4 G Backhaul

8/18/2019 4 G Backhaul

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White Paper

Technology Synergies for Small-CellBackhaul in 4G Networks


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2/13 White Paper | Technology Synergies for Small-Cell Backhaul in 4G Networks

Contents

1. Executive Summary 3

2. Evolution of 4G Networks 4

3. Backhaul as a Service 54. The “Unied Macro- /Small-Cell Backhaul” Perspective 5

5. Technology Options for Small-Cell Backhaul 7

6. An Efcient, Synergistic Solution for Small-Cell Backhaul 87. Converged Backhaul Solutions 10

9. Conclusions 11

10. Glossary 12


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1. Executive Summary

The evolution of 4G networks will initially be realized through the LTE transformation of macro cells, andultimately through the deployment of small cells that will increase the size and capacity of the network. Asignicant advantage of the small-cell approach is the low cost of ownership. The associated challenge is toselect an appropriate backhaul solution that would t the small-cell concept, technologically and economi-cally-wise.

This paper examines the available state-of-the-art technologies for small-cell backhaul in the 2 GHz and80 GHz frequencies, namely Point-to-Point (PtP) and Point-to-Multi Point (PtMP). While every technologyexhibits distinct advantages, as well as some constraints, currently, none of them can be considered asgeneralized solution.

However, an optimum solution for the small cells can be achieved by leveraging synergies between twobest-of-breed technologies: PtMP and E-Band PtP. Such a synergy could overcome inherent constraints,with respect to LOS condition availability, and appropriate range / capacity performance, and at the sametime achieve a very low cost of ownership. The cost-per-bit-per-link, as well as the spectrum licensing fees,

could be quite reduced compared to the costs associated with the macro-cell backhaul technologies. Thisis especially signicant considering the fact that a deployment of 2 to 5 small cells – per macro-cell – isexpected in the upcoming years, scaling up the size and expenses of the network.

In this context, Intracom Telecom is a vendor that can offer a wide variety of state-of-the-art backhaul tech-nologies, but most importantly, can leverage technology synergies to establish an optimum solution forsmall-cell backhaul. Since 2009, Intracom Telecom has already adopted and implemented technology andequipment synergy strategies by means of high equipment integration and a unied management system.

This paper is organized as follows:

• Section 2 outlines the evolution path of 4G networks.

• Section 3 discusses the signicant growth in the access domain that is expected with the introduction ofsmall cells. Backhaul infrastructure owners will be able to provide “backhaul as a service”.

• Section 4 introduces the “unied macro-cell / small-cell concept”, which provides an important perspec-tive of how small-cell backhaul systems can be integrated into the existing infrastructure.

• Section 5 provides a comparison of the candidate small-cell backhaul technologies.

• Section 6 proposes a synergistic solution among the best candidate technologies to choose from.Synergies can leverage the advantages of technologies and alleviate any constraints, leading to efcientnetworks.

• Section 7 introduces the “converged backhaul solution” concept, which is referred to small-cell backhaulas an extension of the existing infrastructure.

• Section 8 concludes this paper.


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2. Evolution of 4G Networks

4G Networks, WiMAX and LTE are a reality today with hundreds of operations worldwide. Currently, theinterest is around the trend of LTE, which is about to prevail as the mobile communication standardof the future. Compared to 3G mobile technologies, LTE can increase the mobile network capacity byapproximately a factor of 10, by just achieving much higher spectral efciency, and by adopting higherchannel bandwidth. Inevitably, a rst transition stage toward LTE will involve system and hardwareenhancement, but will not affect the existing cellular structure and size (cell count) of the network.

Forward-thinking people in the wireless communications industry may believe that the 10-fold capacityincrease will soon be expedited. The mobile communication service demands, due to the expectedintroduction of high-bandwidth services (HD video, TV broadcast, video conferencing, etc.), are about to“consume” the capacity premium within the next few years.

