W-CDMA (UMTS)

Wideband CDMA ( WCDMA) is a CDMA (CDMA: Code Division Multiple Access, code division multiple access ), where the signal to be transmitted is greatly spread, so that it occupies a wider bandwidth and thus is less susceptible to narrowband interference pulses. It may also cause the transmit power per Hz is decreased. WCDMA is used for example in UMTS.

In a 5 MHz wide UMTS frequency band is used for data transmission with WCDMA. While ( Frequency Division Duplex) and TDD ( Time Division Duplex) is used, a chip rate ( spreading code p ) of 3.84 Mcps (Mega chips per second) in the FDD. Furthermore, the so-called narrowband CDMA is defined, which is operated in the TDD of 1.28 Mcps, and only uses a 1.6 MHz wide frequency band. UMTS configurations of the two methods are described in the 3GPP specification 25201.

The codes used by the WCDMA can not influence each other. For this reason, the codes used must be orthogonal to each other. One speaks of an orthogonal code, if the cross-correlation of the coded signal sequences results in zero. In this way, the receiver can decode the composite from several transmitters transmit signal back into the original individual signals.