E.M. Lobov1, N.A. Kandaurov2, E.O. Lobova3, V.I. Lipatkin4, D.N. Shubin5, V.O. Varlamov6

1–6 Moscow Technical University of Communications and Informatics (Moscow, Russia)

1 e.m.lobov@mtuci.ru; 2 kandaurov@srd.mtuci.ru; 3 lizabeth2@mail.ru; 4 lipatkin.24@gmail.com; 5 dshubin@srd.mtuci.ru; 6 varlamov@srd.mtuci.ru

There are no doubts that high frequency (HF) communication is a reliable and economical solution for organizing radio links in remote and hard-to-reach regions of Russia. However, HF communication has some disadvantages in case of using signals with a spectrum width of 100 kHz or more due to the frequency dispersion of the ionospheric channel. It significantly affects the transmitted signal, noticeably distorting it and making it difficult to detect. Therefore, the estimation of the dispersion distortions and its compensation are vital for increasing the reception performance. The main goal of this article is to provide an overview of the scientific results of a team of authors that are devoted to the detection and processing of broadband signals transmitting through the HF communication channel under the condition of frequency dispersion of the Earth's ionosphere. Thus, this article provides an overview of a number of approaches developed by the authors which are directed to estimate and compensate the dispersion distortions, as well as an analysis of the influence of dispersion distortions on the performance of detection. Firstly, the article contains the Rao-Cramer bounds for joint maximum likelihood estimations of the slope of the DC, frequency shift, delay and an initial phase subsequent analysis of the influence this estimation on the detection performance (especially of the slope of the DC). It has been shown that, if dispersion distortions are not taken into account when setting up the detection device (threshold calculation), then the energy loss will be about 2 dB, and the rate of missed detections increases by more than 100 times. Secondly, the use of a dispersion distortion compensator based on a digital filter bank improves the computational efficiency by 1.5–2 times, and the energy gain obtained in experiments was 1.6–3.9 dB, which is close to the results obtained using a matched filter. The tracking compensator based on the extended Kalman filter has a standard deviation is about 1-1.5 µs/MHz for the slope of the DC, and 0.02 rad for the signal phase. Besides, it is well known that the HF band is heavily loaded, so a narrow-band interference suppression system is needed. Thus, the article proposes a device of narrow-band interference elimination based on a digital filter bank. It provides a 1.5 dB gain in comparison with an interference rejector. The obtained results allow developing HF communication lines with an improved reception performance.

This work was supported by the grant № 23-29-00802 from the Russian Science Foundation, https://rscf.ru/project/23-29-00802/.

Lobov E.M., Kandaurov N.A., Lobova E.O., Lipatkin V.I., Shubin D.N., Varlamov V.O. Modern approaches to processing of broadband signals distorted by the frequency dispersion of the Earth’s ionosphere. Radiotekhnika. 2023. V. 87. № 12. P. 17−31.
DOI: https://doi.org/10.18127/j00338486-202312-03 (In Russian)

1. Ivanov D.V., Ivanov V.A., Ryabova N.V., Ovchinnikov V.V. Actualization of parameters of adaptive SDR-equalizer of wideband HF radio channels to effectively correct for frequency intramode dispersion. 2021 Systems of Signal Synchronization, Generating and Processing in Telecommunications (SYNCHROINFO). 2021. P. 9488362. https://doi.org/10.1109/SYNCHROINFO51390.2021.9488362.
2. Rjabova M.I. FChH shirokopolosnyh ionosfernyh kanalov KV-svjazi v uslovijah chastotnoj dispersii sredy. Vestnik PGTU. 2020. № 1(45). S. 6-17. https://doi.org/10.25686/2306-2819.2020.1.6 (in Russian).
3. Ivanov V.A., Ivanov D.V. Miheeva N.N., Rjabova M.I. Issledovanie reguljarnoj i stohasticheskoj dispersii v ionosfernyh shirokopolosnyh vysokochastotnyh radiokanalah. Nelinejnyj mir. 2012. T. 10. № 10. S. 678-686 (in Russian).
4. Ivanov D.V., Ivanov V.A., Rjabova N.V. Aktivnyj sensor s distancionnym upravleniem dlja diagnostiki shirokopolosnyh ionosfernyh radiokanalov OFDM-BPSK-signalami. Radiotehnika. 2022. T. 86. № 12. S. 90-104. DOI 10.18127/j00338486-202212-08 (in Russian).
5. Lipatkin V.I., Lobov E.M., Lobova E.O., Kandaurov N.A. Cramer-Rao Bounds for Wideband Signal Parameters Joint Estimation in Ionospheric Frequency Dispersion Distortion Conditions. 2021 Systems of Signals Generating and Processing in the Field of on Board Communications, SOSG 2021.2021. P. 7. https://doi.org/10.1109/IEEECONF51389.2021.9416074.
6. Lipatkin V.I., Lobova E.O. Algoritm obnaruzhenija shirokopolosnogo signala v uslovijah ego dispersionnyh iskazhenij pri odnovremennoj ocenke mnozhestva parametrov. Jelektrosvjaz'. 2022. № 7. S. 23-29. https://doi.org/10.34832/ELSV.2022.32.7.003 (in Russian).
7. Lobova E.O., Chirov D.S. Kompensator dispersionnyh iskazhenij shirokopolosnyh signalov dekametrovogo diapazona, postroennye na baze banka cifrovyh fil'trov. Teorija i jeksperiment. T-Comm: Telekommunikacii i transport. 2020. Tom 14, №4. S. 57-65. https://doi.org/10.36724/2072-8735-2020-14-4-57-65 (in Russian).
8. Lobova E.O. Determining Channels Number in the Digital Filter Bank for the Wideband Signals Dispersion Distortion Compensation. 2020 Systems of signals generating and processing in the field of on board communications. 2020. P. 6. DOI: https://doi.org/10.1109/IEEECONF48371.2020.9078614.
9. Lobov E.M., Lobova E.O., Varlamov V.O. Synthesis of the Optimal Dispersion Slope and Phase Joint Filtering Algorithm for the Broadband Signal in the Ionospheric Radio Channel. 2023 Systems of Signals Generating and Processing in the Field of on Board Communications, Moscow, Russian Federation. 2023. P. 1-5.  https://doi.org/10.1109/IEEECONF56737.2023.10092032.
10. Shubin D.N., Lobov E.M., Lobova E.O., Kandaurov N.A. A Device for Processing a Wideband Signal of the HF Waveband Using a Digital Filter Bank. 2021 Systems of Signal Synchronization, Generating and Processing in Telecommunications (SYNCHROINFO). 2021. P. 9488356. https://doi.org/10.1109/SYNCHROINFO51390.2021.9488356
11. Lobov E.M., Shubin D.N., Lobova E.O. Reducing the Volume of Broadband Signal Recordigs Using a Digital Filter Bank. 2021 23rd International Conference on Digital Signal Processing and its Applications, DSPA 2021. 2021. https://doi.org/10.1109/DSPA 51283.2021.9535814.
12. Lobova E.O., Kandaurov N.A. Experimental results of dispersion distortion compensation of wideband signals with a device based on a digital filter bank. 2019 Systems of Signals Generating and Processing in the Field of on Board Communications. 2019. P. 8. https://doi.org/10.1109/SOSG.2019.8706758