introduction umts

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Introduction.

UMTS is a substantial advance over existing mobile communications systems. It is being

designed with flexibility in mind above all else ± for users, network operators and service

developers and embodies many new and different concepts and technologies. Far more than

the second generation system, the UMTS is a full third generation global mobile and wireless

system having 2 Mbit/s capability in diverse radio environment with new and innovative

interactive and multimedia services. Mobile communication no longer has the one-dimensional

meaning of not being tied to individual locations for voice telephony. The billions of SMS short

text messages being exchanged clearly point up a need for all-round connectivity. As a

transmission standard of third generation (3G) mobile radio, UMTS will free us up from resource

bottlenecks in network infrastructures, give us access anytime and anywhere to flexible voice,

data, and video communication, and so generate added value through innovative services. A

performance enhancement is in the offing that will lead to more convenience and greater

efficiency. UMTS and the third mobile radio generation are in the process of establishing no

more and no less than a new, mobile civilization able to liberate itself from the restrictions of

time and space. By harnessing excellence in cellular, terrestrial and satellite widebandtechnology, the Universal Mobile Telecommunications System (UMTS) will guarantee access,

from simple voice telephony to high speed, high-quality multimedia services, regardless of

physical location of the user. UMTS will be a mobile communications system that can offer

significant user benefits including high-quality wireless multimedia services to a convergent

network of fixed, cellular and satellite components. It will deliver information directly to users and

provide them with access to new and innovative services and applications. It will offer mobile

personalized communications to the mass market regardless of location, network or terminal

used.

Evolution to 3G

GSM is the leading mobile cellular standard worldwide. There are many GSM networks in

service today that offer GPRS packet-based services. The introduction of GPRS is the

revolution in mobile today, delivering the benefits of IP connectivity and ³always-on´ service

access for the user. This is a fast and cost effective strategy, supporting the first wave of Mobile

Internet services. Users benefit from fast connection set-up ± sending and receiving messages

in an instant, using e-mail on the move, and always-on access to a host of applications and data

sources. GPRS is a fully standardized global solution with open interfaces supporting

GSM/EDGE and WCDMA standardized radio access protocols.

Enhanced Data rates for Global Evolution (EDGE), supports 3G services in-band. Conceived as

the evolutionary steppingstone beyond GPRS, EDGE (sometimes referred to as EGPRS ±Enhanced GPRS) offers data rates comparable with full mobility 3G within GSM operators

existing spectrum allocations. EDGE incorporates improvements to the GSM radio interface with

a new modulation scheme (8-PSK) delivering higher data rates, higher spectral efficiency,

improved transmission performance and improved coverage. EDGE builds on GPRS to deliver

three times the data rate compared with GPRS, as well as providing significant performance

improvements, using a new modulation scheme (8-PSK), at incremental cost.



Future EDGE enhancements include improved voice capacity, coverage and speech quality

features. WCDMA (Wideband CDMA) represents the next step in the technology chain,

delivering the full potential of 3G through its high data rate capabilities. WCDMA, which is used

for UMTS systems, can handle simultaneous access to a variety of voice, data and video

services. WCDMA is capable of delivering what people want at the speeds they need, and is the

best choice of air interface technology for the 2 GHz band.

The Universal Mobile Telecommunications System, UMTS, will take the personal

communications user into the Information Society of the 21st century. It will deliver advanced

information directly to people and provide them with access to new and innovative services. It

will offer mobile personalized communications to the mass market regardless of location,

network or terminal used.

UMTS Deployments.

Universally, the goal of UMTS is to reach the mass market in order to satisfy consumer

demands for personal mobile communications. This depends on the prices subscribers have to

pay for the equipment and service usage. Hence the provision of common standards to build a

widely accepted framework with a low cost mass production for the manufacturers made

possible and open interfaces for the network operators, service and content providers clearly

defined. These standards should be universally established, in the context of ITU¶s IMT-2000

standards in order to enable UMTS ubiquitous service provision anywhere.

From the mobile perspective, UMTS will cater for different kinds of mobility; Terminal and

service mobility. Terminal mobility; user being served while on the move, regardless of network

boundaries. Personal mobility allows a user not to be restricted to a special terminal when

wanting to access his or her services. Roaming based on a common smart card technology and

the provisions of the Virtual Home Environment (VHE; the user will have the same interface andservice environment regardless of location) are major aspects in this context. Service mobility

means that a user can access his or her personalized services independently of the terminal

and serving network.

