This invention is a method about frequency multiplex. We employ numbers of sub-carriers whose frequency spectrum are overlapped each other to modulate the transmitted data sequences, and then we get the complex modulated signals. In the receiver point, we make use of one mapping between the overlapped signals' spectrum and the transmitted data sequences to detect the transmitted data sequences. By overlapping the adjacent sun-carriers, this invention can greatly increase the spectrum efficiency, and the more the multiplicity, the higher the spectrum efficiency.
Furthermore, when the spectrum efficiency increases, the needed number of signal levels for this invention will not have exponential growth, just linear growth in stead, so the requirement for system linearity can be decreased greatly.