Enabling Technologies for Indoor Location-Based Services

Location awareness is one of the fundamental problems in tomorrow’s wireless networks. With the advent of GPS, LBS have found applications in many different fields. Most of the LBS applications offered by wireless carriers as of today are mainly relied on the GPS technology. In areas where there is a clear LOS to GPS satellites, this technique provides a good estimate of the user’s location on the earth. However, in indoor and dense urban environments the GPS signal is typically unavailable, and localization becomes even more challenging. In this paper, we envisioned the UWB radio as a potential technology to realize the indoor LBS applications. Firstly, an overview of some existing and commonly used TOA-based ranging and localization techniques are presented. In particular, we summarize the TOA-based ranging techniques for both time-domain and frequencydomain type of transceivers based on the UWB-IR and MB-OFDM transmission schemes, respectively. Then, we introduce an iterative type of TOA-based localization technique that exploits the channel statistics information and iterates between the ranging and localization steps in order to minimize the localization error. Finally, since NLOS condition is the dominant factor in indoor environment, various NLOS mitigation techniques will also be discussed.