Harald Ludwig, chair, TCCA Technical Forum
Amidst all development within 3GPP, and the mission critical broadband features emerging, national TETRA network operators and users are investigating and preparing to adopt the new mission critical technologies. However, it is accepted that TETRA will be needed to work in parallel with the emerging critical broadband networks, and for that to happen there needs to be a mechanism put in place for the two networks to operate in harmony.
Since 2021, stakeholders in critical communications have been discussing if an interworking function (IWF) is to be made available in the market so it can be used for the communication between the existing narrowband TETRA systems and the 3GPP MCX services. These are mission critical Push-to-Talk (MCPTT), mission critical data (MCData) and mission critical video (MCVideo) collectively known as MCX, running on 4G/LTE and 5G bearers. As mission critical broadband technologies are deployed, this requirement for interworking with existing TETRA systems is becoming increasingly important.
To facilitate the adoption of MCX, and to enable communication between users on each system, a connection between the two types of technology is needed. A means to provide this bridging functionality is under development by ETSI to standardise into a logical IWF that will be located within the TETRA network infrastructure.
TCCA has produced a white paper that describes the relation between the IWF and the TETRA infrastructure from the perspective of operators and users. The focus is on the usage during transition and what the expected features needed from this perspective are. It designates priorities in a clear overview of 1) must-have, 2) nice to have and 3) not prioritised. Included are use cases which are reflections from operators considering how the IWF can be managed during operation.
The white paper puts into an operational perspective how TETRA operators and users might want to use an interworking functionality for pilots, proof of concepts, migration, hybrid deployment and, at a later stage, the transition towards MCX.
From an operator perspective there could be several phases in the IWF deployment cycle. These phases will be part of planning the national migration projects and will have variable durations, hence they indicate the business and use case for the IWF. The four main phases (which have overlaps) can be categorised as:
With all planning ongoing for migration to a next generation infrastructure and ecosystem, it is likely that most of the major TETRA operators will go through these phases when making this transition to MCX, although there are exceptions and not all providers and operators will follow these phases.
The IWF was added to the 7th ETSI Plugtests™ event hosted in Malaga in November 2022 for the first time. A standardised and preferable certified TETRA IWF solution supporting the basic set of voice and data services should be available in the market to facilitate the transition so operators and network owners can start dimensioning future scenarios of making the transition from TETRA to MCX. The white paper ‘Service Overview: TETRA-MCX Interworking (TETRA IWF)’ can be read here
