Research On Channel Estimation Technology Of Subset-based Coherent Fast Frequency Hopping Systems

Fast Frequency Hopping is a mainstream anti-jamming communication technology.In the FFH system,a symbol is transmitted by multi-hop hopping frequency.Besides,its hopping time is quite short.Therefore,it has excellent anti-interference and anti-fading performance and is widely used in modern military anti-jamming communication systems.It is also because of these characteristics of the FFH system that its channel estimation is extremely difficult.Therefore,conventional FFH systems generally employ non-coherent MFSK modulation and demodulation methods that do not require channel estimation.However,although the non-coherent FFH system is easy to implement,it has low spectrum efficiency,non-coherent merger loss,and limited scalability.Therefore,it is urgent to extend the coherent system to the FFH system.For this reason,this paper studies a subset-based Coherent Fast Frequency Hopping(S-CFFH)system.The S-CFFH system provides a feasible solution for solving the channel estimation problem in the traditional FFH system,and has high spectrum efficiency.This article will focus on the channel estimation technology of the S-CFFH system.The work of the thesis is mainly in the following parts:The first part introduces the research background and significance of the paper,as well as the research status and development of the fast frequency hopping technology and channel estimation technology.In the second part,the working principle of S-CFFH system is studied and the system frame format is designed.At the same time,the optimal pilot pattern design of the system is discussed and the system parameters are determined.In the third part,we study the pilot-aided S-CFFH system channel estimation algorithm and its coherent merge and interpolation algorithms.We analyze and simulate the S-CFFH system for LS channel estimation and use maximum ratio combining and linear interpolation whose performance is the best.The fourth part studies the noise reduction algorithms in channel estimation of S-CFFH system,including the average noise reduction algorithm,the denoising algorithm based on wavelet transform,the denoising algorithm based on QR decomposition,and the denoising algorithm based on DFT domain.The simulation results show that the wavelet noise reduction algorithm has the best performance.In the fifth part,the S-CFFH system based on Turbo decoding soft information iterative channel estimation is studied.Compared with the S-CFFH system with only LS channel estimation,the S-CFFH system with Turbo decoding soft information iteration has nearly 1d B performance gain.