Suppressing alignment: An approach for out-of-band interference reduction in OFDM systems

In this work, we introduce a novel approach, called suppressing alignment, to reduce the out-of-band (OOB) interference of orthogonal frequency division multiplexing (OFDM) systems. Suppressing alignment exploits the unavoidable redundancy provided by the cyclic prefix (CP) and the wireless communications channel to generate an OOB interference suppressing signal at the OFDM transmitter. However, after passing through the wireless channel, the suppressing signal is aligned with the CP duration at the OFDM receiver, essentially causing no interference to the data portion of the OFDM symbol. The proposed approach reduces the OOB interference by tens of decibels and does not require any change in the receiver structure of legacy OFDM.