Radio Frequency Time-of-Flight Distance Measurement for Low-Cost Wireless Sensor Localization

Location-aware wireless sensor networks will enable a new class of applications, and accurate range estimation is critical for this task. Low-cost location determination capability is studied almost entirely using radio frequency received signal strength (RSS) measurements, resulting in poor accuracy. More accurate systems use wide bandwidths and/or complex time-synchronized infrastructure. Low-cost, accurate ranging has proven difficult because small timing errors result in large range errors. This paper addresses estimation of the distance between wireless nodes using a two-way ranging technique that approaches the Cramér-Rao Bound on ranging accuracy in white noise and achieves 1-3 m accuracy in real-world ranging and localization experiments. This work provides an alternative to inaccurate RSS and complex, wide-bandwidth methods. Measured results using a prototype wireless system confirm performance in the real world.

I. Introduction

Wireless networks have become a part of daily life, and the addition of location awareness can change the application landscape. Mobile phones have low resolution capabilities today, and this is changing the way people plan, navigate, and consume information. Today's indoor wireless networks are almost universally unaware of device location, but the combination of data communication, location awareness, and low power will enable a new host of applications. Battery-operated wireless devices for tagging, locating, and sensing data in factories, hospitals, and other environments will be widespread, reducing costs and improving quality.