W-CDMA (UMTS)
Encyclopedia
W-CDMA UMTS-FDD, UTRA-FDD, or IMT-2000 CDMA Direct Spread is an air interface
Air interface
In mobile or wireless communication, the air interface is the radio-based communication link between the mobile station and the active base station...

 standard found in 3G mobile telecommunications networks. It is the basis of Japan's NTT DoCoMo
NTT DoCoMo
is the predominant mobile phone operator in Japan. The name is officially an abbreviation of the phrase, "do communications over the mobile network", and is also from a compound word dokomo, meaning "everywhere" in Japanese. Docomo provides phone, video phone , i-mode , and mail services...

's FOMA
Freedom of Mobile Multimedia Access
Freedom of Mobile Multimedia Access is the brand name of the W-CDMA-based 3G telecommunications services being offered by the Japanese telecommunications service provider NTT DoCoMo...

 service and the most-commonly used member of the UMTS
Universal Mobile Telecommunications System
Universal Mobile Telecommunications System is a third generation mobile cellular technology for networks based on the GSM standard. Developed by the 3GPP , UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for...

 family and sometimes used as a synonym for UMTS. It utilizes the DS-CDMA channel access method and the FDD duplexing method to achieve higher speeds and support more users compared to most time division multiple access
Time division multiple access
Time division multiple access is a channel access method for shared medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This...

 (TDMA) and time division duplex (TDD) schemes used today.

While not an evolutionary upgrade on the airside, it uses the same core network
Core network
A core network, or network core, is the central part of a telecommunication network that provides various services to customers who are connected by the access network. One of the main functions is to route telephone calls across the PSTN....

 as the 2G GSM
Global System for Mobile Communications
GSM , is a standard set developed by the European Telecommunications Standards Institute to describe technologies for second generation digital cellular networks...

 networks deployed worldwide, allowing dual-mode operation along with GSM/EDGE
Enhanced Data Rates for GSM Evolution
Enhanced Data rates for GSM Evolution is a digital mobile phone technology that allows improved data transmission rates as a backward-compatible extension of GSM...

; a feat it shares with other members of the UMTS family.

Development

In the late 1990s, W-CDMA was developed by NTT DoCoMo
NTT DoCoMo
is the predominant mobile phone operator in Japan. The name is officially an abbreviation of the phrase, "do communications over the mobile network", and is also from a compound word dokomo, meaning "everywhere" in Japanese. Docomo provides phone, video phone , i-mode , and mail services...

 as the air interface
Air interface
In mobile or wireless communication, the air interface is the radio-based communication link between the mobile station and the active base station...

 for their 3G network FOMA
Foma
Foma may refer to:* FOMA , a Japanese mobile telecommunications service* Sergei Fomenko, nicknamed "Foma", Ukrainian musician...

. Later NTT DoCoMo submitted the specification to the International Telecommunication Union
International Telecommunication Union
The International Telecommunication Union is the specialized agency of the United Nations which is responsible for information and communication technologies...

 (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, as an alternative to CDMA2000
CDMA2000
CDMA2000 is a family of 3G mobile technology standards, which use CDMA channel access, to send voice, data, and signaling data between mobile phones and cell sites. The set of standards includes: CDMA2000 1X, CDMA2000 EV-DO Rev. 0, CDMA2000 EV-DO Rev. A, and CDMA2000 EV-DO Rev. B...

, EDGE
Enhanced Data Rates for GSM Evolution
Enhanced Data rates for GSM Evolution is a digital mobile phone technology that allows improved data transmission rates as a backward-compatible extension of GSM...

, and the short range DECT system. Later, W-CDMA was selected as an air interface for UMTS.

As NTT DoCoMo did not wait for the finalisation of the 3G Release 99 specification, their network was initially incompatible with UMTS. However, this has been resolved by NTT DoCoMo updating their network.

Code Division Multiple Access communication networks have been developed by a number of companies over the years, but development of cell-phone networks based on CDMA (prior to W-CDMA) was dominated by Qualcomm
Qualcomm
Qualcomm is an American global telecommunication corporation that designs, manufactures and markets digital wireless telecommunications products and services based on its code division multiple access technology and other technologies. Headquartered in San Diego, CA, USA...

. Qualcomm was the first company to succeed in developing a practical and cost-effective CDMA implementation for consumer cell phones: its early IS-95 air interface standard, which has since evolved into the current CDMA2000
CDMA2000
CDMA2000 is a family of 3G mobile technology standards, which use CDMA channel access, to send voice, data, and signaling data between mobile phones and cell sites. The set of standards includes: CDMA2000 1X, CDMA2000 EV-DO Rev. 0, CDMA2000 EV-DO Rev. A, and CDMA2000 EV-DO Rev. B...

 (IS-856/IS-2000) standard. Qualcomm created an experimental wideband CDMA system called CDMA2000 3x which unified the W-CDMA (3GPP) and CDMA2000
CDMA2000
CDMA2000 is a family of 3G mobile technology standards, which use CDMA channel access, to send voice, data, and signaling data between mobile phones and cell sites. The set of standards includes: CDMA2000 1X, CDMA2000 EV-DO Rev. 0, CDMA2000 EV-DO Rev. A, and CDMA2000 EV-DO Rev. B...

