LSB: Precise Localization by Superposing Beats

The LSB Setup

Keywords: Indoor Localization, Superposing Beats, Low Cost, FFT, Ubisense

Motivation: Global localization systems, such as GPS, are omnipresent in our everyday life. Despite their successes, they do have certain technical limitations. For example, GPS is not able to yield a resolution of a few millimeters nor can it be used in indoor environments or underneath trees etc. However, some applications, such as and self-organizing smart appliances ensembles and in grain silos operating grain butlers, heavily depend on those properties. Further constraints are a potentially low price and adaptivity to changing requirements.

Goals: The goal of this project is a new localization system that
(1) requires only low-cost tags/receivers,
(2) requires only moderate installation costs,
(3) can achieve a high resolution, and
(4) can be used in indoor environments of all sorts.

Approaches: The starting point of this projects are beats that emerge from the the superposition of sinusoidal signals with very similar frequencies. Since this effect cannot be used for localization with further information, such as a global reference clock, this project explores
(1) to what extent other signal forms can be used,
(2) whether well-configured beats can be used, and
(3) to what extent beats are suitable in order to achieve a high resolution at low costs.

Results: The concept of superposing beats has been implemented in a two different prototypes. These prototypes have shown that
(1) with a 50 MHz global carrier, a resolution of a few centimeters can be achieved,
(2) the transmitters can be configured such that a beat frequency of a few hertz emerges,
(3) a reasonable receivers requires only low-cost standard components, and
(4) the beat-based approach also exhibits some sensitivity with respect noise and other disturbances.

A Performance Figure
Signal at an offset of 50 cm, to beats superpose to this complex signal.

Research Team: Matthias Schneider and Ralf Salomon


Selected Publications: