regulatory body. It is a government organization that regu- lates wire and radio communications. It has played an important role, for example, in the development of worldwide specifications for radiation and susceptibility of electromagnetic disturbances of telecommunications equipment. The Telecommunications Industry Association (TIA) has been developing global third generation cellular systems together with ETSI from Europe and the Association of Radio Industries and Broadcasting (ARIB) from Japan. Its task is to adapt the global standard to the American environment [4]. 1.5.5 Global Organizations The International Telecommunication Union (ITU) is a specialized agency of the United Nations responsible for telecommunications. It has nearly 200 member countries, and standardization work is divided between two major standardization bodies: ITU-T and ITU-R (see Figure 1.7). The Comité Consultatif International de Télégraphique et Téléphonique, or International Telegraph and Telephone Consultative Committee (CCITT/ ITU-T) is presently called ITU-T, where the "T" comes from telecommunica- tions. The Comité Consultatif International des Radiocommunications or Inter- national Radio Consultative Committee (CCIR/ITU-R) is presently known as ITU-R, where the "R" stands for radio. Introduction to Telecommunications Network Engineering ITU-T (CCITT) ISO/IEC ITU-R (CCIR) Figure 1.7 Global standards organizations. ITU-T and ITU-R publish recommendations that are in fact strong standards for telecommunications networks. ITU-T works for the standards of public telecommunications networks (e.g., ISDN), and ITU-R works with radio aspects such as the usage of radio frequencies worldwide and specifications for radio systems. Many parties participate in their work, but only national authorities may vote. ITU-T, formerly CCITT, has created most of the current worldwide standards for public networks. The International Standards Organization/International Electrotechni- cal Commission (ISO/IEC) is a joint organization responsible for t