3G - Third Generation 

3G - Third Generation networks

3G - Third Generation mobile telephone networks are the latest stage in the development of wireless communications technology. Significant features of 3G systems are that they support much higher data transmission rates and offer increased capacity, which makes them suitable for high-speed data applications as well as for the traditional voice calls. In fact, 3G systems are designed to process data, and since voice signals are converted to digital data, this results in speech being dealt with in much the same way as any other form of data. Third Generation systems use packet-switching technology, which is more efficient and faster than the traditional circuit-switched systems, but they do require a somewhat different infrastructure to the 2G systems.

The benefits of higher data rates and greater bandwidth mean that 3G mobile phones can offer subscribers a wide range of data services, such as mobile Internet access and multimedia applications. Compared to earlier mobile phones a 3G handset provides many new features, and the possibilities for new services are almost limitless, including many popular applications such as TV streaming, multimedia, videoconferencing, Web browsing, e-mail, paging, fax, and navigational maps.

The Third Generation mobile communication standard was a programme led originally by the ITU (International Telecommunications Union) under the IMT-2000 project, which generated a family of standards for use in 3G devices and networks, and they are generally defined under the title of Universal Mobile Telecommunication Service (UMTS).

Japan was the first country to introduce a 3G system, which was largely because the Japanese PDC networks were under severe pressure from the vast appetite in Japan for digital mobile phones. Unlike the GSM systems, which developed various ways to deal with demand for improved services, Japan had no 2.5G enhancement stage to bridge the gap between 2G and 3G, and so the move into the new standard was seen as a solution to their capacity problems.

Despite all the good intentions, that the IMT-2000 specification would become a single, global and standardised 3G system, this has not worked out in practice, and three different versions of 3G systems have developed, each one evolved from an existing 2G system. This is an understandable evolutionary route, as leading telecommunications companies have invested vast amounts of resources into their network infrastructure and spectrum allocations, and it was not practical to simply change from one system to another.

The main 3G technologies include UMTS and cdma2000, with Europe settling on the UMTS with wideband CDMA (W-CDMA) as its chosen approach, whilst in the USA the cdmaOne networks will be upgraded to CDMA2000, a multi-carrier CDMA (MC-CDMA).

It is generally accepted that CDMA is a superior transmission technology, when it is compared to the old techniques used in GSM/TDMA. WCDMA systems make more efficient use of the available spectrum, because the CDMA technique enables all base stations to use the same frequency. In the WCDMA system, the data is split into separate packets, which are then transmitted using packet switching technology, and the packets are reassembled in the correct sequence at the receiver end by using the code that is sent with each packet. WCDMA has a potential problem, caused by the fact that, as more users simultaneously communicate with a base station, then a phenomenon known as cell breathing can occur. This effect means that the users will compete for the finite power of the base stations transmitter, which can reduce the cells range W-CDMA and cdma2000 have been designed to alleviate this problem.

The Third Generation of mobile phones is also designed for global roaming throughout Europe, North America and Japan, and will be widely available in many countries during 2004. However there are problems due to the different standards, and so it is still necessary for phones to be multi-band or multi-mode for widespread roaming. A 3G phone may have to make use of existing 2G and 2.5G networks where the 3G service is unavailable.

The operating frequencies of many 3G systems will typically use parts of the radio spectrum in the region of approximately 2GHz (the IMT-2000 core band), which were not available to operators of 2G systems, and so are away from the crowded frequency bands currently being used for 2G and 2.5G networks. UMTS systems are designed to provide a range of data rates, depending on the users circumstances, providing up to 144 kbps for moving vehicles (macrocellular environments), up to 384 kbps for pedestrians (microcellular environments) and up to 2 Mbps for indoor or stationary users (picocellular environments). In contrast, the data rates supported by the basic 2G networks were only 9.6 kbps, such as in GSM, which was inadequate to provide any sophisticated digital services.