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Kaj Grønbæk

Empirical Analysis and Characterization of Indoor GPS Signal Fading and Multipath Conditions

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  • Ion2009

    Forlagets udgivne version, 8,64 MB, PDF-dokument

  • Henrik Blunck, Danmark
  • Mikkel Baun Kjærgaard, Danmark
  • Torben Godsk, Danmark
  • Thomas Toftkjær, Danmark
  • Dan Lund Christensen, Alexandra Institutet A/S, Danmark
  • Kaj Grønbæk
  • Datalogisk Institut

Moving GNSS towards indoor positioning is an important challenge. Increases in receiver sensitivity, the forthcoming increase in number of GNSS satellites and signal design improvements all contribute to addressing this challenge. Another remaining issue for GNSS-based indoor positioning is the impact of signal multipath phenomena in indoor environments. The main objective of our paper is to assess the current state of GNSS as a positioning technology for indoor environments. On the basis of an extensive empirical measurement campaign, we furthermore analyze the factors limiting indoor GNSS availability and accuracy in dependence of the environment and in-building location of the GNSS receiver. In particular, we evaluate the impact of multipath phenomena on GPS accuracy, as observed in a broad variety of indoor environments using state-of-the-art commercial receiver technology.


Results of earlier measurement campaigns to characterize GNSS signal conditions in indoor environments have been published prominently in the GNSS research literature, see, e.g. [1,2,3]. To allow for in-depth signal analysis, these campaigns use a variety of measuring machinery such as channel sounders, mobile signal generators and spectrum analyzers. Furthermore, the use-case-specific usability of GPS as an indoor positioning technology as been evaluated empirically on a higher level, see, e.g. [4]. In this paper we present results of a measurement campaign, designed to characterize indoor GNSS signal conditions. The work presented can therefore be seen as an effort to the campaigns mentioned above. As the focus of our work lies on the real-world usability of current GNSS technology for indoor use, we employ in our measurement campaign foremost commercial receivers with features, typical for the use cases we currently focus on, i.e. enabling positioning and rescue coordination through fire fighter teams and mobile phone based positioning of persons to be rescued, as well as tracking behavioral and motion patterns of barn cattle. Also, we focus in our analysis on parameters critical for the use of positioning technologies, i.e availability and accuracy. For a diverse number of chosen in-building locations, we undertook a series of measurements. We chose the individual experimental setups to cover a variety of instances of parameters known to influence indoor signal reception and multipath patterns: Additional to various satellite elevation and azimuth settings we cover indoor environments with different architectural parameters the such as building superstructure and building materials that the signals penetrate to reach the receiver. Furthermore, we carry out measurements for various receiver positions within every room chosen for experiments, specifically to vary proximity and angles to building elements such as walls, windows, doors and room corners. The indoor environments investigated include office and residential wooden and brick houses, a school, a barn, and a shopping mall.

Somewhat contrary to the common believe, that the weakness of the received signals alone is by far the largest obstacle for any GNSS positioning in an indoor environment, the availability was surprisingly good for most of our measurement locations. Our results indicate, that when making use of such state-of-the-art assisted GNSS receiver technology in such environments, the issue remaining is inaccuracy. Furthermore, consistent with the availability observed, both the signal strength and the constellation geometries observed were often favorable, so that multipath appeared to be the main error source. On the basis of our campaign´s results, we extract indicators for GPS indoor positioning accuracy and also reinvestigate indicators presented by Teuber et.al.[1] for indoor GPS signal strength and reception quality.

TitelProceedings of the 22nd International Technical Meeting of the Satellite Division of the Institute of Navigation (GNSS 2009)
Antal sider2371
Vol/bindSession 2E
ForlagThe Institute of Navigation
StatusUdgivet - 2009
Begivenhed International Technical Meeting of the Satellite Division of the Institute of Navigation (GNSS) - San Diego, CA, USA
Varighed: 23 sep. 200925 sep. 2009
Konferencens nummer: 22


Konference International Technical Meeting of the Satellite Division of the Institute of Navigation (GNSS)
BySan Diego, CA

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