Research On Key Technologies Of Frequency Hopping Communication System With Ultrashort Wave

The ultrashort wave frequency hopping communication system in the field of communication is widely used because of its unique advantages,and its excellent anti-jamming and anti-interception characteristics make it develop rapidly.But it still can't avoid its limitations,such as the synchronization of a long time,confidentiality is poor,the reliability of transmission of information and anti-intercept ability still need to improve and so on.In order to solve the above problems,the pseudo-randomness of the current frequency hopping communication system is poor,the confidentiality is poor,the system reliability and stability can't be taken into account,and the anti-interference ability needs to be improved.(1)The frequency hopping sequence is selected and designed to evaluate the performance of chaotic frequency hopping sequence,and the balance of chaotic sequence is optimized by two methods.In the traditional frequency hopping sequence,the pseudo-randomness is poor and the confidentiality is weak.Therefore,the chaotic sequence with high sensitivity to the initial value is chosen as the frequency hopping sequence to improve its pseudo-randomness,and thus enhance the confidentiality of the system.And the weighting method and compound interpolation method are used to improve the balance of the sequence and enhance the confidentiality of the system.(2)In the multi-domain coding and modulation is combined,effectively balance the effectiveness of information transmission and reliability.In the traditional ultrashort wave frequency hopping system,the channel coding and modulation modules are designed independently of each other.The demodulator and decoder in the receiver adopt the serial cascade structure.As there is no information sharing between the two.It is difficult to balance the validity of the information transmission and reliability.Joint coded modulation technology is the main way to solve the problem,the encoding,modulation,interleaving and iterative decoding effectively combined to maximize the power efficiency and frequency utilization between the best balance points.At the same time,we study the coding and decoding scheme of LDPC codes which can further improve the reliability of frequency hopping system.By selecting the analysis of coding and decoding algorithms,the computational complexity is reduced.(3)The algorithm of signal-to-noise ratio estimation is analyzed and deduced,and an effective SNR estimation algorithm for cascaded LDPC-CPM system is proposed.The adaptive technology is one of the important means to improve the anti-jamming system of frequency hopping system.The core part is the channel quality estimation technique.However,since the SNR estimation algorithm in this module is only suitable for MPSK modulation mode,so we deduce and transform the phase function of CPM modulation method,and the SNR estimation of linear modulation is realized to a certain extent.The influence of parameters such as the number of binary signals and the length of the signal on the estimated performance of CPM is studied,and the computer simulation is also carried out.In view of the above,the objective of the existing ultrashort frequency hopping radio reliability,anti-intercept,confidentiality,anti-jamming performance and other major issues,.The influence of parameters such as code length,bit rate,number of iterations and number of iterations on the performance of the system is studied to select the parameters.The chaotic sequence with better pseudo-random performance is selected as the frequency hopping sequence and its balance is optimized.This paper compares the various modulation and coding schemes used in the traditional frequency hopping system with the LDPC-CPM scheme in this project.The simulation shows that the scheme is more reliable and can be used in the white noise interference.Sound and multi-tone interference,swept interference,tracking interference and other interference,the anti-jamming effect is relatively better.At the same time,the SNR estimation algorithm in the adaptive system is studied,which provides the theoretical basis and reference for the future design of the high reliability frequency hopping communication system.