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Universal Mobile Telecommunications System



Using a cellular router, PCMCIA or USB card, customers are able to access 3G broadband services, regardless of their choice of computer (such as a tablet PC or a PDA). Some software installs itself from the modem, so that in some cases absolutely no knowledge of technology is required to get online in moments.

Using a phone that supports 3G and Bluetooth 2.0, multiple Bluetooth-capable laptops can be connected to the Internet. The phone acts as a router, but via Bluetooth rather than wireless networking (802.11) or a USB connection.

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Interoperability and global roaming

UMTS phones (and data cards) are highly portable - they have been designed to roam easily onto other UMTS networks (assuming your provider has a roaming agreement). In addition, almost all UMTS phones (except in Japan) are UMTS/GSM dual-mode devices, so if a UMTS phone travels outside of UMTS coverage during a call the call may be transparently handed off to available GSM coverage. Roaming charges are usually significantly higher than regular usage charges.

Most UMTS licensees consider ubiquitous, transparent global roaming an important issue. To enable a high degree of interoperability, UMTS phones usually support several different frequencies in addition to their GSM fallback. Different countries support different UMTS frequency bands – Europe initially used 2100Mhz while the USA used 1700Mhz, and a UMTS phone and network must support a common frequency to work together. Because of the frequencies used, early models of UMTS phones designated for the US will likely not be operable elsewhere and vice versa. There are now 11 different frequency combinations used around the world - including frequencies formerly used solely for 2G services.

UMTS phones use a USIM (Universal Subscriber Identity Module) (based on GSM's SIM) and also accept GSM SIM cards. This is a global standard of identification, and enables a network to identify the phone user to authenticate both local and roaming customers. Roaming agreements between networks allow for calls to a customer to be redirected to them while roaming and determine the services (and prices) available to the user. In addition to user subscriber information and authentication information, the USIM provides storage space for phone book contacts - phones can store their data on their own memory or on the USIM card (which is usually more limited in its phone book contact information). A USIM can be moved to another UMTS or GSM phone, and the phone will take on the user details of the USIM - meaning it is the USIM (not the phone) which determines the phone number of the phone and the billing for calls made from the phone.

Japan was the first country to adopt 3G technologies, and since they had not used GSM previously they had no need to build GSM compatibility into their handsets and their 3G handsets were smaller than those available elsewhere. In 2002, NTT DoCoMo's FOMA 3G network was the first commercial W-CDMA network - it was initially incompatible with the UMTS standard at the radio level but used standard USIM cards, meaning USIM card based roaming was possible (moving the USIM card into a UMTS or GSM phone when travelling). Both NTT and SoftBank Mobile (which launched 3G in December 2002) now use the standard UMTS, and their PDC 2G networks run in parallel.

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Spectrum allocation

Main article: UMTS frequency bands

Over 120 licenses have already been awarded to operators worldwide (as of December 2004), specifying W-CDMA radio access technology that builds on GSM. In Europe, the license process occurred at the end of the technology bubble, and the auction mechanisms for allocation set up in some countries resulted in some extremely high prices being paid for the original 2100 MHz licenses, notably in the UK and Germany. In Germany, bidders paid a total 50.8 billion euros for six licenses, two of which were subsequently abandoned and written off by their purchasers (Mobilcom and the Sonera/Telefonica consortium). It has been suggested that these huge license fees have the character of a very large tax paid on income expected 10 years down the road - in any event they put some European telecom operators close to bankruptcy (most notably KPN). Over the last few years some operators have written off some or all of the license costs. More recently, a carrier in Finland has begun using 900 MHz UMTS in a shared arrangement with it's surrounding 2G GSM base stations, a trend that is expected to expand over Europe in the next 1-3 years.

The 2100MHz UMTS spectrum allocated in Europe is already used in North America. The 1900 MHz range is used for 2G (PCS) services, and 2100 MHz range is used for satellite communications. Regulators have however, freed up some of the 2100 MHz range for 3G services, together with the 1700 MHz for the uplink. UMTS operators in North America who want to implement a European style 2100/1900 MHz system will have to share spectrum with existing 2G services in the 1900 MHz band.

AT&T Wireless launched UMTS services in the United States by the end of 2004 strictly using the existing 1900 MHz spectrum allocated for 2G PCS services. Cingular acquired AT&T Wireless in 2004 and has since then launched UMTS in select US cities. After AT&T's acquisition of Cingular, it was renamed AT&T Mobility and is rolling out some cities with a UMTS network at 850 MHz to enhance its existing UMTS network at 1900 MHz and now offers subscribers a number of UMTS 850/1900 phones.

T-Mobile's roll-out of UMTS in the US will focus on the 2100/1700 MHz bands just auctioned.

Initial rollout of UMTS in Canada will also be undertaken using the 850 and 1900MHz bands due to the large areas that will be needed to cover.

In Australia, Telstra rolled out a national 3G network, branded as NextG, operating in the 850 MHz band to replace the existing CDMA network (April 2008) and enhance its existing 2100 MHz UMTS network. Optus is currently rolling out a 3G network with the same coverage as its GSM network, using the 2100 MHz band in cities and most large towns, and the 900 MHz band for regional areas. Vodafone is also building a 3G network using the 900 MHz band. The 850 MHz and 900 MHz bands provide greater coverage compared to equivalent 1700/1900/2100 MHz networks, and are best suited to regional areas where greater distances separate subscriber and base station.

