Design Of A Data Link Layer Protocol For HF Communication System

Shortwave communication is a communication technology that can achieve long-distance transmission without the need for additional relay stations,which greatly reduces the cost of investment and maintenance costs,and has an indispensable position in the communication field.The research content of this article is based on the laboratory research and development project "new short-wave intelligent transceiver system".In the system's original technology,further research on the protocol of the data link layer is carried out,the purpose is to design and implement the broadcast module required by the user,improve the efficiency and security of data transmission.The main contents of this paper are as follows:1.Introduce the current hardware composition and overall software design of the new shortwave intelligent transceiver system,and analyze the functions of each software module.On this basis,the explanation of the added broadcast module,improved adaptive variable speed technology,and added data protection module were explained.2.According to user needs,add a broadcast module on the basis of the original system.Through studying the theory of broadcasting,the framework of the broadcasting process is determined,including link establishment and data transmission;in order to improve the efficiency of building chains,an immediate blind connection protocol is designed and implemented;a reliable broadcasting data transmission protocol is designed and a pair of Multi-mode transmission method;at the same time,a file pre-processing protocol that unifies different file formats and a circular buffer that can cache large files are designed;in order to identify the occurrence of abnormal conditions in the process of data transmission,the parity check technology is designed.3.In order to improve the efficiency of data transmission,the original adaptive variable speed technology of the system is improved.By studying the relationship between channel score and rate,the initial rate selection scheme is designed.Combined with the application of the system,an adaptive transmission technology based on error feedback is designed.Through simulation experiments,it is verified that the throughput of this adaptive variable speed technology for transmission is higher than the original variable speed technology,which improves the data transmission efficiency.4.In order to prevent external eavesdropping and interference when transmitting data,a link protection protocol is designed.After clarifying the requirements of the protocol design,the AES encryption algorithm was selected as the core algorithm of the link protection protocol,and a cryptographic feedback mode encryption algorithm was designed.In order to effectively resist active password cracking attacks and passive retransmission attacks,encryption seeds are designed from the three elements of time,frequency and station number to ensure the security of information.Through the indoor test platforms,the above designed protocols are tested to verify the correctness and effectiveness of the adaptive variable speed technology based on feedback,the broadcast protocol,and the link protection protocol.