Research & Development (R&D) scientists and engineers agree that the next step, following the transitionto LTE, will be to boost network capacity by increasing the number of cells and by re-using the frequencyspectrum resources in a more aggressive manner. However, network economics dictate that the operating

costs associated with macro-cell sites do not allow the proportional expansion of the macro-cellularnetwork, of which design was based on aged 2G/3G technologies. Instead, the deployment of full-outdoor,zero-footprint small cells seems to be a more efcient approach for both increasing the capacity andcontrolling the network economics. Small cells deployed at street / curb locations and on wall surfacesor lamp posts, incur much lower site leasing / power supply / maintenance costs, and at the same timeapproximate – more than ever – the premises of the end-users. The latter implies way better connectivityand increased quality service experience.

A phased 4G evolution approach is presented in Figure 1. The rst phase involves the enhancement ofexisting macro-cell sites with an LTE platform and additional spectrum, not excluding the possibility for aminor increase in cell count. The second phase involves the gradual deployment of small cells. The thirdand last phase refers to the transition to LTE-Advanced, co-jointly with the introduction of new spectrum,both for the macro and perhaps for the small cells.

Figure 1: Architectural evolution of mobile networks in phases

3G+

4G4G+

Future

P h a s e 2 : S m a ll-Ce lls d e p l o y m

e n t

P h a s e 1 : M

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c e l l u p

g r

a d e t o L T E

P h

a s e

3 :

U p g r a t e t

o L T E

A d v

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3. Backhaul as a Service

While the main small-cell business is associated with the expansion of 4G mobile network capacity,

more applications gradually emerge. Local ISPs and small network access providers envisage offeringcomplementary wireless services, either through 3G / LTE / WIMAX technology (leasing spectrum fromprimary holders) or through unlicensed technologies such as Wi-Fi. Small-cell wireless connectivity can bealso used for public / private sector applications (municipalities, utilities/smart-grid, security, etc.). The riseof independent small-cell grid networks, mainly localized to specic areas of economic interest, introducesthe opportunity for a new form of business: “Backhaul as a Service”.

With regard to the radio backhaul options, which in most occasions will be more attractive than wirelinebackhaul options, Backhaul as a Service has a great potential for a variety of businesses:

• Mobile operators with backhaul infrastructure and spare capacity can generate revenues from theirnetwork, which primarily incurs operating costs.

• Local service providers, and PtMP spectrum license owners with corporate access business orientation,

can considerably expand their business in the backhaul service domain.Based on the expected wide spread of small cells, and the forecast for the several-billion worth of thismarket in the next decade, the demand for backhaul infrastructure will linearly grow with the number ofsmall-cells, and hence the potential of Backhaul as a Service is expected to increase signicantly.

4. The “Unied Macro- /Small-Cell Backhaul” Perspective

The small-cell approach poses signicant challenges with regard to the integration into the existing mobile

network, especially when considering a dense deployment: • A small-cell establishes individual service coverage, “inside” the terrain clutter (street-level); however its

footprint coexists with, and/or enhances, the macro-cell footprint.

• The capacity that is locally “injected” by a small cell is actually correlated with the macro-cell capacityand can be used for trafc off-loading. Handover, either for mobility or for trafc off-loading, is a processthat bounds these cells together.

• With respect to a macro cell, small-cell equipment is assigned exactly the same role, hence it establishesan S1 interface toward the evolved packet core and serving gateway. The localized trafc from userequipment, either connected through the small cell or the macro cell, follows the same path toward thecore network.

From a network planning perspective and for optimum network performance, the aforementionedconsiderations clearly indicate that small cells must be considered as an integral part of the macro-celllayer, and not individual and independent domains.

For an existing mobile network, the rst step toward small-cell deployment is the acquisition of appropriatelocations (in terms of permission, space and power supply in lamp posts). The second step is to choose anappropriate backhaul solution that will interconnect the small cell to the existing macro-cell infrastructure.


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The available options for backhaul derive from radio, copper or ber technologies. A diversity of radiotechnologies are available – line-of-sight (LOS), Non-line-of-sight (NLOS), PtP, PtMP – while operatingfrequencies range from 2 GHz to 80 GHz. For exibility, efciency and economical reasons, the vast majorityof small-cell positions can best be reached through a radio link. In case an operator owns copper or ber

infrastructure, in close proximity to the small cell, then these options may also be considered.This paper will focus on the radio backhaul options for small cells. The comparative analysis will elaboratethe concept of a unied macro- / small-cell network, both for access and backhaul domains, basedon current architectures. Therefore, any small-cell backhaul system could reach an existing macro-cellinfrastructure in (up to) two or three “radio” hops.