Convergence of telecommunications, computer technology and content provision will be the

springboard for the UMTS enhanced services. Seamless service provision means that service

provision should not be interrupted by the user¶s movements between different networks.

Transparent services, i.e. the possibility to access the same services in different networks (e.g.

fixed, mobile or satellite networks), are mainly seen from the user¶s point of view. Transparency

must be secured also in the pre-UMTS networks that are interconnected to UMTS .The

universal accessibility of fixed and mobile networks as well as satellite and terrestrial networkswill be an important feature. It will be made possible by multi-mode and multilane terminals.

Hence UMTS will provide both narrow and wideband services (e.g. voice, data, graphics,

pictures and video), in combination, on demand and on the move.

The system aspects of UMTS which provides the means for connections to be made for users

anywhere for service provision, service provider interconnectivity, billing and accounting

functions implementation for various interests and network management in a cost and spectrum



efficient manner for security purposes. UMTS will offer the user the opportunity to design his or

her own user profile (supported by service providers). The user profile, in connection with

personalized user interfaces independent from the current serving network (e.g. VHE), should

be the tool for his personalized service offerings. UMTS will provide mobile users with access to

an exploding market of innovative and interactive services. Multimedia in terms of Internet

services, plus the independent use of different media components within the same session, arekey features for UMTS. The integration of fixed and mobile networks, the convergence of some

fixed and mobile services and of telecommunications and information technology will hence find

its place in the rollout of UMTS.

Since UMTS is market driven and technology enabled, technology relevant for third generation

systems such as UMTS will feature a significant step forward compared to second generation

technologies, mainly in terms of advanced multimedia wideband capabilities. This technology

aims at the integration of mobile and fixed networks providing global coverage and mobility in

terms of terminals and services. New technology will have an impact on, inter alia, competition,

cost vs. performance issues, terrestrial and satellite network integration aspects and the

interfaces to be standardized. The new technology will also play a central role in theconvergence of telecommunications and IT, encompassing multimedia and entertainment. The

transition from second to third generation systems requires a careful phased approach. Some

aspects of technology deployment that needs to be considered here are explained in the next

section.

Section: UTMS TECHNOLOGY.

This section explains the technology aspects of UTMS under the architecture, cost and

flexibility, integration, convergence and security/privacy.

Network Architecture

A UMTS network is logically divided into two parts, which are referred to with the generic termsCore Network (CN) and a Generic Radio Access Network (GRAN) [2, 8, 10, 11]. The corenetwork reuses several elements already present in GPRS and GSM networks, and consists of two overlapping domains: Circuit-Switched (CS) domain and Packet-Switched (PS) domain. CSdomain is made up of those entities which allocate dedicated resources for user traffic andcontrol signals when the connections are established, and release them when the sessionsfinish. Generally, voice calls are always handled by the components belonging to CS domain.The entities in the PS domain transport user data in the form of autonomous packets, which arerouted independently of each other; this scheme overcomes the limitations of 2G networks totransmit data efficiently. It is through the CN that the user can set up a connection to and fromexternal packet data networks. Some of the functions performed by its components are: Management of radio resources Power control both in the downlink and the uplink direction Handover management and allocation of channels for transmissionSince several components in the CN are legacy of GSM/GPRS networks, they allow theconnection to GSM radio access networks as well. As a consequence, GSM¶s Base StationSubsystems (BSSs) and UMTS¶ Radio Network Subsystems (RNSs) can coexist within a publicmobile network¶s UTRAN.



Basic architecture of a UMTS mobile network (Release 99) (from [11]).

The network architecture defines entities that are likely to be collections of physical equipment

located in one place. Figure 20 shows the sites of these entities and shows the physical links

between them. The network architecture also defines the functions that each of these entitiesmust perform and their interfaces with each other so that the entities in each network can work

together to perform operations such as handover between networks [SSD].

The lower part of the diagram in figure 20 depicts the usual terrestrial arrangement of sites in

mobile networks. In cellular networks such as GSM the CSS handles coordination,

concentration and inter-working with the core network and may be connected to tens of BSs. A

micro or macro cellular CSS would have a SCP and DP associated with it to handle terminal

mobility intelligently in a manner optimised for that cellular network. Each BS would take care of

transmission layer functions using antennas at one or more cell sites.



