The Challenge of Implementation of Long Term Evolution / System Architecture Evolution (LTE/SAE)

Transcription

1 The Challenge of Implementation of Long Term Evolution / System Architecture Evolution (LTE/SAE) Alma Skopljak-Ramović 1, Senad Pivač 2 Core Network Planning, Radio Network Planning, BH Mobile, BH Telecom, Ul. Obala Kulina Bana br. 8, Sarajevo, Bosnia and Herzegovina 1 alma.skopljak@bhtelecom.ba 2 senad.pivac@bhtelecom.ba Abstract Current 3GPP Release-8 is addressing Evolved- UTRAN or LTE as a new access network and SAE / EPC as an improved version of 3,5G core based on All-IP infrastructure. This paper describes the objectives of the actual LTE / SAE standard related to its deployment in Bosnia and Herzegovina and suggests how to implement it smoothly in a mid-size network. I. INTRODUCTION Initiated in 2004, LTE standard has been developed as an improvement of existing UMTS terrestrial radio access (UTRA) network, and today it is already a part of 3GPP (3rd Generation Partnership Project) Release-8; it incorporates a new standard of mobile communications not only for radio network, but also for architecture of the core. In defining LTE, the objectives were not only to have better performances, reflected in significantly higher access transmission data rates, but an entire improvement of the network such as a better utilization of radio spectrum, simplified system design and high economic efficiency. Research and development experts, representing some 60 operators, manufacturers and research centers worldwide, participate in joint work on standardization of LTE radio-access and core networks. [1] Fig.1. Development path of mobile network standards 3GPP Release-8 (Rel-8), stating LTE as a Global Mobile Broadband network (GMB), was accomplished in December 2008, and is still waiting for its ratification. (ASN.1 code is concluded in March 2009). Since this standard has been mainly focused on improvement of UMTS toward the forth generation (4G) of mobile communication technologies, and to all-ip flat architecture of the system, some sources state that LTE is actually 3.9G, as a starting point for ITUdefined development process of mobile networks towards IMT Advanced. [2] Rel-8 standard, in its present form, is sufficient for hardware manufacturers to design and produce adequate LTE devices, testing equipment and base stations. Testing equipment for LTE has already been presented in February 2008 at the Mobile World Congress in Barcelona by several equipment manufacturers who, together with operators, started testing of LTE networks and they will publish the results as so-called LTE Initiators (LTSI). [3] The development path of mobile network standards can be seen in Fig. 1. II. FREQUENCY RANGE Frequency range (or ranges) for LTE has not been definitely determined yet. The operators test LTE / Evolved (E)- UTRAN in 700 MHz, 800 MHz and 2.6 GHz bands, trying to reconcile the requirements for broadband, mobility and allowed frequency range. [2] Most European regulators, as well as TV broadcasters, followed an example of the USA (FCC offered 62 MHz range at 700 MHz for LTE in auction), and have already started to free UHF spectrum and switch from analog to digital TV. It is considered that primary LTE range in Europe is: MHz which is also referred to as a digital dividend range, but 2.6 GHz range will also be used (2x70 MHz for Frequency Division Duplex - FDD and 50 MHz of unpaired Time Division Duplex - TDD for WiMAX). There are also some ideas to free GSM 900 MHz band by pushing users to 3G network, so it could also be used for LTE (especially for 1.4 MHz channels) or to use e.g MHz band. The regulators in the European countries have already announced auctions (Norway and Sweden have launched a trial for LTE). In Asia, they support recycling of the UMTS range. III. MAIN FEATURES OF LTE/SAE The general main objectives of LTE, comparing to 3.5G, are as follows: improved spectral efficiency and making the best use of the new spectrum possibilities, better permeability, higher network responsiveness rate for more sophisticated /10/$ IEEE 1241

2 services, decreased costs (CAPEX and OPEX) by avoiding construction of complex network architectures and unnecessary interfaces, optimization of network protocols and enabling a multi-vendor environment. LTE will also result in improvement and enrichment of services, plug & play implementation of services and it is expected that LTE will smoothly integrate with the existing open standards, i.e. enable a transparent connection with GSM and (W)CDMA standard, but also with WLAN and WiMAX. The network architecture which should result from these requirements is called EPS - Evolved Packet System. EPS actually unites E-UTRAN at the access side and EPC, evolved packet core. This core is also known as SAE - System Architecture Evolution, and for the access part instead of E- UTRAN, more common term is LTE. 3GPP Rel-8 standard includes the following features and requirements