Methods spectral efficiency improvement of the OFDM system in digital broadcasting networks

This paper is devoted to the methods for efficiency improvement of orthogonal frequency-division multiplexing that do not comprise additional computational complexity of signal processing algorithms on the transmitter maintaining the subcarriers orthogonality. Proposed method is based on applying the window function to the guard interval of symbol while the original part remains unchanged. This approach provides the off-frequency emission decrease, which depends on the selected fast Fourier transform mode, broadcasting standard, and shaping parameters for window function. The gain in off-frequency emission decrease is from 5% to 26% in contrast with the "rectangular" window function, the increase of symbol rate is up to 5%, and gain in spectral efficiency is up to 0.05%. The analysis of subcarriers frequency characteristics shows that reduce of resulting signal level by 2-4 dB compared to the raw symbol, which minimizes the frequency emissions at transient times between the guard interval and the useful part of the symbol.