Universal Mobile Telecommunication System (UMTS) is part of the third generation (3G) cellular radio system and is often referred to as WCDMA. UMTS is standardized via 3GPP (ETSI, ARIB, T1P1, TTA and others), and is compatible with the GSM core network.
Using the radio spectrum around 2 GHz, UMTS has three different air interfaces:
1. FDD (Frequency Division Duplex)
2. TDD (Time Division Duplex)
3. TDD low chip rate (TD-SCDMA, from CWTS)