Performmance Analysis Of A Compressed Spectrum Turbo-DFH System

HF communication is a long distance military communications technique, it is transmited signals through the ionosphere reflection. However, this technology has many technical difficulties, such as signal interference and channel fading. Besides, the HF communication channel is quite crowed because of the limited frequency bandwidth, so how to solve these problems and improve the HF communication quality have become more and more important.Differential Frequency Hopping(DFH) technology, which is mainly determined by the design of G function, can effectively improve the performance of HF system. Therefore, it has broad application prospects in the field of HF communication. Based on the G function of DFH system, this paper provides an improved Viterbi decoding algorithm and compares it with the conventional Viterbi decoding algorithm.In addition, through the combination of DFH with Compressed Spectrum technology, this paper presents a Compressed Spectrum DFH(CS-DFH) system, and the simulation performance of this system is also analyzed in this part.In order to improve the performance of DFH system, combining the Turbo code with G function will be one of the main directions, in which the DFH system can develop. In this paper, the Turbo-G function normalized decoding algorithm theory and simulation analysis have been carried out. By analyzing the performance of three kinds of zero forcing interveaver algorithm, this paper firstly makes a thorough research on interleaver, which has a great influence on the performance of Turbo-G function. Secondly, by combining the compressed spectrum technology with Turbo-G fuction, this paper proposes a Compressed Specturm Turbo-DFH system and puts forward the implement method of the frequency mapping function F. Finally we simulated the CS-Turbo-DFH system in different parameters, and analyzed the anti-jamming performance by comparing it with the Turbo-DFH system in AWGN channel and Rayleigh channelThis paper is divided into five chapters. Chapter one describes the principle of HF communication and the conventional FH/DS system, depicting the application and development of DFH technology, besides, this part provides a view of the framework of the thesis. In chapter two, according to the characteristic of G function, we propose an improved Viterbi decoding algorithm, and make the theoretical deduction and simulation verification. The third chapter introduces the coding and decoding structure of the Turbo-G function, and derives the normalized decoding algorithm of Turbo-G function and the complexity in its computation. Chapter four makes an introduction of the CS-Turbo-DFH system and presents the implement method of the frequency mapping fuction F, besides, this part simulation the CS-Turbo-DFH system in different parameters, and analyzes the anti-jamming performance of CS-Turbo-DFH and Turbo-DFH in different channels. The last part presents the research results of this paper, the direction of the future research is also given out.