A method of aligning sub-carriers of radio signals of two adjacent frequency channels and devices therefor are described. The method comprises aligning a first plurality of sub-carriers of a first radio signal and a second plurality of sub-carriers of a second radio signal within an overlapped frequency region in-between the two adjacent frequency channels by shifting a center frequency of the first radio signal with a frequency offset. The first radio signal and the second radio signal are adapted for transmission over the two adjacent frequency channels and the first frequency channel is one of the two adjacent frequency channels.