Wireless emergency alerts (WEA), such as severe weather warnings and Amber Alerts for notifying the public about abducted children, were first proposed after the WARN Act was passed in the United States in 2006. Since then, several major wireless carriers have opened their networks to WEA messages, which are sent from cell towers geographically located within the alert’s targeted area.
Now, TeleCommunications Systems Inc. (TCS) has been approved to continue its research into using radio frequency coverage to improve the accuracy of WEA messages. The research, which is sponsored by the U.S. Department of Homeland Security (DHS) Science and Technology Directorate (S&T), is entering its second phase after an initial development period last year.
The research is focused on the development of enhanced geo-targeting algorithms, using commercial off-the-shelf (COTS) code, to send messages to mobile subscribers based on geographic location. More specifically, the research will work to standardize algorithms and data management processes that will be used to transmit WEA notifications more accurately to the areas that need them.
TCS has partnered with ClearTalk Wireless, which provides cellular coverage across the country typically in densely populated areas, to test the capabilities of the algorithm with the carrier’s mobile network. The eight-month research project, which began this past June, includes field tests with to validate the theoretical concepts demonstrated last year in simulations.
Instead of using just the physical location of cell towers, the company has suggested using cellular RF coverage to target recipients of emergency alerts. If a particular area that needs an emergency alert falls within the RF propagation area of a cell tower, the tower will transmit the message to all the users within the RF footprint.
The current iteration of the WEA program is slightly outdated. The geo-targeting capabilities of the WEA program are defined by a Federal Information Processing Standard (FIPS) standard, according to a TCS research summary published last year. The FIPS algorithm is based exclusively on the coordinates (latitude and longitude) of the cell tower transmitting the message to mobile users.
However, only using geographic location to distribute the messages can result in alerting too many people or not notifying certain people who might need the alert. The radio towers will send a notification—for instance, one from the National Weather Service about a flash flood warning—not only to the targeted area, but also to every region where the radio tower sends wireless signals.
In counties with large geographic areas, for instance, an alert could be sent to mobile subscribers in an entire region, even though only a small part is affected. On the other hand, a mobile subscriber might not receive an alert because the serving cell tower is physically located outside of the area designated by the FIPS code.
Although the RF footprint approach has the potential to be more accurate than using geographic location, it does have several obstacles to widespread usage. One of the major issues is the process of collecting, converting, and importing cell coverage RF data into a database. For the algorithm to work correctly, it must know exactly how far the cell tower propagates its RF signal, and whether it can reach the area where the WEA message is required. The problem arises from the fact that cell towers frequently change their areas of coverage, typically on a daily basis.
According to TCS, the algorithms can be deployed without changes to existing hardware, networks, protocols, or handset software. The method is also being designed to complement the Communications, Security, Reliability, and Interoperability Council (CSRIC) within the Federal Communications Commission (FCC). The CSRIC works to ensure the security and reliability of communications systems in public safety.