Patent ID: 7848437

Claim:
A sub-carrier diversity method on an MB-OFDM (multi-band orthogonal-frequency-division-multiplexing) system repeatedly transmitting an identical frequency band of an identical symbol, the method comprising: setting a value of a TDS (time domain spreading) of sub-carriers depending on a transmission rate; in response to the value of the TDS being a multiple of two, cyclically shifting positions of the sub-carriers by a first predetermined unit at a first through a third stage and shifting positions of the sub-carriers by a second predetermined unit at a fourth through a sixth stage, so that the sub-carriers diverge in frequency bands, wherein the first predetermined unit is a different value than the second predetermined unit; and transmitting the frequency bands in stages such that after every third stage a cycle begins and the frequency band is shifted to a different frequency band to prevent transmitted frequency bands from overlapping, the frequency band of the fourth through the sixth stage is different from the frequency band of the first through third stages, and the first through third stages each have the same frequency band.