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MULTIPLE ACCESS IN GSM AND (E)GPRS This chapter discusses features of the GSM air interface from phase 1 recommendations through to the specifications released in 1999. This entails GSM voice, circuit-switched data, and High Speed Circuit-Switched Data (HSCSD) services. A key topic is the matter of radio resource utilisation, hence on top of summarising the relevant system features, we present also some research results dealing with resource utilisation under heterogeneous GSM and HSCSD traffic load | Multiple Access Protocols for Mobile Communications GPRS UMTS and Beyond Alex Brand Hamid Aghvami Copyright 2002 John Wiley Sons Ltd ISBNs 0-471-49877-7 Hardback 0-470-84622-4 Electronic 4 MULTIPLE ACCESS IN GSM AND E GPRS This chapter discusses features of the GSM air interface from phase 1 recommendations through to the specifications released in 1999. This entails GSM voice circuit-switched data and High Speed Circuit-Switched Data HSCSD services. A key topic is the matter of radio resource utilisation hence on top of summarising the relevant system features we present also some research results dealing with resource utilisation under heterogeneous GSM and HSCSD traffic load. The main focus however is on the General Packet Radio Service GPRS since from the perspective of multiple access protocols this is the most interesting aspect of an evolved GSM system. The MAC layer and in particular the random access protocol are explained in considerable detail. Again this includes the presentation of some research results which were fed into the GPRS standardisation process and influenced the design of the employed random access algorithm. Additions to GPRS contained in the 1999 release of the specifications known under the heading EGPRS are also discussed. The further evolution of the GSM system beyond release 1999 is a topic of Chapter 11. 4.1 Introduction 4.1.1 The GSM System Various incompatible analogue first generation cellular systems emerged in Europe during the 1980s. By contrast a concerted effort was made to arrive at a single standard for 2G digital cellular telephony. This pan-European standardisation effort was initiated by the Conference Européenne des Administrations des Postes et des Télécommunications CEPT in 1982 with the formation of the Groupe Special Mobile GSM 3 . Initially nine radio technology candidates were submitted to GSM two proposing hybrid CDMA TDMA six TDMA and one FDMA as basic multiple access schemes. At the beginning of 1987 based on .