of LTE/SAE network: Downlink transmission rate: min. 100 Mb/s, i.e. 3-4 times more than HSDPA (High Speed Downlink Packet Access) Rel-6; peak value: 326.,4 Mb/s for 4x4 antenna system, Mb/s for 2x2 antenna system, for each 20 MHz of spectrum; Uplink transmission rate: 50 Mb/s, i.e. 2-3 times more than HSUPA (High Speed Uplink Packet Access) Rel-6; peak value for upload: 86.4 Mb/s for each 20 MHz of spectrum; Five different classes of terminals, from the class meant for speech processing and transmission to the class capable of data processing at highest possible transmission rates. Each of the classes will be able to process signals at 20 MHz range; Capacity: at least 200 simultaneously active users in each 5 MHz cell; Response rate of Radio Access Network (RAN) subsystem: <10 msec, i.e. <5 ms for small IP packets within unloaded system, as the values for users data flow, and similar applies for the control level, i.e. signaling data flow; Higher flexibility of spectrum usage, from range of 1.4 MHz, for 1.6 MHz, 3 MHz, 3.2 MHz, 5 MHz, 10 MHz, 15 MHz, to the range of 20 MHz for TDD as well as for FDD duplex; Optimal cell radius: 5 km for relatively good performances, 30 km with lower quality degradations allowed and 100 km radius for acceptable performances; High mobility: LTE network should be optimized for usage in the motion of 0-15 km/h, to have excellent performances and at speed of km/h, but also to support service at speed of km/h. The quality of services used under such conditions should be at least good as with UTRAN; Coexistence with existing standards, i.e. 2G and 3G(+) operators: customers can initiate a call or data transmission in the area covered by LTE standard, and then transparently continue using the service in the area covered by GSM or W-CDMA/UMTS signal (i.e. cdmaone or CDMA2000); Support MBSFN (Multicast Broadcast Single Frequency Network) while enabling services such as Mobile TV on LTE infrastructure, which is a direct competition to DVB-H (Digital Video Broadcasting Handheld/Terrestrial) based TV broadcast; PU 2 RC (Per-User Unitary Rate Control) as a practical solution for multi-user MIMO antenna systems, leading to development of LTE-Advanced. The main tasks of implementation of SAE include the total simplification of the system architecture in transition from the existing UMTS circuit + packet switched combined network to all-ip flat architecture. [4] IV. LTE/SAE ARCHITECTURE In comparison with the architecture of 3G-UMTS network, LTE/SAE architecture has no RNC (Radio Network Controller) whose functionalities are partly transferred to enode-b, which becomes an improved base station having connections with the other enode-b base stations (X2 interface) and with the Evolved Packet Core (EPC) network (S1 interface). Circuit switching in the core LTE is not supported; hence, there is no switching center type MSC (Mobile service Switching Center) or MSS (Mobile Soft Switch). Evolved Packet Core (EPC) or SAE core serves GGSN (Gateway GPRS Support Node) for LTE, with the same role as in GPRS network, and also represents a generic controller for non- 3GPP networks. The elements inside EPC and other core network elements are as follows: Serving GPRS Support Node (SGSN) provides connection for GERAN and UTRAN networks; it is the local mobility anchor for UTRAN mobility; PDN (Packet Data Network) Gateway is the permanent IP point-of-attachment access for the UTRAN; it manages IP services such as traffic routing, addressing, security management, provision of access to non-3gpp networks; Mobility Management Entity (MME) manages signaling traffic, authentication and authorization; User Plane Entity (UPE) manages user s data, coding, routing of packet traffic and mobility according to TR ; 3GPP platform manages mobility in 2G/3G networks and LTE/SAE; SAE platform manages mobility for non-3gpp RAT; Policy Control and Charging Rules Function (PCRF) manages charging method and quality of service (QoS). Fig.2. below shows the LTE/SAE architecture which includes relations and interfaces between EPC and other (core) networks according to Rel-8. V. CORE SAE / EPC: ALL-IP (AIPN) In 2004, 3GPP proposed TCP/IP protocol for NGN (Next Generation Network) core and feasibility study on transition into All-IP network (AIPN) was initiated. 3GPP defines IPbased flat architecture as a part of SAE. The LTE/SAE architecture and concept are designed to support the mass usage of IP-based services (high data transmission rates, high response rate, etc). 1242

