In this paper, we estimate the upper limit of the transmission data rate in airborne ultrasonic communications, under condition of the optimal power allocation. The presented method is based on frequency response of a channel in case of single-path LOS propagation under different climatic conditions and AWGN background noise model, and it can be easily extended to the case of frequency-dependent noise. The obtained results go beyond the discrete distances for which experimental SNR values were available, and are more accurate than the previous calculations in the literature, due to the inclusion of the channel frequency response and its changes over the distance. The impact of air temperature, relative humidity and the atmospheric pressure on the channel capacity is also investigated. The presented results can serve as a reference during the design of airborne ultrasonic communication systems operating in the far-field region.
The paper analyzes the prospects for the formation and implementation of digital data transmission technologies on railways of Kazakhstan, taking into account the potential for the development of high-speed railway transport (HSRWT), as well as new approaches for solving the development problems of advanced automated dispatch control systems (ADCS). It was shown that the solution of these problems is possible by automatization of the train traffic coordination based on the use of the potential of the GPRS data transmission technology. The work further developed models and algorithms used in ADCS of the railway transport. There has been carried out the formalization of the tasks of navigation data transmission for ADCS and for the subsystems of the railway rolling stock movement coordination, including HSRWT using GPRS data transmission technology. Also, the article describes a modernized algorithm for simulation of the GPRS channels operation in ADCS. The proposed algorithm differs from the existing ones by the ability to make predictive estimates for determination of the railway rolling stock location. Also, the developed algorithm provides opportunities for coordination of the trains movement, taking into account the optimization of the GPRS resources use.