Conceptually, a unied backhaul network is represented in Figure 2. There is a point-of-presence (centercell), where all the backhaul trafc is aggregated toward the core. Macro-cell trafc is collected by theexisting backhaul infrastructure (for simplicity purposes, a star architecture of PtP radio links is shown onthe left). The radio link architecture can be also ring, repeater, or tree-like, but the star has the advantage ofproviding dedicated link capacity per LTE base station. Most small cells are directly interconnected with thenearby (or the center) macro cell, depending on LOS availability and range, and ideally through a single-hopradio link.

Figure 2: Backhaul connectivity in a consolidated macro- /small-cell network(left: macro-cell Gigabit backhaul connectivity, right: ideal small-cell connectivity).

The above discussed design approach offers a series of advantages:

i) Consolidation of the overall trafc – through all cells – ensuring optimum quality of service.

ii) Minimization of the small-cell backhaul network hops (and hence improved economics). iii) Minimization of the propagation of signalling (i.e. X2) for mobility and trafc handovers and self-

network optimization.

Macro-CellLayer

Small-CellLayer

Aggregation PoPLTE BS

Macro-Cell BackhaulSmall-Cell Backhaul


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5. Technology Options for Small-Cell Backhaul

Looking back in Figure 2, all small cells are shown to be “ideally” interconnected one-hop-away to the

nearby macro cell. In terms of scalability, the backhaul link count (per small cell) must be reduced downto one, ultimately. At this point, an important question arises: being within the terrain clutter, how easyis to establish the essential LOS connectivity to the closest macro cell and within the existing backhaulinfrastructure? Reality veries that, in several occasions, the direct path will be blocked by terrain orclutter and an alternative solution may be required. Keeping this in mind, Table 1 presents the mainradio technology options for small-cell backhaul, listed by frequency band order. Furthermore, the mainadvantages and constraints per technology are outlined.

The rst technology option involves PtP / PtMP radio systems operating in the 2 GHz to 6 GHz range(licensed and unlicensed bands). Their main advantage is the NLOS radio connectivity, which wouldconsiderably facilitate small-cell deployment. Recently, these technologies have been enhanced with MIMOtechnologies that can potentially double link capacity. The main constraint for such options is the limitedavailable spectrum. Obviously, it would be a great risk to consider the unlicensed bands, which are also

used from Wi-Fi access points. In many occasions, the remaining spectrum is being used by WiMAX systems(operating in frequencies between 3.3 GHz and 3.8 GHz) and is considered very costly. Hence, a limitedchunk of (TDD) spectrum, in the range of 40 MHz for instance, would be sufcient for a nominal 200 Mbit/s(half-duplex) radio link (PtP) or sector (PtMP), but an aggressive frequency re-use is not possible. This isbecause the NLOS propagation, which is based on signal reections, could create signicant interferenceamong adjacent radio links. For a PtMP sector, the 200 Mbit/s capacity is only suitable for two or three LTEsmall cells, while three or four 40 MHz TDD channels are required for a tri- / quad-sector PtMP setup. Also,in practice, the NLOS condition results in signicantly-reduced capacity compared to the nominal values.While such technology can be recommended on certain occasions, it cannot be considered as scalableenough to support the small-cell concept.

MW PtP systems, typically operating between 18 GHz and 42 GHz (in urban areas), are considered amature and technologically-advanced option. However, such systems have higher incurring costs due to

their advanced technology that has primarily been developed for macro-cell backhaul. Even when pricesconverge to an acceptable level, with respect to the price of a small-cell, there are other factors that renderthem as a less attractive solution:

i) The higher frequency bands are already over-utilized.

ii) The ETSI / FCC compliance of such systems impose a minimum antenna size, hence a minimumform-factor.

