The only thing more disconcerting than receiving irrelevant emergency alerts transmitted to cell phones is not receiving the one that was highly relevant.

That inconvenience may soon be eliminated through a new concept called Arbitrary-Size Location-Aware Targeting (ASLAT), developed by The Johns Hopkins University’s Applied Physics Laboratory (APL), in North Laurel.

The new technology allows a more accurate method of delivering certain types of messages and may soon be able to warn users to avoid particular nearby locations in the event of natural disasters, local emergency responses and other dangerous situations.

“Currently, under the Wireless Emergency Alerts (WEA) infrastructure, messages often go out very broadly, generating a large number of false alarms, while other people … in the warning area do not receive those warnings due to poor cell coverage or a few other factors,” said Richard Waddell of APL’s Asymmetric Operations Sector and ASLAT program manager. “ASLAT dramatically reduces both false negatives and false positives.”

For the average cell phone user, this means that warnings of location-specific emergencies such as large building fires, natural gas leaks, flash floods and tornadoes could be delivered more accurately to the correct populations that need to know about them.

APL’s work to develop the technology was undertaken with the support of the U.S. Department of Homeland Security’s (DHS) Science and Technology (S&T) Directorate.

Some Changes Required

According to a final report on ASLAT provided to DHS by APL in June, the technology allows WEA alerts to be broadcast to an area wider than the target area, but the alerts are only displayed to the user if the mobile device is inside the target area.

“ASLAT uses the location awareness of wireless devices … 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 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.”

He explained that the team incorporated Global Positioning System (GPS), mobile-device-based Time of Arrivals (TOA) and Time Difference of Arrivals (TDOA) techniques in their research, as well as proximity to Wi-Fi networks.

“These were all suitable because they don’t introduce new loads on the cellular system — important in an emergency — and they maintain the privacy of the user,” Gunduzhan said.

According to APL’s report, ASLAT can improve the geotargeting accuracy of WEA significantly without consuming excessive mobile device power or radio resources.

Clever Workaround

Although the use of ASLAT does cause a delay as mobile devices determine their location before processing received alerts, highly delay-sensitive alerts, such as earthquake warnings, are able to bypass ASLAT automatically and be processed using default WEA behavior.

The current WEA geotargeting mechanism has limited precision because of the locations of cellular network sites in relation to one another and the areas covered by their relay transmissions, referred to as granularity. According to APL’s report, this granularity can be especially low in suburban areas, where cell towers are typically further away from each other and serve larger areas.

The new ASLAT technology essentially takes advantage of mobile device capabilities to overcome that weakness, enhancing the geotargeting capabilities of WEA beyond what is possible in its current configuration.

APL’s report recommends that the DHS S&T’s Program Management Office work with other stakeholders, including the Federal Communications Commission, Federal Emergency Management Agency, cellular service providers, the Alert Originator community and state and local first responders, to determine detailed requirements for geotargeting accuracy and to analyze alternatives to meet those requirements.

“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. We think the technologies recommended could have benefits to other communications challenges facing the lab’s sponsors.”