Помехоустойчивость когерентного приема сигналов с многопозиционной фазовой манипуляцией и синусоидальной огибающей в гидроакустическом канале связи

Abstract

Goals: The main purpose of this work is to develop a methodology for determining the parameters of signals with multi-position phase manipulation (M-PSK), in 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. To do this, the error probabilities of the M-PSK signal receiver are determined, which is optimal in the absence of distortion. 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 hydroacoustic 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 response and a linear phase-frequency response. The additive boundary of the error probability for coherent reception of M-PSK signals with a sinusoidal envelope is determined. As a receiver, a coherent receiver is considered, optimal by the criterion of maximum likelihood under the action of white Gaussian noise and the absence of distortion in the marine environment. 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 that are relatively invariant to frequency distortions in the marine environment are determined. Results: Expressions are found for the upper bound of the error probability of coherent receivers of M-PSK signals with a sinusoidal envelope for M = 2, 4, 8, 16, 32. 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 sending the signal, the carrier frequency and the number of phases of the signal, as well as on the communication range and the signal-to-noise ratio is determined. On the plane of the carrier frequency, the duration of sending the signal, for each type of signal, a boundary of the region above which the signals are relatively invariant to frequency distortions in the marine environment is constructed. A comparison is made with the case of receiving M-PSK signals with a rectangular envelope. It is shown that invariant signals with a sinusoidal envelope have a shorter duration than signals with a straight-angle envelope. In addition, the duration of signals with a sinusoidal envelope is significantly less dependent on the number of phases of the signal.