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April 03, 2005

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Universal Mobile Telecommunications System
From Wikipedia, the free encyclopedia.

Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) mobile phone technologies. It uses W-CDMA as the underlying standard, is standardized by the 3GPP, and represents the European answer to the ITU IMT-2000 requirements for 3G Cellular radio systems.

UMTS is sometimes marketed as 3GSM, emphasizing the combination of the 3G nature of the technology and the GSM standard which it was designed to succeed.


This page discuss the technology, business, usage and other aspects encompassing and surrounding the standard UMTS, the 3G successor to GSM which utilizes the W-CDMA air interface and GSM infrastructures. Any issues regarding strictly to the W-CDMA interface itself may be better described in the W-CDMA page.

Due to the rapid nature of UMTS development, some information on this page may become outdated even in just 2 or 3 short months. Readers' discretion and additional indepedent researches are strongly advised, their findings are encouraged to be added back to this page for completeness. Contributors are also advised to timestamp their contributions when appropriate in order to help readers to determine their timeliness.



UMTS supports up to 2 Mbit/s data transfer rates, although typical users can expect performance of around 64 kbit/s in a heavily loaded real-world system. However, this is still much greater than the 14.4 kbit/s of a single GSM error-corrected data channel or multiple 14.4 kbit/s channels in HSCSD, and offers the first prospect of practical inexpensive access to the World Wide Web on a mobile device and general use of MMS. The precursor to 3G is the now widely used GSM mobile telephony system, referred as 2G. There is also an evolution path from 2G, called GPRS, also known as 2.5G. GPRS supports a much better data rate (up to a maximum of 140.8kbit/s) and is packet based rather than connection oriented. It is deployed in many places where GSM is used.

Marketing material for UMTS has emphasised the possibility of mobile videoconferencing, although whether there is actually a mass market for this service remains untested.

Other possible uses for UMTS include the downloading of music.


Real-world implementations

The first UMTS network in the world, simply called 3, went live in the United Kingdom in 2003.

3 is an upstart 3G network primarily owned by Hutchison Whampoa and its partners. Its partners vary depending on the country. It soon launched other UMTS networks worldwide, to-date (March 2004) that's including Austria, Denmark, Italy, Hong Kong, Australia, Sweden and Israel.

Most major western european GSM operators plan to upgrade to UMTS in the future, though none of them could commit to a specific timeline.

In December 2003, T-Mobile launched UMTS in Austria, with trials in UK and Germany.

In February 2004, Vodafone has a wide-scale UMTS launch in several European markets, including, UK, Germany, Netherlands and Sweden.

Under a previous agreement with NTT DoCoMo, AT&T Wireless is required to build a 3G network (presumably a UMTS-compatible network operated on the 1900 MHz band only) in 4 major US cities by the end of 2004. At CTIA 2004, AT&T Wireless has confirmed that their 3G network will be a 1900-only implementation of UMTS and will be launched by the end of that year as planned.

See #External Links for a list of UMTS networks (live and under testing).



Note: Most of the underlying technological aspects of UMTS are common among all W-CDMA variants. Plase see W-CDMA for more info. The followings are some technical information specific to UMTS, not shared by FOMA or other W-CDMA implementations.

Simply put, UMTS is the combination of the W-CDMA air interface (the protocol that defines over-the-air transmissions between UMTS mobile phones and towers), GSM's MAP (Mobile Application Part) core (the protocol that provides mobile functionality like to route calls to and from mobile subscriber), and the GSM family of speech codecs like AMR and EFR (the protocols which defines how audio is digitized, compressed and encoded). Techincally speaking, W-CDMA (as per the definition of IMT2000) is merely the air interface, while UMTS is the complete stack of communcation protocols designated for 3G global mobile telecommiuncations and as a direct successor to GSM. However, W-CDMA is frequently used as a general, umbrella term to collectively refer to the family of 3G standards that uses WCDMA as its air interface, that includes UMTS, FOMA and J-Phone.

Like other real-world W-CDMA implementations, UMTS uses a pair of 5Mhz channels, one in the 1900 MHz range for uplink and one in the 2100 MHz range for downlink. In contrast, cdma2000 uses one or more arbituary 1.25 MHz channels of each direction of transmissions. UMTS is frequently being criticized for its heavy bandwidth requirements.

The specific frequency bands originally defined by the UMTS standard are 1885-2025 MHz and 2110-2200 MHz, for uplink and downlink respectively. See #External Links at the bottom of this page for a map of UMTS frequency allocation.

For existing GSM operators, it is a simple but costly migration path to UMTS: most of the rest of their infrastructures may remain the same, but the cost of obtaining new spectrum licenses and overlaying UMTS at existing towers can still be prohibitively expensive.

