Wideband CDMA

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Wideband CDMA ( WCDMA ) is a CDMA method (CDMA: Code Division Multiple Access , code division multiplex method ) in which the signal to be sent is widely spread so that it takes up a larger bandwidth and is therefore less susceptible to interference from narrow-band interference pulses. In addition, this can reduce the transmission power per Hz. WCDMA is used in UMTS , for example, in that different spreading codes are used to distinguish between the participants .

In UMTS, a 5 MHz wide frequency band is used for data transmission with WCDMA. A chip rate (see spreading code ) of 3.84 Mcps (megachips per second) is used in the FDD (Frequency Division Duplex ) and TDD (Time Division Duplex) . The so-called Narrowband CDMA is also defined, which is operated in TDD with 1.28 Mcps and only uses a 1.6 MHz wide frequency band. The UMTS configurations of the two methods are described in 3GPP specification 25.201.

The codes used by WCDMA must not influence one another. For this reason, the codes used must be orthogonal to one another. 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 transmission signal composed of several transmitters back into the original individual signals.

literature

  • Christophe Chevallier, Christopher Brunner, Andrea Garavaglia, Kevin P. Murray, Kenneth R. Baker (Eds.): WCDMA (UMTS) Deployment Handbook. Planning and Optimization Aspects. John Wiley & Sons, New York 2006, ISBN 0-470-03326-6 .
  • Rudolf Tanner, Jason Woodard (Eds.): WCDMA - Requirements and Practical Design. John Wiley & Sons, Chichester 2004, ISBN 0-470-86177-0 .

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