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UMTS FAQ

What does the acronym UMTS stand for?

Universal Mobile Telephone System.

What is UMTS?

UMTS is one of the Third Generation (3G) mobile systems being developed within the ITU's IMT-2000 framework. It is a realisation of a new generation of broadband multi-media mobile telecommunications technology. The coverage area of service provision is to be world wide in the form of FLMTS (Future Land Mobile Telecommunications Services and now called IMT2000). The coverage will be provided by a combination of cell sizes ranging from 'in building' Pico Cells to Global Cells provided by satellite, giving service to the remote regions of the world. The UMTS is not a replacement of 2nd generation technologies (e.g. GSM, DCS1800, CDMA, DECT etc.), which will continue to evolve to their full potential.

What are the different types of 3G networks?

ITU Recommendation ITU-R M.1457 specifies five types of 3G radio interfaces:

  • IMT-2000 CDMA Direct Spread, also known as UTRA FDD including WCDMA in Japan, ARIB / DoCoMo recommendation. UMTS is developed by 3GPP.
  • IMT-2000 CDMA Multi-carrier, also known as Cdma2000 (3X) developed by 3GPP2. IMT-2000 CDMA2000 includes 1X components, like cdma2000 1X EV-DO.
  • IMT-2000 CDMA TDD, also known as UTRA TDD and TD-SCDMA. TD-SCDMA is developed in China and supported by TD-SCDMA Forum
  • IMT-2000 TDMA Single Carrier, also known as UWC-136 (Edge) supported by UWCC
  • IMT-2000 DECT supported by DECT Forum.

For more information about 3G air interfaces, download ITU "What is IMT-2000" presentation (2.5Mb!). Note that page 3 does not classify CDMA2000 1X as 3G, but page 6 does.
Some 2.5G systems (GSM GPRS, IS- 95B and CDMA2000 1X (?)) will be able to deliver 3G services, so it will be difficult for users to see the difference.

What are the different types of 3G core networks?

The IMT-2000 family of 3G systems includes three types of Core Network technology:

  • GSM based (using Mobile Application Part (MAP) protocols on top of SS7 protocols for signalling)
  • ANSI-41 based (IS-634 protocols for signalling)
  • Internet Protocol based (in future, to be specified)

What is the difference between cdma2000 and UMTS?

Cdma2000 and UMTS were developed separately and are 2 separate ITU approved 3G standards. Cdma2000 1xRTT, cdma2000 1xEV-DO (EVolution, Data Only) and future cdma2000 3x were developed to be backward compatible with cdmaOne. Both 1x types have the same bandwidth, chip rate and it can be used in any existing cdmaOne frequency band and network. Backward compatibility was a requirement for successful deployment for USA market. It is easy to implement because operators do not need new frequencies.

UMTS was developed mainly for countries with GSM networks, because these countries have agreed to free new frequency ranges for UMTS networks. Because it is a new technology and in a new frequency band, whole new radio access network has to be build. The advantage is that new frequency range gives plenty of new capacity for operators. 3GPP is overseeing the standard development and has wisely kept the core network as close to GSM core network as possible. UMTS phones are not meant to be backward compatible with GSM systems. (but subscriptions (=SIM card) can be, and dual mode phone will solve the compatibility problems, hopefully). UMTS also has 2 flavors FDD (will be implemented first) and TDD.

Some harmonisation has been done between systems (like chip rate and pilot issues)

What are 1G, 2G, 2.5G, 3G and 4G?

Technically generations are defined:

  • 1G networks (NMT, C-Nets, AMPS, TACS) are considered to be the first analog cellular systems, which started early 1980s. There were radio telephone systems even before that.
  • 2G networks (GSM, cdmaOne, DAMPS) are the first digital cellular systems launched early 1990s.
  • 2.5G networks (GPRS, cdma2000 1x) are the enhanced versions of 2G networks with data rates up to about 144kbit/s.
  • 3G networks (UMTS FDD and TDD, cdma2000 1x EVDO, cdma2000 3x, TD-SCDMA, Arib WCDMA, EDGE, IMT-2000 DECT) are the latest cellular networks that have data rates 384kbit/s and more.
  • 4G is mainly a marketing buzzword at the moment. Some basic 4G research is being done, but no frequencies have been allocated. The Forth Generation could be ready for implementation around 2012.

