Mobile RAN v2 An

Application Note

Growing and Evolving the Mobile RAN Using Highly Scalable Aggregation

This document, which refers to Alcatel, was issued prior to our merger.It has not been modified to refer to Alcatel-Lucent since it is part of our archives.

ABSTRACTMobile wireless network capacity requirements are increasing, partly in response to increased subscriptions but also due to high-speed 3Gservice rollouts. Radio access networks (RANs) are generally increasingin their bandwidth needs and also constantly being re-engineered asnew cells are deployed. The need for a manageable, scalable andinvestment-protected RAN infrastructure is evident.

This paper describes the use of the Alcatel 7670 Routing SwitchPlatform (RSP) in a centralized aggregation role efficiently supportingthe evolving UTRAN. In particular, the crucial role of the Edge ServiceCard is highlighted. As this paper also shows, the 7670 RSP can supportother valuable roles in the MTSO, enabling the efficient interconnectionof mobile network elements. With the powerful and intuitive managementcapabilities supported by the Alcatel 5620 Network Manager (NM),highly efficient configuration and rebalancing of RAN transport ispossible for rapid, cost-controlled service delivery.

This is a field-proven approach with numerous large mobile operatorsenjoying the benefits of Alcatels resilient and scalable aggregationsolutions in their rapidly growing and evolving RANs.

TABLE OF CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Market Conditions and Business Drivers . . . . . . . . . . . . . . . . . 1

Mobile Operators Requirements of the RAN . . . . . . . . . . . . . 2

Radio Access Network Architectural Overview . . . . . . . . . . . . 2

The Alcatel Solution for Centralized Mobile Aggregation . . . 5

Centralized Aggregation of Node B Traffic . . . . . . . . . . . . . . . . . . . . . 5

Multiple Roles within the MTSO . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

A Complete View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Hybrid Centralized/Distributed Aggregation . . . . . . . . . . . . . . 8

Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Introduction

The market for mobile services continues to grow withnew multimedia data services being offered in maturemarkets such as Western Europe, Japan, Korea andUnited States, and traditional voice services gainingstrong momentum in emerging markets, such as Indiaand Africa. China, in particular, is a huge potentialmarket for growth in subscriptions, traffic and networkinfrastructure supporting modern 3G services. As trafficlevels grow the impacts are keenly felt in the radio accessnetwork (RAN) traffic from existing cells increases,new cells and sectors are deployed and heavily loadedcells are split. In turn, this dynamic environment hasimpacts on the transport architecture where strong growthand dynamic re-engineering are the norm.

The combination of the Alcatel 7670 Routing SwitchPlatform (RSP) and the Alcatel 5620 Network Manager(NM) provides a massively scalable, resilient solution thatis field-proven in deployments of 3G R99/R4 and convergedaccess networks. The versatility of this solution andcontinued development by Alcatel ensures investmentprotection as 3G R5/R6 IP and Ethernet-centric RANs are deployed.

Market Conditions and Business Drivers

The forecast for overall mobile subscriptions andespecially traffic is steady growth through to 2010* at least. While 2G base transceiver station (BTS)deployment and traffic will see some leveling off duringthis period, 3G traffic will likely be a key growth area. As shown in Figure 1, while the 3G Node B populationsees moderate growth, the traffic volume generated bythis deployment will increase more steeply, triggered by bandwidth-intensive service enhancements such ashigh speed downlink packet access (HSDPA) and widelyavailable, media-rich applications enabled by the IPmultimedia subsystem (IMS).

The amount of packet-switched data traffic will increaseand eventually exceed the volume of voice traffic by about2009*. Despite this, it is likely that the voice averagerevenue per user (ARPU) will remain the dominant factorin overall ARPU. There is a pressing need for efficientbackhaul transport to maintain operating margins as datavolume increases.


