W-CDMA stands for Wide-Band Code-Division Multiple Access.WCDMA is third-generation technology.it offers Internet access and data exchange at a much higher speed (up to 2 Mbps). The main third generation systems are WCDMA and CDMA2000.It is the technology used in the UMTS 3G network that allows a faster speed than previous networks.It provides a new range of multimedia services such as voice, images, videos, digital sound, etc.This technology is standardized by the International Telecommunication Union (ITU) under the name IMT-2000 Direct Spread.
WCDMA modes of operation.
We must be clear that WCDMA and TD-CDMA are the two standards on which the operation of the 3G network is based .The WCDMA is part of a set of techniques that are called multiple access code separation , where they agree that all users make transmissions at the same time, so there is no time or frequency separation.
In WCDMA there are two modes of operation
TDD : a bidirectional mode, where the transmissions of the up and down links are transported in the same frequency band with the uses of time intervals in a synchronized manner. The time intervals in a physical channel are allocated for the reception and transmission data flows.
The links in the up and down transmissions use separate frequency bands. Two frequency bands that have a specific separation allocated for each link.
In case you buy a mobile that supports TD-CDMA instead of WCDMA you will not have 3G coverage. With the 4G / LTE network we have the FDD LTE and TD LTE standards, although in our country only the FDD LTE standard works.
Power Control in WCDMA
For a multiple access system by means of codes, careful control of the power transmitted by the base station and the mobile units is necessary. This power control must be much more accurate than in other multiple access systems. . The power control is given 2 ways: in closed loop or in open loop. The closed loop control setting is given with a frequency of 1.5 Khz. The frequency of this adjustment is relatively high.