An RF ToF Based Ranging Implementation for Sensor Networks

Localization is important for self-configuring sensor networks. One of the core tasks of localization is ranging (estimating distances) to reference points. In this paper a radio signal based Time of Flight (ToF) measuring ranging system for wireless sensor networks is proposed, designed and prototyped. The prototype measurement error is within -0.5m to 2m while operating at 100Msps sampling rate and using a 50MHz signal in the 2.4 GHz ISM band. The system accuracy is limited by the sampling rate and can be linearly improved with increasing rates. This RF method is more cost effective than acoustic signal based ranging schemes, as it does not require ultrasonic transducers. The system is multipath resilient and can coexist with 2.4Ghz band devices such as 802.11b/g networks.