RF Time of Flight Ranging Using 802.15.4 Radios
Kristofer Pister and Steven Michael Lanzisera
An enabling technology for large-scale sensor networks is the ability to determine a sensor node's location after deployment. Some applications, such as inventory management, use sensors that move regularly, and this spatial information is crucial to the network's operation. A device to wirelessly measure the distance between two network nodes using an RF transceiver will be developed. The distance measurement is performed by calculating a cross correlation between a received and an expected signal. Methods for reducing the effects of noise, clock offset, and multipath propagation have been studied, and mitigation techniques have been implemented. We have demonstrated round trip time of flight (TOF) ranging using an FPGA, 2.4 GHz radio, and a custom PCB. Meter level accuracy has been demonstrated both indoors and outdoors. The end goal is to provide low power, accurate, self-contained, ad hoc localization to mobile sensor nodes.
A new platform, dubbed Waldo by KP, is under development for network scale localization experiments. This platform combines all of the capabilities of the earlier platform with some additional features that will enable improved performance and flexibility. This work, coupled with continued work on a highly integrated technology demonstration provides hardware platforms to test ranging methods and localization algorithms. Theoretical work on the effects of multipath interference is ongoing, and new models are being developed.
- S. Lanzisera, D. Lin, and K. Pister, "RF Time of Flight Ranging for Wireless Sensor Network Localization," Workshop on Intelligent Solutions in Embedded Systems (WISES), June 2006.