Low RF-Based Navigation for Emergencies in Difficult Environments

Crisis modes, following natural or human made disasters, can take place anywhere and anytime. This situation may cause crisis managements to heavily rely on available limited telecommunication and localisation infrastructures during the crisis to support rescue operations. The availability of navigation and communication capabilities in these situations is vital both for distressed users and core operating rescue teams, since obtained position accuracies from the navigation will determine the effectiveness of the recovery of the distressed users or assets. In these situations, a number of challenges need to be addressed in order to provide resilient and reliable navigations to end users, for example, no access to power supplies, non-predictable environments, and the lack of operational terrestrial infrastructures. These challenges are problematic for GNSS-based or terrestrial-based positioning. In addition, considering difficult scenarios such as indoors, urban canyons, catastrophes resulting from avalanches, floods or war, current navigation solutions, especially GNSS-based ones, are not adequate to support the required navigation functionalities. In this paper, the first stage of a flexible and fast-deployable Civilian and Assets Recovery System (CARS), aimed at providing positioning capabilities in crisis situations and overcoming the aforementioned challenges, will be presented. A system prototype for the first stage CARS, consisting of a single Tx-Rx communication link, has been developed and tested in indoor-to-indoor, outdoorto-outdoor and outdoor-to-indoor communication scenarios and in both static and dynamic conditions. The developed system relies on low frequency (Low-RF) transmission in the range 113 MHz – 500 MHz, efficient message and signal structures and Tx-Rx structure based on a portable, reliable, highly configurable and battery-operated software-defined radio devices that emits signals which contain ranging information. Results from experiment in different scenarios demonstrate that the designed and developed Low-RF CARS system is able to receive and successfully demodulate and decode ranging information even in challenging propagation scenarios. The outdoor-to-indoor experimentation results indicate that, with further development, we are facing a promising navigation and positioning technology.