Combined GSM/UMTS mobile backhaul network

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Combined GSM/UMTS mobile backhaul network

  1. 1. Combined GSM/UMTS mobile backhaul network Deployment of UMTS networks and enhancement of GSM/GPRS with EDGE provides more efficient radio interface, thus enabling higher data speed and more capacity for voice. That evolution requires additional transmission capacity to transport extra traffic through mobile backhaul network from Base stations to Mobile Switching Centers. Moreover, UMTS specifies IP or ATM as a bearer, requiring upgrade of TDM based backhaul network used for GSM. Building separate mobile backhaul networks for UMTS and GSM is inefficient and expensive, especially since mobile operators expect UMTS to cannibalize the use of GSM network over time, leaving GSM backhaul capacity unused. This white paper defines a solution for a single mobile backhaul network that supports UMTS and GSM with GPRS and EDGE. The solution reduces mobile backhaul transmission capacity requirements by using advanced lossless compression method for GSM voice, traffic aggregation, and statistical multiplexing of voice and data traffic generated by both GSM and UMTS networks.
  2. 2. Combined GSM/UMTS mobile backhaul network Content 1 Introduction 1 2 Radio Access Network Backhaul 1 3 Backhaul Network Efficiency Considerations 3 4 Improving Backhaul Network Efficiency 3 5 Further Optimizing GSM Backhaul Bandwidth 4 6 Backhaul network options 5 7 Conclusion 7 1 INTRODUCTION Cellular Network Architecture GSM mobile operators have already executed plans or have strong commitments to upgrade their GSM Controller Core network with EDGE (Enhanced Data Rates for GSM Network Evolution) and/or to evolve to UMTS. The way forward Base Station RAN for such cases is to gradually implement UMTS Mobile network architecture to build cost effective converged Station Backhaul section GSM/UMTS network. Along with growth of subscriber base and increase of Figure 1. Backhaul transmission section in the cellular network architecture data traffic (EDGE and UMTS), ensuring sufficient network capacity is turning into an essential issue for network operators. 2.1 GSM/GPRS network Most of mobile service providers lease transmission Backhaul transmission in the GSM networks includes lines for their backhaul network, which creates major transmission lines between GSM Core Network and operational expenses. Base Station System (BSS) network elements: the Base Station Controller (BSC) and the Base GSM/GPRS backhaul transmission is based on a Transceiver Station (BTS). TDM circuit-switched technology, whereas UMTS deployment requires a new backhaul network based Connection between the BTS and the BSC is denoted on IP or ATM. as Abis interface, while the connection between the BSC and the Core Network is denoted as A interface This whitepaper describes evolution of GSM/GPRS (Figure 2). backhaul transmission network to support EDGE and UMTS, and proposes optimized architecture, with a GSM Network particular accent on lossless compression techniques for GSM backhaul network that provides bandwidth BTS savings for further optimization of GSM mobile Abis A GSM transmission network. BSC Core Network BTS Abis BSS 2 RADIO ACCESS NETWORK BACKHAUL Figure 2. Abis and A interfaces for backhaul transmission in Radio Access Network (RAN) is a part of every the GSM network cellular network that facilitates a connection between the end-user mobile station over air interface and the The GSM evolution to 2,5G network (GSM phase 2+) core network over a landline transmission network is facilitated by providing the General Packet Radio usually called – mobile backhaul (Figure 1). Services (GPRS) system upgrade that allows packet- switched mobile data service, where all the data to be sent are broken down into several smaller data packets first. Those packets are then sent individually across the GPRS network and each of those packets KATEKOM 1
