With revenues generated by the mission critical LTE ecosystem set to increase across all major sectors, there is a growing need for efficient and seamless options to interconnect TETRA networks with emerging critical broadband networks.
Industry analysts IHS Markit see the critical communications industry moving towards the adoption of critical broadband as a complementary service that allows users to communicate across both LMR/PMR and cellular networks, depending on specific operational requirements.
A white paper ‘TETRA Connectivity to LTE’ produced by TCCA’s TETRA Industry Group (TIG) provides an overview of the different approaches to enabling TETRA/LTE interworking, with several methods described. The key issue addressed in the white paper is interworking between the LMR/PMR and LTE worlds and particularly the interworking and evolution of PTT services, as group communications capability is the key service in LMR/PMR.
“TETRA networks are expected to be operational for many years to come; new nationwide public safety networks are still being deployed and many are receiving mid-life upgrades. In other sectors such as Transport and Utilities, TETRA remains recognised as the best technology for dedicated mission critical use, with complementary broadband data integration on many operators’ roadmaps,” said Francesco Pasquali, TIG chair and TCCA Board Member, sponsored by Leonardo SpA.
“TETRA will therefore need connectivity to other bearers, particularly LTE, to facilitate long term co-existence, safe migration from TETRA to LTE or as a hybrid communications solution. It is clear now that such interworking can be achieved and that different approaches can be taken to suit various user scenarios.”
It is expected that there will be a standard available for interworking between TETRA and LTE that will meet the needs of critical communications users in the 2019 timeframe – the standard will then need to be converted to products and implemented in LTE networks. Through using standards-based approaches users will have the benefit of open competitive markets for their solutions and the ability to use products from different suppliers.
For those that need solutions now there is a range of company-specific proprietary solutions that will give various level of interworking. These solutions may in time conform to new standards. The deployed commercial LTE systems deliver very good, but best effort, service until hardened, updated to the latest 3GPP Release and potentially having their area coverage expanded.
3GPP has commenced standardisation work on the LMR/PMR/LTE interworking functions in Release 15 and TCCA expects to have this functionality specified in Release 16, currently planned for completion by December 2019.
For interworking with another technology, 3GPP can only standardise half of the solution, and work is therefore in progress in ETSI Technical Committee TCCE (TETRA and Critical Communications Evolution) to standardise the equivalent functionality needed by TETRA to achieve a workable solution. With there being a significant gap between the release of standards and the availability of the associated functionality in products for operational use, it is not expected that there will be a full range of 3GPP compliant interworking solutions deployed until 2021/2022.