  The high time resolution of ultra-wideband (UWB) signals facilitates very
precise position estimation in many scenarios, which makes a variety
applications possible. This paper reviews the problem of position estimation in
UWB systems, beginning with an overview of the basic structure of UWB signals
and their positioning applications. This overview is followed by a discussion
of various position estimation techniques, with an emphasis on time-based
approaches, which are particularly suitable for UWB positioning systems.
Practical issues arising in UWB signal design and hardware implementation are
also discussed.
