P.V. Luferchik1, A.V. Luferchik2, P.V. Shtro3, P.N. Zakharov4,
D.R. Valiullin5, A.A. Milovanov6

1-3 JSC SPE Radiosvyaz (Krasnoyarsk, Russia)

4-6 LLC Microwave Electronics (Moscow, Russia)

1 Luferchikp@gmail.com; 2 DSP@mail.ru; 3 faust_256@mail.ru; 4 zakharov1@mail.ru;
5 vdr91@mail.ru; 6 amilovanov@mwel.ru

Tropospheric radio communication is based on the usage of the electromagnetic energy re-emission in an electrically inhomogeneous troposphere during the propagation of radio waves in it. The electrical inhomogeneity of the troposphere (the inhomogeneity of its dielectric permittivity) is due to random local changes in temperature, pressure and humidity, as well as a regular decrease in these values with increasing altitude. The re-emission of energy occurs in the area of the intersection of the radiation patterns, transmitting and receiving antennas. It is well known that intersymbol interference may occur during data transmission caused by the presence of multipath propagation and frequency-selective fading in the tropospheric radio channel, which can significantly reduce the energy efficiency of communication systems. The purpose of this work was to achieve an increase in bandwidth in the tropospheric radio channel. The energy efficiency of the new operating mode has been confirmed experimentally by route tests. The article describes the main algorithms implemented in the modem, which made it possible to increase the bandwidth in the existing tropospheric station.  The introduction of modern algorithms for digital signal processing into a mass-produced tropospheric communication station has made it possible to increase the energy efficiency of the communication system in the tropospheric channel. SR-FQPSK modulation gave an additional energy gain by reducing the peak factor, the usage of the direct spectrum expansion method allowed to increase the frequency separation and provide resistance to frequency-selective fading, the adaptive equalizer provided effective control in multipath conditions. The article discusses how in the mass-produced tropospheric communication station 'Groza', only through the use of modern digital signal processing algorithms in the modem, it was possible to increase the bandwidth in the tropospheric radio channel from 2 Mbit/s to 25 Mbit/s at a distance of 140 km. Tropospheric communication is actively used in the armed forces and has great potential in the civilian market. In modern warfare, the role of tropospheric means of communication with increased bandwidth is significantly increasing to meet the needs of troops in large volumes of transmitted information. In special-purpose networks, the advantage of tropospheric means over satellite ones is higher survivability in conditions of armed conflicts and/or anti-terrorist measures. There are several similar solutions in the world at the moment, for example, among foreign analogues — tropospheric communication stations of American companies Raytheon and Comtech Systems Inc. Currently, high-speed tropospheric stations are not mass-produced in Russia. Increasing the capacity in the existing mass-produced tropospheric communication station ‘Groza’ will allow providing communication to hard-to-reach settlements where it is technically difficult and economically unprofitable to lay fiber optic or where it is technically difficult and economically unprofitable to build a multi-channel radio relay communication line. Also, the use of high-speed tropospheric communication is a cost-effective alternative to satellite communications, since its use does not require the rental of a satellite channel.

Luferchik P.V., Luferchik A.V., Shtro P.V., Zakharov P.N., Valiullin D.R., Milovanov A.A. Experimental study of the modem of a tropospheric communication station with an energetically efficient mode of operation. Radiotekhnika. 2022. V. 86. № 4. P. 67−75. DOI: https://doi.org/10.18127/j00338486-202204-10 (In Russian)

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