Wideband Code Division Multiple Access

Wideband Code Division Multiple Access (Spanish division multiple access code broadband) whose acronym is WCDMA mobile technology is a third generation wireless increasing rates of data transmission systems using GSM CDMA air interface instead of TDMA (Division Multiple Access Time) and therefore provides data rates much higher in mobile and portable wireless devices than those offered so far.

WCDMA supports a satisfactory rate of data transfer ranging from 144 to 512 Kbps for large coverage areas and can reach up to 2Mbps for more coverage in local areas. In WCDMA systems the CDMA air interface is combined with the networks based on GSM. The WCDMA standard was developed as the project of the society of the third generation (3GPP) which aims at ensuring interoperability between different 3G networks.

The standard that has emerged from this project of society 3GPP, is based on the system of universal mobile telecommunications ETSI (UMTS) and is commonly known as terrestrial radio access UMTS (Utra). The schedule of access to Utra is the division multiple access codes in direct sequence spread spectrum (DS-CDMA). The information is spread across a window of about 5 MHz. This is a wide bandwidth which occupies a channel WCDMA, or Wideband CDMA.

In WCDMA, there are two modes of operation:

* TDD: In this method two-way transmissions of uplink and are transported downward at the same frequency band using time intervals (slots weft) synchronous manner. So the time slots in a physical channel is allocated to the flow of data transmission and reception.

* FDD: The links of transmissions upload (uplink) and downlink (downlink) employ two frequency bands for this method to separate two sides. A couple of frequency bands with a specified separation is assigned to each link. Given that different regions have different patterns of allocation of frequency, the ability to operate in TDD or FDD mode allows the efficient use of available spectrum.

Characteristics of WCDMA [edit]

The operational characteristics of the WCDMA radio interface are listed below:

* High-speed data transmission: 384 Kbps with wide area coverage, 2 Mbps local coverage.

* High flexibility of the service: to help the services vary according to the characteristics of each connection.

* Duplex of the division of the frequency (FDD) and time division duplex (TDD).

* Support for the future capacity and coverage which makes technology to taste the dishes adaptantes, the structures of advanced receiver and transmitter diversity.

* Support for inter often delivered and this is delivered to other systems, including delivery to GSM.

* Access efficient package .