UMTS


The Universal Mobile Telecommunications System is a 3G mobile cellular system for networks based on the GSM standard. UMTS uses wideband code-division multiple access radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators compared to previous 2G systems like GPRS and CSD. The original version of UMTS provides a peak theoretical data rate of 384 kbit/s.
Developed and maintained by the 3GPP, UMTS is a component of the International Telecommunication Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing cdmaOne technology. The technology described in UMTS is sometimes also referred to as Freedom of Mobile Multimedia Access or 3GSM.
UMTS specifies a complete network system, which includes the radio access network, the core network and the authentication of users via SIM cards. Unlike EDGE and CDMA2000, UMTS requires new base stations and new frequency allocations. UMTS has since been enhanced as High Speed Packet Access.

Features

UMTS supports theoretical maximum data transfer rates of 42 Mbit/s when Evolved HSPA is implemented in the network. Users in deployed networks can expect a transfer rate of up to 384 kbit/s for Release '99 handsets, and 7.2 Mbit/s for High-Speed Downlink Packet Access handsets in the downlink connection. These speeds are significantly faster than the 9.6 kbit/s of a single GSM error-corrected circuit switched data channel, multiple 9.6 kbit/s channels in High-Speed Circuit-Switched Data and 14.4 kbit/s for CDMAOne channels.
Since 2006, UMTS networks in many countries have been or are in the process of being upgraded with High-Speed Downlink Packet Access, sometimes known as 3.5G. Currently, HSDPA enables downlink transfer speeds of up to 21 Mbit/s. Work is also progressing on improving the uplink transfer speed with the High-Speed Uplink Packet Access. The 3GPP LTE standard succeeds UMTS and initially provided 4G speeds of 100 Mbit/s down and 50 Mbit/s up, with scalability up to 3 Gbit/s, using a next generation air interface technology based upon orthogonal frequency-division multiplexing.
The first national consumer UMTS networks launched in 2002 with a heavy emphasis on telco-provided mobile applications such as mobile TV and video calling. The high data speeds of UMTS are now most often utilised for Internet access: experience in Japan and elsewhere has shown that user demand for video calls is not high, and telco-provided audio/video content has declined in popularity in favour of high-speed access to the World Wide Web either directly on a handset or connected to a computer via Wi-Fi, Bluetooth or USB.

Air interfaces

UMTS combines three different terrestrial air interfaces, GSM's Mobile Application Part core, and the GSM family of speech codecs.
The air interfaces are called UMTS Terrestrial Radio Access. All air interface options are part of ITU's IMT-2000. In the currently most popular variant for cellular mobile telephones, W-CDMA is used. It is also called "Uu interface", as it links User Equipment to the UMTS Terrestrial Radio Access Network.
Please note that the terms W-CDMA, TD-CDMA and TD-SCDMA are misleading. While they suggest covering just a channel access method, they are actually the common names for the whole air interface standards.

W-CDMA (UTRA-FDD)

W-CDMA, along with UMTS-FDD, UTRA-FDD, or IMT-2000 CDMA Direct Spread is an air interface standard found in 3G mobile telecommunications networks. It supports conventional cellular voice, text and MMS services, but can also carry data at high speeds, allowing mobile operators to deliver higher bandwidth applications including streaming and broadband Internet access.
W-CDMA uses the DS-CDMA channel access method with a pair of 5 MHz wide channels. In contrast, the competing CDMA2000 system uses one or more available 1.25 MHz channels for each direction of communication. W-CDMA systems are widely criticized for their large spectrum usage, which delayed deployment in countries that acted relatively slowly in allocating new frequencies specifically for 3G services.
The specific frequency bands originally defined by the UMTS standard are 1885–2025 MHz for the mobile-to-base and 2110–2200 MHz for the base-to-mobile. In the US, 1710–1755 MHz and 2110–2155 MHz are used instead, as the 1900 MHz band was already used. While UMTS2100 is the most widely deployed UMTS band, some countries' UMTS operators use the 850 MHz and/or 1900 MHz bands, notably in the US by AT&T Mobility, New Zealand by Telecom New Zealand on the XT Mobile Network and in Australia by Telstra on the Next G network. Some carriers such as T-Mobile use band numbers to identify the UMTS frequencies. For example, Band I, Band IV, and Band V.
UMTS-FDD is an acronym for Universal Mobile Telecommunications System frequency-division duplexing and a 3GPP standardized version of UMTS networks that makes use of frequency-division duplexing for duplexing over an UMTS Terrestrial Radio Access air interface.
W-CDMA is the basis of Japan's NTT DoCoMo's FOMA service and the most-commonly used member of the Universal Mobile Telecommunications System family and sometimes used as a synonym for UMTS. It uses the DS-CDMA channel access method and the FDD duplexing method to achieve higher speeds and support more users compared to most previously used time-division multiple access and time-division duplex schemes.
While not an evolutionary upgrade on the airside, it uses the same core network as the 2G GSM networks deployed worldwide, allowing dual-mode mobile operation along with GSM/EDGE; a feature it shares with other members of the UMTS family.