  3. 3. Combined GSM/UMTS mobile backhaul network can take a different route. At the target destination, the GSM/GPRS/EDGE Network packets need to be reassembled. For that reason, new functionality has to be introduced into existing BTS Abis/Gb GSM network elements, especially for allowing EDGE efficient use of the air interface. Four coding schemes TRX A GSM/GPRS are introduced (CS1 to CS4), with capability that one BSC Core user can occupy more than one timeslot or more than BTS Network EDGE Gb one user can be on a single timeslot. TRX Abis/Gb BSS Depending on coding scheme and number of concatenated time slots, a maximum theoretical data Figure 4. EDGE enhancement for GSM/GPRS network rate of 171.2 kbit/s can be achieved. The “Real life” experience is around 40 kbit/s, which is acceptable for 2.3 UMTS Radio Access Network Internet access and web browsing. To provide GPRS service, upgraded BSS network elements need to be UMTS Terrestrial Radio Access Network (UTRAN) connected with the GPRS backbone system, and that represents an entirely new radio access for 3G can be performed by allocating distinct time slots on networks. Based on the Wideband Code Division existing A link (“nailed-up” connection) or by separate Multiple Access (WCDMA) radio access technique, Gb interface (Figure 3). Both solutions put additional UTRAN provides broader bandwidth and better demand on backhaul capacity. spectrum efficiency allowing high data rates on the air interface. GSM/GPRS Network UTRAN introduces the Node B, as equivalent to 2G BTS, and the Radio Network Controller (RNC), as BTS Abis A equivalent to 2G BSC. The new Iu interface is GSM/GPRS BSC Core introduced to connect RNC to the UMTS core Network network. In addition to UTRAN, GSM/EDGE form a Gb BTS Abis Radio Access Network (GERAN) to provide the same BSS Circuit Switched (CS) and Packet Switched (PS) services as UTRAN. For that purpose GERAN Figure 3. GSM/GPRS network evolution architecture must offer backward compatibility to GSM/GPRS using A and Gb interfaces (Figure 5). 2.2 Introduction of EDGE Release 99 (R99), which is designed to provide smooth transition from GSM, specifies ATM as a Enhanced Data Rates for GSM Evolution (EDGE) is bearer for the Iu interfaces for carrying voice and data another step in GSM/GPRS evolution towards 3G traffic, and that will require a whole new backhaul mobile systems. EDGE introduces a new modulation transmission network for UTRAN. Taking into technique known as 8-Phase Shift Keying (8-PSK) in consideration that most of today’s GSM networks will order to support higher transmission data rates and evolve to converged GSM/UMTS, requirements for increase the network capacity. Similarly like GPRS, cost-effective and efficient backhaul will be of greatest these applications use the same GSM carrier importance. bandwidth and timeslot structure. EDGE also shares the GPRS network elements. EGPRS provides packet A BTS Abis data services using the GPRS architecture and the Gb BSC new EDGE modulation technique and coding BTS Iu schemes. Enabling it requires some hardware Abis GERAN UMTS changes, as well as adaptations in the signaling Core Iub Network structure on the BSS side. Nine modulation and Node B Iu coding schemes are defined for EDGE: MCS-1 to RNC MCS-9. EGPRS can theoretically offer a maximum Node B Iub UTRAN data rate of 473.6 kbit/s. Those data rates can provide more advanced services, such as real time video Figure 5. GERAN and UTRAN in Release 5 streaming or video conferencing. EDGE traffic connections are provided over Gb interface which need to be allocated on Abis interface, which will call for additional optimization of backhaul lines (Figure 4). KATEKOM 2
  4. 4. Combined GSM/UMTS mobile backhaul network 3 BACKHAUL NETWORK EFFICIENCY way of using extra capacity on seldom used lines to CONSIDERATIONS carry overflow traffic from busier lines. Consequently, while service providers can lease additional E1 lines GSM/GPRS mobile service providers incur extensive for BTSs in high-traffic areas, they must absorb the facilities and equipment expenses when they design cost of providing spare backhaul bandwidth for BTSs and build networks to provide backhaul transmission in low-use areas. for services and support of mobile communication. 4 IMPROVING BACKHAUL NETWORK EFFICIENCY In most cases mobile service providers lease multiple E1, E3 or STM-1 lines for backhaul transmission links It seems apparent that the future step toward 3G from the Incumbent Local Exchange Carriers (ILEC), should include a combined GSM/EDGE/UMTS which account for a large part of their operational network where GSM/EDGE network is to fulfill expenses. Continuous growth of voice and data traffic coverage demands, whereas UMTS network is to will result in a need for additional transmission ensure voice and high-speed data in densely capacity, thus increasing mobile operator’s leased populated areas. Release 99, as well as Releases 4 lines costs. and 5, requires IP or ATM as a transport technology for UMTS. Therefore, one option is to build an entirely 3.1 Network Topology new backhaul besides the legacy TDM backhaul Majority of mobile networks still use “star topology” network. Of course, that option would be inefficient architecture in their backhaul, where each BTS is and expensive