NMT approved as standard
The official decision that NMT would be adopted as a Nordic standard was made at the 1975 Nordic Telecommunications Conference. The most important specifications were
• That the system should offer terrestrial coverage over a wide area
• That vehicle-mounted telephones should function like ordinary automatic telephones and be accessible through a telephone number (so without the caller needing to know where the recipient was)
• That frequencies were to be used efficiently through a small-cell structure
• That when necessary, calls could be transferred to another base station while underway, a process known as handover.
A signal scheme was presented for everything to be managed automatically between the mobile station and the base station. A central demand was that the system could accommodate 180 channels, yet another aspiration that aroused a great deal of skepticism outside the NMT group.
Mäkitalo recalls: “During a presentation in 1976, when we described how we had got up to 180 duplex channels using only two 4.5 MHz sections of the frequency band, a man from L.M. Ericsson got up and said that was crazy; it wouldn’t work. He claimed that the duplex filter alone would have a volume of three liters. With the technology at the time, yes, but we knew it wouldn’t when the system came online.”
And Haug adds: “The problem was that the duplex gap [the separation between the two frequency bands] was too small, 10 MHz, in relation to the two broad frequency bands with which NMT operated. The duplex gap had been determined in a CEPT recommendation and nobody felt like deviating from it.” CEPT is the acronym for Conférence Européenne des Postes et Télécommunications, the European Post and Telecom Conference, which in the 1970s comprised the post and telecom authorities of 26 countries.
A joint Nordic large-scale system trial was needed to verify the solutions. This was to take place in 1978, funded equally by all the Nordic telecom authorities.
COLLABORATION AND COMPETITION
Expertise in radio technology was much greater after the Second World War than before it, and there was a large cadre of radio engineers prepared to develop civilian applications. The US was well ahead, as the Nordic countries clearly realized, and it took little time for L.M. Ericsson’s and Televerket’s people to cross the Atlantic and snap up the latest innovations.
Bell Laboratories had a special status among the visitors. Bell Labs, founded in 1925 as a shared development unit for AT&T and Western Electric, could trace its roots back to Alexander Graham Bell. It was a driving force in the development not only of the transistor, but also important inventions such as the solar cell, the laser, the first communications satellite, Telstar 1, and the idea behind cellular mobile telephony. The cell idea had been suggested in an internal memo back in 1947, but was still unrealized at the start of the 1970s.
The war, in which Sweden remained officially neutral, had also brought L.M. Ericsson and the Swedish government closer to each other. Close relationships between the telephone industry and governments were the rule rather than the exception all over the world, largely because of the importance of telecommunications for defense and security. L.M. Ericsson quite simply had the knowledge and the production capacity that the Kingdom of Sweden needed in Cold War Europe.
Author: Svenolof Karlsson & Anders Lugn
Testing of a central processor in a prototype lab