  In this paper, to synchronize Ultra Wideband (UWB) systems in ad-hoc
multi-user environments, we propose a new timing acquisition approach for
achieving a good performance despite the difficulties to get there.
Synchronization constraints are caused by the ultra-short emitted waveforms
nature of UWB signals. Used in [1, 2] for single-user environments, our timing
acquisition approach is based on two successive stages or floors. Extended for
multi-user environments, the used algorithm is a combination between coarse
synchronization based on timing with dirty templates (TDT) acquisition scheme
and a new fine synchronization scheme developed in [3-6] which conduct to an
improved estimate of timing offset. In this work, we develop and test this
method in both data-aided (DA) and non-data-aided (NDA) modes. Simulation
results and comparisons are also given to confirm performance improvement of
our approach (in terms of mean square error and acquisition probability)
compared to the original TDT algorithm in multi-user environments, especially
in the NDA mode.
