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What is Trunking

In two-way radio, a digital trunking system is one that allocates frequency resource to a group of radio users, as opposed to these groups of users always being fixed to specific frequency resource. Sounds complicated, right? So let’s remove the jargon to look at what digital trunking means in real terms and how a trunking radio system can benefit your organisation.

Firstly, it’s important to understand there are different types and levels of digital trunking in the two-way radio world. Legacy analogue MPT1327 systems and TETRA solutions are just two disparate examples of trunked radio networks. Neither example will be relevant for the majority of UK radio users but it’s worth noting that the trunked radio family extends beyond what we’ll overview here. Most of our UK clients take advantage of DMR (Digital Mobile Radio) trunking solutions. These networks can be found in every market sector from aviation to education and it’s these variants of DMR trunking we’ll take a closer look at now.

The most common types of DMR (digital) trunked radio systems in the UK today are sometimes unofficially grouped together and referred to as “DMR Tier 2.5”. They are called this because they are a level above DMR Tier II “conventional” systems – they offer digital trunking. However, they don’t come close to meeting the requirements to be classed as true ETSI Standard DMR Tier III trunking networks. Examples of DMR Tier 2.5 solutions include MOTOTRBO™ Capacity Plus from Motorola Solutions as well as Hytera’s Psuedo Trunking and XPT offerings.

How does trunking work?

“DMR Tier 2.5” digital trunking solutions are popular because, for many, they offer the best of both worlds – mixing the flexible enhancements of trunking with low costs of a conventional digital (Tier 2) system. Let’s see how they achieve this…

You’ve noticed that the Security team only communicate via radio a couple of times a day, whereas the Maintenance radios are always in use. The Maintenance Supervisors have the ability to make one-to-one calls between each other, separate from the Maintenance talk-group. Given that Maintenance only have access to the one time-slot on your existing repeater, you know that whenever the Maintenance Supervisors are making one-to-one calls, the rest of the Maintenance group can’t speak and vice versa. This is causing some problems for the Maintenance Team who are regularly finding their radios emit a “busy” tone when they try to initiate a radio call, due to their time-slot already being in use. Meanwhile the time-slot for Security sits empty and unused 99% of the time.

For the safety and efficiency benefits offered, you have now decided to deploy a TRBOnet PLUS software solution alongside your digital trunked radio system. Data associated with TRBOnet PLUS software such as radio registration and GPS location is also trunked. You work with DTS thoroughly prior to the purchase of TRBOnet PLUS to assess what impact adding data features and extra talk-groups onto your trunked radio system will have. DTS recommends the deployment of TRBOnet WATCH software to continually check how busy your system is as part of this assessment.

This is just one example of an existing client of ours. It demonstrates how they went from a small single-repeater system to a solution with hundreds of radios and dozens of advanced safety-driven features over the course of 18 months.

When our client opened a second manufacturing facility 15 miles away from their main site, we were there to help again. We deployed a new repeater site and linked it to their head office via IP, allowing cross-facility communication and creating a Capacity Plus Multi-Site network. Up-to 15 Capacity Plus sites can be linked in this manner to extend radio coverage or connect remote sites. We touch more on the benefits of multi-site systems HERE.

We’ve covered Capacity Plus and touched on other forms of DMR “Tier 2.5” trunking. So why would you ever need a higher-level DMR Tier III solution?

For many organisations, DMR Tier 2.5 is perfectly designed to meet their radio communication needs, as we saw in the example above. But for those relying on their radio system for large, mission-critical operations like airports, power stations and ports, a higher tier of radio network may be required.

DTS tend to recommend a DMR Tier III solution, such as MOTOTRBO™ Capacity Max instead of DMR Tier 2.5 in the following circumstances:

  • Massive Coverage Requirements: If you need more than 15 radio sites to meet your needs, Capacity Max is the solution for you. It offers up to 250 sites on a single radio network.
  • Massive User Requirements: For organisations with more than 1600 radio users in a single location, Capacity Max offers up-to 29 voice and data repeaters per site. A further 12 dedicated data repeaters can be added on top of this for every single site in the network giving you unmatched capacity for up-to 3000 radio users per site alongside support for data-heavy operations.
  • Increased Resiliency: While DMR Tier 2.5 systems offer a generous amount of fail-over, MOTOTRBO™ Capacity Max networks provide multi-level resiliency and can be run with no single points of failure in the majority of cases. This makes Capacity Max the intelligent choice for organisations where radio downtime is simply not an option.
  • True Priority Calling & Pre-emption: With DMR Tier 2.5, initiated radio calls access the system on a first-come, first-served There is no priority on the system. You can create the illusion of priority levels via functionality like transmit interrupt but this can prove clunky. With a DMR Tier III solution like MOTOTRBO™ Capacity Max, you can set true priority levels for your radio talkgroups, allowing less important conversations to be automatically superseded by critical ones. This is a useful feature during day-to-day operations but, in a crisis, priority call levels mean there is always space for users that need it. In the most extreme cases, this can be the difference between life and death.
  • Dynamic Site Light-Up: For organisations operating different groups at different sites, MOTOTRBO™ Capacity Max analyses whether repeater site resource needs to be allocated during specific group calls by knowing which radio users are using which group on each site. For example, a large city council deploys an 8 site radio system to support refuge collection, parking wardens, street cleaning and 10 other teams, each with their own radio talkgroup. There are two repeaters at each site. As each council radio user could be anywhere within the city at any given time, with a DMR Tier 2.5 solution, every group call would have to be rebroadcast at every single site. This results in wasted resource as, most of the time, sites are rebroadcasting a call with no radio users listening to that group. It also means there’s only the capacity for 4 concurrent radio calls across the entire network. With Capacity Max, the infrastructure checks whether a radio user connected to a site is set to a given talkgroup before rebroadcasting the call on that repeater site. If no one’s listening, it won’t “light up”. With Capacity Max’s intelligence, the council can best make use of its infrastructure.

In many cases, infrastructure from DMR Tier 2.5 systems can be upgraded for use as part of a DMR Tier III system. For example, you can utilise Motorola Solutions SLR5500 or SLR8000 repeaters as part of analogue, digital (DMR Tier II) conventional, Capacity Plus Single Site, Capacity Plus Multi Site or Capacity Max networks. DTS work alongside your organisation from the outset to ensure all aspects of your system are right for you now and are future-proofed as your company evolves and expands.

The image below helpfully sums up the differences between conventional DMR, IP Site Connect, DMR Tier 2.5 (Capacity Plus) and DMR Tier III (Capacity Max/Connect Plus) systems.

Now you understand a bit more about trunking solutions, we’d be delighted to discuss your requirements. We offer free onsite consultancy and site survey visits which subsequently allow us to compose a quotation offer that takes into account your needs and your budget. We are more than happy to provide multiple options as well as indicative costs for future upgrades and ongoing maintenance.

If you want your new trunked radio system to be packed with useful features, proactively overseen by experts and with costs spread across the length of a 3-year or 5-year term, ask about our Managed Service contracts. More info on Managed Services from DTS can be found here.