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UMTS Basics, Version 3.0 T.O.P. BusinessInteractive GmbH of 12

1 Introduction


1.1 UMTS - The New Standard...........................................................31.2 Current Trends (1/3) .....................................................................41.2 Current Trends (2/3) .....................................................................51.2 Current Trends (3/3) .....................................................................61.3 Demands on UMTS (1/2) ..............................................................71.3 Demands on UMTS (2/2) ..............................................................81.4 Standardization (1/2) ....................................................................91.4 Standardization (2/2) ..................................................................101.5 Stages of Development (1/2)......................................................111.5 Stages of Development (2/2)......................................................12


1.1 UMTS - The New Standard

The abbreviation UMTS stands for "Universal Mobile Telecommunications System" anddescribes a standard which will enable the flexible and high data rate transmission of anykind of data over the air interface. This system is to be run in parallel with the existing 2ndgeneration digital GSM mobile systems. It is also called 3rd generation mobilecommunication.


1.2 Current Trends (1/3)

As the information society enters the third millennium, new developments are beginning toemerge:1. A trend towards integration: the three traditional fields of telecommunication technology -telecommunication, computer industry and multimedia services - will merge even further.2. A trend towards convergence: the dividing line between these three branches, with theirindividual requirements for high speech transmission quality, high data rates and theprovision of new applications will become blurred.3. A trend towards globalization and mobility. In future, the mobile subscribers will be globallyreachable under one number, and be able to use the available services without anylimitations, no matter where they are in the world.4. Existing 2nd generation mobile systems will reach their limits of capacity, while at thesame time the users' need for mobile communication will increase.



In mobile communications, the general trend is towards high data rates. This is the result ofnew services being introduced on the basis of increasingly powerful computer technology,and the developments of corresponding applications.This will show in the applications that are being developed on the basis of UMTS. Forexample, multimedia applications for User Equipments, such as video telephony and videoconferencing, will be offered to a greater extent.Also, the users will be able to surf the net with high data rates. A range of undreamt-ofopportunities will open up to e-commerce suppliers. The term "m-commerce" is alreadyestablished as a name for e-commerce via mobile phones.Mobile access to intranets and Local Area Networks will provide the users' access to dataand company information whenever and from wherever they like.This could be useful tosalespeople on the road, for example, who will be able to check if certain articles are in stockand place their orders on the spot.



Let's summarize the reasons for the introduction of a new system.The mobile users' increasing data volumes, together with the simultaneous increase in usernumbers, are pushing the existing GSM mobile systems to their limits.These systems wereoriginally intended exclusively for digital speech transmission.In addition to speech transmission, the new UMTS system has been designed for the wholerange of mobile data services. It will meet the demands for fast and more flexibletransmission of large amounts of data. In some cases, peak data rates of up to 2 Mbit/s canbe achieved. The net performance will be comparable to the transmission capacity of fixeddata networks.


1.3 Demands on UMTS (1/2)

One user, one User Equipment and one subscriber number. Unlimited availability throughglobal roaming, with optimum transmission of speech and data. The UMTS standard willmake this vision come true. As the basis of future mobile telecommunication networks, it willbridge the gap between today's mobile radio networks and one universal multimedia network.The foundations for the mobile information society, the global village, have been laid.


1.3 Demands on UMTS (2/2)

The UMTS network will transmit both speech and data. In cellular mobile radio, the airinterface specifies the wireless transmission between the mobile equipment and the basestations.In GSM networks, the air interface is optimized only for speech transmission. Its lowtransmission capacity is insufficient for modern demands on wireless data transmission.Thus the basic requirements for the UMTS system are: UMTS must provide a powerful airinterface for the transmission of speech and data in one system. To protect the networkoperator's previous investments, and to keep the costs for new equipment as low aspossible, the new UMTS system will be based on and use the existing network infrastructure.


1.4 Standardization (1/2)

The UMTS standard is important, because for the first time the rules for a global mobile radionetwork will be binding for everyone. This will make global roaming possible.The term UMTS was fixed by the European Telecommunication Standards Institute. In thecontext of the International Telecommunication Union (ITU) we speak of IMT-2000. In theglobal standardization process, the American National Standards Institute (ANSI) will makesure that the existing American Standards are taken into account. The Association of RadioIndustry Business (ARIB) will make sure that the existing Asian guidelines are observed.The responsibility for the standardization lies with the 3GPP, or 3rd Generation PartnershipProject, where network operators, producers and national regulation committees havebundled their activities.


1.4 Standardization (2/2)

The basic demands we have already mentioned define the most important requirements ofthe UMTS standard.For the air interface, two things are particularly important:- The transmission frequencies must be allocated and the transmission method needs to bespecified.- The new network should be based on existing networks as far as possible, and haveunlimited access to them. The system interfaces for data transmission to the GSM networksand their GPRS enhancements, which will soon be introduced, are to be defined accordingly.Thus the UMTS system consists of two main components. An independent subnetwork forradio coverage, and the Core Network, which provides routing and switching.Now let us take a look at the basic UMTS structure.


1.5 Stages of Development (1/2)

Let us start with the GSM network. The Base Station Subsystem (BSS) provides completeradio coverage. The Network Switching Subsystem (NSS) is used to switch the circuit-switched connections in the mobile radio network, and to forward them to the fixed datanetwork.With the introduction of GPRS, the GSM networks are being enhanced for the transmissionof higher data rates.The transmission capacity is increased by adapting the existing GSM air interface to theparticular requirements of packet-switched data transmission, and by setting up a specialGPRS network.In the next step, the UMTS standard will be implemented by setting up a subsystem forUMTS radio coverage, the UTRAN. With its reserved transmission bandwidths and its newtransmission methods at the air interface, it will overcome the limitations that arecharacteristic of GSM.The subnetwork for transmission and switching, the Core Network (CN), is based on the twoindependent subnetworks we already know. The UTRAN is connected to the GSM andGPRS networks via its respective system interfaces, or InterWorking Units (IWU), as we callthem.


1.5 Stages of Development (2/2)

Let's have a look at the air interface. The air interface specified in the UMTS standard iscalled UTRA (Universal Terrestrial Radio Access) and uses CDMA technology. UTRA andCDMA will be described in detail in a separate chapter. At this point we will just look at theiressential characteristics.In UMTS, specific frequency ranges between 1.9 and 2.2 Gigahertz have been planned forradio transmission. The required system capacity can only be achieved through the efficientuse of this limited spectral resource.This is done with the help of the CDMA access method. Its outstanding features are itsspectral efficiency, and its flexible transmission rates.The CDMA method will be implemented into two different transmission modes: the WidebandCDMA, or W-CDMA, is used with the FDD mode. It regulates the simultaneous flexibleaccess of several subscribers to one FDD frequency pair. This means that one frequencyband is used for sending and the other is used for receiving. The spacing between thesefrequency ranges is fixed.In TDD, which uses one frequency for both directions at different times, the TD-CDMAaccess method allows efficient subscriber access to the available timeslots.

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Engineering

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abbreviation umts

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