3 Fig.2. LTE/SAE architecture according to Release-8 The architecture actually represents the evolution of existing GSM/WCDMA packet core network, with simplified operations and with development based on elimination of unnecessary expenses. Such a core network will include IMS and it will be connectable with networks having current standards (2G, 3G), including WLAN, WiMAX, etc. [5] It is important to emphasize that voice services will also use packet core, i.e. packet switching (Voice over IP - VoIP), instead of earlier circuit switching. All-IP network is foreseen to be based on IPv6 protocol, and that all THE services, from voice to multimedia, will be transmitted on the top of IPv6 stack. With introduction of IPv6, instead of existing and widely spread IPv4, service provision will be flexible and scalable from the point of development of this standard (according to IETF). [6] IPv6 will enable an optimal traffic routing, simplified network and transparent mobility. However, it is necessary to choose an appropriate strategy for migration from IPv4 to IPv6. In relevant literature, it is stated that the most suitable method includes allocated data links, for both economic and technical reasons. [7] Introduction of LTE based on IPv6 raises the question of privacy and security, surely slowing down the process of acceptance of new technologies. Operators are aware of advantages of the uniform (IP) infrastructure, convergent communication technology ready for connectivity with different types of customers and systems, but on the other side they are very cautious, having in mind the risk associated with this architecture. Obviously, it is necessary to deal with the following issues: authentication, authorization and monitoring of users, security of infrastructure, protocols, communication and data storage, software integrity, provision of end-to-end QoS, etc. [8] VI. E-UTRAN The E-UTRAN radio interface, according to 3GPP Rel-8 (Evolved-UTRAN, the prefix E is adopted as a common prefix for all developed equivalents of existing UMTS components) [9], will be gradually introduced by UMTS operators during development of their mobile networks. Proposed E-UTRAN system uses OFDMA (Orthogonal Frequency Division Multiplex Access) in downlink, and FDMA in uplink, and technique of MIMO Multiple- Input/Multiple-Output antennas (up to 4 antennas per mobile device). The scheme of channel coding for transmission of blocks is turbo-coding and contention-free quadratic permutation polynomial turbo code internal interleaver. Usage of OFDM system, where allocated spectrum is shared between many different frequency (sub)carriers and each of them carrying a part of a signal, makes E-UTRAN much more flexible, i.e. with a higher spectral efficiency comparing to an old CDMA system which was in 3G networks. [10] LTE also supports FDD and TDD modes of operation. Each mode has its frame structure for LTE, but the modes are mutually harmonized so that the same HW can be used in base stations and terminals, which is cost-effective. TDD mode is harmonized with TD-SCDMA (Time Division-Synchronous Code Division Multiple Access) in LTE. A. Downlink LTE uses OFDM for downlink, fulfilling the LTE requirements for a high spectral flexibility, i.e. for costeffectiveness with multitude of broadband carriers and for high transmission rates. Basically, big radio signal is divided into smaller ones transmitted by different frequency carriers to the receiver. The main advantage of OFDM technique is mutual orthogonality of frequency (sub)carriers, providing a high spectral efficiency (1 bit/s/hz). It means that carriers can be close to each other and interference is, due to orthogonality, almost completely pushed. OFDM is a smoothrunning technology and already used in the IEEE standards a/b/g, , HIPERLAN-2, DVB and DAB. In time domain, radio-frame of 10 ms is divided into 10 sub-frames of 1 ms. Each sub-frame consists of two time slots of 0.5 ms. In frequency domain, the distance between carriers is 15 khz. Twelve neighboring carriers form a resource 1243

4 block, so one block is 180 khz wide. Six resource blocks are equal to the carrier of 1.4 MHz width and hundred resource blocks to carrier of 20 MHz width. The maximum number of (sub)carriers on downlink is 2048 and base stations support 72 (sub)carriers. Increase in the capacity in OFDM networks, i.e. increase in permeability for data transfer, is achieved by means of multiple antennas, both on the sender and on the receiver side. MIMO antennas with associated software for signal processing exactly use the multipath feature of UHF waves spreading. Using OFDM, leakage in signal transmission is also reduced. B. Uplink On the uplink, LTE uses non-coded version of OFDM, linear, called SC-FDMA, Single Carrier FDMA. This type of multiplex approach is a compensation for the shortage of simple OFDM whose ratio of peak and average power (PAPR) is very high. Such PAPR requires expensive and nonefficient, more linear power amplifiers and it all makes the price of terminal higher, with a faster discharge of its battery. SC-FDMA solves this issue by grouping resource blocks, hence generally decreases requests for linearity and power consumption in the amplifier. Lower value of PAPR results in a better coverage and better network performances on the cell edges. The modulations supported on the uplink for data transmission are BPSK, QPSK, 8PSK, 16QAM and also 64QAM. If virtual Multiple