On optimal multi-symbol preambles for highly frequency selective FBMC/OQAM channel estimation

Recently, there has been a significant progress in the study of preamble-based channel estimation for filter bank-based multicarrier systems using offset QAM (FBMC/OQAM), addressing the more demanding highly frequency selective scenario. In this context, analytical optimization of the preamble has been only considered for short preambles consisting of a single pilot FBMC symbol. Optimization of longer preambles with the FBMC/OQAM modulation is considerably more challenging in view of its well-known intrinsic interference effect, and may allow for the estimation of very high dispersion channels. However, this problem has only been studied for per-subchannel estimation via iterative techniques as well as for the low frequency selective case. This paper is concerned with the multi-symbol optimal preamble design for highly frequency selective channels, exhibiting the challenges and difficulties of the problem for preambles of two pilot symbols. For this case, preliminary design examples are provided and simulation results involving highly frequency selective channels are reported and discussed.