Data link system and wireless digital communication system 1
This paper introduces the basic features of data link system, and discusses the differences and connections between data link and wireless digital communication system.
This paper analyzes the different application modes and functions of data link and wireless digital communication system from the perspective of practical application.
Keywords: data link; Wireless communication system
Basic characteristics of 1 data link system
1. 1 information format
Data link generally has a set of relatively complete message standards, which describe the parameters of static and dynamic information including command and control, reconnaissance and monitoring, platform coordination and joint action.
The formatting of information content refers to the fixed or variable length information coding, and the members of the data link network have the same understanding and interpretation of the semantics of the coding, so as to enjoy the information.
1.2 integration of transmission network
The data link mainly adopts wireless transmission channel. According to the characteristics of high mobility and flexibility of some application platforms, after comprehensive digital technology processing, with frequency hopping, spread spectrum, burst and other communication methods and encryption means, it has anti-interference and confidentiality functions.
Sharing transmission information resources on demand is the key point in the process of data link networking. Each network node can not only receive and share the information sent by other member nodes in the network, but also allocate the total information transmission bandwidth and transmission time according to the priority of real-time information.
1.3 Diversification of media
Generally, the data link can adopt various transmission media and modes to meet the different information exchange requirements of various application platforms, including point-to-point single link transmission, point-to-multipoint and multipoint-to-multipoint network transmission, and the network structure and communication protocol can take various forms.
The data link can adopt short wave communication, ultrashort wave communication, microwave communication, satellite communication and wired channels, or combined channels to transmit information to adapt to different application environments and requirements.
1.4 link object intelligence
Data link has a strong digital ability and intelligent level, and the linked objects undertake important functions such as information collection, processing and transmission. They form close ties through data link to realize the automatic flow and processing of information, so as to better complete the task.
Close linking is mainly reflected in two aspects: first, the information resources sharing relationship is formed between the linked objects in the data chain; The second is to integrate the internal functional unit information of each linked object.
1.5 real-time information exchange
The real-time transmission of information in data link is designed by various technologies: first, the design always grasps the reliability and stability of transmission and abides by the principle of real-time; The second is to adopt a relatively fixed network structure and a fast information transmission path instead of a complex routing scheme; Thirdly, choose efficient and practical handover protocol, and give priority to the limited wireless channel resources to the information with high transmission level; Fourthly, considering the transmission characteristics of the channel, the signal waveform, communication control protocol, networking mode and message standard are optimized as a whole.
2 the relationship between data link system and wireless digital communication system
The important technical basis of data link includes wireless digital communication technology, which are not completely equivalent.
Generally, data link should complete data transmission function, and at the same time, it should process data and extract information.
Moreover, the networking mode of data link is closely related to the application, and the application system can adjust the network configuration and mode to match it according to the situation.
The main function of wireless digital communication is only to transparently transmit data from the sender to the receiver according to certain requirements, and usually only completes the bearer task, regardless of the information represented by the transmitted data.
2. 1 has different correlation with application requirements.
The design of data link network is to decide what data each specific terminal can access, transmit messages and relay according to specific tasks.
According to the task, the network design scheme of data link is determined, and a design configuration is selected from the pre-planned network library and loaded on the terminal during initialization.
The networking configuration of data link directly depends on the tasks, participating units and use areas currently faced.
The practical application of data link is directly restricted by the command and control relationship, platform system control requirements, information provision methods and other factors, and is highly related to application requirements.
However, the configuration and application of wireless digital communication system have relatively low correlation with these factors and are not closely related to application requirements.
2.2 Different purposes in actual use
Data link is used to improve command and control, situational awareness and platform collaboration, so as to realize synchronous control of the platform and improve the real-time application of the platform.
Wireless digital communication system is used to improve data transmission capacity and achieve the purpose of data transmission. Wireless digital communication technology is one of the main technical foundations of data link.
2.3 Different information transmission requirements
The data link transmits the real-time information needed by the application unit, and the data should be reasonably integrated and processed to extract valuable information; Wireless digital communication is generally transparent transmission, generally to ensure the quality of data transmission, and does not identify and process the information content contained in the data.
In addition, wireless communication systems generally do not consider the relationship between users' absolute time reference and spatial position, and their relative time synchronization solves the problem of transmission accuracy.
2.4 The specific methods adopted are different.
Can the data link be directly linked with the command and control system, sensors and platforms? One machine, one machine? A way to exchange information, which is commonly used in wireless digital communication systems? A person, a machine, the way a person sends information.
Wireless digital communication terminals are usually plug and play, and the communication network will not be replaced after being configured once.
However, the use of data link devices is highly targeted. Before each action, a more complex data link network planning should be carried out according to the current task requirements, and the data link network structure and resource planning must be optimally matched with this task.
3 Conclusion
Wireless digital communication system is to solve the universal problem of various users and information transmission, and data link is to complete the real-time information exchange task when users use it.
Wireless digital communication system involves transmission channels, transmission procedures and information exchange, but does not care about information content, which can be vividly compared to container transportation in commodity circulation.
The requirements of data link are much stricter, involving not only these contents, but also information format, information content, linked objects, real-time performance and so on.
[References]
[1] Luo Guangming. Data link [M]. National Defense Industry Press, 2008.07.
Data error correction method in digital communication system II
Communication system mainly includes digital communication system and analog communication system.
At present, most communication systems rely on computers for communication, because computers have strong data processing and analysis capabilities, and the process of transmitting data through computers is communication.
However, no matter what kind of communication mode, the reliability of the communication system is very high.
At present, the scale and level of China's communication system is comparable to that of the international communication system, but there are still some problems in the reliability of data transmission in the communication system, mainly because the receiver can find and correct the wrong information caused by external factors. This system is called error control system.
