Reducing Out-of-Band Emission of Multicarrier Signals: Challenges and Tradeoffs

Multicarrier modulation has established itself as the main signaling format in many wireless standards in the form of Orthogonal Frequency-Division Multiplexing (OFDM), and also constitutes the backbone of recent proposals such as Orthogonal Time-Frequency-Space (OTFS) and Affine Frequency-Division Multiplexing (AFDM). Despite its many advantages, the spectra of multicarrier waveforms typically exhibit large sidelobes, which can cause severe interference to signals in adjacent frequency channels. Inserting guard bands by turning off subcarriers is a simple but very inefficient means to address this issue, due to the slow decay of sidelobes. In this context, we provide an overview of the different multicarrier sidelobe reduction techniques that have been proposed over the years, exposing their different tradeoffs in terms of Out-of-Band Emission performance, transmitter/receiver complexity, and impact on data and error rates.