Fundamental limits in signal time-of-arrival estimation in AWGN and multipath scenarios with application to next-generation GNSS

It is known that parameter estimation is present in any type of navigation systems. Signal Time-Of-Arrival (TOA) estimation accuracy is fundamental to the functioning of Global Navigation Satellite Systems (GNSS). This work investigates the Ziv-Zakai bound (ZZB) as a theoretical performance limit in TOA estimation. This bound has no constraint in terms of applicability, but becomes not attractive nor useful in the presence of nuisance parameters (carrier amplitude/phase, channel coefficients) because it reveals (very) cumbersome to compute. This contribution introduces a variant of the ZZB named here modified ZZB (MZZB) to overcome this problem. The procedure is akin to that found in the literature to obtain the so-called Modified Cramér-Rao Bound (MCRB) for the well known Cramér-Rao Bound (CRB). Application of the (M)ZZB and numerical results are shown for multicarrier modulations in Additive White Gaussian Noise (AWGN) channel and in a Multipath (MP) channel.