Design of filters based on generic function model for reducing out-of-band emissions of the F-OFDM systems

The Filtered-OFDM (F-OFDM) systems use filters to filter signals in the time-domain to achieve rapid attenuation of side-lobes and reduces mutual interference caused by multi-scene access. In general, signal filtering in the F-OFDM system is obtained by using the classical window functions to truncate the sinc function. In this paper, based on the intrinsic characteristics of window functions in the frequency-domain, a generic function model is proposed to design window functions with high energy concentration and fast side-lobes attenuation. The window function is defined as an even function and expressed as a Fourier series, and then the Fourier series is solved numerically to obtain the window function expression. The optimized windows functions with different attenuation rates can be obtained by modifying the rising index. The optimized window functions are applied to the F-OFDM systems for the purpose of evaluation, and the results show that they all achieve a lower OOBE degree than the classical windows, while their bit error rate (BER) is basically the same as that of the classical windows in the additive white gaussian noise (AWGN) channel.