TeleCommunication Systems, Inc. (TCS) carried out research and development on constructing an algorithm that utilizes Radio Frequency (RF) cell site propagation footprints. Research focused on using RF coverage area footprints to improve geo-targeting granularity and accuracy for delivery of Wireless Emergency Alert (WEA) messages. This report documents the field testing activities, findings and the analysis of the results that used the enhanced geo-targeting algorithm previously developed for this research.
The WEA standard (J-STD-101) defines two methods that can be used to select cell towers to deliver WEA messages for a given targeted geographical area. The first method calls for the ability to determine the cell towers at the county level of granularity. This level of granularity is a minimum requirement for all mobile carriers that offer the WEA service. The second method is optional and allows the targeted area to be defined by polygons instead of fixed county boundaries and determines if the targeted cell tower physical position (latitude/longitude) is found inside the target area polygon. Both of these methods have been found to be highly inaccurate as the alert target areas become smaller and therefore cannot be used to issue alerts that require target area size to be within a few square miles. This inaccuracy introduces situations known as "over-alert"—when an alert reaches population that is not intended for—or "under-alert"—when the alert does not reach the people in harm’s way.