for mobile service providers. A better connected directly to the BSC over dedicated E1 lines. solution would include integration of 3G-backhaul Since each E1 line is dedicated to a particular BTS, elements into the existing 2G-backhaul, thus creating each Transmitter-Receiver (TRX) of that BTS must be a single common, cost-effective 2G/3G backhaul assigned to dedicated channels on a given E1. The network. Star topology offers easiest deployment and maintenance, especially in initial stages of network 4.1 Combined 2G/3G ATM-based backhaul development, but in case of extensive growth of network subscribers and installed network base this solution, ATM as a bearer technology offers an integrated however, increases costs of delivering mobile solution for voice and data, and guarantied QoS. ATM services. Vast majority of mobile networks are Adaptation Layer 2 (AAL2) is designed to increase designed and dimensioned to comply with the efficiency when transporting delay-sensitive voice over requirements of worst-case conditions in which busy an ATM network, AAL2 enables switches to fill ATM hour or peek traffic demand can arise simultaneously cells more quickly by multiplexing multiple voice calls in all of the backhaul network elements. To meet into the same ATM cell. Data services such as Frame capacity demands, the TRXs are assigned to each Relay (FR) are efficiently mapped into ATM BTS according to busy hour call usage projections. Adaptation Layer 5 (AAL5), which is compliant with The busier an area is, the more TRXs need to be Frame Relay Forum-FRF.5 and FRF.8 specifications, installed in the BTSs to provide sufficient capacity, while emulation of legacy TDM circuit switched voice and the more backhaul bandwidth is required to and data services are supported by AAL1 Circuit transport increased traffic. There is also a coverage Emulation Service (CES). demand, so the mobile service providers will add additional BTSs to insure full service coverage for all 4.2 Inverse Multiplexing over ATM (IMA) areas (urban, sub-urban and rural), regardless of usage remaining low in some areas. Mobile service providers usually lease E1 or E3 lines for their backhaul transmission. Because of a huge This will lead to situation where the traffic channels in bandwidth gap between E1 (2 Mbit/s) and E3 (34 one system are rarely simultaneously busy and the Mbit/s), operators requiring more bandwidth than a result is - inefficient allocation of limited network single E1 and less than the much more expensive E3, resources. are faced with very expensive alternatives. IMA addresses this issue and provides a solution where 3.2 TDM technology as a bearer the bundles of parallel physical E1 links are combined Another issue that must be taken into account is into a single logical connection. That offers an inherent inefficiency of using traditional circuit- aggregate bandwidth. IMA is also a very robust, switched TDM technology for backhaul. Because of offering a great immunity to service interruptions. If the static multiplexing nature of TDM connections, for one of its constituent E1 links fails, transmission of each and every channel on the air interface, traffic will continue as long as at least one of its regardless if carrying traffic information or not, the constituent links is operating. This will result in appropriate channel resource must be allocated on decrease of available bandwidth of all connections, the Abis interface. Thus the service providers have no KATEKOM 3
  5. 5. Combined GSM/UMTS mobile backhaul network however, an overall service availability and reliability 5 FURTHER OPTIMIZING GSM BACKHAUL in the backhaul network will increase. BANDWIDTH 4.3 Access Aggregation Even though the GSM speech coding techniques ATM access devices, such as Lucent PacketStar already have low bit rates, there is still some space for (PSAX) multiservice media gateway, offers access further savings in the bandwidth. Another method to aggregation for a large number of TDM E1 links to additionally save backhaul bandwidth, without facilitate connection of Abis interfaces, from BTSs to compromising voice quality, is to suppress or remove BSCs and further to the MSC. Once Node Bs and redundant information from speech transmissions, on RNCs are deployed, Iub and Iu can be connected to Abis and Ater interfaces. the same ATM aggregation devices. PSAX multiservice gateways are capable of utilizing existing 5.1 Mapping of channels on Abis /Ater interface TDM interfaces as a physical layer for ATM The Abis/Ater interface utilises a TDM connection transmission links. In that way we get a common using standard E1 links