“When we started the specification work here, you had maybe 14·4?kbit/s in the GSM network. But this has changed dramatically. We expect to get approximately 80?kbit/s TEDS and I think I can say that there is very little experience on the supplier side here. For instance, we have to be sure that the data user – let’s say he is within a TEDS coverage area and then he moves out of the TEDS coverage area – we have to be sure that he can be handed over to a multi-slot packet data area, that we have all over the country. And the next question is what throughput are you getting within TEDS and out of TEDS.

“I really wonder what multislot data is being used for in other countries. We discover so many basic things here. And that is a little bit unexpected. When I say basic things, I mean very low throughput. To have, say, decent throughput in a multi-slot area, that seems to be a problem. The rates that we see are very low – I would say unacceptably low.”

“We are looking into why that is”, Dagfinn Sjøvik puts in. “We haven’t, or the supplier hasn’t, been able to conclude on this. But we expect higher rates than what we’ve seen so far in multi-slot. And it’s yet to be seen on the TEDS carriers.

“Of course, it’s also interesting to see how applications can be used also to roam between TETRA carriers and commercial carriers. I think the users (right now there’s a lot of stuff that is being implemented here), they need to walk before they can run, and I think that’s some of the key experiences from Phase 0, the first roll-out area.

“It actually takes quite a while for them to get up and running on the basic usage, and also basic usage within an agency and across agencies. And then of course on top of that come all the data discussions. So I think it will take quite a while before we and the agencies understand how they will use TEDS in the best possible way.”

TEDS is not yet running on the network, but it will be added during the next contract year as part of the Step 2 deployment, on existing sites in the Oslo area as well as on some of the new sites. “There are discussions about where we should have TEDS base stations and where we should not”, Mr Lyngstøl says. “You might say that ideally we should have it everywhere. Maybe we’ll end up with that; I don’t know. But what we will do is we will make good TEDS coverage where we build it. We want the users to have a good user experience. That is the principle we follow everywhere.”

Inter-System Interface

Besides pioneering TEDS, DNK has placed itself in the forefront with another innovation in TETRA systems – ISI, the Inter-System Interface. This long-awaited development will enable TETRA radio systems to be linked in a standardized way, so that (for example) agencies using neighbouring TETRA networks can intercommunicate and roam seamlessly on to each other’s system, making use of at least a basic set of TETRA service features and functions.

Mr Lyngstøl comments: “It is very hard to explain to politicians in Norway and Sweden – where the parliaments of both countries have allocated money for heavy investments in public safety digital radio systems – it’s very hard to explain to them why can’t we cross-communicate.

“This is an issue that I really don’t understand, that ISI hasn’t moved forward faster. But now it is going to happen. We have allocated finances for it on our side and the Swedes have done the same on their side.”

For both countries, the need for ISI arises mainly from their long shared border, although the border forces will have to wait until 2015 to make use of this new facility.

It will involve interconnecting TETRA networks from different infrastructure manufacturers: Norway’s network is by Motorola, but Sweden’s is from Cassidian. “Along the border, the first responders are very co-operative”, Mr Lyngstøl says. “They need this tool. But now ISI is going to happen. The first roaming agreements were set up between Norway and Sweden for GSM. Now you will see the first ISI along this border. So we will push this.

“Both this ISI initiative and the fact that we are now implementing TEDS, I think it will be to the benefit of the TETRA community. We really look forward to this process.”

Educating the decision-makers

What experience would the DNK team pass on to other operators planning a new TETRA network?

“There are a number of, let’s say, high-level learnings”, begins Mr Lyngstøl. “One of them is that the three public safety agencies are not as similar as we thought they were. I think we handle them now much more independently than we thought was necessary in the beginning.

“Maybe another learning is that every country is special. And then of course it has been very important in this project to have a good contract with the vendor.”
(中國集群通信網 | 責任編輯：陳曉亮)