Patent ID: 8170064

Claim:
A method for a wireless communication system to transmit a digital signal, the method comprising: determining a number of subcarriers, to be assigned to each of a plurality of subcarrier groups, based on a bandwidth of each of available frequency bands, wherein each of the subcarrier groups comprises at least one subcarrier, and at least two subcarrier groups among the plurality of subcarrier groups have different numbers of subcarriers and different frequency bandwidths; splitting the digital signal at baseband into a plurality of signals, according to the determining; performing inverse fast Fourier transformation (IFFT) on each of the plurality of signals to generate the plurality of subcarrier groups; and transmitting each of the subcarrier groups through each of the available frequency bands, respectively, wherein the transmitting comprises: low-pass-filtering each of the subcarrier groups; modulating each of the low-pass-filtered subcarrier groups independently using different radio frequency (RF) signals; and transmitting the modulated subcarrier groups, and wherein the different RF signals have different frequencies from one another, and are generated by at least one of a frequency divider and a frequency multiplier using a signal output from a phase-locked loop (PLL) circuit.