d by Metcalfe and Broggs (Xerox) [2]. 1968-1969 Digitalization of telephone network begins. 1970-1975 PCM standards developed by CCITT. 1975-1985 High-capacity optical systems developed; the breakthrough of optical technology and fully integrated switching systems; digital signal processing by microprocessors. 1980-1983 Start of global Internet based on TCP/IP protocol [3]. 1980-1985 Modern cellular mobile networks put into service, NMT in Northern Europe, AMPS in the United States, OSI reference model is defined by International Standards Organization (ISO). Standardization for second generation digital cellular systems is initialized. 1985-1990 LAN breakthrough; Integrated Services Digital Network (ISDN) standardization finalized; public data communica- tions services become widely available; optical transmission systems replace copper systems in long-distance wideband transmission; SONET is developed. GSM and SDH stan- dardization finalized. Initial proposal for a Web-linked document on the World Wide Web (WWW) by Tim Berners-Lee (CERN) [2]. 1990-1997 The first digital cellular system, Global System for Mobile Com- munications (GSM), is put into commercial use and its break- through is felt worldwide; deregulation of telecommunications in Europe proceeds and satellite TV systems become popular; Internet usage and services expand rapidly because of the 1997-2001 Telecommunications community is deregulated and business grows rapidly; digital cellular networks, especially GSM, Introduction to Telecommunications expand worldwide; commercial applications of Internet expand and a share of conventional speech communications is transferred from public switched telephone network (PSTN) to Internet; performance of LANs improves with advance of gigabit-per-second Ethernet technologies. 2001-2005 Digital TV starts to replace analog broadcast TV; broadband access systems make Internet multimedia services available to all; telephony service turns to personal communication service as penetration of cellular and PCS systems i