W-CDMA (
Wideband Code Division Multiple AccessCode division multiple access is a channel access method utilized by various radio communication technologies. It should not be confused with the mobile phone standards called cdmaOne and CDMA2000 , which use CDMA as an underlying channel access method.One of the basic concepts in data...
),
UMTS-FDD,
UTRA-FDD, or
IMT-2000 CDMA Direct Spread is an
air interfaceIn mobile or wireless communication, the air interface is the radio-based communication link between the mobile station and the active base station...
found in 3G
mobile telecommunicationsMobile telecommunications is the assisted transmission of signals over a distance for the purpose of communication to or from a mobile device or user...
networks. It is the basis of Japan's
NTT DoCoMois 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...
's
FOMAFreedom 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
UMTSUniversal Mobile Telecommunications System is one of the third-generation mobile telecommunications technologies, which is also being developed into a 4G technology. It is specified by 3GPP and is part of the global ITU IMT-2000 standard...
family and sometimes used as a synonym for UMTS. It utilizes the DS-CDMA channel access method and the
TDDTime-Division Duplex is the application of time-division multiplexing to separate outward and return signals. It emulates full duplex communication over a half duplex communication link. Time division duplex has a strong advantage in the case where the asymmetry of the uplink and downlink data...
duplexing method to achieve higher speeds and support more users compared to most
time division multiple accessTime 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 his own time slot. This...
(TDMA) schemes used today.
While not an evolutionary upgrade on the airside, it uses the same
core networkA core network is the central part of a telecom network that provides various services to customers who are connected by the access network.- Primary Functions :Core networks typically providing the following functionality:...
as the 2G
GSMGSM is the most popular standard for mobile phones in the world. Its promoter, the GSM Association, estimates that 80% of the global mobile market uses the standard...
networks deployed worldwide, allowing dual-mode operation along with GSM/EDGE; a feat it shares with other members of the UMTS family.
Technical features
Only key features are cited below.
- Radio channels are 5MHz wide.
- Chip
In digital communications, a chip is a pulse of a direct-sequence spread spectrum code, such as a pseudo-noise code sequence used in direct-sequence code division multiple access channel access techniques....
rate of 3.84 Mcps
- Supported mode of duplex
A duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions...
: frequency division (FDD)
- Employs coherent detection on both the uplink and downlink based on the use of pilot symbols and channels.
- Supports inter-cell asynchronous operation.
- Variable mission on a 10 ms frame basis.
- Multicode transmission.
- Adaptive power control based on SIR (Signal-to-Interference Ratio).
- Multiuser detection and smart antennas can be used to increase capacity and coverage.
- Multiple types of handoff (or handover) between different cells including soft handoff, softer handoff and hard handoff.
Development
In the late 1990's, W-CDMA was developed by
NTT DoCoMois 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...
as the
air interfaceIn 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
FOMAThe word Foma has several meanings:* Foma is a term in the fictional Bokononist religion in Kurt Vonnegut's novel Cat's Cradle. It is a comforting lie that has value independent of its truth ....
. Later NTT DoCoMo submitted the specification to the
International Telecommunication UnionThe International Telecommunication Union is the second-oldest international organization still in existence , established to standardize and regulate international radio and telecommunications. It was founded as the International Telegraph Union in Paris on 17 May 1865...
(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
CDMA2000CDMA2000 is a hybrid 2.5G / 3G technology of mobile telecommunications standards that use CDMA, a multiple access scheme for digital radio, to send voice, data, and signalling data between mobile phones and cell sites. CDMA2000 is considered a 2.5G technology in 1xRTT and a 3G technology in EVDO...
,
EDGEEnhanced Data rates for GSM Evolution is a backward-compatible digital mobile phone technology that allows improved data transmission rates, as an extension on top of standard GSM. EDGE is considered a 3G radio technology and is part of ITU's 3G definition...
, 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
QualcommQualcomm is a wireless telecommunications research and development company, as well as the largest fabless chip supplier in the world, based in San Diego, California.-Corporate history:...
, 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. IS-95 evolved into the current
CDMA2000CDMA2000 is a hybrid 2.5G / 3G technology of mobile telecommunications standards that use CDMA, a multiple access scheme for digital radio, to send voice, data, and signalling data between mobile phones and cell sites. CDMA2000 is considered a 2.5G technology in 1xRTT and a 3G technology in EVDO...
(IS-856/IS-2000) standard. Qualcomm created an experimental wideband CDMA system called CDMA2000
3x which unified the W-CDMA (3GPP) and
CDMA2000CDMA2000 is a hybrid 2.5G / 3G technology of mobile telecommunications standards that use CDMA, a multiple access scheme for digital radio, to send voice, data, and signalling data between mobile phones and cell sites. CDMA2000 is considered a 2.5G technology in 1xRTT and a 3G technology in EVDO...
(
3GPP2The 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 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-licencing of patents 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,
FOMAThe word Foma has several meanings:* Foma is a term in the fictional Bokononist religion in Kurt Vonnegut's novel Cat's Cradle. It is a comforting lie that has value independent of its truth ....
, was launched by NTT DoCoMo in
Japanis an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, People's Republic of 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.
Documentation
See also
- CDMA
Code division multiple access is a channel access method utilized by various radio communication technologies. It should not be confused with the mobile phone standards called cdmaOne and CDMA2000 , which use CDMA as an underlying channel access method.One of the basic concepts in data...
- 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 UHF band is also shared with Television, Wi-Fi and Bluetooth transmission...
- DECT
- Evolution-Data Optimized/CDMA2000
CDMA2000 is a hybrid 2.5G / 3G technology of mobile telecommunications standards that use CDMA, a multiple access scheme for digital radio, to send voice, data, and signalling data between mobile phones and cell sites. CDMA2000 is considered a 2.5G technology in 1xRTT and a 3G technology in EVDO...
- FOMA
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
GSM is the most popular standard for mobile phones in the world. Its promoter, the GSM Association, estimates that 80% of the global mobile market uses the standard...
/EDGEEnhanced Data rates for GSM Evolution is a backward-compatible digital mobile phone technology that allows improved data transmission rates, as an extension on top of standard GSM. EDGE is considered a 3G radio technology and is part of ITU's 3G definition...
- HSDPA
- PN sequences
- Spectral efficiency comparison table
- UMTS
Universal Mobile Telecommunications System is one of the third-generation mobile telecommunications technologies, which is also being developed into a 4G technology. It is specified by 3GPP and is part of the global ITU IMT-2000 standard...
- UMTS frequency bands
UMTS frequency bands or frequency ranges are the radio spectrum frequencies designated for the operation of the UMTS / HSDPA / HSUPA / HSPA+ / LTE system for mobile phones.- UMTS-FDD :UMTS-FDD is designed to operate in the following paired bands:...
- W-CDMA 2100
External links