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Eurocontrol considers STDMA

The North European ADS-Broadcast Network - NEAN - (see ATC NEWS, 22 January 1996, page 5) comes a step closer to completion with the expansion of the network into Germany earlier this month.

The first of five base station installations was made in Germany in mid April and all five were expected to be completed and operating autonomously in test mode by the end of the month.

Connection between the five stations - Berlin, Bonn, Braunschweig, Bremen, and Frankfurt - will take longer, and the final phase of the network set-up will involve connecting the German network to the Danish network. Connection of the Danish and Swedish networks has already been completed. Bo Redeborn, Manager Air Traffic Management with the Swedish Civil Aviation Administration, told ATC NEWS that the whole system is expected to be up and running by September this year. "With Germany coming on line, the final set-up and phased implementation of the network is pretty much established," said Redeborn.

The Self-Organising Time Division Multiple Access (STDMA) data link, which is the corner stone of the NEAN trials, is already being used in commercial service on a trials basis as part of the North European ADS-B Trials (see ATC NEWS, 19 February 1996, page 5).

Eurocontrol is currently discussing with the NEAN consortium the possibility of using the TTDMA in the second phase of its Preliminary Eurocontrol Test of Air/Ground Data Link (PETAL 2) project.

"We need to ascertain how far that infrastructure is suited to execute the applications that PETAL has in mind, which are oriented towards the CNS/ATM-1 package," Eike Meyenberg, Head of the EATMS Architecture and CNS Infrastructure Section of the Eurocontrol Future Concepts Division, told ATC NEWS.

"STDMA seems to provide an appropriate infrastructure and NEAN will offer a large fleet of equipped aircraft operating specifically within continental European airspace," he said, pointing out that ADS Europe was more oriented to the North Atlantic and intercontinental operations.

Redeborn said that NEAN and Eurocontrol were trying to finalise how such a co-operation effort could be developed.

Maastricht from which direct controller/pilot data link communications (CPDLC) would be run over an STDMA data link," he said.

From an ATN point of view, Meyenberg admitted that use of STDMA in the PETAL trials would be an "opportunistic" move.

"We would like to use something that is more ATN compliant, but there isn't anything," he said, "it is too puristic to say that we should not use STDMA because it is not currently ATN compliant; we have to be more pragmatic. Whenever there is a specific subnetwork that provides appropriate services, we should put it through operational concept trials.

"We would have liked to have Mode S available as a candidate for this type of data link trials, but in order to sustain the momentum of Mode S for surveillance purposes, Eurocontrol has decided to give priority to the Mode S enhanced surveillance programme and to handle the data link issues in the following phase, for which plans are now being developed. As long as Mode S Is not available for data link trials on this large scale, we have to use alternatives which currently are VHF and satellite in the European region." he said.

However, Meyenberg stressed that using STDMA as an infrastructure for operational trials was quite different from considering it as a global-use data link. "For that to happen, it must fulfil the technical requirements equivalent to those currently being standardised by ICAO for VDL TDMA (VHF Data Link Time Division Multiple Access). It is also essential that STDMA can be integrated into the ATN."

He said that it would be worth evaluating STDMA against these requirements and pointed out that there were technical solutions to enable its migration to the ATN, one of which would be to consider it as a specific subnetwork with interfaces to the ATN as is the case for Mode S.

Meyenberg pointed out that the original NEAN proposals had included integration of STMDA into the ATN, but this had been shelved in light of European Commission budget constraints on the overall project.

The NEAN consortium is currently applying for funds from the European Commission for a complementary project, known as NEAP, which will provide more applications capabilities. Meyenberg said that the current trials were suffering because of applications limitations which were again the result of EC funding constraints.