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时间:2013-03-05 22:01来源:中国集群通信网 作者:admin 点击:
Equally enthusiastic about the TETRA system is Nkanyiso Msomi, acting director of engineering services at City Power. Oh, it works !, he exclaims, genially. It definitely does work, and it has saved

Equally enthusiastic about the TETRA system is Nkanyiso Msomi, acting director of engineering services at City Power. “Oh, it works!”, he exclaims, genially. “It definitely does work, and it has saved us a lot of time from the communication point of view. If you look at the nature of our business, it’s all communication. During the day, after hours – throughout, it’s all about communication. It’s all voice and data.”

Mr Msomi is also enthusiastic about proposals to bring other groups and other utilities on to the system. “We have been in discussion with them and they would be willing definitely to join us and come and utilize it”, he says. “If you look at what we did during the World Cup, we were running on TETRA and we got savings from the operational cost point of view in terms of what we would have spent, and what we spent using TETRA. During the World Cup it literally paid for itself.

“It was definitely a good decision. We have presented it now to the AMEU [South Africa’s Association of Municipal Electricity Undertakings] so that other municipalities as well can come and join.

“We started with 11 sites, we’re putting in an extra seven sites, and that shows that it has got a huge thumbs-up from everybody.”

Southern Africa: taking a different approach

In Africa, TETRA is ready to flourish – but it needs an approach which differs from the European one. So believes Roelf Kloppers, vice-chairman of the Southern African TETRA Association and an independent consultant steeped in decades of experience across the mobile radio business.

“Traditionally we are, on average, about eight years behind a new technology once it starts being implemented in places like Europe”, he says. “The reason is that our regulatory environment has to get sharpened up for that, and frequency spectrum has to be cleared. That’s a whole process to go through. Standards have to be decided on – and although we are in [ITU] Region 1, our regulator follows a policy of not being obliged to follow Region 1 all the time. So they sometimes will allow, for certain applications, Region 2 or other technologies, and in different frequency bands – which leads to a stretched-out period of introduction.

“Then, distribution in Southern Africa of TETRA is much different to what we see with conventional mobile radio. And a lot of people didn’t catch on to that early. Because they were a distributor for one of the big internationals in South Africa for mobile radio, automatically they considered themselves to be experts wanting to do the TETRA distribution and not understanding the technology. At the beginning it was a big problem. It’s a big technological and commercial leap.

“And then because of the costs, we find that, to implement it on a national basis, our needs differ vastly from that in Europe in that we have huge geographical areas with low volumes [of radio traffic]. Again, our total systems approach is different to that of Europe, where you have a lot of low base station sites with high volumes of users. We have high sites – very high sites – with low volumes of users. And that is a costly way, then, to provide infrastructure.”

This, Roelf Kloppers explains, is why the City of Cape Town and the populous Gauteng Province, which includes Johannesburg and Pretoria, were the first to have TETRA networks – systems for public safety and security services. Next came the Eastern Cape Province with the major centres of Port Elizabeth and East London. Perhaps next in line will be KwaZulu-Natal, with Durban and Pietermaritzburg.

“But it still doesn’t take away the problem of the remote areas”, Mr Kloppers continues. “They still are on the conventional analogue spectrum that has to be cleared up again for other technologies in 400?MHz. They are going to have hybrid systems for a long time. And you will find that there have got to be gateways in existence for a long time.”

Some provinces, he believes, may never see TETRA at all – for example, the remote Northern Cape. “I don’t think they will even think of introducing a public safety and security system there in the next 10–15 years, because the population is too low. A base station site sitting on a high mountain covering five or ten mobiles and five or ten handhelds doesn’t justify the cost. And they are pretty well covered by existing analogue systems and even with upgraded analogue. I shouldn’t say this in the TETRA environment, but I can see that DMR is possibly going to have an effect in there.”

The Southern African TETRA Association: www.sata.org.za

Not just a walkie-talkie, not just a cloud – a radio solution

Though the original motive power for TETRA came from the needs of public safety bodies, Roelf Kloppers finds that innovation in data communications, including telemetry and Scada systems, has transformed TETRA over the past two or three years into an attractive choice for many smaller systems.
(中国集群通信网 | 责任编辑:陈晓亮)

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