What are all the different international organisations doing?

European Telecommunications Standards Institute (ETSI) is working in Europe to develop technical standards for UMTS. 3rd-Generation Partnership Project (3GPP) is a co-operation between international standards bodies will make UMTS and third generation mobile telephony technical specifications. The founding members are: ARIB and TTC of Japan, ETSI of Europe, T1 (ANSI) of the U.S. and TTA of Korea. The work of these organisations will be announced globally by the International Telecommunication Union (ITU). ITU coordinate world-wide spectrum and IMT2000 standardisation, harmonises regional regulatory policies and is a foundation and framework for 3G convergence across regions and technologies. UMTS Forum represents the opinions and views of the telecommunication industry and operators and GSM Associates is a mobile operator organisation. European Radiocommunications Committee (ECR) in European Conference of Postal and Telecommunications Administration (CEPT) handles European radio frequency related issues. European Union (EU) harmonises its 15 members UMTS implementation.

How is UMTS different from current second generation networks?

  • Higher speech quality that current networks - Addition to speech traffic UMTS, together with advanced data and information services, will be a multimedia network.
  • UMTS is above 2G mobile systems for its potential to support 2Mbit/s data rates.
  • UMTS is a real global system, comprising both terrestrial and satellite components.
  • Consistent service environment even when roaming via "Virtual Home Environment" (VHE). A person roaming from his network to other UMTS operators, user will experience a consistent set of services thus "feeling" on his home network, independent of the location or access mode (satellite or terrestrial)

Why is WCDMA called "Wideband"?

3G WCDMA systems have 5MHz bandwidth (one direction). 5MHz is neither wide nor narrow; it is just the bandwidth. New 3G WCDMA systems have wider bandwidth than existing 2G cdma systems (cdmaOne 1.25MHz), that's why the "Wide". There are commercial cdma systems with 20MHz bandwidth.

Are GSM/GPRS networks compatible with UMTS networks?

UMTS networks can be operated with GSM/GPRS networks. Systems use different frequency bands, so BTSs and mobiles will (should) not interfere with each other. Some vendors claim their core network (MSC/HLR/SGSN ect) and BSC/RNC are UMTS compatible, but most operators will prefer to build a totally separate/independent UMTS network. Some of the latest GSM BTSs can also have UMTS radio parts and share the same rack.

UMTS specification is design so that there is maximum compatibility between GSM and UMTS systems. Late 2002 there will also be dual/multi band phones that can be used in GSM and UMTS networks. Eventually phones will be able to do handovers between networks.

Is there a transition period between UMTS and the present system

There will probably not be a "transition" period in that sense, because GSM systems will keep on operating at least next ten years. (some old 1G networks are still running round the world). Only limitations for operators are the GSM license terms and customer preferences. UMTS networks will just be added to mobile landscape.

My GSM operator did not get a 3G license. What is going on?

Several GSM operators (like in UK, Sweden, Denmark and France) failed / did not want / missed initially to get an UMTS license, but do not count them out yet. Existing operators have great assets like customer base, image, retail network, BTS site locations, transmission system etc., which help them to make deals with 3G license holders. Hutchison 3G in UK and Telia with Tele 2 in Sweden are good examples.

What is the 3G status in the USA?

Some operators have taken the path cdmaOne - cdma2000 1x - cdma2000 1x EV-DO - cdma2000 3x some D-AMPD - EDGE and some have chosen a GSM1900 - EDGE ( - possible UMTS) route. New cellular frequencies allocations have been postponed, so operators will have to use their existing frequencies, which naturally limits the available capacity. Read more about the USA 3G situation.

What is the 3G status in the China?

China has been testing the TD-SCDMA 3G system. License allocation and possible adaptation of other 3G technologies are still open. Read more about the China's 3G situation.

What is the "Beauty Contest" when 3G licenses are issued? ... and Why?

