In this paper we report on  the architecture and implementation status of  a low
-cost experimental Ultra- Wideband  (UWB) local positioning system,  designed to
enable  practical  evaluations of  UWB  based positioning  concepts.  The mobile
devices use  the avalanche  effect of  transistors for  simple generation  of bi
-phase  pulses  and  are TDMA  multi-user  capable.  After high-speed  analog-to
-digital conversion, the receiver is implemented in software and employs  direct
cross-correlation with maximum  detection to localize  the mobile unit  via Time
- Difference-Of-Arrival (TDOA) algorithms. One direct solution and one nonlinear
optimization approach are implemented. First measurement results are  presented,
showing accuracy in the order of decimeters.