Simulation of digital corrector of intersymbol signal distortions in the information transmission channel

Abstract

A method of modeling a digital corrector of intersymbol distortions of signals in the information transmission channel, determining the optimal values of the weighting correctors when passing a sequence of random binary signals, checking the efficiency by determining the number of demodulation errors in signal distortion by noise. The demodulator adaptation model is shown, which is reduced to the calculation of the weighted sum of 4 samples of the input signal and the comparison of the obtained sum with the threshold. The basic operations on adaptation of weight coefficients of the corrector of the signals distorted by intersymbol interference at various types of transfer function of the channel of transfer of discrete signals are defined. The algorithm of the program for calculation of number of errors of demodulation at signal distortion by noises of intersymbol interference is offered. The calculation of the corrector optimization criterion is performed by the method of coordinate descent with the possibility of visualizing the iterative procedure of calculating the corrector optimization criterion at the selected values of the correction coefficients and calculation accuracy. The formation of the input and output signal is carried out using the built-in inverse fast Fourier transform function of the mathematical package MathCAD. The mathematical model of the digital corrector, which is a kind of FIR filter, allows us to investigate the effectiveness of compensation between character distortion and stationary linear distortion of information signals provided in discrete channels of information message transmission. The initial data for the calculation of the digital corrector are the readings of the pulse response, taken at time intervals in accordance with the conditions of Kotelnikov's theorem. To solve the system of linear algebraic equations when finding the coefficients of the digital corrector, the vector - matrix method of calculation and programming operators of the MathCAD system are used.