Design And Performance Study Of High Efficiency Frequency Hopping System In DFS Channel

Frequency hopping technology is an important anti-interference and anti-interception communication method in the field of communication countermeasures.However,there are some technical problems of the traditional frequency hopping technology,such as the difficulty in adding and removing frequency hopping points and and the complication of frequency synthesizer,which restricts the development of frequency hopping technology.With the continuous advancement of frequency hopping interference technology,its targeting is getting more and more stronger,meanwhile it also promotes the development of traditional frequency hopping technology to cognitive frequency hopping,adaptive frequency hopping and other directions.A new frequency hopping communication scheme based on OFDM framework is proposed.This scheme replaces the frequency synthesizer in the frequency hopping system with the IFFT/FFT framework,thereby it makes the system structure simpler and more flexible,and easy to implement on hardware platforms,at the same time,it provides the new idea to enhance the anti-fading performance of system,load efficiency and other demandsThe content of this paper is mainly divided into three parts,the details as follows:Firstly,based on the shortcomings of frequency hopping system,the advantages of OFDM framework are combined,then a new frequency hopping system framework is proposed.In the new system scheme,the key technical schemes of the hopping state word formation,MPSK and MFSK mapping modes and other modules are designed,and the OFDM frame-based frequency hopping system in MFSK mapping mode is mainly studied.According to the characteristics of this system,two receiving algorithms,band-pass filter reception and full-band reception,are designed in this paper.Secondly,based on the two receiving algorithms,we mention above this paper used the theroy and simulation to analyze the performance in high white and Doppler frequency shift channels.It concluded that the reception performance of the bandpass filter in the high white channel is basically consistent with the error performance of the conventional FSK system.In the full-band receiving method,the error performance of the two sub-channel amplitude comparison methods is basically consistent with the coherent reception error performance;the performance of the whole sub-channel amplitude comparison method is poor.Drawn from the Doppler frequency shift channel,the full-band receiving method has certain anti-Doppler capability.In order to improve the performance of the system in high white channel and Doppler frequency shift channel,an improvement for the full band receiving method is proposed.The effectiveness correctness of the improved method is verified by simulation.Finally,in order to further improve the spectrum efficiency,a message-driven frequency hopping scheme based on this framework is proposed.The implementation of each module in this system is mainly designed and studied.The performance and spectral efficiency of the system under high white channel and Doppler channel are theoretically derived and simulated.It concluded that when the high white noise and the normalized frequency shift are less than 0.5,the error performance in the channel is basically consistent with the total sub-channel amplitude comparison method,but the spectrum efficiency is improved.An improved pseudo-random message-driven frequency hopping is proposed for the problem that message-driven frequency hopping adjacent hopping points may be duplicated.It concluded that the system error rate is consistent with the error performance of the message-driven system.The spectral efficiency is related to factors such as frequency hopping rate and number of subchannels,but the randomness of the system hopping point is improved.