—In this paper the Cramér-Rao lower bound (CRLB) of an ultra-wideband (UWB) pulse amplitude modulated (PAM) signal with time hopping (TH) code is derived for the practical case where there is an initial unknown relative clock offset between the transmitter and receiver. However, it is assumed that there is a priori information about the probability density function of clock offset. CRLB expressions are developed for both the dataaided (DA) case with an assumed deterministic pilot for synchronization and for the non data-aided (NDA) case based on blind synchronization. It is shown that the influence of the unknown clock offset on the synchronization performance becomes negligible as the number of multipath components increases emphasizing an advantage in UWB links where the multipath is typically rich. Another observation made is that as the SNR decreases, the difference in the CRLB for the NDA and DA cases increases emphasizing the significance of a pilot. Having a priori informatio...