The purpose of this paper is to study the data error correction method in digital communication system.
At the same time, the author also talks about how to control the bit error rate in the process of telegraph transmission and processing in the maintenance of civil aviation automatic relay system.
Digital communication; Transmission; Data coding; correct an error
There are many ways and methods of data error correction in digital communication system, including improving the power of transmitted signal, improving the signal-to-noise ratio of received signal, and adopting coding, all of which are methods of data error correction in digital communication system, and the conditions for using these two methods are limited.
Its effect is often limited by various conditions, and error control coding technology has been widely used in recent years. Using information coding to improve the transmission power can effectively suppress the interference of the noise signal at the receiving end, so as to extract and recover the transmission signal you need from the noise signal more effectively.
Improving the transmission signal power is equivalent to error control coding.
1. Data error correction method in digital communication system
There will inevitably be some biased information in the data transmission process in the communication system, which requires the system itself to have the ability to find and correct the wrong information to ensure the reliability of the data in the transmission process and control the error within the minimum acceptable range.
Error control methods can be divided into two types, one is feedback error correction, the other is forward error correction, and a hybrid error correction is derived from these two types.
1, feedback error correction.
In data transmission, the receiver encodes and checks the error of the received signal to determine whether there is an error in each unit frame of data during transmission. When correcting wrong coding, feedback retransmission is generally used to check.
In this way, the sender can find some codes with transmission errors to a certain extent, and re-encode and transmit these codes, adding a small number of supervision symbols, while the receiver checks these coded information according to the laws of these codes. When the wrong code is found, it will send a signal to the sender for retransmission.
After receiving the signal, the sender retransmits the part of the information with transmission error until the information is correct.
The found error code does not necessarily know the specific location, only one or several errors are known.
2. Forward error correction.
Forward error correction (FEC) is a complex coding method, which can correct some wrong information generated in the process of data transmission during decoding, so that the receiver can not only find the wrong transmission information, but also correct the wrong information.
This method does not need repeated feedback information or retransmission information. Although the equipment for error correction is complex, the information with tight transmission time and no long delay is very important.
3. Mixed error correction.
The hybrid error correction method is that the automatic error correction of the receiver can not correct the information with serious errors, which is beyond the ability of self-correction. It is necessary to send the error information back to the sender and ask the sender to resend it.
This method is a mixture of feedback error correction and forward error correction.
Second, how does the civil aviation automatic relay system control the error code in telegraph transmission?
Digital communication is widely used in various fields. In the era of big data, the civil aviation telegraph network serves the safe flight of civil aviation passenger planes and a wide variety of general-purpose aircraft, and the number of various business telegrams has surged. Business telegrams such as navigation information, flight dynamics, weather situation and weather forecast should be transmitted to each other in real time at civil aviation airports and air force airports all over the country through the civil aviation automatic telegraph network, so as to share information. The reliability and accuracy of transmission are extremely important.
At present, small and medium-sized airports use automatic transponders produced by domestic manufacturers, which are connected to the higher-level automatic transponders through wired lines and enter the civil aviation telegraph network.
First of all, the interference in the transmission process is effectively reduced by using optical fiber lines with strong anti-interference. Secondly, the increasingly mature automatic repeater used in small and medium-sized airports has a great guarantee in reliability.
At present, the server of automatic forwarding system usually adopts industrial computer with stable performance, and the fault-tolerant structure of dual-machine hot standby makes the system highly reliable.
When the automatic forwarding system works normally, after the basic work such as channel configuration and routing is completed, the system provides line alarm and timing detection functions, which can monitor the line condition.
In particular, monitoring personnel should pay attention to the fact that civil aviation telegrams have a fixed format. The system can give warning information by making judgments such as grade error, power generation address error, routing error and time group error in the title. However, once individual error codes appear in the message, the system can't distinguish where there are errors, and the message containing the wrong characters continues to be automatically processed and forwarded, which is where the automatic forwarding system can't correct errors.
Therefore, in order to control the bit error rate in the transmission of aviation fixed telegrams at a low level, the most basic conditions are that the lines are not disturbed and the relay system is normal.
Three. Concluding remarks
This paper studies the data method in digital communication system, and introduces the advantages and functions of error control system in modern communication. It is a reasonable method to effectively solve data transmission errors in modern communication systems. It can find out the wrong information and correct it, so as to ensure the efficiency and reliability of information in the transmission process and complete the effective transmission of information.
Take the exam and contribute.
[1] Green Ling Bo; Lu Rui; Zheng Min; Teng Qizhi; He xiaohai. Hierarchical distributed video coding based on iterative decoding algorithm [a]; Proceedings of the 5th 15 National Conference on Image Graphics [c]; 20 10 year
[2] He Yejun; Zhu Guangxi. A new parallel iterative decoding algorithm for Turbo product codes [a]: Progress in modern communication theory and signal processing ―― Proceedings of the 2003 annual conference on communication theory and signal processing [c]: In 2003
Application and development of digital communication system in hospital 3
Abstract: Digital communication system is widely used in hospitals. It has gradually entered more patient-centered applications from the simple office telephone, and has become an important management tool for hospitals.
Based on this background, this paper briefly expounds the concept of digital communication system, and emphatically introduces the application and development of digital communication system in hospitals.
Keywords: digital communication system; Hospital; develop
With the progress of social economy, people's living standards are constantly improving, and the requirements for medical services are getting higher and higher.
The important means to improve the service quality to meet people's needs is the development of digital communication system, which has been widely used in hospitals, such as mobile collaborative service for medical staff and the application of call centers.