  We consider the problem of obtaining relative location information between
two wireless nodes from the differences in their ultra-wideband (UWB) channels
to observer nodes. Our approach focuses on the delays of multipath components
(MPCs) extracted from the observed channels. For the two different cases of
known and unknown MPC association between these channels, we present estimators
for the distance and for the relative position vector between the two nodes.
The position estimators require both MPC directions and MPC delays as input.
All presented estimators exhibit very desirable technological properties: they
do not require line-of-sight conditions, precise synchronization, or knowledge
about the observer locations or about the environment. These advantages could
enable low-cost wireless network localization in dynamic multipath
environments. The exposition is complemented by a numerical evaluation of the
estimation accuracy using random sampling, where especially the position
estimators show the potential for great accuracy.
