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Digital


markets needing that kind of system. T ere are tensions between other systems and other technologies – but that’s probably engineer- speak as much as anything else, because, from the customer’s perspective, they have a certain set of requirements which they’re meeting. And the requirements are not just about the modulation scheme or the organization of the spectrum channels – they are about what ac- tually works.”


Options for updating Taking as an example a “decent-sized” radio user who cur- rently obtains good value from his existing analogue radio system, Mr Cull considered some of the options for replacing it. “T e public communications operators, the LTE fraternity, of course, will be strong contenders because there are certain commercial effi ciencies that can be achieved associated with that and like strategies”, he said. “However, that might be as far as it goes,


DMR mobile, from a Tier III trunking range by Tait which will be available from September. Handportables and a base station repeater will also be included


because these commercial networks of course are commercial networks and they tend to run extremely close to the maximum capacity for profi t margin reasons. If you have an extreme- ly peaky traffi c usage profi le, you need to be aware of that. “So the migration from where you are today


on your old system to a public network may not be a simple question at all. And even if it


is low-cost (and you have to argue whether it is or not), there is a public liability issue in the event that something goes wrong and you are held liable, that there are better systems work- ing. So you have a due diligence issue whereby you appear to have taken one course, where due diligence should have driven you down another course.” On the other hand, he went on, much of


Channels for trunking: a way out of the spectrum shortage? D


espite the shortage of available PMR frequencies in many cities in the UK, Kevin Delaney, of the business radio group at Ofcom, argued that there is an opportunity now to expand the use of trunked radio. “We have spectrum in the lower frequency bands – 68–88 and 171–191 MHz – which is a great deal of spectrum that is not being used”, he said. “Theoretically, that is the sort of spectrum that should be used for trunking systems, because trunking systems have to be an exclusive assignment.” However, Ofcom was not yet clear about the exact spectrum


requirements of Tier III systems, and neither did it know what demand for trunked radio there might be. “We don’t know at the moment whether, in the popular bands, we are actually meeting customer demands”, Mr Delaney continued. ”Is there a wide-area market out there, a trunked market, which isn’t being addressed because customers perceive there’s no spectrum available, or manufacturers don’t support the spectrum that potentially could support wide-area systems? “From our perspective, yes, trunking is very effi cient. But is there equipment that can meet our spectrum capabilities? Or, conversely, have we got spectrum that can meet the customer requirements?” A table provided by Mr Delaney showed 9·5 MHz of unassigned VHF spectrum in Band I, 3 MHz in Low Band and just over 3·5 MHz in Band III. “If no-one can use it or no-one wants it, it just sits there lying fallow”, he lamented. However, Adrian Grilli, whose company serves many Low Band users in the power utilities, pointed out drawbacks to using those frequencies: the large size of the antennas needed, an increased risk of long-range interference and a higher level of background noise. But Jamie Bishop, of Tait, emphasized: “From a manufacturing perspective, we really need signifi cant volume.” Only through efforts by regulators to agree harmonized blocks of spectrum in Europe extending beyond a single country could manufacturers build the justifi cation for investing in production, he explained.


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Improved value propositions “What we have to understand”, Tim Cull continued, “is that the customer will be moving forward to expect greater and greater value propositions from any investments they want to make. And that will include the radiocommunications system. The concept of having a harmonized band whereby they can actually get a system and have it deployed is much more value than talking about relative gains on very long-distance communications, where there might be protocol interchange, timing problems and so on, with or without interference.” Nevertheless, he added, there is a great virtue in moving to digital technology on some of these bands, because the receiver is continuously protected from interference by virtue of the digital modulation. This results in an immediate improvement perceived by the user. “So there’s an extremely high potential leverage to gain from


fi nding a band to harmonize on across Europe”, he concluded. “I think that is something that can be done and should be done – and should be done any time. Tomorrow morning would be nice.” But Kevin Delaney urged: “Don’t think 12½ kHz all the time.... If you’ve got a technology and we’ve got spectrum, you can increase the channel width to whatever you need to meet your business requirements. So if you need 30, 40 kbit/s, it may need a huge, wide channel.”


Jamie Bishop pointed out that if what you want is portable usage,


there are limitations in what bands will be acceptable to you. In Low Band, mobiles might be more practical than handhelds. But is Tier III DMR even implementable in a Low Band handheld radio? “It is implementable”, he confi rmed. “But from a Tait perspective, don’t expect it in the same format as our VHF or UHF product!” Tom Mockridge added: “The standard was designed to go down that low – it’s in the specs. It’s about demand, which is a volume issue, and volumes dictate prices.”


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