 (3GPP2
3rd Generation Partnership Project 2
The 3rd Generation Partnership Project 2 is a collaboration between telecommunications associations to make a globally applicable third generation mobile phone system specification within the scope of the ITU's IMT-2000 project...

) network technologies into a single design for a worldwide standard air interface. Compatibility with CDMA2000 would have beneficially enabled roaming on existing networks beyond Japan, since Qualcomm CDMA2000 networks are widely deployed, especially in the Americas, with coverage in 58 countries . However, divergent requirements resulted in the W-CDMA standard being retained and deployed.

Despite incompatibilities with existing air-interface standards, the late introduction of this 3G system, and despite the high upgrade cost of deploying an all-new transmitter technology, W-CDMA has been adopted and deployed rapidly, especially in Japan, Europe and Asia, and is already deployed in over 55 countries .

Rationale for W-CDMA

W-CDMA transmits on a pair of 5 MHz-wide radio channels, while CDMA2000 transmits on one or several pairs of 1.25 MHz radio channels. Though W-CDMA does use a direct sequence
Direct-sequence spread spectrum
In telecommunications, direct-sequence spread spectrum is a modulation technique. As with other spread spectrum technologies, the transmitted signal takes up more bandwidth than the information signal that is being modulated. The name 'spread spectrum' comes from the fact that the carrier signals...

 CDMA transmission technique like CDMA2000, W-CDMA is not simply a wideband version of CDMA2000. The W-CDMA system is a new design by NTT DoCoMo, and it differs in many aspects from CDMA2000. From an engineering point of view, W-CDMA provides a different balance of trade-offs between cost, capacity, performance, and density; it also promises to achieve a benefit of reduced cost for video phone handsets. W-CDMA may also be better suited for deployment in the very dense cities of Europe and Asia. However, hurdles remain, and cross-licensing
Cross-licensing
A cross-licensing agreement is a contract between two or more parties where each party grants rights to their intellectual property to the other parties.-Patent law:...

 of patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

s between Qualcomm and W-CDMA vendors has not eliminated possible patent issues due to the features of W-CDMA which remain covered by Qualcomm patents.

W-CDMA has been developed into 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, and system interfaces are specified allowing free competition on technology elements.

Deployment

The world's first commercial W-CDMA service, FOMA
Foma
Foma may refer to:* FOMA , a Japanese mobile telecommunications service* Sergei Fomenko, nicknamed "Foma", Ukrainian musician...

, was launched by NTT DoCoMo in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 in 2001.

Elsewhere, W-CDMA deployments are usually marketed under the UMTS brand. See the main UMTS article for more information.

See also

  • CDMA
    Code division multiple access
    Code division multiple access is a channel access method used by various radio communication technologies. It should not be confused with the mobile phone standards called cdmaOne, CDMA2000 and WCDMA , which are often referred to as simply CDMA, and use CDMA as an underlying channel access...

  • Cellular Frequencies
    Cellular frequencies
    All cellular phone networks worldwide use a portion of the radio frequency spectrum designated as ultra high frequency, or "UHF", for the transmission and reception of their signals. The ultra high frequency band is also shared with television, Wi-Fi and Bluetooth transmission...

  • DECT
  • Evolution-Data Optimized/CDMA2000
    CDMA2000
    CDMA2000 is a family of 3G mobile technology standards, which use CDMA channel access, to send voice, data, and signaling data between mobile phones and cell sites. The set of standards includes: CDMA2000 1X, CDMA2000 EV-DO Rev. 0, CDMA2000 EV-DO Rev. A, and CDMA2000 EV-DO Rev. B...

  • FOMA
    Freedom of Mobile Multimedia Access
    Freedom of Mobile Multimedia Access is the brand name of the W-CDMA-based 3G telecommunications services being offered by the Japanese telecommunications service provider NTT DoCoMo...

  • GSM
    Global System for Mobile Communications
    GSM , is a standard set developed by the European Telecommunications Standards Institute to describe technologies for second generation digital cellular networks...

    /EDGE
    Enhanced Data Rates for GSM Evolution
    Enhanced Data rates for GSM Evolution is a digital mobile phone technology that allows improved data transmission rates as a backward-compatible extension of GSM...

  • HSDPA
  • PN sequences
  • Spectral efficiency comparison table
  • UMTS
    Universal Mobile Telecommunications System
    Universal Mobile Telecommunications System is a third generation mobile cellular technology for networks based on the GSM standard. Developed by the 3GPP , UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for...

  • UMTS frequency bands
    UMTS frequency bands
    The UMTS frequency bands are radio frequencies used by third generation wireless Universal Mobile Telecommunications System networks.They were allocated by delegates to the World Administrative Radio Conference held in Málaga-Torremolinos, Spain between February 3, 1992 and March 3, 1992...


Documentation

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