The Third Generation mobile cellular technology developed by 3GPPTM - known variously as Universal Mobile Telecommunications System (UMTSTM), Freedom of Mobile Multimedia Access (FOMA), 3GSM, ..., is based on wideband code division multiple access (W-CDMA) radio technology offering greater spectral efficiency and higher bandwidth than GSMTM.


The UMTS Radio Access Network (UTRAN) technology is specified in the 3GPP TS 25.-series specifications on the 3GPP website (see also ETSI standards search). The specifications cater for Frequency Division Duplex (FDD) and Time Division Duplex (TDD) forms, with high (3.84 Mc/s) and low (1.28 Mc/s) chip rate flavours. (Low chip rate TDD was developed in China, but may well be deployed elsewhere.) Other chip rates (e.g. 7.68 Mc/s) were subsequently added. Maximum commonality between FDD and TDD variants is assured by a single set of higher layer protocols and shared physical layer parameters, as far as possible.

UTRAN was originally specified for operation in several bands in the 2 GHz range (3GPP TS 25.101 on the 3GPP website). See also ETSI standards search. Subsequently, UTRAN has been extended to operate in a number of other bands, including those originally reserved for Second Generation (2G) services. Nominal carrier spacing is 5 MHz (1.6 MHz for the low-rate TDD option, 10 MHz for the 7.68 Mc/s option). Contrast this with GSM's 200 kHz channel spacing.

The UTRAN radio technology is direct-sequence CDMA. Each 10 ms radio frame is divided into 15 slots, with 2560 chips/slot at 3.84 Mc/s. Modulation is 16QAM and turbo coding gives high speed packet access. A flexible radio protocol allows multiplexing of several services (speech, video, data...) on a single carrier. Real-time and non-real-time services are catered for by configurable quality of service parameters (delay, bit error probability, frame error ratio). The architecture allows for point-to-point and also point-to-multipoint services (broadcast, multicast).

As a development of the original radio scheme, a high-speed download packet access (HSDPA, offering download speeds potentially in excess of 10 Mbit/s), and an uplink equivalent (HSUPA, also sometimes referred to as EDCH) were developed. Collectively the pair are tagged HSPA, and permit the reception of multimedia broadcast/multicast, interactive gaming and business applications, and large file download rivalling traditional terrestrial or satellite digital broadcast services and fixed-line broadband internet access. The radio frames are divided into 2 ms subframes of 3 slots, and gross channel transmission rates are around 14 Mbit/s.

3GPP's radio access undergoes continuous development, and the 'long-term evolution' exercise aims to extend the radio technology to keep UMTS highly competitive to potential rival technologies, with data rates approaching 100 Mbit/s by the end of the decade.

See the ETSI standards search for the 3GPP 25.-series of ETSI standards, ordered by most recent publications. Via this interface you can also subscribe for alerts on updates of ETSI standards.

For work in progress see the ETSI Work Programme on the Portal.