A Testbed for Evaluation of the Effects of Multipath on Performance of TOA-Based Indoor Geolocation

Real-time performance evaluation of time-of-arrival (TOA) based geolocation systems in multipath rich indoor areas has posed a serious challenge for the research community. This is due to the wide variety of performances observed with these systems under different multipath conditions in indoor areas, the diversity and complexity of the localization algorithms, sensitivity of the design to device implementation, and the challenges encountered in creating controllable and repeatable multipath conditions. In this paper, we present a real-time performance evaluation system for TOA-based indoor geolocation devices operating in different multipath conditions using instrumentation and measurements in a laboratory testbed. This testbed is capable of producing repeatable multipath conditions. The heart of this testbed is a multichannel real-time radio propagation emulator capable of emulating up to eight multipath fading channels simultaneously. We define four different multipath scenarios occurring in a typical office building at the Worcester Polytechnic Institute, Worcester, MA, USA, exhibiting a wide range of expected performance for the TOA-based geolocation systems. We use ray tracing software to simulate different multipath conditions caused by these scenarios and we map the multipath conditions into the real-time channel emulator to add the effects of fading. Then we measure the performance of a typical commercial product in this laboratory environment. To show the validity of this method, we compare the results of measurements in the testbed with empirical data obtained from actual measurements made in the same building.