Mission Critical Applications

Description

Mission Critical Applications are a category of communication applications defined by 3GPP that exhibit mission critical characteristics such as low latency, high reliability, and priority handling. They are traditionally grouped into three main types: Mission Critical Push To Talk (MCPTT), Mission Critical Video (MCVideo), and Mission Critical Data (MCData). These applications are built on the Mission Critical Services (MCS) framework, which specifies the architecture, protocols, and procedures to deliver these services over LTE and 5G networks. The term 'Mission Critical Applications' is used to collectively refer to these applications and any future extensions that share the same critical requirements.

The architecture for Mission Critical Applications is defined in 3GPP TS 22.280 (requirements), TS 23.280 (architecture), and the media and signaling specifications TS 26.281, TS 26.880, and TS 26.881. The core of the architecture is the Mission Critical Service (MCS) server, which may be deployed as an MCPTT server, MCVideo server, or MCData server. These servers handle group management, session control, media distribution, and interaction with the core network. The UE hosts the corresponding clients (MCPTT client, MCVideo client, MCData client) that provide the user interface and media handling. Communication between the UE and the server occurs over the LTE/5G air interface and the IP Multimedia Subsystem (IMS) or directly via HTTP-based protocols.

MCPTT provides push-to-talk voice communication with group calls, private calls, and emergency calls. It uses a floor control mechanism to manage speaking rights, ensuring that only one user talks at a time in a group call. MCVideo extends this to real-time video, supporting group video calls, video streaming, and video sharing. MCData enables real-time data communication, such as text messaging, file sharing, and location sharing. All three applications support both on-network and off-network modes. Off-network mode allows direct communication between UEs using Proximity Services (ProSe) sidelink when network coverage is unavailable.

Mission Critical Applications rely on the core network for QoS, priority, and security. The core network establishes dedicated bearers with appropriate QoS parameters (e.g., QCI 65 for MCPTT voice) and enforces priority and pre-emption through the Policy and Charging Control (PCC) framework. Security is provided by mutual authentication, encryption of signaling and media, and authorization checks. The applications also support interoperability with legacy systems like TETRA and P25 through gateways.

The evolution of Mission Critical Applications continues with enhancements for 5G, including support for network slicing, edge computing, and integration with 5G New Radio (NR). The specifications are updated in each release to add features such as improved video codecs, enhanced data services, and better scalability. The term 'Mission Critical Applications' thus encompasses a growing set of services that leverage cellular technology to meet the demanding needs of public safety and critical industries.

Purpose & Motivation

Mission Critical Applications exist to provide reliable, secure, and prioritized communication for public safety and critical infrastructure users. Before their standardization, these users depended on narrowband Land Mobile Radio (LMR) systems like TETRA and P25, which offered voice but limited data and video capabilities. The need for broadband multimedia communication led 3GPP to develop Mission Critical Applications starting in Release 14. These applications leverage commercial cellular networks to deliver push-to-talk voice, real-time video, and data, enabling first responders to share video feeds, access databases, and collaborate more effectively.

The motivation was to unify critical communications onto a single broadband platform, reducing costs and improving interoperability. However, commercial networks required enhancements to guarantee priority, pre-emption, and QoS. 3GPP addressed this by defining the Mission Critical Services framework, which includes the necessary protocols, architecture, and QoS mechanisms. The applications are designed to operate even under congestion or network failure, with features like off-network direct communication and redundant servers.

Over time, Mission Critical Applications have expanded to include new capabilities such as MCVideo and MCData, and to support 5G features like network slicing and ultra-reliable low-latency communication (URLLC). They continue to evolve to meet the changing needs of public safety and other vertical industries, ensuring that critical users have the communication tools they need.