Design And Realization Of HF Fast Broadband ALE System

Because HF communication has the characteristics of long communication distance,equipment being simple and easy to maintenance,and strong anti-destroy capability,it has been widely used in military communications and emergency communications.With the development of short-wave communication technology,users have highly requirements for link establishment in short-wave communication.A multi-channel receiving fast broadband link establishment system is designed and realized in this thesis.Firstly,the hardware platform for the fast link establishment system has been introduced in this thesis.The core of the hardware platform is the "DSP + FPGA" information processing module.The main function of the FPGA is to capture the synchronization headers from the multi-channel data received by the RF unit roughly,DSP mainly completes the process of link establishment information and the realization of the entire link establishment process.The main work of this thesis is realized on the DSP.And the function and configuration information of some main module of DSP and the data transmission interface between DSP and FPGA have been mainly introduced.Secondly,the asynchronous link establishment protocol without time synchronization has been designed in this thesis.The link establishment protocol is designed for multi-channel receiving and broadband 12 KHz link establishment system and it resides on one channel group.The link establishment waveforms,protocol data units,link establishment flow,and link timing are described in detail.And then,several key technologies such as synchronization header acquisition,frequency offset estimation,service transmission bandwidth and rate selection,and CRC check in fast link establishment have been discussed in the thesis,and the software implementation process of these methods were given.Next,this fast broadband link system was tested and analyzed in the laboratory and actual channels,and the test results were given,the results show that the system still maintains a high probability of link establishment under poor channel conditions and meets the requirements of actual projects.Finally,a synchronous link establishment protocol that can scan multiple channel groups was introduced,and the protocol design flow was given.A method for replacing GPS to provide time synchronization for synchronous link establishment is discussed in detail,the method uses the short-wave timing signals issued by the national timing center to extract the synchronization time,simulation analysis about the synchronization time extraction and detection method is given.The actual test shows that this method can meet the requirements synchronization time accuracy for synchronous link establishment.