This article deals with spectrally efficient frequency-division multiplexing signals (SEFDM). Authors considered symmetrical and asymmetrical iterative algorithms to prevent BER performance degradation. These algorithms reduce inter-channel interference (ICI) between the subcarriers, which leads to better value of BER performance. The authors analyzed complexity and results of the algorithms, and determined the best conditions for a symmetrical algorithm with different number of subcarriers and different frequency multiplexing coefficient.