GSM Air Interface
GSM Signal Processing
Setup of a GSM Phone
First GSM Devices

Global System for Mobile Communication

In 1959, a common agency was founded by 19 European countries: CEPT. Conférence Européenne des Postes et des Télécommunications Administrations. Translated: European Conference of Postal and Telecommunications Administrations. The aim was to collaborate on the standardization and use of telecommunications systems.

Foundation of Group Special Mobile

In 1982, standardization for mobile communications was poor. The first car phone systems were national technologies and standards. This situation did partly improve with the first cellular communication systems. At least AMPS/TACS and somehow NMT where open and widely adopted standards and there was wide global use. This was beneficial for the corresponding cellular market. But Europe was still unable to agree on a common standard. The market was split between C-Netz, NMT450, NMT900, TACS and a proprietary French system. This was not good for the vision of a European market with no barriers. Instead of focussing to a common standard, huge investments where made just for local solutions that did never payed off.

There was hope, that this could change in the next decade. Already in 1979 Europe had agreed to free up a new band for the next generation mobile communication around 900 MHz. A new standard should be created for this band. A „pan European standard“. In 1982 a special group was formed by CEPT to define such a new standard. This group was called Group Special Mobile (GSM). Back in the early eighties the assumption had been to define another, more efficient analog standard. There was an early initiative between Germany and France to work out such an analogue system called S-900.

In 1983 the C-Netz was still not rolled out and the German telecommunication minister Christian Schwarz-Schilling was visiting Siemens to review the progress. Siemens was far behind. Roll out was not expected before 1985. The minister was upset. He had another visit with competing SEL, a German Telecommunication Infrastructure provider belonging to the ITT group. When asking SEL for alternatives to the C-Netz, SEL proposed a „digital System“. SEL had worked for military application and knew the advantages of digital systems. With government funding they developed a proposal for a pure digital cellular system. Anyhow, it was to late for a C-Netz alternative but the Minister was intrigued by the digital approach and gave SEL a special permission to participate in the S-900 project.

Back then, there were a lot of doubts in the industry about the advantages of a digital system. This was because this technology was a revolution rather than a evolution for the engineers. Therefore it was projected that it would take at least until the year 2000 until a digital system could work. Digital signal processing was a complete new area of engineering and only very few experts really had knowledge in that area.

In the end France stepped back from the S900 system and promoted their own analog system Radium 2000.

But a „digital system“ was still in the „head“ of the politicians who paid in research for such a system for a long time already. To go digital was probably more a political decision than the decision of the industry that tried to avoid this step. France and Germany (Francois Mitterand and Helmut Kohl) agreed internally that the next generation mobile phone system should be digital. Therefore the group special mobile was asked to focus on a digital system. To avoid, that one of the two parties (Germany or France) would dominate the standardization process, the Italian where invited to participate as well. So the three states signed a Memorandum of Understanding in 1985. One year late also the UK followed this project.

Standardization was no longer a task of one or two nations asking one or two telecommunications companies to come up with a standard. 26 European telecommunication companies participated in the GSM Taskforce. They did not simply took over what SEL had developed so far but brought in own ideas. So GSM was mainly a consortium that tried to merge somehow all the different approaches.

The new European mobile communications standard was not specified by a single company or organization but by a consortium of different companies in the communications industry. Proposals were developed and approved together.

It was a major breakthrough when a common system was agreed upon in 1987. There were different concepts under discussion. Germany, France and England in particular had to come to an agreement. England were initially not enthusiastic about a new standard. They would have preferred more frequency bands for the newly established TACS system. There were certainly voices who were quite satisfied with NMT, for example, and only wanted expansions there. It was also not sure whether an advanced CELP coder should be used for speech coding. There were alternatives that were not comparable in voice quality but were much easier to be implemented. Another mayor discussion point was the bandwidth of the system. Wideband TDMA or Narrowband TDMA. Both had advantages or disadvantages. In the end, it was decided to use Narrowband TDMA.

A crucial meeting took place in the spring of 1987 on the Portuguese island of Madeira. The most important European ministers came to an agreement and a little later, 13 European countries signed a memorandum of understanding to introduce the new standard for a “Pan European Mobile Network”. The abbreviation of Group Special Mobile, GSM, was selected as the name for the new standard. But now GSM stood for Global System for Mobile Communication. Everybody spoke of the „GSM system“. In 1990, a 6,000-page specification of the system became available. All that remained was to develop the associated devices and infrastructure equipment.

In 1988, the CEPT founded a special standardization committee that should take care of the GSM standard, the European Telecommunication Standardization Institute (ETSI). The ETSI was based in a small town called Sofia Antipolis on the Cote d’Azur in southern France.

New elements of the GSM System

The main difference of GSM compared to the first generation systems is that all information, speech as well as control information, is transmitted digitally. This primarily influences the way the so-called air interface is specified. This is described in more detail here:
GSM air interface.

Furthermore the GSM System has the following new elements:

• Encryption
• Source and channel coding, especially speech coding and convolutional codes for error correction
• Frequency hopping

These functions are described here:
GSM signal processing

A GSM phone had a very complex architecture. In the early nineties it was quite challenging and required newest technology especially when handheld where designed. The structure of a GSM phone is described here:
Structure of a GSM Phone

The first GSM devices were like the first generation car phones. But attractive handheld devices came up soon and car phones quickly became unattractive.
First GSM devices