Emergency Messages in the Commercial Mobile Alert System

The U.S. Department of Homeland Security initiated the Commercial Mobile Alert System (CMAS) to ensure that emergency situations are effectively communicated to the general public. CMAS uses the existing commercial telecommunications infrastructure to broadcast emergency alert text messages to all mobile users in an area affected by an emergency. One of the limitations of CMAS is that the maximum message size is 90 characters of plaintext. This paper proposes an enhancement to CMAS that provides more detailed information within the 90-character text using an encoding technique. The viability of the enhancement is demonstrated using a prototype that generates and broadcasts CMAS emergency alerts to Android phones, on which an emergency response application intercepts, decodes and displays the alerts to users.