Bounds on performance of hybrid WiFi-UWB cooperative RF localization for robotic applications

Precise localization has attracted considerable traction in the area of cooperative assignments for robots in indoor applications. When dealing with indoor applications we are limited to the type of signals that can be used for precise localization which is our prime goal. There are limitations to the well known GPS and also vision-based modality where the non-line-of-sight (NLOS) conditions can significantly degrade the results. Hence there is a need for alternative approaches for more precise indoor localization. Precise localization information is an enabler for better coordinated tasks where multiple robots are at play. In this paper, the hybrid cooperative localization accuracy for a multi-robot operation is examined. We use a mix of empirical and theoretical models for ranging estimates in a typical indoor environment on the third floor of the Atwater Kent Laboratory (AKL) at Worcester Polytechnic Institute. The two widely used ranging techniques are Time Of Arrival (TOA) using Ultra-wideband (UWB) and Received Signal Strength (RSS) using WiFi signals. The Cramér-Rao-Lower-Bound (CRLB) on the performance of hybrid localization techniques are determined in our multi-robot operation scenarios based on empirical data for UWB TOA-based and the theoretical WiFi RSS-based ranging. The performance of the hybrid localization of robots are examined when the robots are equipped with UWB radios and operate in cooperative mode using known WiFi Anchors.