In MB-OFDM-based UWB systems, the different CFOs for different bands can be obtained by only estimating the OFO. To achieve OFO estimators with wide estimation ranges, we benefit from the certain relationship between the different CFOs. The OFO is attained by estimating the CFO difference and the correlations between different bands are used. The estimator I for the TFC 1 to 4 derives the BLUE estimator with the phases of the correlations. The estimator II dedicated for the TFC 1 and 2 can achieve an even wider estimation range by exploiting the equally spaced preamble structures.