Input Multiple Output (MIMO) / Spatial Division Multiple Access (SDMA) technique is used, data transmission rate on the uplink is increased proportionally to the number of antenna elements in the base station. With this technique resources can be reused. VII. SOME ASPECTS OF DEVELOPMENT OF LTE/SAE TECHNOLOGY IN BOSNIA AND HERZEGOVINA There are a few major obstacles related to LTE/SAE as a new technological initiative. LTE/SAE, as the capital cost of some network/operator, is a fraction of the total cost of ownership, so vendor selection for LTE/SAE products is critical for the operator. Operators must be able to assess that products work as advertised during the vendor selection process, which includes all phases of testing, especially if it is expected from vendors to add some extensions to the basic specification in order to differentiate their solutions in the marketplace. That could help the operator to avoid waste of his resources and to verify that LTE/SAE can be integrated successfully into the network. New products and protocols, as they are parts of LTE, are more susceptible to reliability, availability and security issues than the field-proven legacy technology. LTE services must meet, if not exceed, the % gold standard for uptime. Customers are quickly frustrated with poor service quality, which leads to customer churn, an increase in support costs and decreased revenue per user. As operators turn up higher-speed mobile services, the LTE network must support legacy users to protect the current revenue base. Legacy subscribers will be more likely to switch providers if their current service is negatively impacted by the roll out of next generation services and vice versa. [11] It is difficult to give a precise answer on the question when it can be expected for LTE technology to be deployed in Bosnia and Herzegovina. But there are several parameters surely affecting some of network operators to decide to implement this technology. Considering the developed infrastructure in 2G/3G access networks of existing three operators and already widespread 2G access network which provides a high percentage of the territory coverage in Bosnia and Herzegovina, existing mobile operators will for sure have an advantage while deploying LTE technology in terms of implementation period and CAPEX. The general parameters which will influence on the deployment of LTE/SAE technology are determined by the following: development of LTE/SAE technology in terms of its commercial implementation of Rel-8, further development of LTE/SAE technology in terms of standardization through Rel-9 and Rel- 10 (LTE-Advanced), development of LTE terminal equipment, development of enodeb equipment with Software Defined Radio (SDR) and multi-radio technologies, as well as issues of the spectrum usage. The special parameters relate to the particularities of Bosnia and Herzegovina such as: telecommunications market, customer demands, current broadband technologies and related return of investments, development of other technologies from the aspect of releasing frequency spectrum, competition and so on. A. Development of LTE/SAE technology - commercial implementation of Rel-8 After the standardization of Rel-8, which had been accomplished at the end of 2008 with several additions in March 2009, and in the coming period the significant development of LTE equipment for core and access network and related terminal equipment is expected. [12] The first solutions have already been demonstrated by the leading vendors in the field of mobile communications. Also, the first commercial rollouts were announced, so several world leading operators included LTE/SAE technology in their portfolio in However, it might be possible that some child sickness will appear in the first commercial implementations, and that it will take some time until the technology becomes mature. Considering earlier experiences related to implementation period of new technologies in Bosnia and Herzegovina, it would be expected for LTE technology to be implemented in Bosnia and Herzegovina not before This is only an assumption grounded on previous practices, when mature technologies were implemented in Bosnia and Herzegovina after they had satisfied the expectations from the other operators deployments. B. Development of LTE/SAE technology LTE-Advanced During 2009, 3GPP together with ITU-R, has started the activities in terms of creating a new standard for LTE- Advanced access technology to make a part of specifications as described in Release

