V.G. Kartashevsky1, I.V. Grigorov2, V.A. Cymbal3

1,2 Povolgsky State University of Telecommunications and Informatics (Samara, Russia)

3 Branch of the Military Academy of the RVSN named after Peter the Great (Serpukhov, Russia)

1 vgkartash@ya.ru; 2 igor-grigorov@mail.ru; 3 tsimbalva@mail.ru

This paper examines the application of OFDM to frequency-hopping communications in environments where OFDM symbol envelope samples (or envelope structural components) are transmitted individually on a dedicated carrier frequency using simple narrowband signals in channels with common fading.

A processing algorithm for transmitted signals at the receiving end is proposed. Using maximum likelihood estimates of the amplitude and phase of received narrowband signals at each frequency, it generates estimates of the QAM vectors that "modulate" the complex exponential functions within the IDFT structure during transmission. New, "improved" QAM vector estimates are generated from the QAM vector estimates obtained from the received channel signals using the orthogonality property of the sum of complex exponentials according to the minimum mean square error criterion. These estimates allow for the "assembly" of complex OFDM symbol envelope samples. After a DFT operation at reception, these estimates effectively solve the demodulation problem for identifying the transmitted binary sequence.

Statistical modeling demonstrated the high performance of the proposed algorithm: the power loss of the presented OFDM signal processing system compared to the optimal Kotelnikov receiver (for orthogonal signals) is 3 dB over a bit error probability range of 10-2 to 10-6.

It should be noted that the presented frequency hopping system based on OFDM technology is designed to achieve a fairly high level of system security without the use of special coding. For example, when using KAM-16, this is achieved by the fact that there are 1616 options, unknown to an outside observer, for establishing a correspondence between the transmitted value of the KAM-16 “modulating” vector and the transmission frequency used, one of 16 possible.

Kartashevsky V.G., Grigorov I.V., Cymbal V.A. OFDM technology in fast frequency-hopping systems // Radiotekhnika. 2026. V. 90.
№ 6. P. 102−111. DOI: https://doi.org/10.18127/j00338486-202606-10

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