Sidelobe Suppression with Cancellation Carriers for OFDM Based Overlay Systems

Abstract

Orthogonal frequency-division multiplexing (OFDM) systems exhibit significant out-of-band radiation caused by high sidelobes of the modulated subcarriers. Especially in OFDM based overlay systems the suppression of these sidelobes is one of the most important issues in order to enable the coexistence of two systems in the same frequency band. In this paper, we propose a new technique for sidelobe suppression characterized by the insertion of a few so-called cancellation carriers (CCs) on the left and right hand side of the used OFDM spectrum. These special subcarriers are not employed for data transmission, but carry complex weighting factors which are determined such that the sidelobes of transmission signal and CCs cancel each other. Simulation results show that with the proposed method a significant sidelobe suppression is achieved with only a small loss in bit error rate performance. This loss can be minimized by a slight modification of the receiver.