The development of wireless communication has gone through more than one hundred years. In this process, many new technologies have been produced, and at the same time, they have been continuously integrated with other technologies, so that a series of communication methods have emerged and been improved and developed to meet the growing social needs.
From the whole development process of radio communication, it is not difficult to see that wireless communication can be roughly divided into three important development stages: short-wave communication in the 1920s and 1930s, microwave relay communication (including satellite communication) in the 1950s and 1970s, and mobile communication from the 1980s to the present.
This paper describes the development trend of mobile communication technology, the fastest and most complex system at present.
By July of 20xx, the number of global mobile users has exceeded 5 billion, and this number is expected to exceed 6 billion this year.
The rapid development of mobile communication is mainly because it realizes the communication between objects that are not limited by any time and place.
From the point of view of equipment networking, mobile communication network can be regarded as an extension of wired communication network, which consists of wireless and wired parts.
The wireless part provides access to mobile user terminals, including the realization of most network functions such as data exchange, user management, roaming and authentication, or through fixed networks.
1. Development history of mobile communication
From the mid-1970s to the mid-1980s.
This is a period of vigorous development of mobile communication.
At the end of 1978, bell laboratory successfully developed the mobile phone system (AMPS) and built a cellular mobile communication network.
According to the development history of mobile communication, its development course and direction can be divided into three stages:
1) first generation analog cellular communication system
From the late 1970s to the mid-1980s, mobile communication technology developed rapidly.
At the end of 1978, bell laboratory successfully developed the Advanced Mobile Phone System (AMPS) and built a cellular mobile communication network, namely the first generation mobile phone network.
The first cellular system AMPS (Advanced Mobile Phone Service) became a reality in the United States in 1979.
Due to the limitation of transmission technology, the first generation of mobile phone users can't realize long-distance roaming, which means that mobile phone users can only realize mobile communication in a certain area. In addition, the system still has some fatal weaknesses, such as insufficient system capacity, incompatibility between systems, poor communication quality, weak confidentiality and inability to provide data transmission services. Therefore, the first generation of analog cellular mobile communication was eventually replaced by the second generation of digital cellular mobile communication.
However, networking technology is still applied in the next generation system.
2) The second generation digital cellular mobile communication system
In order to overcome the shortcomings of the first generation of analog cellular communication systems, digital cellular mobile communication systems were widely used from the mid-1980s to the early 20th century, and their representative technologies were GSM in Europe and CDMA in the United States, commonly known as 2G (Second Generation Digital Cellular Mobile Communication System).
The second generation digital cellular mobile communication system mainly adopts time division multiple access (TDMA) or narrowband code division multiple access (CDMA) technology.
The most representative TDMA series are pan-European GSM, American D-AMPS and Japanese PDC. Narrowband code division multiple access (N-CDMA) series is mainly based on IS-95 developed by Qualcomm, which is a widely used technology at present. Its application technical standard is IS-95, which was issued by the United States in 1993, and now it has become a commonly used international standard.
2. The characteristics of mobile communication
Mobile communication is a communication mode based on the mobile state of end users.
It has the following characteristics different from wired communication:
1) Because of the uncertainty of the user's location, it must use radio waves to transmit information with the base station in communication.
Because radio waves travel along a straight line, they will be influenced by mobile stations, obstacles, terrain and ground objects and spread multipath, which will seriously interfere with the quality of mobile communication.
2) Mobile communication works in a strong interference environment, including intermodulation interference, adjacent channel interference and co-frequency interference.
3) Limited communication skills.
As a resource, frequency must be arranged and allocated reasonably. In order to alleviate the contradiction between a large number of users and limited resources, in addition to developing new frequency bands, various measures have been taken to effectively use frequencies, such as increasing compressed frequency bands, narrowing channel spacing and multi-channel sharing, that is, adopting effective utilization technologies of spectrum and wireless channels;
4) Communication system is much more complicated than fixed network.
