DMR Tier III: the open standard for radio communications

Private mobile radio is fast becoming an essential communications solution to support the operational needs of utilities companies, airports, oil and gas pipelines and emergency services.

When compared to public cellular services, it delivers improved coverage, reliability and resistance, contention, security, group communications and performance.

The digital landscape is crowded, though, with a number of public safety digital standards such as TETRA, P25 as well as low cost digital solutions including DMR (Digital Mobile Radio), dPMR (digital Private Mobile Radio), NXDN and PDT (Professional Digital Trunking).

DMR is coming out on top thanks to the open standard nature of DMR Tier III trunking, which is driving its emergence, ongoing development and adoption across global markets.

But do open standards matter? While open standards are less important in the small system market, they are critical to the long-term case for the radio system in the medium to large systems sector, and it is here that open standard DMR Tier III will dominate.

Essentially, DMR Tier III trunking features a control channel on each radio site and allocates traffic channels on demand making it frequency efficient and enabling a large number of users to share a relatively small number of channels. Radio sites can easily be inter-connected, usually using IP connections, making it possible to deploy systems ranging from a single site to hundreds of sites spread over a large geographical area.

The open standard way

The DMR standard includes the facility for implementers to provide ‘manufacturer extensions’, enabling manufacturers to provide proprietary features within the framework of the DMR air interface definition. This allows them to complement the standard set of DMR call functions with their specific facilities.

This has the advantage of enabling customers to request specific functionalities to support the manufacturer’s business operation needs and also enables them to provide innovative features that differentiate their solutions from others implementing the same standard.

One disadvantage to this offering is that interoperability can only be possible for those features that are fully defined by the standard and that customers using manufacturer extensions are effectively locked in to a single manufacturer solution rather than enjoying the vendor choice that a standard enables.

To address the pros and cons, the DMR Association (DMRA) has struck a balance between robustness and cost with their interoperability process, which focuses on testing the conformance of products against the published standard that describes the over-air signalling. The DMRA facilitates testing between a terminal manufacturer and an infrastructure manufacturer, and the two parties carry out the testing against a standard test specification. Test results and logs of all messages sent over air are recorded during the testing and then are inspected by one or more independent third parties during a detailed review meeting. Only after the independent third parties are satisfied that the equipment under test has conformed to the open standard specification is an interoperability certificate issued.

Ongoing standards development

Whilst this facility can be useful, extensive use of manufacturer extensions would call into question whether DMR was a standard that delivers interoperability (and therefore vendor choice) or whether it results in proprietary solutions rather than following an open standard.

The answer to this lies in the work of the DMR Association. The DMRA has a technical working group – made up of competing manufacturers – who collaborate to ensure the standard succeeds. Any proprietary features from the manufacturers, which are believed to have wide market appeal or have useful features the standard doesn’t yet specify, are debated in the group. They are then developed to further advance the standard to the benefit all of the manufacturers and indeed the customers who choose to implement DMR technology.

The DMRA is further developing the standard to meet future market demands by identifying important new features and ensuring these are developed and included in new releases of the ETSI standards.

The future of DMR Tier III

Open standards are critical to providing long-term support and stability to customers. The adoption of the standard by a critical mass ensures its longevity over other similar competing technologies that have lower levels of support by offering the market vendor choice and maintaining low costs.

Is DMR Tier III radio communications’ open standard for the future? Yes. Due to DMRA’s authority, the robust and well-supported interoperability programme and the long-term commitment of a large number of manufacturers, it is emerging as the most successful low cost digital technology for complex projects – and therefore the open standard that no other private mobile radios can contend with.

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