Global System for Mobile Communications (abbreviation: GSM) – behind this boring term lies the democratization of mobile telephony. The then Prime Minister of Finland, Harri Holkeri, spoke with the deputy mayor of Tampere, Kaarina Suonio, about the commercial launch in Finland on July 1, 1991. Telenokia and Siemens had set up the network used for phone calls. At the same time, the expansion of the network began in reunified Germany. However, it took another year before you could buy cell phones and make digital calls on the go.
Telekom’s predecessor, Deutsche Bundespost, set up Network A in what was then the Federal Republic of Germany from 1958. The former FRG thus became one of the first countries in the world to offer mobile communications. In principle, since then, one can “call” or be called on the move. But the A-Netz devices were so heavy, bulky, and power hungry that they could only fit into larger cars. The calls were made by hand, the auto-dialing service which is taken for granted today did not even exist in all parts of the fixed network in the Federal Republic of Germany. The “public portable radio telephone” (öbL) technology initially cost around 15,000 D-Marks, the equivalent of three VW Beetles. With a maximum of 11,000 participants, the network was hopelessly overloaded in the early 1970s. It was followed by Network B and then Network C. But this too was exploding in the early 1990s with around 700,000 users, and in metropolitan areas, there was often no passage.
It doesn’t work without new technology
It was clear: if calling on the go were not to be reserved for businessmen and fiddlers, new technologies and new networks would have to be found. The GSM developed from 1982 was supposed to do this. Digital voice transmission instead of analog transmission uses the radio channels more efficiently, leaving room for more conversations and participants. The switch to higher frequencies (German C network: 400 to 470 megahertz – MHz, millions of oscillations per second) of 900 initially, then to 1800 MHz (internationally also 800 and 1900 MHz) for GSM seems absurd to the seen from range, because frequencies propagate better. In fact, this only helps in a network with few radio towers and participants. The network of base stations designed for GSM must be tightly meshed – a mast only needs to cover a radius of a few kilometers. Too much range would even be counterproductive, because then the signals from individual cells would interfere with each other. In open field, a 900 MHz tower covers a maximum radius of 35 kilometers, an 1800 MHz mast about eight. For the record: The GSM specifications also contain the frequency bands 400 to less than 800 MHz – but they have never been used.
Since users needed to be able to move freely between individual base stations and talk without interruption, they needed and needed to be able to make calls from mast to mast. This handover was introduced with network C. In previously operated networks A and B, however, the connection was interrupted when leaving the radio cell. Also known from the C network: the SIM card, with which you can be reached on different devices under your number.
Efficiency by time slot
However, the significant increase in efficiency at the time resulted in – in addition to the use of data reduction for voice transmission – the combination of frequency and time multiplexing. In the original D network, 124 channels were available for transmission in the range 890-915 MHz and the same number of channels for reception between 935 and 960 MHz (frequency division multiple access – FDMA). Each of these channels could be used by several subscribers at the same time because one of the eight time slots, each short of 577 microseconds, is allocated to each mobile phone using time division multiple access (TDMA).
In early 1991, Deutsche Bundespost demonstrated its GSM-based D network at the former Stuttgart trade fair in Killesberg – but there was no telephone yet. The technology reached consumers exactly one year later, when Telekom started with D 1. Rival Mannesmann started a day earlier, June 30, 1992. 29 years ago, prices were solid: Telekom wanted D1,190 -Marks for their cheapest – initially hardly available – mobile phone, the call minute in D 2 reached 1.44 D -Mark in beech. There was also a base charge of almost 80 D-Marks per month. No wonder the technology got off to a cautious start – the terminals were a bit cheaper than those on Network C, but still a far cry from today’s bargain prices.
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