B.G. Barabashov, A. S. Ogar

The method of predicting statistics of propagation errors for discrete message transmission via a narrowband HF channel is described. Prediction is based on the simulation model of HF channel accounting for actual mechanisms of radio wave propagation in magneto-active spatially non-uniform ionosphere with connection to specific helio- and geophysical conditions. Based on this method, the quality of transmission can be predicted real time. The prediction procedure is implemented as the software package which comprises the following blocks: generator of the transmitted trial digital sequence having arbitrary shift keying modulation; the simulation model of HF signal field; noise generator; model of a decision circuit; error detection block. The main focus is given to description of deterministic simulation model of a narrowband channel. As input parameters, the model takes current diagnostics data of the ionosphere. According to these data, initial ionization distribution is being adjusted. The model outputs the average signal voltage at a receiver input, and the sequence of impulse response samples. The algorithm of predicting the quality of reception assumes the following sequence of operations. The trial sequence samples are generated, and then run through the model. The resultant output comprises samples of quadrature components of the signal, and noise, with signal-to-noise ratio being given. Having been processed by the decision circuit, the sequence goes to error detection block where it is compared with the initial trial sequence. At its final step, the algorithm predicts the current expected number of errors in the binary message of given length.