Probabilistic Estimation of Noise Immunity of Composite Video Transmission Radio Lines in Conditions of Mutual Interference

The transition to automated regulation systems at unguarded railroad crossings has necessitated the solution of their safety issues. The most rational solution to this problem is the use of video surveillance systems that provide the transmission of images both to the railroad stations, in the area of responsibility of which the railroad crossings are located, and to the locomotives of rolling stock. For this purpose, information transmission systems organized on the basis of broadband and LTE networks are actively used. But since the operation of such networks is organized along the railway tracks, including in conditions of active application of various radiating devices, they are characterized by violation of electromagnetic compatibility conditions, leading to failure of operation as a result of inadvertent blocking of separate channels. Therefore, the analysis of conditions under which the failure of the video transmission network occurs, as well as the predictive calculation of the parameters of radio lines, which provides a given level of stability of the network, is relevant. Technologies and peculiarities of LTE standard networks operation are considered. Indicators and criteria for evaluating the functioning of video transmission lines within the technical capabilities of the standard are substantiated. The mathematical formulation of the research problem is carried out. The initial data for the development of an analytical model of probabilistic assessment of video transmission network functioning are determined. The analytical apparatus for calculating the probability of channel blocking, taking into account the mutual intensity of frequency traffic usage by conflicting devices, is developed. The requirements of GOST R 53111-2008, defining the conditions under which the stability of public communication network operation is ensured, are analyzed. The expression of probabilistic estimation characterizing the probability of disruption (blocking) of network operation determined by both channel noise and fading, and unintentional interference from third-party sources of radio emissions due to violations of electromagnetic compatibility is obtained. The results of analytical modeling are presented, revealing the conditions under which the successful functioning of the video surveillance transmission network is ensured. It is substantiated that the operation of video transmission networks under conditions of mutual interference in violation of electromagnetic compatibility requirements is more sensitive to changes in the ratio of intensity values of network streams and sources of third-party radiations operating in the mode with programmed tuning of the operating frequency than to energy ratios of useful and interfering signals.