The Future of Mission Critical Communications

In December 2015, the UK Government signed contracts with Everything Everywhere (EE) and Motorola Solutions as part of the Emergency Services Mobile Communications Programme (ESMCP).

They join Kellogg, Brown and Root in a commitment to deliver the UKs £1bn Emergency Services Network (ESN).

The system currently deployed is based upon an ageing circuit switched technology - Terrestrial Trunked Radio Access (TETRA), primarily designed for the dominant mode of communication used by the emergency services – voice. As the potential benefits of access to high speed data services become apparent, TETRA as a technology will be unable to satisfy the demands of the future.

Long Term Evolution (LTE), first introduced in 2008 in release 8 by the 3rd Generation Partnership Project (3GPP), is an evolutionary 4G cellular system capable of offering broadband mobile services. Together with the economies of scale sought from using existing equipment, LTE makes a favourable technology for a future ESN.

LTE however, although capable of data rates in the order of tens of megabits per second, ultimately hundreds, is an all Internet Protocol (IP) system that offers no circuit switched capability, presenting problems in the delivery of real-time services, such as voice, and therefore an unlikely choice for an ESN.

However, solutions have since been developed within an LTE environment to allow for the transport of real time data, two of which dominate. The first is a technique known as Circuit Switched Fallback (CSFB), which effectively reuses the services of existing legacy CS capable networks, such as GSM and UMTS by redirecting an LTE device to a circuit switched cell when a real time transaction is triggered.

The second is known as VoLTE (Voice over LTE), which employs Voice over IP (VoIP) techniques to offer real time services via an IP Multimedia Subsystem (IMS). The IMS has been around for quite some time; however it represents an extremely complex and expensive network upgrade and many operators have been resistant to the idea of deploying one.

VoLTE is likely to be the best solution for handling real time services in the future, eradicating the need to handover services to legacy networks. LTE however, typically sets up point to point connections whereas a police control room for example, relies on the ability to communicate with multiple users at the same time.

real time transaction is triggered.

Release 8 of the LTE standards does not support what is known as Push to Talk (PTT) services, which enable group calling. Release 13, scheduled for March 2016 aims to do just that.

3GPP has been conducting studies to assess how LTE can be used most effectively for Mission Critical Communications (MCC). The service requirements for Group Communication Service Enablers (GCSE) have already been defined in release 12 with Mission Critical Push to Talk (MCPTT) 66% complete at the time of writing.

Additionally, to support the needs of first responders, Proximity Based Services (ProSe) provide a replacement for the Direct Mode of Operation (DMO) used with TETRA handsets.

ProSe will allow responders to locate colleagues in close proximity and communicate directly without the need for network infrastructure. These methods of communication are not simply for voice but will also support multimedia services. Use case examples include video streaming from a police camera; medical information sent from an ambulance to a hospital while in transit; and thermal imaging data passed to the incident control room.

With services such as PTT and ProSe to be defined this year, LTE is gearing up to become the technology of choice for mission critical communications, although it will be some time before the capabilities are truly realised.