Like an ordinary telephone
One fundamental idea was to create a joint signal system for all the Nordic countries. During 1972, at NMT’s request, the Danish company Storno, at the time the leading radio company in Scandinavia, conducted numerous comparisons of signal-transmission systems in different types of terrain, ranging from Norwegian forests to large urban areas in Sweden, to identify patterns and sources of failure.
Storno recommended a tone signaling system with tones of 100 ms (millisecond) duration, and with each tone representing a digit. The system was claimed to be very reliable.
This was, however, rejected by the NMT group. Mäkitalo says: “We could see that the system had far too low a transmission capacity, just over 30 bps, and would moreover be far too complex for other applications apart from selective calling. The system was, in other words, unsuitable for mobile telephony in the future.” Instead the NMT group went for a binary system with a data-transfer rate of 1200 bps and which used an error-correction code to attain the required transmission reliability.
The report of the telecommunications conference group in 1973 forecast that the NMT system could not be operational before the end of the decade at the earliest. The group assumed that the service life of the system would be at least 15 years and therefore the facilities it offered should be “specified with a view to the demands that subscribers can be expected to make during the 1980s.”
TAKE THE DRAMA OUT
It was also important to take the drama out of mobile telephone calls and make the phones easy to use. Mobile phones should therefore work like ordinary telephones no matter where the user’s vehicle was.
One important requirement was that calls be charged to the caller and that the tariff within a country would be the same irrespective of which country the caller lived in.
Another linchpin was that the system could not demand any appreciable modification of the fixed network. “This was an extremely important point and it was later to be handed down to GSM,” Haug says. “We realized that if we did not comply with it we would probably never gain any acceptance at all for any system.”
Mäkitalo comments: “On the radio side we had great respect for the way in which the fixed network functioned and never thought of anything but linking the base stations to special mobile telephone exchanges that would interact with the fixed network on the fixed network’s conditions.”
The NMT group was genuinely a Nordic one, Haug says: “At times there could be 10–15 staff from Televerket in Sweden involved in work for the NMT group, and two or three from its Norwegian counterpart. The authorities in Denmark and Finland did not have their own radio laboratories but shared the costs and undertook other kinds of tasks. During this time, each country made decisive contributions. We felt that who ended up paying was of secondary importance.”
“SCANDINAVIAN” THE LANGUAGE
The work also benefited from using “Scandinavian” as its working language – Swedish, Norwegian and Danish were used interchangeably. The Finnish speakers were not at ease with this, especially early on. One Finnish member expressed “a strong opinion against Swedish” and wrote a memo proposing that the group should switch to English. But language became less of a problem as the group became more coherent. It is undeniable that work on the NMT system was undertaken in an informal atmosphere, with the focus on results and nobody trying to win “points.”
Even Haug, who later acquired much experience running international working groups, describes the NMT project as “a quite outstanding example of international cooperation with no issues of national prestige. On the other hand, there were lots of heated discussions between advocates of different aspects of telecommunications technology, but that’s another story.”
By modern standards, the group had an unrepresentative gender split. The only woman involved at any stage in the NMT meetings was Helene Sandberg from Norway. As Haug comments: “This was of course because the different agencies did not send any women to participate, which was probably due to the extremely small numbers of women engineers.”
Author: Svenolof Karlsson & Anders Lugn
NMT GROUPS SKETCH