MT Mobile terminal UNI User to networkinterface

SAT

Satellite link

BS Base station DP Data pointFES

Fixed Earth station SCP Service controlpoint

CSS

Cell site switch LE Local exchange

UMTS network sites

In a pico cell environment the CSS may or may not be required. In a business environment,

such as an office building or hotel, CSS functions would be needed and handled by the cordless

PBX. In the home, there is likely to be only one line available and no need for switching. In this

case the BS would interface directly with the LE (local exchange) through a fixed telephone line.

The LE is the interface of any access network (twisted copper pairs, radio access, etc...) to the

core transit network. Even though the CSS performs some switching functions it is still on the

"user" side of the UNI (user to network interface). The LE is the part of the core network that

handles call control such as providing dial tone and it is still required in all FPLMTS. It would

often be located in the same building as a large CSS. The function of the core network "cloud" is

to guarantee robust interconnection and routing of calls between LEs.

In the satellite environment, FESs are necessary to provide an interface between satellites(which in turn are connected to the mobile terminals) and networks on the ground. The FES

includes (but is not limited to) the radio transceivers for the feeder links between the FES and

satellites and the multiplexing of channels on those feeder links. Additional functions such as

radio resource management (co-ordination with the other FESs to avoid mutual interference)

and network functions (call control, network routing and location management) may or may not

be included in the FES. An FES will cater for access to mobile terminals within its well-defined

geographic coverage area.



The coverage of an FES is a very large area, often spanning many countries. The FES is still

the fixed, known entry point to an access network and is on the "user" side of the UNI. This

means that the call control functions of a "local" exchange are still required. It is, however, worth

noting that usually the LE equipment will be dedicated to the satellite access network and not

shared with any other access means. Typically it would be colocated with the FES and connect

into the core network at an international switching centre or transit exchange level, dependingon the nature of the traffic expected to be carried from its coverage area.FESs will need to communicate with each other to effectively manage sharing of radioresources, call handover between FESs and the location of mobile terminals in areas coveredby more than one FES. For example, a FES might not normally be involved with a call handledthrough another FES and yet it would be affected if there was a satellite handover usingfrequencies shared by both FESs. Clearly, some level of coordination is required. To do this anarrangement could be considered where a CSS role is to control a number of BS-like FESsdirectly, in a hierarchical model, as shown in figure 21. The CSS in figure 21 would not be thesame entity (or have all the same functions) as a CSS in terrestrial radio access networks butwould need to be specific to the satellite system to co-ordinate the satellites and FESseffectively.

Satellite acc ess network Core network

Figure 21 Hier ar chi cal FE S struc ture wit h separ ate C SS s

Given the expected large geographical separation of FESs, a better architecture is to connect

each FES directly into the core network and merge the CSS and BS functions into the single

FES entity. Co-ordination is performed by functional entities distributed among all the FESs and

communications for co-ordination among FESs can be carried through the core network or

through the satellites themselves. This is the UMTS architecture as presented in figure 20.

Cost, Flexibility and Integration

UMTS should meet the users expectations of advanced services, with a better service quality,

wider coverage and seamless operation at low cost. The users should be able to choosebetween price and quality of service. This technology will stimulate and enable the offer of UMTS services at attractive prices. It must enable flexible solutions allowing all of the UMTSmarket players to compete and offer customized solutions in an open, liberalized market.



The integration of fixed and mobile network standards and technology is a key attribute of UMTS which will enable truly personal communications to be delivered. It will ensure lower costs as well as providing wideband services which appear truly seamless to the user.Integration at a service level across different independent public and private operatingenvironments is feasible, offering consistent business and personal customer services to theuser wherever he roams. It may prove neither economic nor feasible to extend terrestrial

telecommunications infrastructure into sparsely populated areas. Today, significant areas arestill not covered by terrestrial cellular systems, and terrestrial UMTS is not likely to provide trulyglobal coverage either. Satellite technology has the potential of providing global coverage andservice from the first day and so it can play an important role as an extension of UMTSterrestrial coverage. Integration of the terrestrial and satellite components of UMTS is highlydesirable to provide actual global coverage at least for a subset of UMTS services.