Because users move at any time and other reasons, communication systems need to have tracking technologies such as communication channel switching, frequency and power control, address registration, switching and roaming access according to signal strength.
This makes the signaling design of mobile communication system much more complicated than that of fixed network.
There are also special requirements for network access and billing methods;
5) The requirements for mobile stations are high.
The mobile station is in an unfixed position for a long time, and the external influence is unpredictable, which requires the mobile station to have strong adaptability.
In addition, it also requires stable and reliable performance, convenient carrying, small size, low power consumption and high and low temperature resistance.
At the same time, it should be as convenient as possible for users to operate, adapt to the development of new businesses and technologies, and meet the needs of different groups of people.
This brings great difficulties to the design and manufacture of mobile stations.
3 the development trend of mobile communication
Technological innovation is essentially to meet people's growing needs.
In the past few decades, mobile communication has made great progress in technology and business, and these changes have also greatly changed people's life and work style.
With the acceleration of global integration and the continuous improvement of people's living standards, such as the development of new technologies such as the Internet of Things, people will put forward more and higher requirements for future mobile communication technologies.
Although the digital cellular mobile communication technology is constantly improving, with the continuous expansion of the number of users and network scale, it can be predicted that in this rapidly growing market demand, frequency resources have become a bottleneck, the call quality is not satisfactory, and the transmission rate is not high, which can not really meet the needs of mobile multimedia and Internet of Things.
To sum up, we can generally foresee that the future mobile communication technology will be improved in the following directions: 1) With the improvement of the degree of data and grouping of network services, the mobile Internet will gradually take shape;
2) In order to solve the problem of frequency exhaustion, mobile communication will be applied to higher frequency bands, and the frequency utilization rate will be greatly improved;
3) With the continuous improvement of people's personalized needs, providing personalized services will become the trend of business development, so the intelligence and miniaturization of network equipment will also become inevitable;
4) Under the background of great convergence of information and communication technology, the convergence of mobile network and fixed network, mobile network and Internet has become inevitable, the convergence of network and service will become a trend, and the popularization of mobile Internet will also become inevitable;
5) With the further improvement of globalization, video mobile services will become more and more popular, and high speed, high quality and low cost are the next higher requirements for mobile services.
At present, the second generation digital cellular mobile communication technology is still used in most parts of the world, and the third generation mobile communication technology (3G) is gradually popularized. However, due to more demand, people have put forward the idea of the fourth generation mobile communication technology (4G).
The 4G standard is more powerful than the previous generation.
3. 1 Third Generation Digital Mobile Communication System
The third generation mobile digital communication system (3G) is a mobile communication system based on the second generation, mainly based on broadband CDMA technology, which can provide integrated voice and data services and mobile multimedia services at the same time. It is an advanced mobile communication system, which can completely solve the main shortcomings of the first and second generation mobile communication systems.
In order to adapt to the development of high-speed data and image telecommunications services in the field of mobile communication, and hope to unify the standards in the third generation system, ITU has made various efforts.
In May 2000, three 3G standards, W-CDMA, CDMA2000 and TD-SCDMA, were determined and written into the 3G technical guidance document International Mobile Telecommunication Plan 2000 (IMT-2000 for short), which was adopted by most countries at the wireless communication plenary meeting held by the International Telecommunication Union in Geneva on June 5438+1October 09, 2007.
Compared with the previous two generations of mobile communication, the third generation of digital mobile communication is a multimedia mobile communication that can cover the whole world.
It has two main characteristics different from the previous two generations of mobile communication:
1) can realize global roaming, making it possible to communicate with anyone anytime and anywhere.
In other words, every user has a personal communication number, and people can find you wherever the user goes in the world. Conversely, when you go anywhere in the world, you can easily communicate with domestic users or users from other countries, which is no different from domestic communication.
2) High-speed data transmission and broadband multimedia services can be realized.
In other words, the third generation mobile phone can not only make ordinary paging and calls, but also read newspapers, check information, download files and pictures online; Due to the improvement of bandwidth, the third generation mobile communication system can also transmit images and provide videophone services.
