Critical communications in a process-driven world

To face this challenge, Ian Carr, Simoco puts the case for DMR as the worthy successor to TETRA.

In the world of critical and emergency services communications in EMEA, TETRA has been the gold standard for over 15 years. Prior to its development we had a world of fragmented, stand-alone PMR systems that were wholly inadequate to face up to the challenge of crime and public safety, which require national co-ordination and no-compromise performance. The UK Airwave system has been a flagship success story for the ETSI standard. Similar TETRA systems such as BOSnet in Germany are equally battle proven and highly valued. Indeed, TETRA has been widely adopted in various forms and, along with the P25 standard, has been successful with public safety organizations across the world.

TETRA: A tough act to follow

When we look at what TETRA offers it’s not hard to see why its advent was such a step change in critical communications standards. First of all, it offers critical communications functionality that we now take for granted; like instant push-to-talk (PTT) voice and group communication. Based on four-slot TDMA, it offers good range at relatively low power. Its existing implementations in dedicated public safety and high end commercial applications also offer the sort of resilience, redundancy and dedicated high-density traffic capacity that government organizations need to cope with in major emergency situations like the July 7 bombings in London, where the limitations of a publicly accessible cellular system were tragically revealed. A vast array of functionality has also been built into TETRA equipment over the years, tailored to this early customer base of Government networks.

So, TETRA has a lot going for it and any decision to move to another standard needs to be carefully evaluated. However, as an organization that provides TETRA, P25, MPT1327 trunked analog systems and DMR networks, Simoco is seeing an increase in the number of tenders for large critical communications networks that do not specify TETRA as the only option and are increasingly making direct comparisons of value for money between TETRA and DMR or between P25 and DMR.

Everything, even critical communications, has its price

Two reasons to change to another standard emerge. One is that old chestnut of cost and the other is based on the changing landscape of user and customer expectations. Taking the cost argument; TETRA offers impressive features but at significant cost, both in terms of initial purchase and in costs driven by complexity, which in turn carries the consequential costs in training, maintenance and spares holding. If I were in the emergency services and cost were not an issue, I would want the biggest, the best, the most reliable, the most resilient network as well as features and functionality such as instant PTT, group calling, call handover, Dynamic group Number Assignment, discrete listening and encryption. But many of the features and functions of TETRA networks introduce cost and complexity, which many of today’s customers for PMR systems simply do not need.

When TETRA was introduced it was a state-of-the art solution that came at a state-of-the-art price; a price that only governments could afford. TETRA is more expensive to install and maintain, due to its complexity and the fact that it has a switch-based architecture, which means there is less scope for the use of common components that can be software configured. More commercial implementations of the TETRA standard have emerged over time but these have been adaptations of a fundamentally expensive standard.

A changing landscape

The core requirement for people to talk to each other reliably and quickly has not gone away. Can other standards like DMR give organizations the functionality they need without the higher cost of TETRA? Migration to digital networks and the benefits that migration can bring seem to have been an agenda item for the industry for decades but, with around 80% of the PMR installed base still being analogue, it is a consideration that will not go away. 

In this respect, DMR is a realistic alternative, providing much of what TETRA can offer at a lower overall cost. With fundamentally the same TDMA architecture as TETRA, DMR is a well-supported ETSI standard, offering the coverage characteristics of an analog network which allows migration to digital without the disruption of re-planning the network to take account of the increased density of sites required by TETRA, when compared to an analog network.

Spectrum considerations are a part of any migration plan. Many potential PMR users do not have the UHF 25 MHz of spectrum required for TETRA, and do not require the capacity provided by a four-slot TDMA system. However, many smaller mission critical and high end business critical systems do require other bands such as VHF and the benefits of a trunked radio system, without the disruption of having to re-plan networks, due to transmit power differences or the need to re-apply for spectrum.

Ease of implementation is another critical factor in driving down costs. Training, spares holding, site acquisition and maintenance costs can all be significantly impacted by the network architecture supported by manufacturers.

Simplicity of deployment and maintenance has an obvious impact on an operator’s lifecycle costs.  At Simoco, our approach has been to leverage all the benefits of an IP connected infrastructure to reduce the overall costs for operators. Many of the design features of our DMR offering draw directly from the learning gained from implementing our IP-based, MPT1327 Xfin systems. With no central switching or hierarchical infrastructure, the distributed architecture of the network means that redundancy and resilience are built in at the base station level. Two or more IP base stations, connected via private or public IP can form a fully functioning network, with all the savings that this implies.

Recent tenders to which Simoco have responded have specified options for either TETRA or DMR systems and feedback from these tenders has consistently indicated that the DMR option offers more than 50% saving compared to the TETRA option.

One of TETRA’s key strengths has been interoperability and the lessons of the early TETRA market have been taken up in DMR. Like TETRA, the DMR standard was conceived by ETSI, a not for profit organization with 700 member organizations, drawn from 62 countries, across five continents. The coverage this affords suggests that we have the potential for a truly global community of inter-operable manufacturers.

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