with 32 E0 timeslots, (or ATM-based backhaul (Figure 6). Usage of ATM over channels), which are used to transport both traffic and the same TDM interface produces a single aggregated signaling. Those 32 channels have data rate of 64 physical channel that statistically allows use of less kbit/s each (E0), thus providing 2.048 Mbps overall bandwidth than the sum of bandwidths necessary for throughput over E1 link. The GSM channels in are each separate channel. Since it is highly unlikely all coded in different capacities where 8 and 16 kbit/s are allocated channels will be active at the same time, the most-widely used types. In most cases, there is a service providers can benefit from ATM’s statistical 4:1 multiplexing on the Abis/Ater interface where four multiplexing and can overbook their ATM links. This of 16 kbit/s sub-channels are mapped into one 64 method is usually referred to as Oversubscription, and kbit/s E0 channel. it considerably reduces a total bandwidth needs for all access interfaces (Abis, A, Gb, Iub, Iu) As defined in the GSM standards, channel can carry traffic information or it can be idle. When the Gb, Iu-ps information is transferred on the Abis or Ater interface, 2G A MSC SGSN it is transferred in frames with a fixed length of 320 PSAX bits (20 ms, 16 kbit/s). Those frames are called TRAU Iu-cs 3G MSC frames and they carry speech, data, signaling and PSAX associated control signals. A, Gb Iu BSC Abis Iub RNC I broad terms, we can divide TRAU frames as: Frames ATM for speech services - according to speech codecs PSAX used: Frames for Half and Full Rate (HR and FR), Iub Iub Enhanced Full Rate (EFR) and Adaptive Multi-Rate Abis Abis (AMR) speech, O&M Frames, Data Frames and Idle Node B BTS BTS Node B Speech Frames. In the case where FR, EFR or AMR is used for speech coding, 16 kbit/s traffic sub- Figure 6. Combined 2G/3G ATM-based backhaul network channels, mapped on the Abis interface, would emerge. For Half Rate speech coding, the 8 kbit/s 4.4 Channel grooming traffic channels are used. They are regularly matched Further optimizations of the backhaul bandwidth can in pairs to form one 16 kbit/s sub-channel which is be performed by selectively transmitting only active E0 then mapped on the Abis interface. (Figure 7) channels over a backhaul network. TDM E1 link Abis 4xA normally has an amount of active and inactive E0 Ater MSC BTS BSC TRAU channels depending on usage hour. Regardless the inactivity of E0 channels, they still reserve backhaul bandwidth. PSAXs are capable of eliminating unused 64 kbit/s E0 channels E0 channel from the backhaul transmission, and send TS0 TS1 TS2 ... TS31 TS2 Idle Channels only active E0s. This E0 grooming of only active (64 kbit/s channels) connections can provide diversity effect for GSM TS3 operators and reduce the risk of individual E1 link TS0 TS1 TS2 TS3 TS2 Idle Speech Frames (16 or 8 kbit/s channels) failures, capable of affecting service. 16 kbit/s FR, EFR or AMR channels Figure 7. Mapping of TRAU frames and Idle Channels on the Abis KATEKOM 4
  6. 6. Combined GSM/UMTS mobile backhaul network 5.2 GSM voice suppression methods traffic on the network and voice activity of users that influences the percentage of idle patterns. There are common patterns in Idle Channels and Idle Speech Frames that can be removed from speech In addition to lossless compression of Abis interface, transmissions over backhaul network. That will lead to GSM Idle channel and Idle Speech frame suppression best possible bandwidth reduction and greater trunk methods have important “side effect”. Abis traffic is not utilization, resulting in more operational savings for statically allocated to time slots on TDM interface – it wireless carriers. Lucent PSAX is the only multiservice is transported as ATM AAL2 Variable Bit Rate (VBR) media gateway, available in the market, utilizing two over the backhaul network. This enables bandwidth suppression techniques: reduction because of statistical multiplexing. 