Convergence Technologies for 3G Networks

The word ³convergence´ in the telecom industry means many different things to many differentpeople. For wireless and wire-line carriers it means consolidating networks (converged) into asingle network capable of handling all traffic services. It also means new opportunities for

revenue growth with emerging data service offerings at higher profit margins compared to voiceservices. In the context of this paper, convergence can be defined as the trend towards thelogical merger in a broad sense of the computer and telecommunications sectors, madepossible by their common technological base, electronics. Convergence can impact severalbusiness areas at industry level (e.g. alliance of IT and telecommunication industries) and attechnology level (same core technologies for IT and telecommunicationequipment/infrastructures). A result of convergence which can impact service provisionstructures and organizations is the concept of Full Service Networking. This encompasses theoffering of telecommunication services over CATV infrastructures, ³quasi´ telecommunicationservices (voice/fax) over Internet and broadcast services on telecommunication networks (e.g.through ADSL techniques).Operation and integration of GSM, GPRS, EDGE, UMTS, CDMA2000, IP, and ATM, practical

examples of 3G connection scenarios. Signaling flows and protocol stacks, IP and ATM as usedin a 3G context, issues of QoS and real-time application support IP/SS7 internetworking and IP

soft switching, the architecture of the IP Multimedia Subsystem (IMS) for UMTS

Security and Privacy.The UMTS Forum considers that security and privacy are important aspects of the use of mobileservices, and that they will become even more important in the wider scope of the UMTSservices. These aspects must be studied further in parallel with the development of the UMTSsystem. The UMTS Market Forecast Study identifies as one of the key barriers for the UMTSmarket the ³failure to resolve security issues and convince consumers that electronic commerce

is secure´. Therefore the regulation providing general rules for adequate provision of security onand about individual data must also be applicable to UMTS. Furthermore, binding rules for network access required for lawful interception must be known well in advance so that thestandard includes, for optional use, the necessary equipment specification. UMTS securitybuilds on the security of GSM, inheriting the proven GSM security features. This maximizes thecompatibility between GSM and UMTS i.e. GSM subscribers roaming in a UMTS network aresupported by GSM security features. UMTS also provides a solution to the weaknesses of GSMsecurity and adds security features for new 3G radio access networks and services. An



objective of the UMTS security design was to address weaknesses [1] in GSM. UMTSintroduces new and enhanced security features that are designed to stop threats [2], [3], [4], [5],[15]. These include: Mutual Authentication which allows the mobile user and servingnetwork(SN) to authenticate each other [6], Network to Network security that securecommunication between serving networks which suggested the use of IP security to do so,wider security scope, secure International Mobile Subscriber identity (IMSI) usage, user to

mobile station authentication where more flexibility in that security features can be extended andenhanced as required by new threats and services plus GSM compatibility.

UMTS Security ArchitectureThe security architecture in UMTS is based on three security principles: Authentication,Confidentiality and Integrity.

Authentication Authentication is provided to assure the claimed identity of an entity. A node that wants toauthenticate itself to someone has to show its own identity. This can be done either by showingknowledge of a secret only the nodes involved knows; or by letting a third party that both nodestrusts, vouch for their identities.

Authentication in UMTS is divided into two parts:· Authentication of the user towards the network· Authentication of the network towards the user.

ConfidentialityConfidentiality is to keep information secured from unwanted parties. With more and morepeople using the terminals for both personal and business calls (e.g. online services likebanking) the need for keeping the communication secure grows rapidly. Confidentiality in UMTSis achieved by ciphering communications between the subscriber and the network and byreferring to the subscriber by temporary (local) identities instead of using the global identity,IMSI. The properties that should be confidential are:· The identity of the subscriber

· The current location of the subscriber · User data (both voice and data communications should be kept confidential).

IntegritySometimes a message¶s origin or contents have to be verified. Even though it might come froma previously authenticated party, the message may have been tampered with. To avoid this,integrity protection is necessary. The message itself might not even have to be confidential; theimportant thing is that it¶s genuine. The method for integrity protection in UMTS is to generatestamps to be added to messages. The stamps can only be generated at the nodes that knowthe keys derivate of the pre-shared secret key, K. They are stored in the Universal Subscriber Identity module (USIM) and the Authentication Centre (AuC). It is very important to offer integrityprotection, especially since the SN often is operated by another operator than the subscriber¶s

own operator. The property that should be integrity protected is: Signaling messages andsignaling data.