Beauty Contest means that the government asks all applicants to provide a plan how to build a network and manage their future 3G business. A plan typically includes things like: How many new jobs are created, what kind of services will be available and when, how much domestic products are used, how will less developed areas (rural areas) benefit from this, what kind of financial plan is in place to guarantee the success and avoid bankrupts etc. So government wants to decide what is best for the country, not who is willing to pay most. (In USA and Australia some highest bidding operators have gone bankrupt and government has to pay unemployment etc payments and it is also embarrassing for the government).

By charging high license fee government imposes an indirect tax which mobile uses have to bear by paying more for making calls. By giving "free" licenses government can create a good environment for technology start up companies, because operator has more money to invest and less up-front fees.

Which network vendors can build a turn key 3G network?

No network vendor can supply all equipment and components to the full a 3G network, but quite a few can be a main contractor to build a turn-key 3G network. Normally network vendors can bring in partners like service and applications providers, hand set manufactures, civil work and acquisition companies etc. Current short list of main vendors for turn-key UMTS networks:

  • Alcatel
  • Ericsson
  • Lucent
  • Motorola
  • Nokia
  • Nortel
  • Siemens/NEC

Current short list of main vendors for turn-key cdma2000 networks:

  • Ericsson
  • LG Electronics
  • Lucent
  • Motorola
  • Nortel
  • Samsung

How much does 3G network cost to build?

Good source of information is to contract announcements and annual reports. Those usually tell how much money an operator will spend on infrastructure. In every country each carrier has to spend around same amount of money to build a same size 3G network, so if you see one of the operator's spending figures, all other operators use similar sums of money per subscriber.

Sometimes spending figures include services (planning, logistics, commissioning, integration, testing etc.), but almost never civil works on base station sites. Press reports claim that operators in Europe have spend around 650 euro per 3G subscriber for infrastructure + planning services + site civil works, this figure should drop to around 400 euros within couple of years.

Infrastructure cost are only small part of total network related cost and operators also have license fees, financing fees, cost of running the organisation, sales and marketing costs etc.

Download 3GPP specification:

  • TS 25.331 Radio Resource Control (RRC) protocol specification
  • TS 25.304 UE Procedures in Idle Mode and Procedures for Cell Reselection in Connected Mode Those documents have all the details.

Tell me about WLAN and 3G interoperability.

Vendor as busy showing their WLAN-3G capabilities, roaming and network handovers are the hot topics. Lucent Technologies announced demonstration of 3G high-speed mobile data and voice capabilities, Nokia shows the WLAN implementation and British Telecom has announced the WLAN hot spot implementation.

3GPP specs show two related docs:

  • 22.234 (reserved for future WLAN I/w stage 1), not available yet and
  • 22.934 Feasibility study on 3GPP system to Wireless Local Area Network (WLAN) interworking

You can download 22.934 from: ftp://ftp.3gpp.org/specs/Latest-drafts/ Earlier FAQ Answer gives you some help how to download those.

Other place to look technical data is IEEE 802.11 Group and search for "3G" etc. You can find documents like: http://grouper.ieee.org/groups/802/11/Minutes/Cons_Minutes_Mar-2002.pdf and search for 3G in that document and you see the current status.

Will the future 3G handsets be compatible with 2G systems and PCs?

Some of the 3G mobiles will be dualband UMTS/GSM handsets (available late 2002?) and will be able to perform UMTS-GSM handovers. Current GSM phones will not work in 3G networks. Several SIM card manufacturers now offer cards compatible with 2G and 3G systems. Cellular3G, for example, will offer PCMCIA W-CDMA 3G-modem cards for PCs.3G cdma2000 phones will be backward compatible and will work in cdmaOne networks. Airprime, for example, offers CDMA2000 1xEV-DO PC cards for 3G networks.

How many Base Stations are needed for an UMTS network?

There are several factors:

  • Required coverage areas according to a license agreement (link budget will determine the cell spacing)
  • Required capacity according to license agreement and initial customer and operator demands.
  • Amount of frequencies carries have. (More frequencies, less interference, longer cell spacing)
  • Ability to get BTS site locations. (Normally co-location requirements with used 2G sites)
  • Financing available for network build.
  • Economical factor to build sites.
  • Design opinions and experience of companies and people bidding for the design job and eventually implementing the plan.
  • And probably in a long run the capacity, service, and coverage requirement from customers.