Judging from the situation in recent two years, with the intelligent development of terminal mobile phone equipment, 3G services are increasingly reflected in people's lives, such as WAP services, MMS services, location services, OTA download services and other emerging services have been greatly developed.
China spent three 3G licenses, namely TD-SCDMA China Mobile (China technology), WCDMA China Unicom (European technology) and CDMA2000 China Telecom (American technology).
With the increasing competitive pressure of operators, it can be predicted that Chinese consumers will enjoy better emerging 3G services and more favorable tariffs.
3.2 the fourth generation mobile communication technology
Although after years of research and development, the third generation mobile communication has encountered many problems in practical application, so people began to pin their hopes on the research of the fourth generation that appeared in advance.
So far, the technology of the fourth generation mobile communication (4G) is only a conceptual idea. People can call it broadband access and distribution network, wireless Internet technology or post-3G technology. In the definition of 4G, people can't give a standard for its technical parameters, international standards, network structure and even business content.
But its general outline has been recognized by the industry.
Looking ahead, we can see that 4G communication will have the following characteristics:
1) information transmission rate is faster.
The original intention of people to study 4G is to solve the problem of fast Internet access for mobile terminals. The realized 4G should have faster wireless communication speed in application.
According to the published data, the maximum data transmission rate of 4G exceeds 100Mbps, while that of 3G network is only 2Mbps.
2) wider network scope
In order to improve the transmission speed of information, the bandwidth required in 4G network is much higher than that in 3G network. It is estimated that the bandwidth of each channel will reach 100MHz, which is 20 times that of 3G.
3) Greater capacity
It is estimated that after 10 years, the amount of information people get every day will be at least 3-4 orders of magnitude higher than today, and the capacity of 3G will be far from meeting this growing business demand. Therefore, 4G will adopt new network technologies to greatly improve the capacity of the system, such as SDMA (Space Division Multiple Access) technology, to meet the demand for a large amount of information in the future.
4) strong compatibility
In order to make 4G communication accepted by people as soon as possible, 4G should consider making an easy transition to with the least investment.
Therefore, 4G will adopt the characteristics of large area coverage, mutual compatibility of various networks, and easy upgrade and transition of terminals and networks.
Realize true global roaming.
5) Higher intelligence
The 4G system is smarter.
In the aspect of network system function, it can allocate resources adaptively, handle changing business flows and adapt to different channel environments; The design and operation of its user terminal will also be more intelligent. It is no longer a traditional mobile phone. It can be regarded as a portable TV, which reminds its owner what to do or not to do at the moment by integrating various factors.
It will be able to realize many functions that people can't imagine now.
6) Higher quality multimedia communication can be realized.
4G communication will greatly improve the shortcomings of existing 3G multimedia communication, such as poor quality and low data transmission rate, and provide feasible solutions for high-speed and high-quality transmission of various multimedia streams.
7) Communication charges are cheaper.
Due to the solution of compatibility problems and the realization of smooth transition, the communication deployment of 4G will be much easier and faster than other technologies.
This can effectively reduce operating costs, and daytime competition will make people enjoy cheaper communication charges.
For today's people, the future of 4G communication is really mysterious, but the development of technology will make 4G communication a reality.
Realize the functions that 3G can't achieve, and realize real personal communication.
4 conclusion
With the advent of the information age, people rely more and more on the convenience brought by mobile communication.
It is conceivable that in a few years, we will usher in a truly omni-directional, broadband and multi-functional communication mode, which can meet people's multi-angle and all-round needs anytime and anywhere.
refer to
Wang Wenbo. Principle and application of mobile communication [M]. Beijing University of Posts and Telecommunications Press, 2004.
[2] Chang Yonghong. The third generation mobile communication system and technology [M]. Beijing: People's Posts and Telecommunications Publishing House, 2004.
Xie, et al. The fourth generation mobile communication technology based on time division duplex [M]. Electronic Industry Press, 2005.