Written by: Olof Billström, Lars Cederquist, Magnus Ewerbring, Gunnar Sandegren and Jan Uddenfeldt
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This year marks fifty years since Ericsson introduced the world’s first automatic mobile telephone system for a few hundred subscribers in Stockholm and Göteborg (Gothenburg), Sweden. The associated mobile units were colossal 40kg blocks of radio equipment designed for installation in the baggage compartment of a car.
The extraordinary success of mobile communications, from those early pioneering efforts to today’s miniature telephones and advanced services – the result of global technical labors of the highest art – reads like a page from a storybook. From the outset, Ericsson has been a major player, driving many facets of development and helping to create the standards that prevail in the industry today.
The expertise Ericsson gained from its first systems, and a steady ambition to create an optimum, automatic network, laid the groundwork for a vision that has stood the test of time. Ericsson continues to forge ahead as a technical leader in the field of mobile communications – perhaps more so now than ever before thanks to high-speed packet access (HSPA), the turbo version of the 3G network.
1956: 0G – the first networks
Enthusiasts at Ericsson and elsewhere had long nurtured the idea of creating a radio-based mobile communications system. In the mid-1950s, a handful of systems were tested in several countries around the world. For Ericsson’s subsidiary, Svenska Radioaktiebolaget (SRA), this development was a natural next step – it had been selling private mobile radio systems to the police and other groups since the 1940s. Now, users would dial numbers on a telephone to call other telephones.
What set Ericsson’s system apart from the others was that it was fully automatic – it did not require manual control of any kind. The system, called MTA, operated in the 160MHz band using pulsed signaling between the terminal and base station (MTB, an upgrade introduced in 1965, used dual-tone multifrequency signaling). SRA developed and supplied the base stations and mobile units (Figure 1).
Initially, mobile telephony was synonymous with car phones or voice communication over a mobile radio in a car. It did not matter, therefore, that the equipment was bulky or heavy. The equipment was also power hungry, because for signals from the mobile unit to reach the base station, the output power from the mobile unit had to match that of the base station.
The Swedish Telecommunications Administration (Telia, formerly Televerket) took the first MTA system into operation on April 25, 1956, but real system tests had begun two years earlier, in 1954. During the 1960s, Televerket simultaneously operated two systems. The two were more or less identical except for a minor difference in signaling and how users connected to the network.
Each system consisted of one transmitter and several receivers and was built using relays and radio tubes. Four duplex channels enabled the systems to handle approximately 100 users apiece. The majority of subscribers were salaried professionals, such as doctors or lawyers. The main system shortcomings were limited coverage and subscriber density. Ultimately, Televerket concluded that it would have to take a radical new approach in order to successfully create a national or multinational mobile network.
1981: 1G – the analog era
NMT (Nordic Mobile Telephone) was the first truly mobile system. Ericsson and Televerket deployed this open standard in Scandinavia in 1981. At about this same time, Ericsson also supplied a turnkey system, consisting of switches, base stations and mobile units, to
Shortly afterward, Bell Labs in the USA developed what came to be known as AMPS (Advanced mobile phone system). The first AMPS system was deployed in 1984. One other system, TACS (Total access communication system, a modification of AMPS), was developed and inaugurated in Great Britain in 1985. Ericsson manufactured equipment for each of these standards and quickly grabbed a 40% global market share of analog systems. In fact, Ericsson was the first supplier to take a TACS system into operation (for Racal, currently Vodafone).
These early systems were all analog systems based on frequency-division multiple access (FDMA) technology, which allocates a distinct frequency channel to each user. Today, we think of these standards as first-generation (1G) mobile systems, but in their day they were considered fourth-generation systems. We would remind the reader that the systems were designed for telephony from cars – apart from the handset, all mobile subscriber equipment was installed in the baggage compartment of a car.
It took nearly ten years to develop NMT, mainly because system designers wanted to make the most of coming finesses in micro- electronics: microcircuits, digital frequency synthesis (to combine radio channels in a terminal), digital signaling, digital switching methods (which were necessary for managing and controlling telephone switches and rapid change-over during handover between cells), and so on.
The system was composed of mobile stations, base stations, and telephone switch equipment. The mobile stations, essentially small radio stations with keypads, were often packaged in a module that could be mounted in the cockpit or dashboard of a car. The telephone switches consisted of a subsystem (called MTS) of AXE. The base stations could thus connect to the switch via ordinary telephone lines. And thanks to their modular design, the AXE switches could coordinate mobile and public transit traffic. Initially, the AXE switches were considered to be too powerful (and expensive) for mobile systems, but rapid network growth soon validated this design choice.