  In this paper we develop a new technique for estimating fine clock errors and
range between two nodes simultaneously by two-way time-of-arrival measurements
us- ing impulse-radio ultra-wideband signals. Estimators for clock parameters
and the range are proposed that are robust with respect to outliers. They are
analyzed numerically and by means of experimental measurement campaigns. The
technique and derived estimators achieve accuracies below 1Hz for frequency
estimation, below 1 ns for phase estimation and 20 cm for range estimation, at
4m distance using 100MHz clocks at both nodes. Therefore, we show that the
proposed joint approach is practical and can simultaneously provide clock
synchronization and positioning in an experimental system.
