Investigation of Impact of Periodic Frequency Sweeping Radio Interference on LoRa Radio Channel

Most of modern short-range radio suppression means are built on available commercial modules designed for radio interference formation. Their emission is a sinusoidal oscillation with altering frequency that is changed according to a linear law within a given suppression band. Such radio-frequency emissions are classified as periodic frequency sweeping radio interferences. The power of those radio interferences has an inhomogeneous distribution in the frequency domain. This article presents that the jamming transmitter operating range depends on the suppression coefficient, the value of which is determined by the structures of the LoRa radio signal and interference. When the interference power is homogeneously distributed in the frequency domain, the suppression coefficient is constant and equal to the reciprocal value of the critical signal-to-interference ratio. The algorithm for calculating the suppression coefficient in the case of interference with a normal probability distribution impact on the LoRa radio channel is presented. An analytical expression is obtained for calculating the power distribution of periodic frequency sweeping radio interference in the frequency domain. It is shown that the energy spectrum of this radio interference has a series of peaks at frequencies multiple of the inverse interference period value. Mathematical expressions are derived for calculating the dependences of the periodic frequency sweeping radio interference power in LoRa radio channel and the suppression coefficient on the operating frequency of the LoRa radio channel and the interference period. Determined that, depending on the selected frequency of the radio channel, the difference in the interference power required for its suppression can be more than 50 dB. Developed mathematical apparatus for calculating the impact of periodic frequency sweeping radio interference on the LoRa radio channel is verified by simulation modeling in the MATLAB software environment. The dependences of the suppression coefficient on the LoRa radio channel frequency obtained as a result of the simulation coincide with the analytical calculations.