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“T e power you can get from SDS and simple data is quite immense”, Mr Hamill said. David Taylor mentioned one further data


enhancement that was in the offi ng – the pro- vision of a USB connector on future terminals that would allow users to connect to multiple data accessories while on the move. He added later that there were also proposals to include a fi rewall within every Tetra terminal on the PEI (peripheral equipment interface) port, because of concerns that the port would become a vul- nerable data path into the radio system.


Strategic direction Next, some of the strategic issues facing the mobile industry were examined by Tim Cull, a telecoms consultant who works on projects for the Federation of Communication Services (a body which represents about half of the UK’s business radio companies). Among these issues was the continuing need


to highlight business radio’s value to society. “People want business radio because it enables them to do their job”, Mr Cull said. “T ere is a fundamental diff erence on the strategic level between a GSM or a big cellular mobile com- munications business paradigm, where the ac- tual use of the radio is the business, and busi- ness radio, where the actual use of the radio enables some other unrelated activity to take place successfully.” He emphasized the high gearing between


the costs attached to the use of the radio sys- tem and the benefi t delivered. “T at is a key Government policy point which has to be un- derstood”, he said. “If business radio ever loses the ability to lever that, then the justifi cation for business radio goes with it.” But as business radio becomes more deeply


embedded in our economy and society, its need for resilience will grow. “Remember who we are dealing with”, Mr Cull said. “We are deal- ing with people who need this stuff to work every time, all the time – all day, all night. If it doesn’t, then the relative value of this compared to the public network will be undermined.” At the same time, the resilience of the pub-


lic networks was declining, he argued. “Some people already think it’s insuffi cient for their particular use”, he said. “T e gap between the professional use and the public use – for the support of some of these important functions customers have – will grow. And it will become a natural choice to move to what experience has shown for others is a good solution – away from the public networks.”


Packing them in Focusing on the threats to business radio and the benefi ts to be derived from it, Mr Cull fi rst considered access to spectrum. “First off , the spectrum has to be reorganized


LAND mobile October 2011


Why are channels for private Tetra systems so diffi cult to get in the UK?


I


n the UK, no dedicated Tetra band is available for business radio users. Ofcom is


willing to assign frequencies where it can – but to provide two usable 25 kHz channels for the uplink and downlink of a single-carrier Tetra site, its engineers must piece together adjacent pairs of 12½ kHz business radio channels which have a suitable separation between them. “There are limits within the standard as to the transmit-receive spacing”, explained David Taylor, of Analysys Mason. “You have to have a certain spacing, and trying to assemble channels could possibly be a nightmare.”


National channels A spacing of 10 MHz is common in Tetra systems. However, Adrian Grilli, of JRC, de- scribing his experience in seeking Tetra chan- nels for the energy industry, found this ideal impossible to realize. “Working with Ofcom, we have got four 25 kHz national channels”,


so that it can accommodate much better data carriers”, he said. “We have a 12½ kHz para- digm which we then subdivide or multiply up. What about concatenation of those together so you can have aggregation of service carriage? What about introduction of new technologies?” Taking an imaginary block of 20 UHF chan-


nels as a numerical example, he showed how a progressive relaxations of Ofcom’s sharing cri- teria, allowing more users to be crammed in, could produce some quite signifi cant increases in utilization of the channels. “We are excited in the FCS with the oppor-


tunity to make a signifi cant contribution to a review on this subject”, he said. “I would en- courage FCS members, of which there are some around the table, to contact me regarding con- tributions to that review. “It’s quite a complicated subject, and we are


very cognizant of the fact that there are some re- farming issues here which could get very nasty. However, it’s got to be done or else there is no growth. And that is an unacceptable situation.”


Open standards Adrian Grilli, of JRC, presented a view from the energy industry, which has not only MPT trunks to replace but also some very extensive MPT 1411 telemetry and control networks.


he said. “The duplex spacings of two of them are 6·35 MHz, one is 6·3 MHz and one is 6·25 MHz. So we go to the Tetra manufactur- ers and say, ‘We’ve got these four national channels – could you do us a system?’ They’re not very enthusiastic about it!” “That may change”, responded Jonathan


Hamill, of Sepura, cryptically. He added that his company has been trying to help by stretching the frequency span of its Tetra radios.“We’ve got, as an example, a 407–473 MHz radio, which is very wide compared with what we used to have”, he said. Meanwhile, Ofcom acknowledges that it


has no idea of the demand for business Tetra systems in the UK. “It is chicken and egg”, admitted Kevin Delaney. “We don’t know the potential of Tetra use in this country because traditionally we have always been 12½ kHz and 6¼. Therefore you don’t know the size of the Tetra market because you don’t have the spectrum to offer to people.”


“Tetra has been there for 20 years, and we don’t want to go back to something which is propri- etary”, he said. “So we are very keen on open standards and multi-vendor.” However, he went on, bringing in a new


network is not easy, even when frequencies are available. “As we discovered in trying to plan this new trunked system for Scottish and Southern (SSE), planning trunked systems is very diffi cult within the licensing regime which Ofcom have got. Basically you need to get a load of channels over an area and, when you can’t get lots of dedi- cated channels, you’ve got to start moving them all around, like a jigsaw, to try to get more pieces to fi t together. And within the existing licensing framework this has caused an immense head- ache for both Ofcom and ourselves.” Ofcom’s planning tool, he said, was simply


not designed for this shuffl ing of channels. “So in that sense, looking ahead to Tier III DMR, if you haven’t got area-assigned spectrum, if you use Ofcom spectrum, we’ve got to fi nd a way now whereby we can enable these wide-area sys- tems.” But he continued: “When we do go to fully-


trunked DMR, then it’s got potentially some quite exciting things. “For the fi rst thing, we’d like full-duplex voice on our PMR system. T at is going to get


Business radio: ‘We are dealing with people who need this stuff to work every time, all the time – all day, all night’


35


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