Design And Implementation Of Fast Automatic Link Establishment System In HF Voice-Bandwidth

HF communication is of high anti-destruction ability,as it is the only long-distance communication that does not rely on any man-made facilities as the intermediate hub.Thus,it still plays an irreplaceable position in military,emergency,disaster relief and other fields.With the occurrence of MIL-STD-188-141 A of the US Military standard,the automatic link establishment technology about HF communication is developed rapidly.Moreover,the present of MIL-STD-188-141 B of the US Military standard makes the automatic link establishment technology more mature.A fast automatic link establishment system of HF voice-bandwidth is designed and implemented in this thesis.Firstly,3G-ALE and the formation process of burst waveform are studied in this thesis.In addition,several spectrum sensing methods are briefly discussed,and it is found that spectrum energy detection is most suitable for this system.Secondly,the asynchronous fast link establishment protocol and voice short message transmission scheme based on 3G-ALE standard are designed.Among them,fast link establishment protocol includes burst waveform,protocol data unit,and protocol flow and so on,demonstrating the data structure of protocol data unit,the realization process of sounding,link establishment,terminating,scanning and voice message.Then,the designed system is realized,including the functions,configuration information and data interface between the DSP and the external chip used on the DSP chip.The hardware platform of the fast automatic link establishment system is introduced,the ALE module of which is mainly composed of two FPGA and one DSP.FPGA1 is responsible for downconversion processing of the signals sampled by A/D to obtain 360-channel complex signals.FPGA2 mainly carries out multi-channel acquisition for these 360-channel signals at the same time,and selects a single channel signal of the largest peak value which exceeds the decision threshold.DSP completes the control of the whole ALE system and the sending and receiving of waveforms.Finally,the key technology of burst waveform reception are introduced and realized,such as acquisition of synchronous lead sequence,frequency offset estimation and CRCverification.At the same time,the development environment of the system is introduced.Then,the system is tested and analyzed under different channel conditions,and the results show that the system meets the requirements of the actual project.