Indoor localization has become an important field of research with its potential
for  applications  in  private  and  industrial  environments.  Especially   for
production logistics,  factory and  building automation  or security  and safety
applications two technologies  seem to be  appropriate candidates to  fulfil the
desired functionality. Wireless LAN (WLAN) is widely used for communications and
data transfer, and enhancements to deal with industrial situations exist.  Ultra
Wideband (UWB) is just starting for high-rate, short-range multimedia  transfer,
but research  and standardization  activities show  lower-rate and  longer-range
concepts.  Although the  localization potential  of UWB  is always  stressed, a
direct comparison to WLAN is missing. The goal of this paper is hence to compare
the localization  capability of  the two  technologies theoretically  as well as
practically by means of time-of-flight range estimation in an
industrial context.

The necessary parameters for WLAN are defined by the IEEE 802.11 family and  for
UWB by the regulatory boundaries of  FCC and ETSI as well as  the self-developed
pulse generator  of the  IKT. In  the first  part, the  derivations of the range
estimation  minimum  variances  using  the  Cramer-Rao  Lower  Bound  show   the
theoretically achievable  performance of  both technologies  and the fundamental
predominance of UWB.  Here, variations of  the bandwidth of  the UWB signal  are
also  considered.  The  second  part  describes  the  measurement  campaign  and
respective results,  which has  been performed  to get  a practical  view of the
technologies´ performance.  Different ranging  measurements varying  the channel
conditions  (line  of  sight,  obstructed  line  of  sight)  in  an   industrial
environment  are  analysed using  interpolation  and optimal  filtering  to gain
ranging statistics  of the  best possible  receiver architecture  (without any a
priori  knowledge).  The  better  ranging  accuracy  as  well  as  the  superior
capability of distinguishing between line of sight and obstructed line of  sight
confirms the result of the theoretical analysis in general favour of UWB.