Wireless Emergency Alerts: Cell Radio Frequency (RF) Propagation Algorithm Operational Assessment   [open pdf - 1MB]

Taken from the Executive Summary: "TeleCommunication Systems, Inc. (TCS) carried out research and development on constructing algorithms that utilize 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) alert messages. Today, 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. For the first method, based on Federal Information Processing Standard (FIPS) code in counties with very large geographic areas, an alert is sent to all mobile subscribers even though the alert area may impact only a portion of the county, resulting in an 'over-alert' condition. Conversely, an uncovered area or 'gap' condition occurs when a mobile subscriber in harm's way does not receive an alert because the serving cell tower is physically located outside of the FIPS code defined boundary. Since RF cell site propagation is not taken into account, similar over-alert and under-alert conditions will be encountered for any solution that uses polygons as a target area."

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FirstResponder.gov: http://www.firstresponder.gov/
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