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W-CDMA

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W-CDMA' ('Wideband Code Division Multiple Access) is a type of 3G cellular network. W-CDMA is the technology behind the 3G UMTS standard and is allied with the 2G GSM standard. 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).

History

W-CDMA was developed by NTT DoCoMo as the air interface for their 3G network FOMA. Later NTT DoCoMo submitted the specification to the International Telecommunication Union (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.

Features

Only key features are cited below.

- Supports two basic modes: Duplex (telecommunications) and Duplex (telecommunications) modes

- Employs coherent detection on uplink and downlink based on the use of pilot symbols

- Inter-cell asynchronous operation

- Variable mission: on a 10 ms frame basis

- Multicode transmission

- Adaptive power control based on SIR

- Multiuser detection and smart antennas can be used to increase capacity and coverage

- Multiple types of handoffs between different cells including soft handoff, softer handoff and hard handoff

Misconceptions

W-CDMA is based on the Direct Spread CDMA technique. Qualcomm collects royalties for both standards. Qualcomm also collects royalties for another standard called TD-SCDMA (Time Division-Synchronous Code Division Multiple Access), which is also based on Qualcomm's CDMA standard. 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 (IS-95) and CDMA2000 (IS-2000 and Evolution-Data Optimized). The CDMA multiplexing technique existed long before Qualcomm used it for its IS-95 Protocol (computing). However, this protocol is now widely referred to as "CDMA" for its principal characteristic of using the CDMA multiplexing scheme to share multiple connections divided by different codes (Protocol (computing). However, this protocol is now widely referred to as "CDMA" for its principal characteristic of using the CDMA multiplexing scheme to share multiple connections divided by different codes (PN sequences) over the same spectrum channel, as opposed to other spectrum division schemes (e.g. GSM's TDMA). Qualcomm's research solved several problems thought to be intractable related to using the multiplexing technique with a cellular phone system (including but not limited to the near-far problem), and thus Qualcomm was able to introduce the first mobile protocol relying upon the CDMA multiplexing technique, associating the multiplexing technique with the name of the protocol. W-CDMA also uses the CDMA multiplexing technique, due to its advantages over other multiple access techniques such as TDMA, and has many similarities to the Qualcomm standards. Indeed, Qualcomm receives royalties due to the unavoidable use of its patents and research in the implementation of the CDMA multiplexing technique in W-CDMA. 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. In summary:

- 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, although drawing on Qualcomm's research

- The CDMA family of standards (including cdmaOne and CDMA2000) are not compatible with the W-CDMA family of standards

Implementations

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. J-Phone Japan (now Vodafone) soon followed by launching their own W-CDMA based service, originally branded "Vodafone Global Standard" and claiming UMTS compatibility. The name of the service was changed to "Vodafone 3G" in December 2004. 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, New Zealand in August 2005 and Australia in October 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 began offering HSDPA service in December 2005. Rogers in Canada is currently trialing HSDPA on W-CDMA at 1900MHz and plan the launch the service commercial in Q3, 2006. TeliaSonera opened W-CDMA service in Finland October 13th 2004 with speeds up to 384 kbit/s. Availability only in main cities. Pricing is approx. 2€/MB. [http://www.teliasonera.com/ts/teliasonera/sidtypTS_press.do?tabId=4&channelPage=%2FsidtypTS_press.do&channelId=-1073820211&mainUrl=http%3A%2F%2Fwww.startsidan.telia.se%2Fcom%2Ftelia%2Fics%2Fportal%2Fapps%2Fpress%2FPressReleasePage.html%3Fid%3D109036%26disclaimerId%3D%26lang%3DEN] SK Telecom and KTF, two largest mobile phone service providers in South Korea, have each started offering W-CDMA service in December 2003. Due to poor coverage and lack of choice in handhelds, the W-CDMA service has barely made a dent in the Korean market which was dominated by CDMA2000. In Norway, Telenor introduced W-CDMA in major cities by the end of 2004, while their competitor, NetCom (Norway), followed suit a few months later. Both operators have 98 % national coverage on NetCom (Norway), followed suit a few months later. Both operators have 98 % national coverage on EDGE. Maxis Communications and Celcom, two mobile phone service providers in Malaysia, started offering W-CDMA services in 2005. In Sweden, Telia introduced W-CDMA March 2004.

Technology

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.

See also

- UMTS

- PN Sequences

External links

- Qualcomm W-CDMA Resources

- CDMA University

- UMTS/3G Resources

- Radio-Electronics.Com Free WCDMA tutorial

- Nokia - Wideband Code-Division Multiple Access

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