As was mentioned in the previous chapter, the era of mobile telephony began with the development and operation of the First Generation (1G) of cellular systems in the late 1970s. Although these systems have found widespread use and are still used nowadays, the evolution of technology has enabled the industry to move to Second Generation (2G) systems, the successors of 1G systems. 2G systems overcome many of the deficiencies of 1G systems mentioned in the previous chapter. Their increased capabilities stem from the fact that, contrary to 1G systems, 2G systems are completely digital. . | Wireless Networks. P. Nicopolitidis M. S. Obaidat G. I. Papadimitriou and A. S. Pomportsis Copyright 2003 John Wiley Sons Ltd. ISBN 0-470-84529-5 4 Second Generation 2G Cellular Systems Introduction As was mentioned in the previous chapter the era of mobile telephony began with the development and operation of the First Generation 1G of cellular systems in the late 1970s. Although these systems have found widespread use and are still used nowadays the evolution of technology has enabled the industry to move to Second Generation 2G systems the successors of 1G systems. 2G systems overcome many of the deficiencies of 1G systems mentioned in the previous chapter. Their increased capabilities stem from the fact that contrary to 1G systems 2G systems are completely digital. Compared to analog digital technology has a number of advantages Encryption. Digitized traffic can be easily encrypted in order to provide privacy and security. Encrypted signals cannot be intercepted and overheard by unauthorized parties at least not without very powerful equipment . On the other hand powerful encryption is not possible in analog systems which most of the time transmit data without any protection. Thus digital systems provide an increased potential for securing the user s traffic and preventing unauthorized network access. Use of error correction. In digital systems it is possible to apply error detection and error correction techniques to the user traffic. Using these techniques the receiver can detect and correct bit errors thus enhancing transmission reliability. This obviously leads to signals with little or no corruption which of course translates into a better voice call qualities b higher speeds for data applications and c efficient spectrum use since fewer retransmissions are bound to occur when error correction and error detection techniques are used. Furthermore digital data can be compressed which increases the efficiency of spectrum use even more. It is actually this
