WCDMA stands for Wideband Code Division Multiple Access. This is a 3G cellular network developed by NTT DoCoMo, a Japanese operator for their 3G network. Later, NTT DoCoMo submitted the specification to an organization called ITU (International Communication Union) for it to be classified as 3G standard called IMT-2000. ITU later accepted WCDMA as a standard separate from it’s then existing 3G technology such as CDMA2000, EDGE and DECT. It is used across IMT-2000 frequency bands. The term can also refer to a spread-spectrum 3G mobile telecommunication air interface which uses Code Division Multiple Access (or CDMA the general multiplex scheme, and not the standard CDMA) and supports more users compared to implementation of time division multiplexing (TDMA) popular in 2G networks. The technology supports high-speed data transmission, and also for images and voice at a speed of 2Mbps for local area access or 384 Kbps for wide area access. Providing a cost-efficient for modern mobile multimedia and telephone services was a key design consideration.
The user data in WCDMA is spread over a bandwidth of around 5 MHz; the 5 MHZ is neither too wide nor to narrow (some commercial CDMA systems have been known to operate on a bandwidth of around 20 MHz). The reason behind the adjective “wideband” is that the new 3G cellular networks enjoy much wider bandwidths compared to the 2G CDMA systems, which only use up abut 1.25 MHz of bandwidth. The data transfer rates are higher and the diversity of broadcast frequency also brings performance benefits to users. If used with a relatively new technology called HSDP (for High Speed Downlink Packet Access), WCDMA is likely to bring down even higher downlink speeds over their networks.
WCDMA has two modes of operation:
· TDD-Here, the uplink and downlink transmission happen in the same frequency band via synchronized time intervals. The time slots in the physical channel are separated into reception and transmission parts.
· FDD. In FDD on the other hand, the downlink and uplink transmissions use two partitioned frequency bands for this duplex method. Two frequency bands are used for a connection. Because different regions have varying frequency allocation schemes, the ability to work using either FDD or TDD mode means there is efficient utilization of the spectrum available.
Overall, WCDMA offers a much wider bandwidth than CDMA2000, its nearest 3G rival technology. It, however, does not employ direct sequence transmission like CDMA2000. From an engineering standpoint, CDMA provides not only cost benefits, but also capacity performance and density. It also holds much promise for cost reduction of video phones handsets. It also has much better suites to densely populated metropolitans that are common in Europe and Asia. Perhaps the biggest challenge will be in the cross-licensing of patents between WCDMA vendors and those of Qualcomm, as some features of WCDMA have remained covered in Qualcomm patents. Although there are issues surrounding this 3G technology such as incompatibility with existing air-interface standards, WCDMA has been accepted in many countries (56 as of 2006) in Asia and Europe.
Perhaps the biggest challenge will be in the cross-licensing of patents between WCDMA vendors and those of Qualcomm, as some features of WCDMA have remained covered in Qualcomm patents. Although there are issues surrounding this 3G technology such as incompatibility with existing air-interface standards, WCDMA has been accepted in many countries (56 as of 2006) in Asia and Europe. GSM is still the dominant form of cellular network, servicing Afganistan (“Afghan Wireless“), Venezuela (Telefnica Mviles Venezuela), Tunisia (Tunisie Telecom), and more than 200 other countries throughout the world.
Additional Reading on WCDMA:
