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More technically, W-CDMA is a wideband spread-spectrum 3G mobile telecommunication air interface that utilizes code division multiple access (or CDMA the general multiplexing scheme, not to be confused with CDMA the standard).
W-CDMA was developed by ETSI NTT DoCoMo as the air interface for their 3G network FOMA. Later NTT Docomo submitted the specification to ITU as a candidate for the international 3G standard known as IMT-2000. The ITU eventually accepted W-CDMA as part of the IMT-2000 family of 3G standards. Later, W-CDMA was selected as the air interface for UMTS, the 3G successor to GSM.
Despite the similarity in name, W-CDMA has very little to do with CDMA. How little depends on the point of the viewer.
In the mobile phone world, the term CDMA can refer to either the Code Division Multiple Access spread spectrum multiplexing technique, or the CDMA family of standards developed by Qualcomm, including cdmaOne (or IS-95) and CDMA2000 (or IS-2000).
The CDMA multiplexing technique existed long before Qualcomm used it for its IS-95 protocol. However, this protocol is now widely referred to as "CDMA" because for its principal characteristic of using the CDMA multiplexing scheme to share multiple connections over the same spectrum, as opposed to other spectrum division schemes (e.g. GSM's TDMA).
W-CDMA also uses the CDMA multiplexing technique, and has many similarities to the Qualcomm standards. However W-CDMA is more than a multiplexing standard. W-CDMA is a complete set of specifications, a detailed protocol that defines how a mobile phone communicates with the tower, how signals are modulated, how datagrams are structured, etc.
- The term CDMA in the mobile world typically refers to the CDMA family of standards developed by Qualcomm. They are protocols, sets of defined specifications of mobile communications
- CDMA (the multiplexing technique) is used as the principle of the W-CDMA air interface protocol, as well as Qualcomm's CDMA protocols
- W-CDMA strictly refers to a mobile phone protocol with detailed specifications, as defined in IMT-2000
- The W-CDMA protocol was developed independently of the CDMA protocol developed by Qualcomm
- The CDMA family of standards (including cdmaOne and cdma2000) are not compatible with the W-CDMA family of standards
The world's first commercial W-CDMA service, FOMA, was launched by NTT DoCoMo in Japan in 2001. FOMA is not compatible with UMTS. But the effort for migrating the FOMA specifications to UMTS are indicated by Japan.
Beginning in 2003, Hutchison Whampoa gradually launched their upstart UMTS networks (simply called 3) worldwide.
Most Western European GSM providers plan to offer UMTS sometime in the future, though few have committed to an actual timeline. Some of them have begun launching UMTS networks at the end of 2003.
Vodafone launched several UMTS networks in Europe in February 2004. Vodafone also has plans to launch UMTS networks in other countries, including Australia and New Zealand. Vodafone New Zealand have been upgrading their exisiting base stations for UMTS and have applied to various City Councils for permission to build new 3G base stations. Vodafone New Zealand plans to launch the UMTS service by the end of 2005.
AT&T Wireless (now a part of Cingular Wireless) has deployed UMTS in several cities. Though advancements in its network deployment have been delayed due to the merger with Cingular, Cingular has now announced plans to deploy W-CDMA along with HSDPA in 2005.
Please see UMTS for more info.
- GCF: Global Certification Forum (GCF) is the world leading forum for 2G/3G testing certification.
- PTCRB: provides the framework for GSM Mobile Equipment (ME) Type Certification in North America.
W-CDMA may use unpaired or paired spectrum, though the current implementations of W-CDMA (i.e. FOMA and UMTS) all use a pair of 5MHz spectrum, one for uplink and one for downlink. See Spread spectrum for more information.FOMA uses 16 slots per radio frame, where as UMTS uses 15 slots per radio frame
Comparison with other standards
In contrast to CDMA2000, which can use multiple 1.25 MHz carriers, W-CDMA uses 5MHz channels. WCDMA can operate in two modes FDD(Frequency Division Duplex) and TDD(Time division Duplex). In the ITU's IMT-2000 standard, W-CDMA is known as CDMA Direct Spread.
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