ses can be updated after The main IMT-2000 recommendation is ITU-R each set of TSG meetings, which occur 4 times a year. The M.1457, which identifies the IMT-2000 radio interface 3GPP documents are divided into releases, where each specifications (RSPC). The recommendation contains release has a set of features added compared to the pre- a 'family' of radio interfaces, all included on an equal vious release. The features are defined in Work Items basis. The family of five terrestrial radio interfaces is il- agreed and undertaken by the TSGs. The releases up to lustrated in Figure 4.1-4, which also shows what Stan- Release 7 and some main features of those are shown in dards Developing Organizations (SDO) or Partnership Figure 4.1-3. The date shown for each release is the day Projects produce the specifications. In addition, there are the content of the release was frozen. For historical several IMT-2000 satellite radio interfaces defined, not reasons, the first release is numbered by the year it was illustrated in Figure 4.1-4. frozen (1999), while the following releases are numbered For each radio interface, M.1457 contains an overview 4, 5, etc. of the radio interface, followed by a list of references to For the WCDMA Radio Access developed in TSG the detailed specifications. The actual specifications are RAN, Release 99 contains all features needed to meet the maintained by the individual SDOs and M. 1457 provides December 1999 Rel-4 March 2001 Rel-5 CS and PS March 2002 Rel-6 R99 Radio Enhancements March 2005 Bearers TD-SCDMA HSDPA Rel-7, 8, Enhanced Location AMR-WB Uplink Services Speech WLAN-UMTS HSPA Evolution Interworking Figure 4.1-3 Releases of 3GPP specifications for UTRA. CHAPTER 4.1 Background of 3G evolution ITU-R Family of IMT-2000 Terrestrial Radio Interfaces (ITU-R M. 1457) IMT-2000 CDMA Direct Spread IMT-2000 (UTRA FDD) CDMA Multi-Carrier IMT-2000 (CDMA2000) CDMA TDD (UTRA TDD) 3GPP2 IMT-2000 TDMA Single-Carrier IMT-2000 (UWC 136) FDMA/TDMA (DECT) ATIS/TIA Figure 4.1-4 The definition of IMT-2000