Being a carrier-grade backhaul option and more technologically-advanced, such MW PtP systems are ratedhigher than sub-6 GHz systems.

Frequency RadioInterface

Main Advantages Main Constraints Solution Rating

Sub-6 GHz PtP / PtMP NLOS, low-cost Limited spectrum,interference sensitive,non carrier-grade

18-38 GHz PtP (Nodal) Main macro-cell backhauloption

Congested spectrum, LOS

26 / 28 GHz PtMP Backhaul optimization,low-cost

LOS, spectrum availability

60 GHz (unlicensed) PtP Extremely low cost-per-bitsolution

LOS, very short hop

70 / 80 GHz (E-Band) PtP New spectrum, Gigabit,low-cost

LOS, short hop

Table 1: Small-cell radio backhaul options; rating denotes t to the small-cell concept

from technological, economical and practical perspective.


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For the last decade, PtMP systems operating in the 10.5 / 26 / 28 GHz bands have successfully beendeployed for 2G/3G backhaul applications. Such systems represent an interesting case, as they match thesmall-cell backhaul economics better than MW PtP systems. Currently, a PtMP sector can achieve morethan 314 Mbit/s (full duplex), which is sufcient for 3G/LTE small-cells. The radio resource sharing nature of

PtMP, which matches the bursty prole of LTE trafc, can accommodate several small cells per sector, whilea base station can be deployed with only two 56 MHz channels. The major advantage of PtMP is the per-channel frequency license, instead of the per-link of MW PtP. Hence, as the small-cell density increases, thebackhaul cost decreases, equipment and license-wise. Compared to sub-6 GHz PtMP systems, superioritycomes from the higher capacity, carrier-grade nature, spectrum availability and considerably-lowerspectrum licensing.

E-Band PtP solutions operating in the 60 GHz (unlicensed) and the 70 / 80 GHz (licensed) bands, attractquite attention as well. Due to the distinct propagation characteristics, such as the extremely-high path loss(atmospheric and rain attenuation), 60 GHz systems can establish links of up to 600 m range. Despite theirshort-haul nature, such systems present unique advantages inclusive of: no need for spectrum license,very compact prole – they can be “invisible” on lamp posts – and a cost-per-bit ratio equivalent to thatof a small cell. The 60 GHz systems are a more suitable solution for within-clutter radio backhaul, i.e. for

connecting adjacent small cells along a street. The 70 / 80 GHz systems are full-edged PtP solutions,especially suitable for Gigabit macro-cell backhaul deployments. They can operate on higher channelbandwidths, but under a light-licensing scheme that considerably reduces the spectrum fees compared toMW PtP systems. The larger form-factor and the specications of such systems allow ranges of up to 3 km.

Balancing the advantages and the constraints of the available technologies, one can conclude that thereis no “killer” option. Inevitably, technology synergies will be deemed necessary to achieve a generalizedsolution and a viable strategy for small-cell backhauling.

6. An Efcient, Synergistic Solution for Small-Cell Backhaul

In the current telecommunications business environment, network economics is a very important aspect.In fact, the evolution of 4G networks, through the deployment of small cells, is mainly justied by a lowcost of ownership (cost-per-bit) for the access segment. The technologies that exhibit lower costs in Table 1(equipment and spectrum licensing-wise) seem as the obvious options. In this context, 26 / 28 GHz PtMPand 60 GHz PtP systems are winners, albeit with the constraint of LOS operating condition.

“Technology synergies, co-jointly with a “smart” network planning approach, can overcome the LOSconstraint and constitute a generalized and efcient solution for small-cell backhaul applications.”

The concept is visualized in the preceding Figure 2 (on the right). As already explained, the minimization ofradio link hop count has instant impact on network economics. The radio planning objective is to achieve asingle-hop radio connection to existing infrastructure:

i) Ideally toward the aggregation point, or alternatively

ii) toward the nearby macro / small cell.


