A novel RF ranging method

Localization and tracking of wireless nodes have been active research areas in robotics, mobile ad-hoc networks, and wireless sensor networks. While several phenomena have been utilized for this purpose, RF signals have many advantages. Signal strength and time-of-flight are the two typical ways of extracting range information. Recently, radio interferometry was proposed to solve this problem using phase and/or Doppler shift measurements across severely resource-constrained devices. The former requires many measurements at multiple frequencies, while the latter needs motion to generate a usable signal. This paper introduces a novel ranging method based on a rotating antenna generating a Doppler shifted RF signal. The frequency change can be measured using the radio interferometric technique even on low-cost, resource constrained devices. This simple idea provides a surprising number of different ways for estimating range and location. The paper outlines these techniques and describes one of them in more detail with experimental and simulation results.