and private, indoor and outdoor. By providing users with the best services for the most suitable available networks, they can cope with the expected growth of Internet-based communications, add new frequency bands, expand the spectrum resources, provide different types of communication interfaces, and use routing technologies as the mainstay. To develop a hardware architecture based on the Fourier transform to implement a network architecture. Mobile communication will develop towards data, high speed, broadband, and higher frequency bands. Mobile data and mobile IP will become the mainstream services of mobile networks in the future.

Related history

The wireless telephone was a major invention of the 20th century. Although radio communication was invented in 1895, radiotelephones only appeared after the vacuum triode was invented in the early 20th century.

Transatlantic radiotelephone communications were successfully implemented for the first time in 1915; commercial radiotelephones were opened between the United States and Britain in 1927. At that time, transoceanic radiotelephone communications used the characteristics of short-wave radio waves to refract from the ionosphere and return to the ground. Ultrashort waves were discovered in the 1930s and microwaves were discovered in the 1940s. Neither ultrashort waves nor microwaves can be reflected from the ionosphere. They have the property of rectilinear propagation and can pass through the ionosphere; they can only propagate on the ground at line-of-sight distances. People use this characteristic to develop multiple wireless relay communications. Ultra-shortwave relay communication can transmit telephones under 30 channels; microwave relay communication can transmit thousands of telephones, and can also be used to transmit color television. The so-called relay communication is to set up a relay station in the line-of-sight range (about 50 kilometers in the ground plain area) to receive and forward. The longer the communication distance, the more relay stations are set up. ^[2]