Evaluation of the Impact of Doppler Effect on Quality of HSR Radiocommunications

The article proposes a methodology for evaluating radio signal distortions caused by Doppler effect (DE; also, Doppler shift) under the conditions of highspeed train traffic (HSR, high-speed rail). The objective of the work is to develop criteria for assessing quality of radiocommunications with moving objects in HSR environment. For this, a technique is proposed for calculating the probability of an error arising from Doppler effect. A rationale for relevance of the topic is that radiocommunications are used on railways for controlling train traffic and ensuring safety and achieving required quality of radio signals is a major challenge. Quality assessment is especially important for organization of broadband communication channels with locomotive drivers using mobile networks. To solve this problem, a model for assessing quality of radiocommunication influenced by DE is considered. Distortions of signals in a radio channel due to DE are proposed to be estimated using the reduced dispersion of the total error, which consists of two components: dynamic and interference. Calculations of the total reduced signal error and the error probability for speeds above 100 km/h are described. Estimates of the effect of DE on a coherent receiver, in which errors may occur due to changes in duration of radio pulses, are suggested. Effectiveness of the receiver’s automatic frequency control (AFC) system is analysed as a means of challenging DE. For this, the concept of an instantaneous spectrum of parasitic frequency modulation due to DE was introduced and quality of radio communication was calculated using the reduced dispersion of the total error. The efficiency of using AFC has been proven after comparing the evaluations of reception quality with and without AFC in the form of the ratio of error probabilities. The features of the use of mobile communications on railways under the conditions of DE are formulated.

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