Shortwave Channel Models Of Differential Frequency Hopping Communication Technology

High frequency (HF) communications mostly uses F layer to communicate in a super long distance. It featuring simple equipments, low cost and strong anti-destruction ability plays important role in military communications. But it is poor of communicating quality and it is difficult to operate at high data rates. Differential frequency hopping (DFH) is a novel frequency hopping technique. The radio using the technique implemented the hopping rate of 5000 hops/s and provided the date rate of up to 19.2 kbps over HF channel. The DFH technique improves low data rate due to bandwidth constrains and unreliable performance because of the time varying nature of the communications channel, and enhances the ability of anti-tracking and anti-fading. So the DFH become an attractive military HF communications technique.The most important work of this thesis is through studying the key technologies, design of frequency transition function and DFH demodulation technique which is based on the features of DFH technique, emulating and comparing the DFH system. The work achieved included:First, this thesis summarizes the features and the neoteric research findings in comparison with the conventional frequency hopping technique.Secondly, through analyzing the based theories and the design rules of frequency transition function, compares two schemes which is based on theory of the same arithmetical compliment or based on the theory of the states of registers.Thirdly, studying the features of the conventional DFH demodulation and detection algorithm, this thesis analyzes and compares the difference of kinds of algorithms. Through emulation to find a frequency transition function which is more adapt to the DFH. At the same time, this thesis analyzes the MAP algorithm which can provide soft output in order to the research afterward.Fourthly, studying the system with Turbo-DFH technique and analyzing the iterative algorithm of Turbo-DFH. The thesis expatiates on the infection which is caused by various parameters through emulating.Lastly, the thesis offers the emulation of a new system which is used Non-binary Turbo-DFH. Through emulating, the thesis explains the features of Non-binary Turbo-DFH and the infection caused by parameters. At last, the thesis also compares the different between Turbo-DFH and Non-binary Turbo-DFH.