Digital
experience of implementing systems in Tier II DMR”, he said, “and early experience sug- gests a very promising future, certainly with the same frequency band operating on DMR as opposed to analogue. We’re seeing a good increase in performance as far as area coverage. Obviously, speech clarity is very good – nice, quietened signals, even working in noisy en- vironments, so the vocoder as used in Tier II seems to work very well.” And he added: “Whether it’s out of im- patience or seizing the opportunities, some manufacturers have chosen to enhance the Tier II functionality to allow them to have pseudo-trunking and wide-area coverage, and those sorts of facilities are certainly in great demand. So I think the future for Tier III is extremely promising.”
Taking the chair for Land Mobile’s round-table discussion was Adrian Grilli, of JRC, the radio spectrum management organization owned by National Grid and the Energy Networks Association. “We have blocks of VHF and UHF spectrum to manage on behalf of the industry, licensed nationally from Ofcom or in various other chunks and then assigned to our members”, Adrian explains. “I’m also on the European Utility Telecom Council as technical advisor as we look to the future to an environment where we have increasingly challenging energy targets imposed upon us”
On-site, wide area Kevin Delaney disclosed that in Ofcom’s think- ing it had been assumed that the vast majority of DMR would be on-site systems. “No, far from it”, protested Tim Sunder-
land. Already a good proportion of it was ‘pseudo-Tier III’, he said. Furthermore, on- site systems were becoming larger and larger, and interlinked too. “If you take, for example, a distribution centre for a major supermarket, where they used to be able to get coverage eas- ily from a single site, if you look at some of the distribution centres now, they’re huge! And it’s not even two sites, it’s three and four.” “A lot of conventional DMR has been de-
ployed in local authorities”, said Tom Mock- ridge. “T ere’s a couple in the UK. T ere’s been US school bus companies using it – peo- ple who don’t have the density that would jus- tify going to a trunked system. But there are many on-site examples – lots of football clubs are using it, shopping centres.” “I’ve yet to see any county-wide systems,
but there’s lots and lots of two- and three-site systems”, returned Tim Sunderland. “I think that next step up to regional systems will only really come with proper Tier III.”
Tom Mockridge is DMR industry director at Motorola, but here he participated as chair of the technical working group of the DMR Association, which he helped set up about three years ago. “Certainly the promise of DMR Tier III is that it will be a cost-effective alternative in the market to other forms of digital trunking”, he said
18
Out of the vehicle Next Mr Sunderland steered the discussion back towards frequencies and their suitability for what he saw as changed usage patterns in PMR. “Even people that were previously using vehicle-mounted equipment, they don’t want to any more”, he said. “T ey want something that they can take away from the vehicle, even if they are vehicle-based. “I think the safest thing is to assume that
you want systems to operate with portable coverage. If you then get a vehicle-based user, there’s no need to tie him to his vehicle when he gets to wherever he’s going. I know that there have been solutions in the past that al-
The price of DMR W
ill Tier III DMR radios be as pricey as Tetra – or cheaper than MPT 1327? “The general rule of thumb is that it
should be lower cost – somewhere under Tetra and P25, and aiming at people who don’t want all the bells and whistles”, said Tom Mockridge, of the DMR Association. “But there are lots of low-end Tetra makers who will be out there offering special deals, so it will be quite a competitive marketplace. “There are certain things which DMR
trunking systems have – in VHF, where there is no competition from Tetra in that space, or the migration from MPT 1327 systems, which DMR has been optimized for. That’s the kind of sweet spot, if you like.” “The other thing to keep remembering is
the migration issue”, added Jamie Bishop, of Tait. “I haven’t seen a Tetra radio which is capable of analogue FM and MPT 1327. And wide-area networks are a long-term project in terms of that migration. People are looking at a 25-year system or a 15-year sys- tem.... There are quite a number of systems that are being replaced piecemeal, and there will be over the coming years, so legacy sup- port is key.”
lowed you to go in your vehicle and then be based around your vehicle, and they serve a purpose. But they are always going to be a fairly small market. So I think the exploration of 177–191 MHz as one possibility would be interesting to look at. Band III would be inter- esting to look at.” Adrian Grilli suggested that a solution for
users such as delivery companies could be a PMR radio in the boot of the vehicle coupled to a Bluetooth or Wi-Fi or other short range radio device, so that the network could be de- signed for mobile coverage yet still off er the driver the convenience of a handportable. In the US, David Taylor said, some public
safety organizations operated a Wi-Fi device in the vehicle so that data collected by offi c- ers would be stored on the vehicle – if they lost their data device, they would not lose the data too. “So, a Wi-Fi local area network con- necting to a DMR radio that then talks back to an infrastructure: why not, if it meets the user requirement?” Tim Cull extended the idea a stage further,
off ering the driver a standard VHF or UHF handportable which would communicate with base via an onboard repeater. With a range of a couple of miles, the radio would allow the driver to stray as far from the vehicle as he was ever likely to.
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