A Zero-Configuration Tracking System for First Responders Networks

In emergency scenarios, tracking first responders is essential. While in open areas the quality of the Global Positioning System (GPS) service is typically acceptable, in partially obstructed environments, such as urban canyons, or indoor, it could be either unavailable or hindered by very coarse and unacceptable estimates. Moreover, most of the proposals for overcoming these limitations could be unsuitable in emergency scenarios. We propose a localization and tracking system based on the combined usage of WiFi and GPS. Essentially, when the GPS coverage is scarce, our localization solution allows augmenting it by using the WiFi access points as virtual satellites. When GPS coverage is not available at all, we use WiFi trilateration based on received signal strength, even maintaining the same coordinate system used in the GPS. The tracking protocol makes use of session initiation protocol messaging over a WiFi network. The proposed system is characterized by ease of deployment and usage, since it does not require any particular configuration. In order to assess its feasibility, we implemented a proof-of-concept prototype made up of low-cost commercial off-the-shelf components and open-source software. The performance tests carried out by using this prototype confirm the effectiveness of the proposed system.