It’s time for a little roleplaying.

Imagine you’re the director of a large communications system for a city with both high-density metro (7 to 8 talk paths required) and low-density rural radio users (1 to 2 talk paths required). Your system consists of more than 100 repeater sites and serves users who primarily need voice capability with wide-area coverage, but they also need to transmit text messages, as well as AVL and some SCADA data.

You have an important decision to make: Do you keep the emphasis on voice communications and choose a migration path for DMR Tier 3, or do you open up more opportunities for data applications with TETRA?

“This one could go either way,” Morné Stramrood, senior sales engineer and subject matter expert on TETRA and DMR for Sepura, said in an IWCE’s Urgent Communications webinar. “Both technologies have got points that favor them in this kind of application.”

The webinar, which is sponsored by Sepura, is titled “TETRA and DMR Tier 3: Which Open Standard Digital Trunking is Right For Me?” The presentation, which explains the key differences between TETRA and DMR, is now available on demand via this link.

In the scenario outline above, DMR would have the edge on wide-area mobile coverage, and it would also satisfy the city’s limited data requirements. TETRA, on the other hand, offers portables with low-power base stations, in-call site handover and the ability to use mobiles in rural, low-density area with a mobile gateway to provide portable coverage. TETRA would enable a lower RF channel count in urban areas while achieving the same number of simultaneous call.

Given this, TETRA wins out in this scenario, according to Stramrood.

“The key here … is the fact you have those high-density metro areas that are included,” Stramrood said during the webinar. “If you didn’t have that, then this would lean toward DMR. That high-density metro area gives you the fact that you can use TETRA for portable coverage within that dense area and use the mobiles in TETRA with the gateway feature to augment that coverage, so now you space your sites quite a bit farther when you’re outside of that urban area.

“DMR will work for fine for that whole area. The biggest thing issue is—when you’re in that metro area—DMR does not have the handover, so you still have to make sure that you’re sites are a little bit larger-area covered with it.”

Meanwhile, in another use case, DMR Tier 3 is the clear choice.

Consider another system with more than 100 repeater sites with a moderate amount of channels (two to four) that serves a low density of users whose primary use is voice communications, but who occasionally need text messaging and AVL.

In this scenario, wide-area coverage is paramount, Stramrood said.

“DMR is a very good fit for something like that, because, first of all, every single repeater that you put up will get you two talk paths beyond the first one that gives you the control channel,” he said. “You get wide-area coverage, and, yes, you get a little more range out of DMR, so you’ll have fewer sites out in the rural areas and there’s a fairly limited data requirement.”