Wireless Alarming and Routing Protocol for Earthquake Early Warning Systems

The total cost of an Earthquake Early Warning System (EEWS) can be substantially decreased by using Wireless Sensor Networks (WSNs), which are inexpensive computer networks whose nodes communicate wirelessly using a license-free spectrum in a self-organized manner. The Early Warning System triggers on the small-amplitude, but fast P-wave in order to shutdown critical infrastructures before the destructive, but slow S-waves arrive only a few seconds later. It demands low-latency communications of high robustness. Our shakeboard-based measurements show that already for the slight shaking related to P-waves representative for strong (Mw > 6) and nearby (epicentral distance < 40 km) earthquakes, the performance of the wireless communications can be considerably affected at the very moment when the Early Warning system is supposed to be used. We observed swift link quality oscillations of up to 10 dB within only half a second caused by multi-path interference and shadow fading. We propose a new alarming and routing protocol in order to meet the challenges of swiftly changing link qualities and low latency communications of high robustness as required by EEWSs. Our protocol is based on the new paradigm of anypath routing and optimized for the unique application of Earthquake Early Warning. Extensive simulations are conducted using topologies realistic for user deployed networks, i.e. with several bridges and articulation points. Our evaluation yields good results for WSNs of up to 500 nodes. For networks of more sensor nodes the results are acceptable but can still be improved.