Rollout will be very similar to 2G network rollouts. First phase of rollouts in UK size market will probably be 1000 base station in urban areas. Within 5 year about site count will increase to 5000 sites and eventually up to 10000 sites depending how successful the business is.

How to calculate a WCDMA link budget?

To calculate it you need to know:

  • Type of service (data type and speed)
  • Type of environment (terrain, building penetration)
  • Behaviour and type of mobiles (speed, max power level)
  • System configuration (BTS antennas, BTS power, cable losses, handover gain)
  • Required coverage probability

What are the UMTS frequencies and channel spacing?

  • 1900-1920 and 2010-2025 MHz Time Division Duplex (TDD, TD/CDMA) Unpaired, channel spacing is 5 MHz and raster is 200 kHz. Tx and Rx are not separated in frequency
  • 1920-1980 and 2110-2170 MHz Frequency Division Duplex (FDD, W-CDMA) Paired uplink and downlink, channel spacing is 5 MHz and raster is 200 kHz. An Operator needs 3 - 4 channels (2x15 or 2x20 MHz) to be able to build a high-speed, high-capacity network.
  • 1980-2010 and 2170-2200 MHz Satellite uplink and downlink

What are the UMTS air interface logical channels?

  • Broadcast Control Channel (BCCH)
  • Paging Control Channel (PCCH)
  • Dedicated Control Channel (DCCH)
  • Common Control Channel (CCCH)
  • Dedicated Traffic Channel (DTCH)
  • Common Traffic Channel (CTCH)

What are the UMTS data rates of the services?

  • 2.048Mb/s for pico-cell (and micro-cell) applications.
  • 384kb/s for medium size cells. (micro and small macro cells)
  • 144kb/s and 64kb/s for large cell applications. (Large macro cells)
  • 14.4kb/s for continuous low speed data applications in very large cells.
  • 12.2kb/s for speech (4.75kb/s - 12.2kb/s)
  • 9.6kb/s globally (satellite)

How does UMTS paging work?

First, get the latest 3GPP specifications 25-211, 25-304 and 25-331

Note:

  • PI = Paging Indicator (value calculated by higher layers)
  • Pq = Paging Indicator (indicator set by physical layer)

Which modulation scheme is being used in UMTS?

UMTS WCDMA modulation is Quadrature Phase Shift Keying (QPSK) with Root-raised cosine pulse shaping filters (roll off = 0.22)

Where can I find information about MAC and RLC protocols?

Download and read 3GPP documents about RLC/MAC, start with 25 series. Documents also show message mapping to channels:

  • 25.321 Medium Access Control (MAC) protocol specification
  • 25.322 Radio Link Control (RLC) protocol specification
  • 44.060 General Packet Radio Service (GPRS); Mobile Station (MS) - Base Station System (BSS) interface; Radio Link Control/ Medium Access Control (RLC/MAC) protocol

How is data compression done in UMTS?

Video and music compression will be done in application level. 3G phone (and network application servers) will have programs (or you will be downloading them) that records and displays video or music. Those programs have build-in data compression features. Good examples are MP3 and other music programs. MP3 codec includes data compression and most current music player understands it. For image and video there are several standards including JPEG, MPEG-4, H.263, Microsoft media player etc. available.

From 3GPP 26.234 7.4 Video:

ITU-T Recommendation H.263 [22] profile 0 level 10 shall be supported. This is the mandatory video decoder for the PSS. In addition, PSS should support:

  • - H.263 [23] Profile 3 Level 10 decoder;
  • - MPEG-4 Visual Simple Profile Level 0 decoder, [24] and [25].

These two video decoders are optional to implement.

NOTE: ITU-T Recommendation H.263 [22] baseline has been mandated to ensure that video-enabled PSS support a minimum baseline video capability and interoperability can be guaranteed (an H.263 [22] baseline bit stream can be decoded by both H.263 [22] and MPEG-4 decoders). It also provides a simple upgrade path for mandating more advanced decoders in the future (from both the ITU-T and ISO MPEG).

Is there any interface from UMTS core network to other mobile networks?

