Noice immunity of the modem of noise signals multiple access taking into account the effect of quadratic component

The current state of the development of the elemental base of radio systems stimulates both the improvement of the characteristics of existing traditional systems and the study of alternative methods of information transmission. The research of modems with the use of a signal with an extended spectrum as an information carrier is of great importance in improving the information transmission systems. The issue of improving the modems with noise signals involves an increase in the accuracy of theoretical analysis of noise immunity of the proposed methods of demodulating the signal information components. The demodulator, for which the analysis is carried out, is characterized by the fact that in the functional for the evaluation of the received information bit there are components with different probability distribution laws. The consideration of the quadratic component influence on the noise immunity of the modem of multiple access in the analysis is performed for the first time. The article investigates the noise immunity of the modem of multiple access, which uses noise Gaussian signals as a carrier. The analytical expressions for calculating the noise immunity of the modem, when every user of the system uses a binary digital demodulator of transmitted signal, are obtained. The noise immunity of the modem of multiple access is analyzed taking into account the influence of input components of the signal, which are approximated by Gaussian and Chi-squared laws of probability distribution. Theoretical estimations of the noise immunity of the digital modem of multiple access, checked on the simulation model, are obtained. Theoretical results of the analysis have allowed to determine the dependence of the noise immunity of the digital demodulator on the amount of input signal readings at the clock interval. The optimum values of the amount of input signal readings, depending on the number of users of the system and the excess of the signal over the interference in the additive Gaussian communication channel are established