Помехоустойчивость когерентного приема двоичных сигналов с прямоугольной огибающей в гидроакустическом канале связи

Abstract

Goals. The main purpose of this work is to develop a methodology for determining the parameters of binary signals, at which the signals become relatively invariant to frequency distortions in the marine environment. The frequency distortion of the signals is caused by the uneven frequency response of the attenuation of the marine environment. The main part of this technique is to assess the effect of frequency distortion of signals on the noise immunity of reception. In accordance with this, the error probabilities of signal receivers with various types of manipulation are determined, which are optimal in the absence of errors. Methods. The provisions of applied hydroacoustics, the theory of random processes and the theory of transmission of discrete messages are used. The main content. The paper considered a model of a single-beam hydro-acoustic communication channel, characteristic of the deep sea, when the receiver or transmitter is located in the depths of the sea. The transmission coefficient of the channel is used as a transmission coefficient with a Gaussian amplitude-frequency characteristic and a linear phase-frequency characteristic. The error probabilities of coherent binary signal receivers with amplitude, frequency and phase manipulation with a rectangular envelope are determined. Coherent receivers optimal by the criterion of maximum likelihood under the action of white Gaussian noise and the absence of distortion in the marine environment are considered as receivers. A logarithmic measure of increasing the probability of error is introduced, which characterizes the deterioration of noise immunity due to frequency distortions in the channel. For some typical cases, the values of signal parameters are determined that are relatively in-variant to frequency distortions in the marine environment. Results. Expressions of the error probability of coherent binary signal receivers with amplitude, frequency and phase manipulation with a rectangular envelope are found. A logarithmic measure of the relative increase in the probability of error compared to the case of no distortion is introduced. The functional dependence of this measure on the duration of the signal transmission, the carrier frequency and the initial phase of the signal, as well as on the communication distance and the signal-to-noise ratio is determined. On the plane of the carrier frequency, the duration of the signal, for each type of signal, a boundary of the region is constructed, above which the signals are relatively invariant to frequency distortions in the marine environment. For communication ranges R = 1.5 km and 3 km and typical carrier frequencies, the minimum values of the duration of invariant signals are given.