WCDMA stands for Wideband Code Division Multiple Access. It is one of the main systems used for third generation, or 3G, mobile communication networks. The term is often used interchangeably with UMTS, which stands for Universal Mobile Telecommunications Systems. Technically WCDMA is merely one example of UMTS technology.
The most prominent use of WCDMA is in Japan where the country's largest mobile phone operator, NTT DoCoMo uses the technology. It was DoCoMo which originally developed WCDMA. The firm then successfully lobbied for it to be accepted as an international standard.
WCDMA is used across the world in dozens of countries. It is most prominently used in Asia and Europe. Outside of Japan, the UMTS name is generally used for marketing the system.
The WCDMA system combines two main types of mobile phone technology: CDMA and GSM, which stands for Global System for Mobile communications. In the United States, most cellphone network providers use only one of these two technologies. One of the main reasons WCDMA has struggled to get a foothold in the US is that it uses two channels, each covering 5Mhz. This is a relatively large "chunk" of the airwaves, which has been problematic as the US was slow to allocate new frequencies specifically for 3G systems.
There are several key advantages to WCDMA. One is that each transmitter is assigned an identification code. This means that data from multiple transmitters can be carried over the same frequency in the same geographical area at the same time without interference or loss of signal strength.
The system also uses power control. This adjusts the strength of the signal transmitted by each cellphone so that it reaches the nearest transmitter at the same strength, regardless of how far away the phone is. This avoids the transmitter receiving signals which are excessively strong or weak, which could limit the transmitter's efficiency.
Another benefit is that WCDMA can cope particularly well when there are many devices in one area. This makes it particularly suitable for densely populated areas such as some major Asian cities. The system is also well suited to the technical requirements presented by video calls.
The main disadvantages of WCDMA are that it is not used throughout the entire world, which limits take-up of compatible handsets among people who travel internationally, and that it is a relatively complex system which can be expensive to introduce into a new market.