Chapter 1: Introduction to the GSM System

This chapter provides an overview of the GSM cellular system, with a focus on the radio interface. The purpose is not to give a detailed description of the many features supported by the system, but to summarize the elementary concepts of GSM, as an aid to reader comprehension of the subsequent chapters. In-depth presentation of the GSM system can be found in [1, 2].

1.1 Introduction

1.1.1 Birth of the GSM System

The first step in the history of GSM development was achieved back in 1979, at the World Administrative Radio Conference, with the reservation of the 900-MHz band . In 1982 at the Conference of European Posts and Telegraphs (CEPT) in Stockholm, the Groupe Sp cial Mobile was created, to implement a common mobile phone service in Europe on this 900-MHz frequency band. Currently the acronym GSM stands for Global System for Mobile Communication; the term "global" was preferred due to the intended adoption of this standard in every continent of the world.

The proposed system had to meet certain criteria, such as:

• Good subjective speech quality (similar to the fixed network);

• Affordability of handheld terminals and service;

• Adaptability of handsets from country to country;

• Support for wide range of new services;

• Spectral efficiency improved with respect to the existing first-generation analog systems;

• Compatibility with the fixed voice network and the data networks such as ISDN;

• Security of transmissions.

Digital technology was chosen to ensure call quality.

The basic design of the system was set by 1987, after numerous discussions led to the choice of key elements such as the narrowband time-division multiple access (TDMA) scheme, or the modulation technique. In 1989 responsibility for the GSM was transferred to the European Telecommunication Standards Institute (ETSI). ETSI was asked by the EEC to unify European regulations in the telecommunications sector and in 1990 published phase I of the GSM system specifications (the phase 2 recommendations were published in 1995).

The first GSM handset prototypes were presented in Geneva for Telecom '91, where a GSM network was also set up. Commercial service had started by the end of 1991, and by 1993 there were 36 GSM networks in 22 countries. The system was standardized in Europe, but is now operational in more than 160 countries all over the world, and was adopted by 436 operators.

The growth of subscribers has been tremendous, reaching 500 million by May 2001.

1.1.2 The Standard Approach

The thousands of pages of GSM recommendations, designed by operators and infrastructure and mobile vendors , provide enough standardization to guarantee proper interworking between the components of the system. This is achieved by means of the functional and interface descriptions for each of the different entities.

The GSM today is still under improvement, with the definition of new features and evolution of existing features. This permanent evolution is reflected in the organization of the recommendations, first published as phase I, then phase II and phase II+, and now published with one release each year (releases 96, 97, 98, 99, and releases 4 and 5 in 2000 and 2001).

As stated, responsibility for the GSM specifications was carried by ETSI up to the end of 1999. During 2000, the responsibility of the GSM recommendations was transferred to the Third Generation Partnership Project (3GPP). This world organization was created to produce the third-generation mobile system specifications and technical reports . The partners have agreed to cooperate in the maintenance and development of GSM technical specifications and technical reports, including evolved radio access technologies [e.g., General Packet Radio Service (GPRS) and Enhanced Data rates for Global Evolution (EDGE)]. The structure and organization of the 3GPP is further described in Section 2.5.