Pairwise subcarriers weighting for suppressing out-of-band radiation of OFDM

Abstract

This paper proposes a subcarrier weighting technique to suppress the out-of-band radiation of OFDM signals. By mapping and weighting the same data on an adjacent pair of subcarriers, the spectrum sidelobes are suppressed perfectly through sidelobes mutual cancellation. The optimum weighting factor is derived based on a rectangular pulse-shaped OFDM spectrum model. Compared with existing out-of-band suppression schemes, the proposed scheme not only requires less computational burden but also achieves better spectral roll-off. For example, when the cyclic prefix of a one-eighth OFDM-block length is added, the proposed scheme suppresses the 10-dB radiation at the center frequency between two subbands which are using cognitive radio. Analytical and simulation results also show that the proposed scheme improves the system carrier-to-interference ratio by 10 dB at a normalized frequency offset above 0.1, which leads to the performance improvement in terms of the BER on AWGN channel and multipath fading channel. Copyright © 2011 John Wiley & Sons, Ltd.