"Third generation" (3G) is a new network technology being deployed in many mobile networks today. The motivations to develop a new technology when existing wireless technologies are quite mature and serving users very well are these:
■ Demand for high-speed data
■ Capacity limitations of existing networks
■ Demand for seamless roaming worldwide
■ Demand for more mobile data centric services
■ Wireless multimedia services
■ Convergence between telecommunication, IT, media, and content
■ Desire to access data anywhere and anytime
■ Seamless service environment—wireless, wireline, home, office, on the move.
The International Telecommunication union (ITU) started the efforts to create a common radio interface technology on a global basis under the umbrella IMT-2000 family of standards.
The key objectives set by the ITU for Third Generation networks are:
■ Integration of residential, office, and cellular services into a single system
■ Enable high-speed data applications, i.e., 144-Kbps data for high-speed vehicular environments, 384-Kbps data for pedestrian or low-speed vehicular environments, and 2-Mbps data for stationary environments
■ Unique subscriber number independent of the network and service provider
■ Capacity and capability to serve more than 50 percent of the population
■ Integration with satellite components
■ Seamless roaming
■ Quality of service commensurate with that of terrestrial networks at an affordable cost
Several regional standardization bodies have supported the ITU IMT-2000 initiative. The regional standard organizations, such as TIA and T1 in the United States, ETSI in Europe, TTC and ARIB in Japan, CWTS in China, and TTAin Korea submitted their proposals on radio access technologies for open review. The five accepted radio access technologies are:
■ IMT-2000 CDMA direct spread (IMT-DS), referred to as UTRA-FDD, UMTS FDD, WCDMA
■ IMT-2000 CDMA multicarrier (IMT-MC), referred to as CDMA2000
■ IMT-2000 CDMA TDD (IMT-TC), referred to as UTRA-TDD, and in China as SCDMA
■ IMT-2000 CDMA single carrier (IMT-SC), referred to as UWC-136/EDGE
■ IMT-2000 FDMA/TDMA (IMT-FT), referred to as DECT
Anew 3GPP-Third Generation Partnership Project organization was formed in collaboration with ETSI and other regional standards bodies to define and maintain a Universal Mobile Telecommunication System (UMTS) specification. The current organizational partners are ARIB, CCSA, ETSI, ATIS, TTA, and TTC. UMTS embraces WCDMA as its radio technology. WCDMA is the dominating technology today. Most of the operational networks are based on WCDMA. It uses new spectrum with 5-MHz carrier. The description in this section is mainly based on UMTS specifications.