Carriers in South America are now also rolling out 850 MHz networks.

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Other competing standards

There are other competing 3G standards, such as CDMA2000 and TD-SCDMA, though UMTS can use the latter's air interface standard.

On the Internet access side, competing systems include WiMAX and Flash-OFDM. Different variants of UMTS compete with different standards. While this article has largely discussed UMTS-FDD, a form oriented for use in conventional cellular-type spectrum, UMTS-TDD, a system based upon a TD-CDMA air interface, is used to provide UMTS service where the uplink and downlink share the same spectrum, and is very efficient at providing asymmetric access. It provides more direct competition with WiMAX and similar Internet-access oriented systems than conventional UMTS.

Both the CDMA2000 and W-CDMA air interface systems are accepted by ITU as part of the IMT-2000 family of 3G standards, in addition to UMTS-TDD's TD-CDMA, Enhanced Data Rates for GSM Evolution (EDGE) and China's own 3G standard, TD-SCDMA.

CDMA2000's narrower bandwidth requirements make it easier than UMTS to deploy in existing spectrum along with legacy standards. In some, but not all, cases, existing GSM operators only have enough spectrum to implement either UMTS or GSM, not both. For example, in the US D, E, and F PCS spectrum blocks, the amount of spectrum available is 5 MHz in each direction. A standard UMTS system would saturate that spectrum.

In many markets however, the co-existence issue is of little relevance, as legislative hurdles exist to co-deploying two standards in the same licensed slice of spectrum.

Most GSM operators in North America as well as others around the world have accepted EDGE as a temporary 3G solution. AT&T Wireless launched EDGE nationwide in 2003, AT&T launched EDGE in most markets and T-Mobile USA has launched EDGE nationwide as of October 2005. Rogers Wireless launched nation-wide EDGE service in late 2003 for the Canadian market. Bitė Lietuva (Lithuania) was one of the first operators in Europe to launch EDGE in December 2003. TIM (Italy) launched EDGE in 2004. The benefit of EDGE is that it leverages existing GSM spectrums and is compatible with existing GSM handsets. It is also much easier, quicker, and considerably cheaper for wireless carriers to "bolt-on" EDGE functionality by upgrading their existing GSM transmission hardware to support EDGE than having to install almost all brand-new equipment to deliver UMTS. EDGE provides a short-term upgrade path for GSM operators and directly competes with CDMA2000.

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Problems and issues

Some countries, such as the United States and Japan, have allocated spectrum differently from the ITU Recommendations, so that the spectrum bands most commonly used for UMTS (UMTS-2100) have not been available. In those countries, alternative bands are used, preventing the interoperability of existing UMTS-2100 equipment, and requiring the design and manufacture of different equipment for the use in these markets. As is the case with GSM 900 MHz today, traditional UMTS 2100 MHz equipment will not work in those markets. However, it appears as though UMTS is not suffering as much from handset band compatibility issues as GSM did as many UMTS handsets these days are being designed to be multi-band in both UMTS and GSM modes within the one handset. Quad band GSM (850/900/1800/1900 MHz) and tri-band UMTS (850/1900/2100 MHz) handsets are becoming more common place.

In the early days of UMTS there were issues with rollout:

  • overweight handsets with poor battery life;
  • problems with handover from UMTS to GSM, connections being dropped or handovers only possible in one direction (UMTS → GSM) with the handset only changing back to UMTS after hanging up, even if UMTS coverage returns—in most networks around the world this is no longer an issue;
  • for fully fledged UMTS incorporating Video on Demand features, one base station needed to be set up every 1–1.5 km (0.62–0.93 mi). This was the case when only the 2100 MHz band was being used, however with the growing use of lower frequency bands (such as 850 and 900 MHz) this is no longer so. This has led to an increase in the interest in the lower band networks by operators since 2006/2007;

Some of these issues may still be ongoing; for instance, Apple, Inc. cited[9] UMTS power consumption as the reason that the first generation iPhone only supported EDGE. Their release of the iPhone 3G quotes talk time in 3G mode as half that of the 2G mode.

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See also

Other, non-UMTS, 3G and 4G standards:

UMTS is an evolution of the GSM mobile phone standard.

Other useful information

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Literature

  • Martin Sauter: Communication Systems for the Mobile Information Society, John Wiley, September 2006, ISBN 0-470-02676-6

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References

  1. ^ The FCC's Advanced Wireless Services bandplan
  2. ^ Huawei E270 GSM/UMTS modem specifications. Retrieved on 2008-06-08.
  3. ^ ^ For an example of tether mode: http://thenokiablog.com/2007/08/21/how-to-tether-your-nokia-to-a-mac-to-access-the-net-via-bluetooth/
  4. ^ ^ http://network.nationalpost.com/np/blogs/tradingdesk/archive/2008/04/30/what-to-expect-from-rogers-iphone-offering.aspx
  5. ^ ^ http://www.canalys.com/pr/2008/r2008021.htm.
  6. ^ Industry Leaders Announce Open Platform for Mobile Devices (HTML) (English). Open Handset Alliance (2007-11-05). Retrieved on 2007-11-05.
  7. ^ Google's Android parts ways with Java industry group.
  8. ^ Open Handset Alliance Releases Android SDK (HTML) (English). Open Handset Alliance (2007-11-12). Retrieved on 2007-11-12.
  9. ^ ^http://online.wsj.com/article/SB118306134626851922.html

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