For decades, MC (Mission Critical) communications have run on dedicated narrowband radio systems such as TETRA (Terrestrial Trunked Radio) in Europe and P25 (Project 25) in North America. These systems are excellent at one thing: group voice. But they were never designed for the data, images and video that frontline teams increasingly rely on.
This is where MCX (Mission Critical Services) comes in. MCX is the umbrella term for the 3GPP’s Mission Critical services, which deliver push-to-talk voice, data and video over 4G and 5G mobile networks. Emergency services around the world are now moving to MCX.
It is important to note that MCX isn’t only for the police, fire and ambulance services. Other users include transport, utilities, nuclear, stadium security teams, events, train stations and airports.
MCX is made up of three services, all built on a common architecture defined in 3GPP TS 23.280. Users and groups can be given any combination of the three services depending on what their role requires.
Figure 1 - Key MCX Services
MCPTT is the voice service and the direct replacement for traditional radio systems. It provides the functionality first responders expect from TETRA and P25, such as calls, private calls, emergency calls and talker priority. MCPTT was standardised in 3GPP Release 13.
MCVideo and MCData followed MCPTT in Release 14, completing the MCX family:
MCVideo lets users make one-to-one or group video calls, and stream video to a group from a drone, robot, body-worn camera or security camera. Video can be captured, stored, annotated and analysed. Like the other MC services, it supports end-to-end confidentiality and low latency.
MCData handles everything that isn’t voice or video. This includes SDS (Short Data Service) messages, file sharing and database queries, such as a vehicle registration check from the roadside. It also supports computer-aided dispatch, event management, robot control, and the gathering and sharing of intelligence.
MCX (Mission Critical Services) is an application layer service environment delivered over 4G or 5G connectivity, as well as other non-3GPP networks such as Wi-Fi and fixed networks. Figure 2 illustrates an end-to-end view that includes the MCX client, 4G/5G RAN (Radio Access Network), 4G/5G packet core, IMS (IP Multimedia Subsystem) and MCX service servers. In addition, operational applications can also connect at the MCX application layer.
Figure 2 - End-to-End MCX Service Environment
Generally, the architecture is there to support MCX services, which involve a combination of signalling and control, which register MCX clients and establish or manage communications. In addition, the media or application data also needs to be transported between the MCX clients and applications, which may be related to the MCPTT, MCVideo or MCData services. In addition, the common architecture will include services such as:
MCX was first designed for LTE (4G), but from 3GPP Release 16 onwards, it is also supported over the 5G System. Because MCX is an application layer, the same MC services can run over 4G and 5G, and public safety networks can evolve alongside commercial networks rather than being rebuilt with every generation. 5G brings several capabilities that suit mission-critical use:
The UK’s ESN will replace Airwave, the TETRA-based system that police, fire and ambulance services have relied on for many years. ESN runs over BT/EE’s commercial 4G/5G network and uses Samsung’s MCX application. IBM is responsible for systems integration and the services users interact with.
The program has faced significant delays and is now being delivered in stages:
Full voice readiness is currently expected in 2028. Airwave will then be switched off region by region, and only once each emergency service is satisfied that ESN is operationally safe. Until then, Airwave remains in place under extended arrangements.
In the US, FirstNet shows what a nationwide public safety broadband network looks like at scale. Built and operated by AT&T in partnership with the FirstNet Authority, it serves nearly 8 million connections across more than 30,000 public safety agencies. It uses dedicated spectrum, gives first responders priority and pre-emption over commercial users and is being extended with satellite connectivity for areas without terrestrial coverage.
MCX brings mission critical communications up to date through the implementation of MCPTT, MCVideo and MCVoice. Underneath it, we see a common architecture that can be applied across different access network types and a 4G/5G network which aims to make MCX as reliable and available as possible.
This blog has only briefly touched on the concept of MCX. If this is a topic you’re interested in and want to discover it further, please check out our 20-minute MCX insight videos.