UMTS consists of five security feature groups:

1) Network Access Security (A in diagram below) provides users with secure access to UMTSservices and protect against attacks on the radio access link.2) Network Domain Security (B in diagram below) protects against attacks on the wirelinenetwork and allows nodes in the provider domain to exchange signaling data securely.



3) User Domain Security (C in diagram below) provides secure access to mobile stations.4) Application Domain Security (D in diagram below) allows the secure exchange of messages between applications in the user and in the provider domain.5) Visibility and configurability of security allows the user to observe whether a security

feature is currently in operation and if certain services depend on this security feature

TE: Terminal EquipmentUSIM: User Service Identity ModuleSN: Serving NetworkHN: Home NetworkMT: Mobile Termination

AN: Access NetworkFigure : UTMS security groups.

Unlike GSM, which has authentication of the user to the network only, UMTS uses mutualauthentication which means the mobile user and the serving network authenticate each other,providing security against false base stations. This mutual authentication uses an authenticationquintet which helps to ensure that a bill is issued to the correct person. Also UMTS provides anew data integrity mechanism which protects the messages being signaled between the mobilestation and the radio network controller (RNC). The user and network negotiate and agree oncipher and integrity algorithms. Both the integrity mechanism and enhanced authenticationcombine to provide protection against active attacks on the radio interface.

UMTS provides enhanced encryption which ensures that messages are not available tounauthorized users. With UMTS, encryption is completed in the radio network controller (RNC)

rather than the base station, as is the case with GSM. The improved confidentiality has comeabout by using longer encryption key lengths, which (along with other UMTS security functions)are easier to upgrade than the GSM counterpart. Also, as GSM¶s ciphering keys were notsecure, UMTS added a confidentiality algorithm.

UMTS also provides different security features for maintaining identity confidentiality.

1) User identity confidentiality is maintained by ensuring the permanent user identity (IMSI) of

a user using the service cannot be eavesdropped on the radio link.



2) User location confidentiality means that one cannot determine whether the presence of auser by eavesdropping on the radio access link.3) User untraceability ensures that it cannot be determined if different services are available to

the same user by eavesdropping on the radio access link.

However UMTS also has security problems. For example everything that could happen to a

fixed host attached to the internet could also happen to a UMTS terminal. Also if encryption isdisabled hijacking calls is possible. And if the user is drawn to a false base station, he/she isbeyond reach of the paging signals of the serving network. Finally when the user is registeringfor the first time in the serving network the permanent user identity (IMSI) is sent in clear text.

Implementation of UTMS

A UMTS network consists of three interacting domains, Core Network (CN), UMTS TerrestrialRadio Access Network (UTRAN) and User Equipment (UE). The basic Core Networkarchitecture for UMTS is bases on GSM network with GPRS. All equipment has to be modifiedfor UMTS operation and services. The Core Network is divided in circuit switched and packetswitched domains. Some of the circuit switched elements are Mobile services Switching Centre(MSC), Visitor location register (VLR) and Gateway MSC. Packet switched elements areServing GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN). Somenetwork elements, like EIR, HLR, VLR and AUC are shared by both domains. Wide band CDMAtechnology was selected for UTRAN air interface. UMTS WCDMA is a Direct Sequence CDMAsystem where user data is multiplied with quasi-random bits derived from WCDMA Spreadingcodes. In UMTS, in addition to channelization, Codes are used for synchronization andscrambling. WCDMA has two basic modes of operation: Frequency Division Duplex (FDD) andTime Division Duplex (TDD). UMTS offer global radio coverage and world-wide roaming. For that purpose the URAN will be built in hierarchical way in layers of varying coverage as depictedin Fig. 2.

