Long Term Evolution (LTE), with its wide-scale commercial deployment and the ability to support a wide variety of services from high bandwidth data to real-time communication, has been selected as a technology for mission critical mobile broadband communications and public safety by numerous of public safety organizations including the Association of Public Safety Communications Officials (APCO), the TETRA & Critical Communications Association (TCCA) and the National Public Safety Telecommunications Council (NPSTC). Since LTE was not initially designed for critical communications, the 3rd Generation Partnership Project (3GPP) has collaborated with such organizations as TCCA and NPSTC to enhance LTE to be fully compliant with the mission and safety critical requirements. As a result, 3GPP has recently created a new working group, called SA6, specifically to tackle the challenges associated with mission critical applications, with an initial focus on group communication. To position LTE as a technology for critical communications, various efforts have been conducted in the release 12 (Rel-12) and Rel-13 of the 3GPP specifications. Especially, the potential capability of evolved
Multicast/Broadcast Multimedia Service (eMBMS, a.k.a. LTE Broadcast) to transmit the same content to a large group of users simultaneously and effectively makes eMBMS a solution for group communication, which is an essential application in public safety.
In this chapter, we first highlight the fundamental background on eMBMS. We then focus on two essential applications for public safety and mission critical communications which rely on eMBMS: the Group Communication (GC), and the Mission Critical Push to Talk (MCPTT).