Channel estimation in filter bank-based multicarrier systems: Challenges and solutions

Filter bank-based multicarrier (FBMC) techniques have attracted a lot of interest in the last decade as a competitive alternative to the long established OFDM, particularly in wireless applications. Their potential stems from their increased ability to carrying a flexible spectrum shaping together with a major increase in spectral efficiency and robustness to synchronization requirements, features of fundamental importance in future mobile networks. A particular type of FBMC, the so-called FBMC/OQAM system, consisting of pulse shaped OFDM carrying offset QAM (OQAM) symbols, has received increasing attention due to, among other features, its potential for maximum spectral efficiency. It suffers, however, from an inherent inter-carrier/inter-symbol interference that complicates signal processing tasks such as channel estimation. The goal of this paper is to concisely present the state-of-the-art in channel estimation for FBMC/OQAM, putting emphasis on the problems that are still open and outlining related on-going research. Preamble-based channel estimation is given special attention in the realistic scenario of highly frequency/time selective channels and some new results are reported in this context.