Narrowband interference suppression in Long Term Evolution systems

Narrowband interference (NBI) is a known problem in wireless communications. However, analyses found in the NBI literature often model the signal of interest as a generic transport channel with all subcarriers conveying information of the same kind, e.g. user plane data. By taking the analysis down to physical channels´ level, this paper aims to obtain a deeper understanding of the impact exerted by NBI on both the user and control planes of Long Term Evolution (LTE) systems. First, field measurements are carried out to characterize the narrowband systems operating in the recently standardized LTE Band 31 (450-470 MHz). On the basis of these findings, requirements for NBI suppression in the LTE downlink are established. Some prominent time-frequency distributions (TFDs) are then evaluated via computer simulations with respect to their ability to fulfill such requirements. Among the TFDs considered, wavelets offer the best compromise in terms of complexity and signal distortion regardless the type of physical channel. For those cases where information about the NBI center frequencies is not available a priori, we propose a blind timedomain canceller based on the Wigner-Ville distribution.