Wireless Emergency Alerts in arbitrary sized target areas: Mobile location aware emergency notification

Wireless Emergency Alerts (WEA) is a public safety system that uses broadcast from cell towers to send geographically-targeted alerts and warnings to cell phones. It is one of the dissemination channels for the Integrated Public Alert and Warnings System (IPAWS). WEA typically broadcasts an alert in the cells with at least some portion affected by the emergency event. When the affected area includes only portions of one or more cells, there could be a high proportion of False Positives (people who should not have been notified get the message on their cell phones) and/or False Negatives (people who should have been notified but are not notified). We propose a scheme that uses the mobile devices´ knowledge of their own location and the target area described in the cell broadcast message to filter the messages in the cell phone and notify the user only when the mobile device´s estimated location is within the target area. We evaluate the new scheme in terms of false negatives and positives, radio resource requirements, and notification latency, and compare it with various other geotargeting schemes. We also discuss mechanisms to communicate the target area information efficiently in the limited bandwidth available in cellular broadcast channel. Finally, we discuss ways for allowing a broader set of contexts to determine whether a user should be notified of a given emergency.