Fundamental issues in time-delay estimation of multicarrier signals with applications to next-generation GNSS

Multicarrier (MC) signals, now well-known and widely adopted in the field of terrestrial wireless communications, are being adopted also in the field of satellite communications with the DVB-SH standard. The main motivation of MC signaling is its intrinsic ronbustness to multipath (frequency-selective) channels. On the other hand, multipath is known to be one of the dominant sources to the error budget in global navigation satellite systems (GNSSs), mainly due to the bias it arises in time of arrival (TOA) estimation. From this viewpoint, it can be argued that MC signals could be adopted in a long-term horizon as ranging signals in GNSSs. In this paper we focus onto the issue of TOA estimation for Filter Bank Multicarrier Modulation (FBMCM) signal. FBMC is preferred as opposed to the well-known OFDM for its stricter spectral limitation and its frequency orthogonality of the subchannels. TOA estimation for FBMCM signals is investigated in terms of Cramer-Rao bound (CRB), with particular emphasis on the comparison with the case of single carrier modulation. As a corollary, it is also shown that MC signals with uneven power distribution can be adopted as an easy implementation of a cognitive positioning system (CPS).