1. GSM Idle Channel Suppression and Gains of statistical multiplexing are especially significant in case of traffic aggregation for the whole 2. GSM Idle Speech Frame Suppression. region. Single region typically has a mix of dense urban, urban, rural and road base stations, with 5.2.1 GSM Idle Channel Suppression different daily and yearly traffic distribution, busy hour Whenever no traffic is received from the radio at differet times of a day and different overall base interface (e.g. channel is not allocated to a call, frame station load. stealing applies, layer 2 fill frames are received, etc.), Practical results for aggregation of regional traffic a channel is considered idle. In that case, the “Idle shows that PSAX achieves reduction of transmission Patterns” or the “Idle Channels” are generated on bandwidth of average 40% compared to the best corresponding channels on the Abis interface. PSAX possible optimization with TDM. GSM Idle Channel suppression feature detects “Idle Channels" and removes them from the data stream to be transported over Abis/Ater interface. Using the PSAX, transmission in the RAN will be 6 BACKHAUL NETWORK OPTIONS handled by the ATM cell technology so the GSM traffic has to be sent over ATM links between PSAX GSM mobile operators which have acquired licenses systems. ATM statistical multiplexing extended with for UMTS have to decide which way to go in evolution suppression feature can ensure substantial backhaul of their backhaul network. The decision they make is bandwidth savings, which can go up to 80% (in the probably one of the most important ones, second only ideal case) allowing for service providers to minimize to the decision to take a part in the 3G game itself. the number of leased E1 in the backhaul network. There are several ways to go and failing to chose the right one might cause tremendous damage to their 5.2.2 GSM Idle Speech Frame Suppression backhaul network efficiency and subsequently to their revenues. There are four main options whose For a regular voice call it is common for one person to advantages and disadvantages are to be presented: speak for 50% of the time, while the rest of 50% of the time there is a silence while listening to what the other 1. Direct E1 links for Iub person is saying. Speech information can be carried over FR, EFR or AMR speech frames, but if no 2. Combined GSM/UMTS backhaul with speech is received (e.g. during periods of silence on fractional E1s calls), the Idle Speech Frames will be generated and 3. “Standard” ATM combined GSM/UMTS transported instead of the FR or EFR speech frames. backhaul Those Idle Speech Frames don’t carry useful information but still allocate the same bandwidth as 4. PSAX combined GSM/UMTS backhaul FR or EFR speech frames. PSAX advanced logic detects Idle Speech Frames and suppresses 6.1 Direct E1 links for Iub transmission of these frames over the ATM trunk and This approach is probably the easiest to deploy but it regenerates them at the far end of the ATM network to hides the greatest possible treat called: “GSM assemble Abis interface. This provides an additional Cannibalization”. Newer and more attractive UMTS transmission bandwidth savings. services will gradually take over GSM services and successively the UMTS backhaul traffic will increase, 5.2.3 Transmission bandwidth reduction leaving the GSM backhaul with less traffic and more considerations inefficient utilization of scarce transmission resources. The actual savings realized with these two supression Moreover, such approach requires much more features depend on the network topology, the number interface capacity on RNC that incures unnecessary of E1 interfaces strapped together, type of base capital expenses. With direct E1 connections, capacity station (dense urban, urban, rural, road) types of of RNC interface is equal to sum of all capacities of KATEKOM 5
  7. 7. Combined GSM/UMTS mobile backhaul network NodeB interfaces. Taking into account that typical 6.2 Combined GSM/UMTS backhaul with network load in busy hours is 40% of overall installed fractional E1s Base station capacity (because of different traffic This approach introduces ATM switches for carrying patterns in dense urban, urban, rural and road Base both GSM and UMTS traffic over fractional E1 links stations), RNC in this scenario has 60% unused from the locations with lower traffic utilization. For interface capacity. higher capacity GSM and UMTS base stations, separate E1 links are used. nxE1 UMTS nxE1 UMTS nxE1 UMTS GSM RNC nxE1 nxE1 UMTS E1 UMTS GSM RNC STM-1 UMTS E1 ATM UMTS GSM E1 UMTS Fractions of E1 nxE1 used for GSM E1 GSM and UMTS Multiple E1s nxE1 BSC DXC DXC E1 E1 GSM GSM E1 BSC DXC DXC E1 GSM Multiple E1s GSM E1 E1 E1 GSM GSM GSM Advantages: Existing GSM backhaul left intact Advantages: Easy to deploy Unused fractions of E1s on GSM connections are provisioned for UMTS traffic Disadvantages: STM-1 ATM interface on RNC can be used to Extreme waste of bandwidth optimize RNC interface capacity GSM Cannibalisation; No capacity benefits from Disadvantages: customer’s migration from GSM to UMTS - freed capacity in GSM backhaul cannot be re- Not applicable for dense populated areas with used for growing UMTS network high capacity GSM and UMTS base stations Waste on RNC interface (typically 60%) With growth of UMTS traffic fractional E1 capacity becomes insufficient No benefits from statistical multiplexing KATEKOM 6
