High-Accuracy Localization Using IEEE 802.11 WiFi Legacy Preamble

Abstract

We explore the use of synchronization bits from a standard 802.11 preamble for highaccuracy localization. The multi-tone short training field present in 802.11 standards that use a Legacy preamble is investigated in comparison to a common remote sensing waveform known as the stepped frequency waveform that shares similar waveform characteristics to the preamble. We present the 802.11 standard and the connection to the stepped frequency waveform, derive the theoretical lower bound on the short training field, present a comparison of simulated results, and present experimental wireless measurements demonstrating ranging accuracies on the order of 1.9 mm.

A C-Band Fully Polarimetric Automotive Synthetic Aperture Radar

“…Most matched filtering based techniques focus on orthogonal frequency division multiplexing (OFDM) waveforms as these are commonly employed in modern communications systems due to their high spectral efficiency and robustness to multipath channel distortion [42]. However, due to the variable nature of the communications payloads, the ambiguity function of the waveform is constantly changing making it challenging to predict radar performance at any given time; to avoid this, other techniques have proposed using communication preambles which commonly include fixed training and channel estimation sequences [5]- [8]. These fields can be used to obtain a consistent deterministic ranging waveform with predictable performance and relaxes the requirement for knowledge of the data being transmitted.…”

“…Currently, high throughput communication standards such as 802.11ac and 802.11ax implement channel bandwidths of up to 160 MHz enabling range resolutions on the order of a meter, or potentially smaller through the use of non-adjacent channel bonding and the wider channel bandwidths proposed for future standards. The accuracy of a ranging waveform in a given scenario is highly dependent on the waveform shape which has many tradeoffs that can be made for ranging accuracy, Doppler tolerance, and side-lobe mitigation, however a recent study using a relatively low frequency, 5.25 GHz 802.11ac legacy preamble as a ranging waveform experimentally achieved a ranging accuracy on the order of 1.9 mm [5], demonstrating the ability for existing 802.11 communications signals to be applicable for SAR applications in the C-band.…”