The detector is an integral part of the device for receiving and processing radio signals. Signals that have passed through the ionospheric channel acquire an unknown Doppler shift and are subject to dispersion distortions. It is necessary to carry out joint detection and parameter estimation to improve reception quality and detection accuracy. Modern hardware base developing makes it possible to implement a device for joint detection and evaluation of signals based on standard processors (CPU) and graphic processors (GPU). The article discusses the implementation of a signal detector that allows for real-time operation. A comparison of implementations of algorithms for estimating the Doppler frequency shift through multiplication by a complex exponent and the fast Fourier transform (FFT) is performed. A comparison of computational costs and execution speed on the CPU and GPU is considered.

Analytical expressions for the Cramer-Rao boundaries are obtained in the article when jointly evaluating a set of parameters for a broadband ionospheric-distorted signal of an arbitrary shape, namely: the steepness of the dispersion characteristic, Doppler frequency shift, delay and phase shift. The corresponding expressions for covariance functions and correlation coefficients are obtained. It is shown that the presence of dispersion distortions leads to additional, previously absent, statistical relationships of estimates of signal parameters. The correctness of analytical expressions is confirmed by the results of simulation. The reported study was funded by RFBR, project number 19-29-06055.

The article deals with the tasks of developing new signal-code constructs for wideband low-speed decameter radio line. At present, the actual task is to expand the bandwidth of the signals used in the decameter range. One of the problems arising from this is the dispersion distortion of broadband signals in the ionospheric channel, which lead to a decrease in reception quality. Signal code constructions based on non-linear pseudorandom sequences and non-binary error-correcting code NB-LDPC code are proposed. In the role of nonlinear binary bandwidths, new sequences with a large ensemble are used. A system based on an advanced Kalman filter is proposed to compensate for dispersion distortion. The results of his work. The results of field tests of the new signal-code constructs are presented.

The article presents the methods and algorithms for compensating for the dispersion distortion of the wideband signals of the decameter radio communication lines. Methods for estimating the slope of the dispersion characteristic, namely, the maximum likelihood estimation method (MLE), the evaluation by dividing the signal into subbands are considered. Methods and algorithms for compensation of dispersion distortion of wideband signals are proposed. The first method: compensation during the detection of a signal by a matched filter. The second method: compensation using digital filter banks. The third method: signal processing by the tracking compensator. The results of field experiments to compensate for dispersion distortion in a wideband signal on a single-track track with a length of about 2900 km are presented.

When using wideband signals, the Digital Down Conversion (DDC) operation is an important operation. The development of a modern hardware base allows the implementation of DDC devices based on standard processors (CPU) and graphics processing units (GPU). The article discusses an implementation based on Overlap And Save algorithm. Comparison of computational costs and execution speed on CPU and GPU is carried out. The estimation of the maximum number of devices implemented on various models of CPU and GPU has been made.

Data transfer in a broadband ionospheric radio channel is an actual problem currently. Ionospheric communication channel are characterized by non-stationarity, a hard interference situation, multipath propagation and dispersion distortion of signals. The frequency dispersion of the ionospheric channel is one of the most significant obstacles to the operation of decameter-band communication systems in a wide frequency band. Dispersion distortions of broadband signals lead to a significant deterioration in the characteristics of noise immunity of the radio link, a decrease in the probability of correct detection of signals in the air and synchronization problems with them. An important task is to estimate the parameters of the frequency dispersion of the ionospheric channel with the subsequent correction of dispersion distortions of broadband signals at the receiving point. Usually this problem is solved with the use of chirp-ionosondes as part of decametre communications. It is of interest to evaluate the parameters of the frequency dispersion of the ionospheric channel directly from the information broadband signal, without the use of the chirp ionosonde, and to ensure their tracking during the reception of information. The article compared the two methods of evaluating the slope of the dispersion characteristics of the ionospheric channel, probing its broadband signals - on the maximum likelihood criterion and the method of indirect estimation, through the evaluation of signal delays in the different sub-bands. There are formulas for calculating the dispersion of the estimates in the paper. Comparison of the calculated values and simulation showed that the method of division into sub-band yields not more than 2 in terms of standard deviation of the maximum likelihood method. Standard deviation of the maximum likelihood estimation varies from 7.5 to 2 us / MHz with an signal-to-noise ratio of 10 to 20 dB, whereas the standard deviation estimation method of division into sub-bands ranging from 15 to 4 us / MHz. The actual value of the slope is equal to 80 us / MHz. Formulas and an algorithm for optimal filtering of the slope of the dispersion characteristic of the ionospheric channel are obtained in the approximation of the linearization of the observation equation. It is assumed that the slope of the dispersion characteristic is a simple Markov random process.