Development

In the late 1990s, 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 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, EDGE, 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 was dominated by Qualcomm, the first company to succeed in developing a practical and cost-effective CDMA implementation for consumer cell phones and its early IS-95 air interface standard has evolved into the current CDMA2000 standard. Qualcomm created an experimental wideband CDMA system called CDMA2000 3x which unified the W-CDMA and CDMA2000 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 globally. W-CDMA has then become the dominant technology with 457 commercial networks in 178 countries as of April 2012. Several CDMA2000 operators have even converted their networks to W-CDMA for international roaming compatibility and smooth upgrade path to LTE.
Despite incompatibility with existing air-interface standards, late introduction and the high upgrade cost of deploying an all-new transmitter technology, W-CDMA has become the dominant standard.

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 and 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 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, FOMA, was launched by NTT DoCoMo in Japan in 2001.
Elsewhere, W-CDMA deployments are usually marketed under the UMTS brand.
W-CDMA has also been adapted for use in satellite communications on the U.S. Mobile User Objective System using geosynchronous satellites in place of cell towers.
J-Phone Japan 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.
Most countries have, since the ITU approved of the 3G mobile service, either "auctioned" the radio frequencies to the company willing to pay the most, or conducted a "beauty contest" asking the various companies to present what they intend to commit to if awarded the licences. This strategy has been criticised for aiming to drain the cash of operators to the brink of bankruptcy in order to honour their bids or proposals. Most of them have a time constraint for the rollout of the service where a certain "coverage" must be achieved within a given date or the licence will be revoked.
Vodafone launched several UMTS networks in Europe in February 2004. MobileOne of Singapore commercially launched its 3G services in February 2005. New Zealand in August 2005 and Australia in October 2005.
AT&T Mobility utilized a UMTS network, with HSPA+, from 2005 until its shutdown in February 2022.
Rogers in Canada March 2007 has launched HSDPA in the Toronto Golden Horseshoe district on W-CDMA at 850/1900 MHz and plan the launch the service commercial in the top 25 cities October, 2007.
TeliaSonera opened W-CDMA service in Finland October 13, 2004, with speeds up to 384 kbit/s. Availability only in main cities. Pricing is approx. €2/MB.
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. By October 2006 both companies are covering more than 90 cities while SK Telecom has announced that it will provide nationwide coverage for its WCDMA network in order for it to offer SBSM handsets by the first half of 2007. KT Freecel will thus cut funding to its CDMA2000 network development to the minimum.
In Norway, Telenor introduced W-CDMA in major cities by the end of 2004, while their competitor, NetCom, followed suit a few months later. Both operators have 98% national coverage on EDGE, but Telenor has parallel WLAN roaming networks on GSM, where the UMTS service is competing with this. For this reason Telenor is dropping support of their WLAN service in Austria.
Maxis Communications and Celcom, two mobile phone service providers in Malaysia, started offering W-CDMA services in 2005.
In Sweden, Telia introduced W-CDMA in March 2004.