October 7, 2015
Smartphones — owned by a record 64 percent of American adults — are increasingly used as effective means to deliver emergency alerts issued by state and federal agencies. In support of the U.S. Department of Homeland Security (DHS) Science and Technology Directorate (S&T), researchers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, have developed a new concept called Arbitrary-Size Location-Aware Targeting (ASLAT) — a more accurate method of delivering certain types of messages that could even warn users to avoid particular nearby locations. The findings are detailed in a report to DHS S&T, published in June:
“Currently, under the Wireless Emergency Alerts (WEA) infrastructure, messages often go out very broadly, generating a large number of false alarms, while other people who are in the warning area do not receive those warnings due to poor cell coverage or a few other factors,” said Richard “D.J.” Waddell of APL’s Asymmetric Operations Sector, and ASLAT program manager. “ASLAT dramatically reduces both false negatives and false positives.”
For location-specific emergencies, such as large building fires, natural gas leaks, or small-scale natural disasters such as flash floods and tornadoes, ASLAT could allow more accurate delivery of the warning to the correct populations. For events requiring very rapid notification such as an earthquake, the ASLAT algorithm would skip any steps that cause even a very minor delay.
“ASLAT uses the location awareness of wireless devices — their internal knowledge of where they are on Earth — to eliminate false negatives and positives when sending an emergency alert across multiple cellular network sites,” said Emre Gunduzhan of APL, technical lead for ASLAT. “Another interesting feature of ASLAT is that it can warn not only people in the immediate vicinity of a hazard, but also people who may have selected that hazard as their destination.”
Many geolocation technologies were studied for suitability with ASLAT, Gunduzhan explained. “The team looked at Global Positioning System (GPS), mobile-device-based Time Of Arrivals (TOA) and Time Difference Of Arrivals (TDOA) techniques, as well as proximity to Wi-Fi,” he said. “These were all suitable since they don’t introduce new loads onto the cellular system — important during an emergency — and they maintain the privacy of the user.”
While these existing technologies can work effectively, some changes in WEA standards and implementations would be required to maximize the effectiveness of ASLAT.
“DHS S&T is looking for methods that can improve how government agencies warn Americans about danger and threats,” Waddell said, “and we brought together APL technical experts to examine the systems in use and formulate some very promising solutions. The ASLAT team at APL is proud to have delivered this report on behalf of our sponsor, and we think the technologies recommended could have benefits to other communications challenges facing the Lab’s sponsors.”
Media contact: Geoff Brown, 240-228-5618, Geoffrey.Brown@jhuapl.edu
The Applied Physics Laboratory, a not-for-profit division of The Johns Hopkins University, meets critical national challenges through the innovative application of science and technology. For more information, visit www.jhuapl.edu.