And in Paris the winner was ... Elab. What decided the issue was the fact that Maseng had developed the equalizer that worked best for his modulation system, ADPM (Adaptive Differential Phase Modulation).
Maseng’s secret weapon was Viterbi’s algorithm. Presented by Italian-American engineer Andrew Viterbi in 1967, it has found applications in many contexts over the years. Maseng’s advantage was in discovering its usefulness as an equalizing code for demodulating a signal.
How did Maseng achieve this?
“Funding from the Norwegian telecommunications agency for four years had given me a chance to test different ideas. At that time radio reflections were considered to be a major problem but I could see that they also offered possibilities in the diversity they provided. That was where the Viterbi algorithm could be used, provided that you measured one channel at a time, roughly like radar,” he says.
Maseng and Trandem also had an assistant: the Cray supercomputer that had been acquired by the Norwegian University of Science and Technology in Trondheim in the autumn of 1986. The Cray had been a gift to the university from King Olav of Norway to celebrate its 75th anniversary.
SURE TO WIN
“When we went to Paris for the week of tests, we were sure we were going to win,” Maseng says. “Odd had carried out thorough simulations of the test situation in Paris using the measurement figures from the other candidates. The results were so clear-cut that we understood we were going to do better than the others.”
Above all, Elab’s system was best at coping with the chaotic signals that resulted from the reflection of radio waves from buildings and other topographical obstacles. “In Norway, there are major topographical challenges,” Maseng points out. He and Trandem had made repeated measurements of how radio waves behaved, not only around the fjord outside Trondheim but also in the urban setting of Stockholm.
One problem can arise where there are multiple signals “hanging in the reflections”, so the listener hears many of them at the same time. “This is the same phenomenon you can get in a church, when hymns have to be sung slowly. If you sing quickly, the melody gets lost in an acoustic porridge because of echoes from everywhere,” Maseng says.
The same thing happens with radio waves. Maseng and Trandem were the only ones during the test who were able to alter the frequency band and monitor how it reflected their measurements. This meant that they could work out the optimal bit rate, with the assistance of Sweden’s Televerket, which helped with the measurements in central Stockholm.
“Perhaps we won because we were able to play around more than the others. Our competitors had enormous, heavy project organizations and were under pressure to make a profit,” Maseng says.
He was a popular winner – he had been an underdog and did not represent any major manufacturer. His victory was proclaimed as a world championship in technology. But the interesting thing was that all the Nordic solutions were similar to each other.
Author: Svenolof Karlsson & Anders Lugn
Odd Trandem at ELAB in Trondheim
Odd Trandem with the prototype for a GSM terminal on his back