The specification of UMTS is done in phases. Specifications are grouped into “Releases”. A mobile system can be constructed based on the set of all specifications which comprise a given Release. Each new Release adds new functionalities to the system.
So far 3GPP has issued the following Releases:
- UMTS Release 991
- Based on GSM,
- Backward compatible with GSM,
- Interoperation between UMTS and GSM;
- Definition of the UTRAN
- UMTS Release 4
- Seperation of user data flows and control mechanisms,
- UMTS TDD Time Division CDMA (TD-CDMA),
- High data rate UMTS TDD with 3.84 Mchips/s,
- Narrowband TDD with 1.28 Mchips/s;
- Position location functionality;
- UMTS Release 5
- UMTS Release 6
- IMS "Phase 2" (IMS Messaging, conferencing and Group Management),
- High Speed Uplink (HSUPA)
- Multimedia Broadcast/Multicast Service (MBMS)
- WLAN interworking
- UMTS Release 7
- Enhanced uplink, other spectrum,
- Multiple Input Multiple Output antennas (MIMO),
- IMS Emergency call handling.
1The first release is based on the year of publication(1999). Later on, 3GPP just gave them a sequence number.