From 3GPP Technical Specification 22.179: “A Push To Talk service provides an arbitrated method by which two or more users may engage in communication. Users may request permission to transmit (e.g., traditionally by means of a press of a button). The Mission Critical Push To Talk over LTE (MCPTT) service supports an enhanced PTT service, suitable for mission critical scenarios, based upon 3GPP Evolved Packet System (EPS) services.” Some of the enhancements that make MCPTT suitable for mission critical scenarios are: Quality of Service (QoS) Class Identifiers (QCIs) that ensure a higher QoS for the MCPTT service, media encryption, Priority – Preemption – Quality of Service (QPP), network-supported authentication and authorization, service continuity features such as off-network communication capabilities or UE-to-network relay, location during emergency or imminent peril communication, and many more. MCPTT is a Push-To-Talk application specifically made for emergency responders such as police officers, firefighters, and EMTs.