The Research On Unpredictability Of Polar Code Based On Permutation Entropy

In secure and covert communication systems,the unpredictability of sequence is an important index to measure the security of the system.In recent years,the unpredictability measurement based on the information entropy theory has been applied to the complexity analysis of chaotic sequences because of the small sample points and simple calculation.This thesis selects the Permutation Entropy(PE),which can effectively measure the unpredictability of one dimensional time series,to study the unpredictability of the polarization codes.The main work is as follows:Firstly,the influence of the 3 parameters of Logistic chaotic sequence,such as embedded dimension,delay time and sequence length,on the permutation entropy is analyzed,and the optimal parameters are obtained by simulation for the problem of the combination of the algorithm parameters.The embedding dimension and the delay time were selected to be 5 ultimately.Secondly,the new method of parameter selection is applied to two improved algorithms of weighted permutation entropy and multiscale permutation entropy.The problem of parameter selection and parameter combination of the two improved algorithms is discussed.The embedded dimension and delay time are also 5.Thirdly,the unpredictability of polarization coding is analyzed with the permutation entropy,and the unpredictability of polarization codes in different channels,different code lengths and different signal to noise ratios is discussed.Among them,the experimental results show that the PE value increases slowly,and the rate of increase is slower and slower with the increase of code length.The signal-to-noise ratio has little influence on PE.From the results of these data,it shows that the permutation entropy algorithm has the characteristics of good noise immunity and less data.Finally,by comparing the unpredictability of polarization codes with that of the convolutional codes and the interleaving codes,the potential application of permutation entropy in channel coding recognition is pointed out.