Channel measurements and preliminary performance results for indoor time-of-arrival localization

We study the performance of time-of-arrival (ToA) localization for an indoor office environment. We transmit 10MHz and 100MHz waveforms over the 5.8GHz ISM band and measure complex I-Q samples using precisely calibrated and synchronized channel sounding equipment in line-of-sight (LOS) and non- line-of-sight (NLOS) channels. The ToA is estimated using a conventional sliding correlator, and we collect ToA bias statistics with respect to a direct LOS path, where the bias is caused by multipath and NLOS reflections. The metal walls create significant ToA bias error, up to a couple hundred nanoseconds (corresponding to a couple hundred feet in ranging error) and a hundred nanoseconds, for 10MHz and 100MHz waveforms respectively. These bias statistics are used for simulations of a ToA localization system, consisting of ideally synchronized access points and using a Bayesian probabilistic multilateration algorithm (BLADE). BLADE is able to significantly mitigate the effects of bias compared to a conventional multilateration algorithm, especially for the 10MHz case. Notably, the 90%-ile error is about 10m, independent of the waveform bandwidth with a relatively dense deployment of access points.