5 Fig.3. 3GPP and ITU-R standardization process of LTE-Advanced This technology will enable new functionalities and performances for data transmission over mobile networks, such as LTE MBMS (Multimedia Broadcast Multicast Service), Self Optimization Networks, enhancements for VoIP in LTE, utilization of multi-radio and multi-band (MRMB) access techniques, etc. [11] Fig. 3. above shows the LTE-Advanced roadmap. The expected peak access rates will be 1 GB/s for stationary users and 100 Mb/s for users moving with high speeds. Commercial implementations of this technology are expected after Concerning the announced improvements in Rel-9., there is a question whether the shortages of LTE have already been noticed in Rel-8. Referring to the above mentioned, one of the issues of implementation of LTE technology in Bosnia and Herzegovina will be the technological indicators in Rel-8 and Rel-9. We can presume that further development of LTE- Advanced will surely have an impact on the choice of appropriate technology for most operators as were not the starters in deployment of LTE Rel-8. C. Development of enodeb equipment by SDR, multi-radio and multi-band techniques One of the most important factors for dynamics of the LTE technology implementation is the development of base stations in access network with SDR multi-radio and multiband (MRMB) techniques. Most leading manufacturers of mobile technologies have already demonstrated and announced a fast development of base stations with a capability for software definition of access technology in different ranges. This can provide an additional advantage for new mobile operators that have not implemented GSM /WCDMA technologies yet, giving them a flexibility when establishing mobile networks. (Fig. 4.) On the other hand, most existing mobile operators possess earlier implemented GSM/WCDMA network defined only for certain technology, so in the case of maintaining this equipment, the essential effects will not be achieved with SDR technology in LTE. However, existing operators will most likely gradually replace their existing base stations in order to gain additional flexibility with SDR base stations, and to perform a regular upgrade and modernization of expiring access networks. Mobile operators in Bosnia and Herzegovina, during implementation of WCDMA/HSPA technology, have provided base stations which can be upgraded for both HSPA+ and LTE technology. In addition, planned development of HSPA technology will surely involve SDR base stations in coming years, which will make more adequate basis for development of LTE technology. Fig.4. SDR multi-radio and multi-band base station general scheme D. Development of LTE terminal equipment As the world leading vendors of mobile network elements are going to develop LTE equipment for access network and the core, we can expect their parallel activities on development of terminal equipment. It should be emphasized that choice and accessibility of terminal equipment for customers have a significant impact on acceptance of new technology. Earlier experiences have shown that several years passed after new technology has been deployed until terminal equipment was acceptable for different customer demands (choice, price, performances, etc.). [11] Similarly as with base stations, more attention is paid to development of SDR MRMB terminal equipment which should result in more flexible usage, since it is one of customer demands. (Fig. 5.) The LTE modems shown at ITU Telecom World 2009 are still very much in the process of development and will be ready for shipment toward the end of next year, according to vendors. The first phones are then set to arrive in Developing them will not be a trivial matter. For the first generation of devices, the challenges will be as usual - power consumption, size and price. Also, the number of different frequencies that chipsets have to support makes the LTE development process complicated. [13] The market of terminal equipment in Bosnia and Herzegovina in most cases responds to the world trends thanks to distributors as being efficient in updating their offerings. But there still remains an issue of (in)solvency of customers in Bosnia and Herzegovina, which can influence on the dynamics of LTE technology deployment in Bosnia and Herzegovina. E. Market of Bosnia and Herzegovina and demand for broadband services Besides the main benefits of LTE/SAE technology, there will be the possibilities for new services and improvement of quality of current services. Together with well-known broadband services requiring significant permeability (browsing, Mobile TV), LTE technology will enable provision of the following services: real time mobile video services, advertising services and tele-shopping, social networking including Fixed Mobile Convergence (FMC). The market/number of customers of data mobile services in Bosnia and Herzegovina is continually growing. However, penetration is globally below 10% of total number of customers. By deployment of UMTS/HSPA technology and therefore by provisioning of new services, it could be 1245