A major difference of UMTS compared to GSM is the air interface forming Generic Radio Access Network (GRAN). It can be connected to various backbone networks like the Internet, ISDN, GSM or to a UMTS network. GRAN includes the three lowest layers of OSI model. The network layer (OSI 3) protocols form the Radio Resource Management protocol (RRM). They manage the bearer channels between the mobile terminals and the fixed network including the handovers.


Spectrum allocation

Over 120 licenses have already been awarded to operators worldwide, specifying W-CDMA radio access technology that builds on GSM. With the technology still emerging, politicians hurriedly set up license auctions, which funneled billions of dollars in license fees into cash starved public budgets. In Germany alone, license holders paid a total 50.8 billion euros. As the technology is still immature, revenue from these licenses will only start to trickle in 2004.

The UMTS spectrum allocated by ITU is already used in the USA. The 1900 MHz range is used for 2G (PCS) services, and 2100 MHz range is used by the military. FCC is trying to free up the 2100 MHz range for 3G services, though it will still mean UMTS in the USA will have to share some spectrums with existing 2G services in the 1900 MHz band. 2G GSM services in most of the rest of the world uses the 900 MHz and 1800 MHz bands and hence do not share any spectrum with planned UMTS services.

Until the FCC allocates new spectrum specifically for 3G, there will be no firm answer to what frequencies UMTS will operate on in the United States. Currently, AT&T Wireless has committed to provide UMTS services in the United States by the end of 2004 strictly using the existing 1900 MHz spectrum allocated for 2G PCS services.


Interoperatibility and global roaming

At the air interface level, UMTS itself is incompatible with GSM. Though all UMTS phones sold today (as of 2004) are UMTS/GSM dual-mode phones, hence they can also make and receive calls on regular GSM networks. If a UMTS customer travels to an area without UMTS coverage, a UMTS phone will automatically switch to GSM (roaming charges may apply). If the customer travels outside of UMTS coverage during a call, the call will be transparently handed off to available GSM coverage.

Regular GSM phones cannot be used on the UMTS networks.

Japan Telecom (now Vodafone Japan) has a 3G network called J-Phone, it uses W-CDMA technology and is compatible with UMTS. This make UMTS the first truly global wireless standard. The current global wireless standard, GSM, is available everywhere in the world except Japan.

NTT DoCoMo's 3G network, FOMA, uses W-CDMA as well, but it's incomaptible with UMTS. However, NTT Docomo has a 20% interest in 3UK and 18% interest in AT&T Wireless. These foreign interests serve as test-bed for their future global roaming solutions. (as of March 2004)

All UMTS/GSM dual-mode phones should accept existing GSM SIM cards. You can possibly roam on UMTS networks using GSM SIM cards (as in the case of how an existing GSM customer may roam on J-Phone's network in Japan).

In the United States, UMTS will initially offered (by AT&T Wireless) on the 1900 MHz spectrum only, due to exisiting limitation of spectrum allocated in the United States. UMTS phones designated for the US will be unlikely to be operatible overseas and vice versa, mirrors the current situation of GSM phones and GSM networks in the US use different frequencies from those used in the rest of the world. However, the FCC has made reasonable promises to free up additional spectrum in the 2100 MHz band, and most UMTS licensees seem to consider ubiquituous, transparent global roaming an important issue. The possibility of ubiquituous, transparent UMTS global roaming remains to be seen. (as of May 2004)


Other competing standards

There are other competing 3G standards, such as CDMA2000 and proprietary systems including iBurst from Arraycom, Flarion and wCDMA-TDD (IPWireless).

Both CDMA2000 and WCDMA are accepted by ITU as part of the IMT-2000 faimly of 3G standards, in addtion to China's own 3G standard, TD-SCDMA, and EDGE.

CDMA2000, being an evolutionary upgrade to cdmaOne, does not require new spectrum allocation and will operate comfortably in existing PCS spectrums.

Most existing GSM operators take a wait-and-see approach to UMTS, due to the prohibitively high cost of obtaining new frequency spectrums and new equipments. So currently UMTS deployment is led by upstart 3, who does not have any existing GSM deployments.

Many GSM operators in the USA seem to have accepted EDGE as a temporary 3G solution. AT&T Wireless launched EDGE nationwide in 2003, Cingular launched EDGE in limited markets, and T-Mobile USA plans to provide EDGE nationwide in the near future. The benefit of EDGE is that it leverages existing GSM spectrums and is compatible with existing GSM handsets. EDGE provides a short-term upgrade path for GSM operators and directly competes with CDMA2000.



Last update: April 03, 2005
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