Low Complexity Positioning System for Indoor Multipath Environments

In this paper, we consider localization based on the Time-of-Arrival (ToA) of Ultra-Wideband (UWB) impulse radio pulses. We present a receiver structure for ToA estimation, which can be implemented with very low complexity and low power consumption. Standard approaches for ToA estimation of UWB pulses require very high speed A/D conversion, which makes them impractical for implementation. Although ToA estimation based on phase estimation of narrowband signals circumvents that problem, the estimation performance suffers strongly from multipath propagation. We propose to combine the advantages of both techniques by performing spectral estimation at the output of a UWB energy detection receiver. This system benefits from resolvability of multipath components due to a large signaling bandwidth, but requires only low sampling rates. The impact of bandwidth on the ToA estimation accuracy is derived analytically and a closed form approximation of the estimation variance for a multipath channel is given. Moreover, we present a performance evaluation based on measured channels and show that accuracy up to 20 cm can be reached in strong multipath environments.