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Phase 1: Planning for the Overlay Single-hop Links

Selecting PtMP as the primary small-cell backhaul technology, the entire macro region can be covered by asingle base station, strategically placed at the aggregation point. In real networks, a careful deployment ofthe PtMP base station can achieve LOS visibility to the majority of the desired small-cell locations, typically

at a percentage of 50% to 70%. Anyway, the expected small-cell footprint range from 100 m to 300 m,which, from the radio planning perspective, provides some exibility with regard to the selection of theappropriate location (lamp post or building), i.e. exibility that could satisfy the LOS backhaul condition.The main advantages of a quad-sector PtMP system are:

i) Single-hop approach.

ii) High scalability (up to 20 small cells per base station).

iii) High reliability (protection at the base Station).

iv) Minimum footprint at the aggregation point.

v) Less operation and maintenance.

A new PtMP terminal, which is about to serve a small cell, can be deployed without visiting the PtMP basestation. In the Figure 3 below, the PtMP backhaul links are denoted with blue lines:

Figure 3: Synergies between PtMP and 60 GHz E-Band technologies result in a exibleand cost-efcient solution for small-cell backhaul.

Phase 2: Planning for the Underlay Links

Deploying LOS backhaul for small cells heavily depends on the network design exibility. When directsight with the PtMP BS is impossible, there exist additional connection points with existing backhaulinfrastructure, i.e.:

i) the surrounding macro cells, or

ii) the adjacent small cells.

Where a LOS condition, between a small cell and the overlaying macro cell, can be achieved, the 60 GHzunlicensed PtP system is an excellent choice that offers minimum incurring costs and zero spectrum fees.Single-hop 60 GHz PtP links are denoted with red lines in Figure 3.

Link

60 GHz1st Hop

2nd Hop

Base St.PtMP

Small-CellLayer


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Small cells are deployed primarily in urban areas where the inter-cell distance among macro cells is veryshort. The range between two backhaul connection points will be considerably shorter and will becomefurther shorter as more small cells are deployed. PtP systems operating in the unlicensed 60 GHz band arealso used to interconnect adjacent small cells, or to provide redundancy, as shown in Figure 3 (and denoted

with magenta and brown lines respectively).Based on what discussed so far, technology synergy not only overcomes the LOS constraint, but also allowsfor exible network architecture. The proposed PtMP / E-Band synergy solution offers distinct advantagescompared to all the other solutions presented in Table 1:

i) More probabilities to achieve LOS between a small cell and an “appropriate” connection point, comparedto any other individual solution. Hence, this specic solution can be considered as generalized or “all-rounder”.

ii) Lower cost of ownership compared with the costs of all other individual solutions.

iii) Future-proof radio link performance in urban environments, where the macro regions are small-sized,and with respect to the requirements for 4G networks. Above all, this performance is achieved with verycompact form factors, which is also essential.

With regard to systems operating in sub-6 GHz frequencies, the proposed solution employs eld-proventechnologies. LOS systems can sustain true link availability, immunity to interference, easy radio planning,and most importantly, predictable capacity. Overcoming the LOS constraint through the proposedtechnologies and by using smart network design, maintains the same backhaul philosophy, which is usedfor the macro-cell layer.

7. Converged Backhaul Solutions

The major part of the backhaul networks is located in urban areas, with the last-mile links representing atypical percentage of 25% to 55%. The majority of small cells will be deployed in such locations, hence,the backhaul network will further concentrate. The 4G mobile network evolution dictates that backhaultechnologies, architecture and products should be capable to evolve toward “smart and efcient, close-space connectivity”.

The backhaul architecture is about to experience signicant transformation:

i) Fiber infrastructure will gradually expand and dominate the transport and aggregation part.

ii) Radio backhaul will be used for one or two hops and mainly in the last mile.

iii) The radio link distance will be shortened, while link density will vastly be increased (especially with thesmall cells).

iv) Radio hop capacity will reach the Gigabit milestone.Considering the aforementioned facts, the concept of a regional aggregation point, serving several macrocells and the associated small cells, is probably the architecture that will dominate in future 4G networks.Such an approach imposes for converged backhaul solutions employing the majority of technologies listedin Table 1. Intracom Telecom has already evolved its R&D strategy toward this direction and has establisheda mature portfolio that covers all the technological, specications and form-factor perspectives.


