The ITU standardized 5 groups of 3G radio access technologies.They are as follows :-

• IMT-DS :-The directr spread technology comprises wideband CDMA (W-CDMA) systems .This technology specified for UTRA-FDD and used by all european providers and the japanese NTT DoCoMo for 3G wide area services . To avoid complete confusion ITU'S name for the technology is IMT-DS ,ETSI called it UTRA -FDD in the UMTS context ,and the technology used is called W-CDMA .Today , standardization of this technology takes place in 3GPP .Details of it will be further provided.

• IMT-TC :- Intially ,this family member called time code ,contained only UTRA-TDD
  systems which uses time-division CDMA (TD-CDMA).Latr on, the chinese proposal ,TD -synchronous CDMA (TD-SCDMA) was added.Both staandards have been combined and 3GPP fosters the development of this technology.It is unclear when and to what extent this technology will be introduced.The initial UMTS installation are based on W-CDMA.

• IMT-MC :- Cdma2000 is a mutli-carrier technology standardized by 3GPP2(third generation partnership project 2, 3GPP2 ,2002 ),which was formed shortly after 3GPP to represent the second main stream in 3G technology version cdma2000 EV-DO has been accepted as the 3G standard.

• IMT-SC :- The enhancement of the US TDMA systems, UWC-136, is single carrier technology originally promoted by the universal wireless communications consortium.It is now integrated into 3GPP efforts .This technology applies EDGE , among others, to enhance 136 standards.

• IMT-FT :- As frequency time technology ,an enhanced version of the cordless telephone standard DECT has also been selected for applications that do not require high mobility.ETSI is responsible for standardisation of DECT.
  

A lot has been written about 3 rd generation networks(3G) in last few years.Let us see how did this start in many countries around the world ? ? ?..First of all International Telecommunicaiotns Union (ITU) made a request for appropriate radio transmission technologies(RTI ) for the internal Mobile communications (IMT) 2000 program (ITU, 2000) .IMT-2000 ,formerly called future public land mobile communications systems( FPLMTS), tried to establish a common world wide communication system alowed for terminal and user mobility , supporting the idea of universal personal telecommunications (upt).Within this context . ITU has created several recommendations for FPLMTS systems e.g: network architecture for FPLMTS systems ,Requirements for the radio interface for FPLMTS frame work for services supported by M.816.
The number 2000 in IMT-2000 should indicate the start of the system(year 2000 + x) and the spectrum used around 2000 MHz .IMT-2000 includes different environments such as indoor use ,vehicals ,satellites ,pedestrian's .The world radio conference bands that should be available worldwide for the new IMT-2000 systems recommendations ITU-R.Within these bands, two times 30 Mhz have been reserved for mobile satellite services.
The ITU frequency allocation together with examples from several regions that already indicate the problem of world wide common frequency band.
The ITU frequency allocation together with examples from several regions that already indicate the problem of world wide common frequency band .In Europe some parts of the ITU frequency bands for IMT- 2000 are already allocated for DECT . The remaining frequencies have been split into bands for UTRA-FDD (uplink: 1920-1980 MHz,downlink: 2110-2170 Mhz ) and UTRA -TDD (1900-1920 MHz and 2010-2025 MHz )The technology behind UTRA-FDD and TDD will subsequently be explained in much more details as the form the basis of UMTS.Currently , no other systems is planned for IMT-2000 in Europe. More bandwidth is available in CHINA for Chinese 3G systems TD-SCDMA or possible other 3G systems.