UMTS specifications do not have any special interface planned for other mobile networks, but all telephone networks can be connected to UMTS core network with standard S7 (or other) signalling system using E1s or T1s. Than enables voice calls to be made to all other telephone networks. If other networks support additional services like "call forwarding", "calling line identity", fax, slow-speed data ect, technically that is possible to implement this between networks.

All telephone networks are designed to work with each other and UMTS networks will use standard interfaces towards all other networks. S7 and IP (internet protocol) will be the most commonly used interfaces standard, but all UMTS vendors can offer tens of different country-specific interface protocols if required.

What will be a 3G Killer Application?

Most people have their own view what the 3G Killer Application(s) will be. Some say that there will not be a single application, but a palette of services. Most likely there will not be only a single application that becomes very popular and at the same time makes a lot of money to the operator. Email, voice(!), messaging, music/video streaming are popular bets for money making applications. If you look any reports about 3G services, m-commerce and location based services are predicted to become very popular. Maybe the pricing will decide what will be a popular service.

Old phrase is "The easiest way to predict the future is to invent it" will apply here. Operators and application providers have an opportunity to create their own killer applications.

What are the UMTS Mobile Multimedia services?

UMTS Forum's Market Aspects Group has identified seven common lifestyle attributes for mobile multimedia applications. Here is a list of possible type of services that will be available in 3G networks:

  • Fun: WWW, video, post card, snapshots, text, picture and multimedia messaging, datacast, personalisation applications (ring tone, screen saver, desk top), jukebox, virtual companion / pet ...
  • Work: Rich call with image and data stream, IP telephony, B2B ordering and logistics, information exchange, personal information manager, dairy, scheduler, note pad, 2-way video conferencing, directory services, travel assistance, work group, telepresence, FTP, instant voicemail, colour fax ...
  • Media: Push newspaper and magazines, advertising, classified ...
  • Shopping: E-commerce, e-cash, e-wallet, credit card, telebanking, automatic transaction, auction, micro-billing shopping ...
  • Entertainment: News, stock market, sports, games, lottery, gambling, music, video, concerts, adult content ...
  • Education: Online libraries, search engines, remote attendance, field research ...
  • Peace of Mind: Remote surveillance, location tracking, emergency use ...
  • Health: Telemedicine, remote diagnose and heath monitoring ...
  • Automation: Home automation, traffic telematics, machine-machine communication (telemetry) ...
  • Travel: location sensitive information and guidance, e-tour, location awareness, time tables, e-ticketing ...
  • Add-on: TV, radio, PC, access to remote computer, MP3 player, camera, video camera, watch, pager, GPS, remote control unit ...

Can UMTS mobile location be tracked?

The wideband nature of the UTRA/FDD facilitates the high resolution in position location. The duration of one chip (3.84Mcps) correspond to approximately 78 meters in propagation distance. If the delay estimation operates on the accuracy of samples/chip then the achievable maximum accuracy is approximately 20 meters. There are other inaccuracies that will cause degradation to the positioning but 20 meters can be considered as best possible positioning performance. UMTS specifies that it will provide location information for mobiles to an accuracy of 50m. With GPS assistance, maybe even 10 meter accuracy is possible.

When are the UMTS networks in service?

Japan and Korea has 3G services running and in December 2001 two UMTS networks have been launched, but UMTS mobiles will arrive 3Q/2002. Quite a few UMTS networks will be launched in early 2003 in Europe.

Will 2G / 2.5G phones be able to use all UMTS' applications?

GSM (or other 2G) phones will not be able to use all features, because of data speed, build in memory and applications, display technology etc. Application providers and operators are very unlikely to try to implement complex feature to GSM, money is going to UMTS services. GPRS phone users will be able to use most of the UMTS services; probably only location based and very high rate data services cannot be implemented. But all this it depends on if operators want to implement those. All basic services like voice and messaging will flow between all systems.

Which level of UMTS standard will the network be launched in 2002?

All vendors have different software schedules and development status is a big secret. Now it looks like top vendors will probably have 3GPP Release 4 (with July 2001 correction) level software by the late 2002 launch date. (Some vendors were considering launching with '99 release in 2002)