Kusy B., Maroti M., Balogh G., Volgyesi P., Sallai J., Nadas A., Ledeczi A., Meertens L., Node Density Independent Localization, IPSN/SPOTS (2006).
This paper presents an enhanced version of a novel radio interferometric
positioning technique for node localization in
wireless sensor networks that provides both high accuracy
and long range simultaneously. The ranging method utilizes
two transmitters emitting radio signals at almost the same
frequencies. The relative location is estimated by measuring
the relative phase offset of the generated interference signal
at two receivers. Here, we analyze how the selection of carrier
frequencies affects the precision and maximum range.
Furthermore, we describe how the interplay of RF multipath
and ground reflections degrades the ranging accuracy.
To address these problems, we introduce a technique that
continuously refines the range estimates as it converges to
the localization solution. Finally, we present the results of
a field experiment where our prototype achieved 4 cm average
localization accuracy for a quasi-random deployment
of 16 COTS motes covering the area of two football fields.
The maximum range measured was 170 m, four times the
observed communication range. Consequently, node deployment
density is no longer constrained by the localization
technique, but rather by the communication range.