6 expected to have a further growth of data service users. The peak access rates of 7.2 Mbps/1.4 Mbps will be a new experience for customers of mobile services and it will satisfy the needs of data service customers for a longer period. F. Current development status of mobile technology in Bosnia and Herzegovina With deployment of UMTS/HSPA technology by BH Telecom in May 2009 and plans of the other two operators to deploy the same technology in the following period, a new era of 3G mobile communications has begun in Bosnia and Herzegovina. In the next two or three years, 3G coverage of all urban and suburban areas should be provided with appropriate development of this technology. Since 3G License determines the dynamics of a long-term development of 3G technology, it is certain that each of the three mobile operators in BiH will hardly decide to additionally invest in implementation of LTE technology, until existing 3G technology is implemented to reach a satisfying level. Fig.5. SDR MRMB terminal equipment general scheme G. Frequency spectrum for LTE in Bosnia and Herzegovina The strategy of transition from analogue to digital terrestrial radio transmission (DTT) using the frequency ranges of MHz and MHz was officially implemented in June 2009 in Bosnia and Herzegovina according to [14], so it will have a strong impact on LTE frequency range(s) hold, especially if it is known that 700/800 MHz is suitable from the aspect of propagation and coverage. The authors suggest that this strategy should be re-considered because the primary LTE range in Europe is supposed to be MHz. The frequency range of 2.6 GHz, which is allocated by the license, is free, but propagation features of electromagnetic waves on these frequencies and smaller service coverage zones in relation to 700/800 MHz do not support usage of this range for the new generation of mobile networks. H. Competition Finally, one of the issues that can have an effect on the dynamics of deployment of LTE/SAE technology in Bosnia and Herzegovina, is the competition as present in the field of mobile communications. Introduction of LTE/SAE by one operator will probably influence on the other two operators to decide to deploy it as well, as was a case with previous new technology deployments. Practically speaking, introducing a new technology the operator gains an advantage on the market as is sometimes characterized with customers transition to the network with a new technology offering them additional capabilities. VIII. CONCLUSION Introduction of the LTE/SAE architecture, whose initial purpose was just to enhance the existing 3.5G network, is not only a process of upgrade of that network. It is necessary to construct a new access network, although the existing 2G and 3.5G base station locations can be used, and its associated transmission systems can be partly used. In addition, requirement of the core LTE/SAE architecture for all-ip flat network based on IPv6 is not a transition that can be made overnight. Indeed, in the very beginning it is possible to use the existing resources, but in a long-term perspective, certain changes are necessary in order to provide maximum capacities that will support the requirements of LTE/SAE according to Rel-8. Furthermore, the frequency range (or ranges) for LTE is not completely defined or agreed among the European operators. According to information provided by the Communications Regulatory Agency (CRA), preferred range for LTE on 800 MHz in Bosnia and Herzegovina is not free, and it seems that transition to digital TV will not free the range. In addition to previously mentioned, production of LTE/SAE equipment is only now in full swing in terms of both network elements and user devices, so it is better to wait for some time before starting implementation of the new technology, but it is strongly recommended for all small and mid-size operators to involve themselves in the process of learning and testing LTE/SAE with vendors existing in their networks. REFERENCES [1] The 3GPP website. [Online]. Available: [2] (2008) LTE's spectrum of opportunity, Motorola ezine, Vol2., [Online]. Available: [3] The LSTI Forum website. [Online]. Available: [4] A. R. Mishra, Fundamentals of cellular network planning and optimization, 2G/2.5G/3G... Evolution to 4G, John Wiley & Sons Ltd, 2004 [5] O. Martikainen, Complementarities creating substitutes possible paths from 3G towards 4G and ad-hoc networks, The Research Institute of Finnish Economy (ETLA) [6] O. Martikainen, All-IP trends in telecommunications, The Research Institute of Finnish Economy (ETLA) [7] S.Glumčević, M.Pidro, Transition IPv4-IPv6, Telecommunications, vol. 27, BH TELECOM, Sarajevo, July 2008 [8] I. S. Misra, S. Dey, D. Saha, 4G All IP integration architecture for next generation wireless Internet [9] The 3GPP specifications: 3GPP TS , 3GPP TS , 3GPP TS , 3GPP TS [Online]. Available: [10] H.Holma, A.Toskala, LTE for UMTS: OFDMA and SC-FDMAbased radio access, John Wiley & Sons, 2009 [11] The MyDynamics website. Top Five Barriers to LTE Success, [Online]. Available: [12] A.Scrase, Overview of the current status of 3GPP LTE, ETSI, Barcelona, Feb [13] Mikael Ricknäs, Lack of LTE Devices Worries Operators, October 2009, [Online]. Available: [14] The CRA of Bosnia and Herzegovina website. [Online]. Available: