To suppress the side-band interferences caused by multiband orthogonal frequency division multiplexing （MB-OFDM）-based cognitive radio systems, a mathematical expression of the side-band signal is derived. Based on this expression, the constraints among the transmitted symbols, which help to suppress the interferences, are obtained. Combined with the constraints, a type of block Turbo code modulation scheme is proposed. In the modulation scheme, the side-band interferences are attenuated quickly. Compared with other techniques, in this scheme, the interference suppression is implemented more easily and sufficiently. Simultaneously, the bit error rate （BER） performance can be improved. Theoretical analyses and simulation results show that it is highly applicable for MB-OFDM-based cognitive radio systems to suffer from Rayleigh fading.
