Research On Third Generation HF Automatic Link Establishment Technologies

The study of this paper was derived from military project. In this paper, we focused on the research on the third generation HF Automatic Link Establishment technologies. The third generation HF radio network is defined by the standard of MTL－STD－188－141B. The scheme of the physical layer of the ALE protocol was designed according to the HF channel characters and the capability of the current DSP system. In this scheme, a new method of synchronization of pseudo-random sequence was proposed. The method was Correlate search and FFT carrier detection, which could solve the problem of the capture of the spread spectrum code under the condition of low SNR and big frequency offset. We also put forward a method, Shift receiving window and Correlate with local sequence, which not only could solve the problem of symbol synchronization but also could acquire the statistics of the multipath. Then we utilized the results of the channel estimation and the technology of RAKE receiver to decode the received spread spectrum sequence and acquire rude information. To a certain extent, this method could overcome the receiving difficulty of spread spectrum system caused by the multipath .First, we tested the scheme under the software environment and adjusted it step by step. Then the scheme was realized under the DSP hardware environment. Under each channel condition, the results of the emulator and the realization reached the linking probability requirements of the 141B standard.