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The company proposes a converged solution that is intended for the 4G network evolution and which it hasexcellent performance characteristics and very low cost-per-bit. This highly-integrated solution perfectlymeets the localized network requirements through the best-t technology / system, presenting thefollowing advanced options:

• The radio subsystems of the backhaul products are re-engineered to all-outdoor form factor. Theobjective is to minimize the footprint, the cost of ownership and get in line with the LTE equipmenttrends. The corresponding Intracom Telecom product lines are OmniBAS-XR (6-38 GHz) and UltraLink (60 / 70 / 80 GHz).

• The PtMP solution is evolved on a carrier-grade base station architecture, for increased reliability, and onfull-outdoor compact terminal stations. The corresponding product line is WiBAS (10.5 / 26 / 28 GHz).

• When it comes to the aggregation of multiple full-outdoor radio units, Carrier Ethernet, telecom-gradeindoor units are provided. The proposed Converged Backhaul and Aggregation Node is fully compatibleand future-proof with upcoming Ethernet and IP technologies. The corresponding product line isOmniBAS-8W /-4W /-2W.

• All radio products and aggregation nodes are managed through a unied management system, uni|MS ,which contributes to the high end-to-end integration. In fact, any type of backhaul network (tree / star,ring, mesh, or hybrid) can be seen as a unied Carrier Ethernet domain, where different products andtechnologies co-exist, sharing the same performance and management principles. Subnetworkconnection management can be established and optimized in just a few steps, from a single NOCposition.

• A core radio planning team, with vast expertise in all backhaul technologies, can assist in choosing theproper technology, while providing optimum network design.

The “unied backhaul solution” ts the single–RAN (Radio Access Network) concept, which has beendeveloped for mobile technologies and has become a trend for all new macro-cell sites. In the proposedunied solution, all technologies are available in a modular platform, and hence, operators have unlimitedoptions to design their networks.

8. Conclusions

Small cells are expected to dominate the evolution of 4G networks, opening a whole new business in thetelecommunications industry. A signicant success factor, however, is the provisioning of an appropriatebackhaul solution that would integrate the small cells into the existing network infrastructure.

The small-cell backhaul concept was thoroughly analyzed in this paper, from various perspectives. Acomparison of candidate backhaul technologies revealed the main advantages and constraints, and itwas shown that no individual option can be considered as an appropriate and generalized solution. Onthe contrary, technology synergies can combine the advantages and alleviate the constraints, leading tooptimum solutions.A synergistic solution can be established with the combination of PtMP and E-Band PtP backhaul options.These technologies have similar performance characteristics and are both very attractive from a techno-economical perspective. The proposed solution consists exclusively of Intracom Telecom product lines andcan achieve optimum backhaul performance, fast and friendly network design, and most importantly, canminimize the equipment investments and spectrum fee operating expenses.

With a mature product portfolio and a signicant track record, Intracom Telecom is a leading vendorthat can realize the “converged backhaul solution” concept, proposing an optimum small-cell backhaulapproach. Since 2009, Intracom Telecom has introduced technology “synergies” in its corporate strategy.All the company’s current product lines are designed to leverage this value toward smart highly-valuedbackhaul solution offerings.


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9. Glossary

HD High Denition

ISP Internet Service Provider

LOS Line Of Sight

LTE Long Term Evolution

MIMO Multiple Input Multiple Output

NLOS Non Line Of Sight

NOC Network Operations Center

PtMP Point-to-Multi Point

PtP Point-to-PointRAN Radio Access Network

TDD Time Division Duplex

WiMAX Worldwide Interoperability for Microwave Access


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02- 2 01 2

www.intracom-telecom.com

All information contained in this documentis subject to change without prior notice.© 2012 Intracom S.A. Telecom Solutions

Intracom Telecom Regional Contacts

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America11360 Technology CircleDuluth, GA 30097USAtel.: +1 770 295 2500fax: +1 770 295 [email protected]

Middle East & AfricaBuilding No. 3 Office No. 204P.O. Box 500517, DubaiInternet City, DubaiUnited Arab Emiratestel.: +971 4 362 5666fax: +971 4 390 [email protected]

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