The Research On Modulation And Improved Scheme For Frequency Hopping Communication System

With the rapidly development of SS (spread spectrum) technique, SS communication is not only becoming increasingly important in the military, but also has obtained more and more extensive attention in the civilian communications in recent years. FH (Frequency Hopping) system plays an important part in the SS communication system and has gone in the fore part of the SS techniques because of its excellent anti-jamming, anti-fading capability and high security.In order to guarantee the reliability of data transferring, it is necessary to find an efficient data modulation. It is very important for both enhancing system anti-jamming performances and bandwidth efficiency. Therefore, on one hand, this article is to research the anti-jamming performances under different FH system environments in terms of different data modulations. On the other hand, the FH-synchronization is the key focus of FH technique field, which is also the key technology. For better instant information receiving and tracking, we need to design exquisite instant programs.First of all, This article analyzed the principles of spread spectrum commucication system, and then described its characteristics and structures. Based on the descriptions of FH system structures and definitions, this article set up a mathematical model, followed by its theoretical analysis in terms of its principles, some key technologies and related indicators about FH system. This article focally described the basic theories, instant methods, and related progress of FH system, followed by related simple analysis of modulation programs.Secondly, it builds different FH system models under the different types of way of modulation (including the binary frequency shift keying BFSK, binary phase shift keying BPSK and Gaussian minimum shift keying GMSK) based on Matlab/Simulink in the article. Then it respectively set up the models of Wideband Noise Jamming, Multi-tone Noise Jamming, Partial Band Noise Jamming and Follower Jamming, and then analyzed the different anti-jamming performances under the three different modulation based on the practical tests. Through analyzing the curves comparatively, we can get a theoretical reference for the modern FH communication system when an appropriate modulation and demodulation scheme is needed.At last, this article shared the detail description of the synchronization program based on TOD (Time of Day) and synchronization-head, and analyzed its synchronization efficiencies based on the simulation. Then an improved scheme of FH-synchronization is proposed based on the basic principle of DFH (differential frequency hopping). The scheme introduces DFH mechanism into the process of FH-synchronization and synchronization information can be detected through the frequency sequence detection algorithm which can correct error detection. Then it analyzes the scheme and the simulation of mathematical algorithms has been given, and the results show that:the FH system can still obtain a higher probability of synchronization-acquisition under the lower SNR condition with correcting error detection and the probability is much higher than that without correcting error detection. Compared with the scheme of FH-synchronization which is based on TOD (Time of Day) and synchronization-head, this synchronization scheme can obtain not only a shorter acquisition-time but also a higher probability of synchronization-acquisition, so it provides a reference to the scholars who study the FH-synchronization scheme.