Modified equivalent time sampling for improving precision of time-of-flight based localization

Applications based on precise indoor and urban area localization are becoming quite popular. The integration of localization in currently existing wireless data communication systems is especially interesting. The popularity comes from the possibility to economically use the same analog front-end for data communication and localization. In indoor environments, where the precision should be under 1 m, because of the limited sample rate of the A/D converters, range binning becomes the main source of errors. Noise is not so much a problem, because for systems used mainly in indoor scenarios, the SNR is usually quite good. One solution, which is used to mitigate range binning is oversampling. Since oversampling requires additional hardware complexity, we propose here a “modified equivalent time sampling” approach. With this approach, no oversampling data converters are needed. The same data converters used for data communication can be used for ranging, but some signal processing before transmission and after reception of the signal is needed. The achieved resolution of the distance measurements is comparable to the solution with oversampling data converters.