TETRA Network Evolution: Public, Private and Hybrid Approaches

By Dudy Cohen

TETRA [(Terrestrial Trunked Radio)], as a voice-centric communication infrastructure, will continue to serve Public Safety organizations around the world for years, if not decades. This does not mean, however, that the Public Safety communication infrastructure is not, or should not be, evolving.

Public safety authorities strive to enrich their operations with new broadband-based applications such as video surveillance, drone camera feeds, body-worn cameras, and massive database queries – all of which require significantly higher capacity than currently available in TETRA networks. On the other hand, the requirements for mission-critical broadband applications are not that different than the ones of narrowband voice applications – namely resiliency, availability, reliability and security.

In order to introduce a mission-critical broadband infrastructure to support those new applications, public safety authorities can typically leverage existing LTE, LTE Advanced and future 5G technologies. Such authorities should consider several options for evolving their networks and services: 

1. Public network-based infrastructure – in this option, the public safety authority uses a public LTE network as a large enterprise user. The additional security level is added at the mobile device level, yet coverage and availability enhancements are up to the mobile operator to provide. 

2. MVNO (mobile virtual network operator) – in this option the public safety authority becomes an MVNO, serving its internal users. A core network is established covering authentication, security and some quality-of-service parameters. The mobile operator is still responsible for coverage and availability enhancements. 

3. Externally operated private LTE network – in this case an end-to-end network is built to accommodate the public safety authority’s requirements. An external entity, typically a mobile operator, builds and operates the network on behalf of (and for) the public safety authority (or authorities). The most obvious example of this type of solution is the FirstNet network in the US.

4. Private LTE network – built and operated by the public safety authority. 

5. A hybrid approach – typically combining option 2 with option 3 or 4.

It is easy to understand that a true mission-critical application can only rely on a private LTE network (options 3 or 4) as such a network will surpass, in terms of coverage and resiliency, any public network. One of the reasons for that is the extended coverage requirement for public safety needs, compared to typical public network coverage. There is, however, a trade-off between the cost and implementation time of a public network versus the security, resiliency and coverage of a private network.

A private network requires site acquisition, frequency acquisition (both for the access network and for backhaul), and a major upgrade in terms of scale and skill of the organization. (Having said that, the latter could be resolved using option 3.) Those tasks usually take a long time to complete, and require significant investment. This is why some organizations argue that option 5, the hybrid approach, is the most pragmatic one. In this approach, an MVNO-based service is first introduced nationwide, while a private network is gradually deployed. Deployment elements such as compact, all-outdoor radio solutions as well as wireless backhaul are used to make network deployment simple and fast. Users, as they enter the private network coverage zone, are seamlessly migrated from the MVNO service to the private network service.

While voice continues to be served by TETRA infrastructure, broadband services are being introduced to improve the performance of public safety authorities, with no compromise on security or availability.