Enhanced Geo-targeting for CMAS

Current public alert and warning systems have limitations when it comes to sending emergency messages to geographical regions of arbitrary size and shape. Lack of an accurate “geo-targeting” capability reduces the level of trust in issued alerts due to previous reception of irrelevant alerts. It also limits the ability to include specific instructions in a public alert targeted only for people located in a relatively small target area. The Commercial Mobile Alert System (CMAS), which allows sending public alerts to cellular devices, emerged as the alert dissemination channel with promising geo-targeting capabilities, since the cellular network infrastructure supports much more accurate geo-targeting capability compared to other systems such as TV or radio broadcast. Accurate geo-targeting is particularly important for CMAS, since the alert messages are limited to 90 characters, which prevents including a description of the target area. However, mandatory geo-targeting support in CMAS is currently specified only at the county level, which means that even if a target area smaller than a county is specified in an alert message, participating cellular service providers may choose to limit their geo-targeting implementation to the mandatory requirement and send the alert to the entire county. Furthermore, even for the cellular service providers that choose to support sub-county level geo-targeting, the granularity will be limited by the size and location of individual cell sites. This causes mismatches between the desired target area and the footprint of the actual CMAS broadcast, causing either coverage gaps in the target area or regions that receive irrelevant alerts.

In this paper we describe a new approach for CMAS geo-targeting, which supports geographical regions with arbitrary size and shape. The new approach is based on leveraging location awareness found in most smart phones. In the new approach, cellular service providers broadcast alert messages to a wider area than the target area, but also include a polygon representation of the target area as metadata. Cellular devices that receive the alert compare their current location with the target area information, and display the alert to the user only if they are inside the target area. If implemented, the new approach would significantly enhance geo-targeting accuracy of CMAS, allowing targeted instructions to specific geographic locations. The new approach can also be leveraged in support of related-targeting whereby a user can choose to be notified when an alert message is issued to an area that includes a location of interest to the user.