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Data throughput What sort of data rates can users expect from DMR Tier III? Tom Mockridge, of the DMR Association, offered a figure of 2400 bits per second of real throughput, per timeslot. “It’s 4600, but by the time you take all the error correction and all those kind of things out, it’s 2400 real throughput per slot”, he explained. “It does offer the possibility of bonding two slots together to get 4800; some manufacturers have talked about that. But then you lose some of it for IP as well. “It’s good for very low data rates, status messages, this kind of thing. But if you want lots of graphics, forget it, really. You can do CCTV – not in real-time – and I know there are applications which will send you a photo- graph. But you will have to wait a few seconds for the thing to arrive!” “On the data rate side, it does depend as

well if you have confirmed or unconfirmed data”, added Jamie Bishop. “Using uncon- firmed DMR traffic channels, we believe we could, at a maximum with the FEC coding rate at full, achieve 3·2 kbit/s at the absolute fringe. Or, with confirmed data, full FEC cod- ing rates, 2·9 kbit/s.” Placing these somewhat frugal data rates

in perspective, Adrian Grilli said: “We all get hung up with mobile operators and everybody talking about smart phones and fantastic data rates. But actually, when we talk to the mobile

operators, they realize they have a fixed number of people in UK which is only growing very slowly, and they have suddenly realized there is a machine-to-machine market which is many times greater than the people-to-people. “Tey are being incredibly aggressive in the

low data rate machine-to-machine market and have got special arrangements in place because they see that as being, in numerical terms, larger than the number of people-operated terminals. So if we undersell the data rates, actually we are neglecting the enormous machine-to-machine market that the mobile operators seem to think is a real growth area. Tat’s relatively low data rate, machine-to-machine.”

Leasing models Focusing on the radio user’s need for cost- effectiveness, Tim Cull highlighted the op- portunity presented by Ofcom’s recent rule changes allowing licensees to lease their spec- trum. “We are entering into a world where there are spectrum issues – like, there isn’t any spectrum, and we have, with Tier III, the op- portunity for control channel assignment on a dynamic basis, day-to-day. Tose two facts together might make the leasing regime, ex- pansion into the second phase, an extremely attractive prospect. “It offers the possibility of completely new

business paradigms for the customer. Tey can consider making an investment into a radio sys- tem and having actual revenue generation from permitting other users on to their system, were that to be appropriate. So, through the leasing regime, you can have one entity buying the sys- tem, deploying it, getting it to do all the various things, and offering capacity to neighbouring potential users, for example, on a site basis. “You could actually invite other users on

a paid basis, and that would dramatically change your payback period.” In such a network, the primary user could

use the priority system within DMR to assign the highest priority to his own users, while allowing other user groups to access the sys- tem with lower priorities. Infrastructure costs would then be defrayed across all the users, as would the spectrum allocation. “If you think there’s a financial model

there”, agreed Kevin Delaney, of Ofcom, “you could create your own network and lease ac- cess to the network, and, as Tim said, start generating revenue on your network.” Tim Cull added: “You are actually increas-

David Taylor (foreground) is a radio engineering consultant with Analysys Mason. “My particular part of the business very much specializes in end user, public safety, utilities, transportation”, he says. His work has included major trunked radio projects for London Buses


ing your revenue without the need to find space in the spectrum plan. So you can reuse the ex- isting frequencies under the leasing regime be- cause you are leasing capacity. It’s a time-based lease rather than a spectrum-based lease.” However, John Mills cautioned: “If you do go down that route, you would be better off

Kevin Delaney is with the business radio team at Ofcom, with responsibility for licensing civil, PMR and maritime use. “I would be interested to see if anybody can make use of Low Band for very wide area systems”, he says. But he warns: “If we’ve got large chunks of spectrum that the PMR industry is not making use of, it gets to a point where Ofcom can’t justify keeping it for land mobile”

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Tim Sunderland recently joined Servicom, the Midlands-based systems integrator. “We’ve got a fair amount of experience in DMR already, and although I’m fairly new to DMR the company has got a number of stories to tell”, he says. “I started in 1983 with Pye Telecom, although they were already owned by Philips then, and I’ve been in the radio industry ever since, with Tait, Zycomm, Cartel and others”

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