  8. 8. Combined GSM/UMTS mobile backhaul network 6.3 “Standard” ATM combined GSM/UMTS 6.4 PSAX combined GSM/UMTS backhaul backhaul Using market unique GSM voice suppression features All GSM and UMTS traffic is transported over a single in PSAX, GSM voice is carried over AAL2. Adding ATM-based backhaul where GSM traffic is transported AAL2 for UMTS voice and AAL5 for GSM/UMTS data via AAL1 layer as CES, while UMTS traffic is services, usage of PSAX within combined GSM/UMTS transported over AAL2 layer. backhaul allows statistical multiplexing gain, ensuring best possible optimisation of backhaul transmission bandwidth. nxE1 UMTS UMTS RNC GSM nxE1, STM-1 STM-1 E1 nxE1 UMTS UMTS E1 GSM GSM RNC nxE1, STM-1 STM-1 E1 ATM ATM nxE1 E1 GSM nxE1 Multiple E1s, nxE1 UMTS E3, STM-1 PSAX nxE1 E1 PSAX nxE1 nxE1 nxE1 IMA, UMTS E3 or STM-1 nxE1 BSC UMTS E1 GSM nxE1 UMTS BSC UMTS GSM UMTS Advantages: Single ATM backhaul network serving both Advantages: GSM and UMTS Single ATM backhaul network serving both Single backhaul network eases network GSM and UMTS - eases network management management and optimizes operating expenses and optimizes operating expenses Statistical multiplexing gain for UMTS traffic Statistical multiplexing of GSM and UMTS only channels ensures substantial reduction of Disadvantages: required transmission bandwidth GSM channels are transported through AAL1 GSM voice suppression features offer additional layer as CES, which consumes around 13% transmission bandwidth savings more bandwidth comparing to ordinary TDM Efficiently solves “GSM cannibalisation” channels – additional leased lines capacity for problem GSM has to be ensured. Future proof - IP transport in 3GPP Rel5 No ATM statistical multiplexing possible among architecture UMTS and GSM traffic channels - bandwidth for GSM permanently dedicated to CES ATM channels KATEKOM 7
  9. 9. Combined GSM/UMTS mobile backhaul network 7 CONCLUSION Service providers about to build UMTS network and All of these benefits make PSAX the most efficient committed to upgrading their existing GSM network and flexible tool for optimization of available to GPRS and EDGE, face the necessity for backhaul transmission bandwidth, which provides the existing optimization in order to ensure sufficient network GSM service providers with smooth and cost capacity for the increased voice and data traffic. effective transition to UMTS. Implementation of ATM as a transport technology into the existing backhaul network architecture enables building of combined backhaul network for both GSM and UMTS, where the most important building block is represented through Lucent Technologies PSAX multiservice media gateway. PSAX provides the most comprehensive range of capabilities required to integrate seamlessly into all mobile network types where the large number of different interfaces can be aggregated into one combined transmission network. Capability of E0 channel grooming to selectively transmit only active GSM channels over backhaul network and IMA over E1 links ensuring robustness and increased immunity to service interruptions, allow further optimization of the backhaul bandwidth. Market unique, GSM Idle Channel Suppression and GSM Idle Speech Frame suppression algorithms are used to suppress transport of redundant information from speech transmissions on GSM Abis and Ater interfaces. Such methods enable Abis and Ater interface information to be transported as Variable Bit Rate traffic through the ATM network, which is a prerequisite for leveragining ATM statistical multiplexing capability. Statistical multiplexing of GSM voice, UMTS voice, GPRS/EDGE data and UMTS data provides considerable backhaul bandwidth savings and is the only method that efficiently solves the problem of cannibalization of GSM services by UMTS. KATE- KATE-KOM is a system integrator providing INNOVATIVE solutions for carriers, service providers and large enterprises. Our KNOWLEDGE comes from highly educated technical team with vast experience in building of telecommunication networks. Our careful STRENGTH is built on our own product portfolio and empowered by careful choice of partners. global reliable partners. That enables us to create "The perfect fit for your network" solutions. "The network" Combined GSM/UMTS mobile backhaul network, v01.00 Copyright © KATE-KOM 2005 All rights reserved. www.kate-kom.com www.kate- For more information please contact: +385 1 3689700 or solutions@kate-kom.com

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