Mask Compliant Precoder for OFDM Spectrum Shaping

In this letter, a precoder for shaping the spectrum of orthogonal frequency division multiplexing (OFDM) is presented. Unlike existing methods that focus on minimizing or forcing the sidelobes to zero, the proposed precoder is designed with the goal of controlling the out-of-band emissions beneath a particular power level without impacting the bit error rate (BER) performance. A small distortion is added to the information symbols forcing the emitted spectrum under a prescribed radio frequency mask. Obtained results show that the BER performance of the proposed precoder is similar to that of uncoded OFDM under relaxed masks. Moreover, the effect of the proposed precoder on edge subcarriers is investigated. Error vector magnitude (EVM) per subcarrier shows the designed precoder introduces more distortion on edge subcarriers. Consequently, the proposed precoder when combined with adaptive modulation provides further improvement in BER performance under strict masks.