W-CDMA – the radio technology of UMTS - is a part of the ITU IMT-2000 family of 3G Standards.

Both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) variants are supported.

W-CDMA is a spread-spectrum modulation technique; one which uses channels whose bandwidth is much greater than that of the data to be transferred. Instead of each connection being granted a dedicated frequency band just wide enough to accommodate its envisaged maximum data rate, W-CDMA channels share a much larger band.

The modulation technique encodes each channel in such a way that a decoder, knowing the code, can pick out the wanted signal from other signals using the same band, which simply appear as so much noise.

UMTS uses a core network derived from that of GSM, ensuring backward compatibility of services and allowing seamless handover between GSM access technology and W CDMA.

W-CDMA specifications originate from the 3GPP Radio Access Network (RAN) groupof 3GPP and were frozen in Release 99;

Nearly 200 specifications and reports reside mainly in the 25 series of 3GPP specifications.