Design And Implementation Of An HF Adaptive Data Transmission System

HF communication has become an indispensable way of modern communication with its own unique advantages.In the communication between the two sides,how to establish efficient and stable communication link is always the difficulty of HF communication.In this thesis,Deep WALE waveform in MIL-STD-188-141 D WALE waveforms is introduced,and wideband automatic link establishing technology is discussed.Moreover,the specific PDUs are designed according to different requirements.In addition,the signals through HF channel will be faded,so how to fight with the fading has been the focus of HF communication.Aiming at this situation,an effective method is the diversity merging which is introduced in this thesis.Also,the eight channels receive combining system is successfully studied based on the original four channels receive combining system.An adaptive technology is adopted to the system,which means that the transmitter attempts to establish a link on eight frequency points,and the receiver selects the optimal frequency point for linking,that is,the multi-frequency detection technology in the Deep WALE waveform is applied to the frequency selection in the eight channels receive combining system.Firstly,the hardware platform about DSP+FPGA is introduced,the key modules used for the automatic link establishment system and diversity merging system are illustrated in this thesis.Meanwhile,the specific configuration is given according to the relevant requirements.Then,Deep WALE waveform is introduced in detail.And specific PDU is designed for specific functions according to the characteristics of waveforms,including link establishment,termination,confirmation,etc.These different protocol data units are used for channel evaluation,selective call,traffic negotiation,data and text message transmission and other functions.In addition,Deep WALE waveform is simulated and tested in MATLAB.The results meet the requirements of US military standard.Next,the diversity merging technique is discussed.The diversity merging technologies about time diversity,space diversity and frequency diversity are briefly introduced,and the related technologies used for the transmitter are given,such as encoding,interleaving,modulation,scrambling,etc.The techniques of synchronous capture and frequency offset estimation used for the receiver are also presented.The advantages and disadvantages of selective merging,equal gain merging and maximum ratio merging are analyzed and discussed,and the simulation comparison is carried out in MATLAB.By comparison,the maximum ratio merging is selected by the eight channels receive combining system.Finally,the eight channels receive combining system is tested on the hardware platform.The test results show that it meets the design requirements.