Tests in Paris
The four Franco-German development projects in digital radio technology were due to submit their final proposals in 1986. The commissioning agencies had reserved the right to allow CEPT to use the results, and now it was proposed that evaluation would take place within the framework of the GSM project, where a working group had already defined the test methodology.
The proposal to the GSM group came from Germany. The Franco-German candidates were represented by Alcatel/SEL, LCT, Philips and Bosch. The GSM group accepted the idea and made it clear that proposals from other candidates were welcome. The laboratories of the French telecommunications agency close to Paris were proposed as the venue for the tests, which would take place at the end of the year.
Östen Mäkitalo recalls: “In the Nordic countries we had not realized until then how serious Franco-German cooperation was.
“We had to sift out our own candidates without delay. So we had a meeting – Televerket, ERA, Nokia and our colleagues in Norway – and decided that we would each develop our own systems. We said that it was important for a narrowband solution to win in the tests because then we would be able to use the same infrastructure as the NMT system. For us, winning this competition became crucial,” he says.
Applications were therefore submitted by Sweden’s Televerket, ERA, Mobira (Nokia) and Elab, a small Norwegian laboratory linked to the Norwegian University of Science and Technology, represented by Torleiv Maseng.
NOT ENOUGH TIME
Mäkitalo attempted to speed up the work at his laboratory that autumn. The concept was dubbed MAX (Mobile Access Extension) and had 10 TDMA channels per carrier wave. However, this could not be made to perform adequately. Above all, it was impossible to devise the “decision feedback equalizer” (DFE) referred to.
In the end he had to admit that his research team did not have enough time to develop a satisfactory solution. On the day before Halloween in 1986, he rang his colleagues at Mobira and ERA to find out how much progress they had made. They were all working on more or less identical solutions with the same type of equalizer but none of them had one ready.
“I was afraid that nobody would be able to develop the equalizer in time. During the weekend I decided to call the project off and use what time was left to prepare an alternative concept, MAX-II, in which time dispersion would not have so much effect and the equalizer would not be as important. This solution with four-channel TDMA was referred to as 8PSK (8-Phase Shift Keying).
“We definitely did not want to give them a walkover but there was no way we could tell the GSM group how untested our solution was. We would never have been allowed to compete,” Mäkitalo says. The team was still working on the details in the bus on the way to Paris. At the border they ran into an unexpected problem: the bus was full of measuring instruments and the French Customs wanted to see valid licenses for them. Finally, the Televerket team was allowed through.
Author: Svenolof Karlsson & Anders Lugn