Fig. 2. Hierarchical cell structure of UMTS to offer global radio coverage



A higher layer will cover a larger geographical area than a lower layer. In the highest layer therewill be satellites covering the whole planet, the lower layers form the UMTS terrestrial radioaccess network UTRAN. They are divided in to macro, micro, pico-layer. Each layer is dividedinto cells. The lower the hierarchical level, smaller the cells. Smaller cells allow for a higher

user-density. Therefore macro-cells are used for land-wide coverage; additional micro-cells areinstalled in areas with higher population density and pico-cells in buildings and for so called ³hotspots´ (e.g. airports, railway stations). The maximum data rate and the maximum speed of theuser are different in each hierarchical layer. In the macrolayer at least 144 k bit/s with maximumspeed of 500 km/h shall be possible. In the micro-layer 384 k bit/s with maximum speed of 120km/h shall be supported. The picolayer offers up to 2 M bit/s with a maximum speed of 10 km/h.It shall be possible for the user to trade off bit error rate versus delay in certain limits. For real-time applications with constant delay (speech, video) the bit error rate can be in the range of 10-3 to 10-7, the maximum delay can be in the range of 20 ms to 300 ms. For non-real-timeapplications (email, SMS) with variable delay the bit error rate can be in the range of 10-5 and10-8. The maximum delay can be 150 ms and more.

Spectrum for UTMSThe spectrum for UMTS lies between 1900 MHz to 2025 MHz and 2110 MHz to 2200 MHz. For the satellite service an own sub-band in the UMTS spectrum is reserved (up-link 1980 MHz to2010 MHz, down-link 2170 MHz to 2200 MHz). The remaining spectrum for terrestrial use isdivided between two modes of operation. In the FDD (Frequency Division Duplex) mode thereare two equal bands for the up-link (1920 MHz to 1980 MHz) and for the down-link (2110 MHzto 2170 MHz). In the operation mode TDD (Time Division Duplex) up-link and down-link are notdivided by use of different frequency carriers but by using different time-slots on the samecarrier. So there is no need for a symmetrical spectrum but the remaining un-paired spectrumcan be used. The spectrum is summarized below;1920 MHz - 1980 MHz FDD Uplink2110 MHz - 2170 MHz FDD Downlink

1900 M Hz - 1920 M Hz TDD 2010 M Hz - 2025 M Hz 1980 MHz - 2010 MHz MSS (Mobile Satellite Service) Uplink2170 MHz - 2200 MHz MSS Downlink

UMTS Network

Figure «.shows how UMTS could be configured. The UTRAN provides the air interface accessmethod for User Equipment. Base Station Controller is referred as Node-B and controlequipment for Node-B¶s is called Radio Network Controller (RNC). It is necessary for a networkto know the approximate location in order to be able to page user equipment. Here is the list of

system areas from largest to smallest. UMTS systems (including satellite) Public Land Mobile Network (PLMN) MSC/VLR or SGSN Location Area Routing Area UTRAN Registration Area Cell Sub-Cell



Figure « Building a UMTS network.

The Asynchronous Transfer Mode (ATM) is defined for UMTS core transmission. ATM Adaptation Layer type 2 (AAL 2) handles circuit switched connection and packet connectionprotocol AAL 5 is designed for data delivery. The architecture of the Core Network may changewhen new services and features are introduced. Number Portability Data-base (NPDB) will beused to enable user to change the network while keeping their old phone number. GatewayLocation Register (GLR) may be used to optimize the sub-scriber handling between networkboundaries. MSC, VLR and SGSN can merge to become a UMTS MSC. The UMTS standarddoes not restrict the functionality of the User Equipment in any way. Terminals work as an air interface counterpart for Node-B and have many different types of identities. Most of theseUMTS identity types are taken directly from GSM specifications.

International Mobile Sub-scriber Identity (IMSI) Temporary Mobile Sub-scriber Identity (TMSI) Packet Temporary Mobile Sub-scriber Identity (PTMSI)UMTS mobile station can operate in one of three modes of operation: PS/CS mode of operation: The MS is attached to both the PS domain and CS domain, and theMS is capable of simultaneously operating PS services and CS services. PS mode of operation: The MS is attached to the PS domain only and may only operateservices of the PS domain. However, this does not prevent CS-like services to be offered over the PS domain (like VoIP).



CS mode of operation: The MS is attached to the CSdomain only and may only operateservices of the CS domain. UMTS IC card has same physical characteristics as GSM SIM card.It has several functions: Support of one User Service Identity Module (USIM) application (optionally more that one) Support of one or more user profile on the USIM Up-date USIM specific information over the air

Security functions User authentication Optional inclusion of payment methods Optional secure down-loading of new applications

introduction umts

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