“…In both cases, one has to cope with the interference effect that is intrinsic to FBMC/OQAM and is well known to present a significant challenge when channels of a non-negligible frequency selectivity are to be estimated [5]. Although considerable advances in preamble-based estimation of highly frequency selective channels have been recently reported (e.g., [5]), the assumption of low frequency selectivity is crucial in almost all of the scattered pilot-based approaches, including techniques based on canceling /approximating the unknown intrinsic interference [7,15,16] and those relying on the so-called help or auxiliary pilot (AP) idea [6] and variants thereof [8,9,10,11,14,17]. The latter consists in choosing the value of a symbol neighboring the pilot one so that the interference to the pilot is (almost) null.…”