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  • Evaluation of empirical models of centimeter and millimeter radio wave propagation in forests

    This article concentrates on the issues of radio wave propagation in forest conditions. The issue of representing the forest mass as a heterogeneous structure with a low dielectric constant is considered. Calculation and comparison of radio signal attenuation using several empirical models were carried out. It is shown that empirical models take into account the heterogeneous structure of the forest when moving from free space to the forest.

    Keywords: radiowave propagation, wooded area, empirical model, radiowave attenuation, path loss, ground mobile communication, electrodynamic characteristics of a heterogeneous structure

  • Synchronization in Direct Sequence Spread Spectrum Systems

    The article conentrates on the problem of synchronization the pseudo-noise sequence in direct sequence spread spectrum systems. Authors propose a method for transmitting information and synchronizing signals on a single carrier frequency, which allows data transmission in complex coditions in radio channel. A brief review of existing solutions for time synchronization direct sequence spread spectrum systems is carried out. The proposed solution is considered in terms of data transmission in broadband systems in the conditions of negative signal-to-noise ratio, while the limitations of the usage of this solution are also considered. A simulation of the scheme that implements the proposed synchronization method is carried out, and the requirements for the signal-to-noise ratio in the information and synchronization channels are determined. The proposed method can find application in systems with code division multiplexing, including modern IoT systems.

    Keywords: time synchronization, direct sequence spread spectrum, broadband communication systems, Internet of Things, BER