A L C AT E L > 1

600,000

400,000

200,000

0

1,200,000

1,000,000

Num

ber of Base Stations

Traffic

(Gb/

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800,000

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2,000,000

1,720,6931,708,4101,674,2841,606,0321,523,2031,423,2421,303,4401,116,974

7,0002G BTS Footprint (Saturation)

Traffic Growth Drivers:> Edge, HSDPA, IMS

3G NodeB Footprint (Moderate Component)6,000

1,800,000

1,600,000

3,000

2,000

1,000

0

5,000

4,000

Total in-service 2G BTS

2004 2005

2G vs. 3G BS andTraffic Growth

2006 2007 2008 2009 2010 2011

941,784921,475860,492738,526594,279434,350292,147174,455Total in-service 3G NB

3476.23453.63385.73240.02769.82299.71845.61554.0Traffic Demand from 2G BTS

6172.85259.84238.22989.11956.11227.0671.1330.9Traffic Demand from 3G NB

2G Traffic (Leveling off)3G Traffic (Key Growth Component)

Figure 1 - Projected 2G and 3G Traffic Growth

As service providers invest to enable 3G migration,they must also invest to control their cost structure sothat they can remain on a viable financial footing. In par-ticular, intelligent investments in the RAN can help tocontrol operationing expenditures (OPEX) and also pavethe way for 3G migration. The costs associated with trans-mission, transport and network and service managementin the RAN are among the main contributors to OPEX.Even if OPEX is not a primary constraint, an effectiveRAN aggregation solution can streamline and simplifyengineering and maintenance procedures, which can greatlyreduce the number and duration of network outages.

Mobile OperatorsRequirements of the RAN

The following list captures the main requirements of the RAN as seen by mobile service providers:> Powerful network and service management for rapid

and scalable installation, provisioning, re-engineeringand repair to support subscriber growth andincreasing bandwidth requirements from the cell siteto the mobile telephone switching office (MTSO)

> High availability and service quality to encourage user loyalty and attract additional traffic

> Efficient asset utilization, especially of ports in theMTSO on mobile network elements such as the radionetwork controller (RNC), serving GPRS support node (SGSN), mobile switching center (MSC), etc.

> Ability to evolve smoothly as newer transporttechnologies become available (e.g., in moving fromR99/R4 UMTS terrestrial radio access network [UTRAN]to R5/R6) with a corresponding rise in the usage of IPand Ethernet (and potentially multilink point-to-pointprotocol [MLPPP])

> A streamlined and simplified network that can supportmultigenerational access via simultaneous support forTDM, ATM (with inverse multiplexing over ATM [IMA]),Ethernet and IP as the access network evolves

> Reduced OPEX for leased transport through efficientand scalable grooming and aggregation

> Strong quality of service (QoS) capabilities for packetaggregation solutions to differentiate traffic flows andto ensure that delay-sensitive traffic characteristics are respected without compromising the economics of statistical gain

> The availability of fully verified and field-provencomponents in an end-to-end mobile services solutionto minimize integration and interoperability challenges

Radio Access NetworkArchitectural Overview

Figure 2 shows a high-level view of the 2G/3G mobilenetwork architecture.

The subject of this paper is the RAN, which links andbackhauls traffic between the radio air interface equipmentand the core network(s). Figure 3 shows the networkingtopological landscape in the RAN at a high level.

In practice, many variations and combinations oftransport media, networking protocols and grooming and aggregation devices will co-exist. A brief summary of the deployable functionality in the cell site, the hubsite and the centralized (MTSO) site follows.

In the cell site there are opportunities for compactdevices that can converge multigenerational trafficstreams and/or adapt legacy base station interfaces ontomodern transport infrastructures (e.g., 2G TDM Abisonto Ethernet). Another possible application in the cellsite is to link a small cluster (or string) of base stationsand groom or aggregate traffic to reduce backhaul costs.

The distributed hub stage is seen in some networks,particularly where backhaul bandwidth is scarce and/orcostly. This device typically performs an aggregationfunction to benefit from statistical gain (see sidebar).

The deployment of centralized grooming andaggregation is particularly effective in controlling costs(e.g., via reduced ports into the RNC) and greatlyimproving the manageability of the constantly evolvingRAN as a whole. The location of the device in the MTSO(where operational skills are likely to be available) isadvantageous from an operations and maintenance pointof view. In practice, devices are often deployed in variouscombinations in cell site, hub and central locations indifferent zones in the network.

The balance of this document primarily examines a centralized ATM Layer 2 aggregation solution as themost effective approach in environments where there ismoderate to good availability of TDM bandwidth betweenthe cell site and the MTSO, for instance via an extensiveSONET/SDH build-out. Note that the deployment of acentralized aggregation capability does not in any waypreclude co-existence of a hub or cell-site device. Theseapproaches are complementary in nature.


2 < A L C AT E L


A L C AT E L > 3

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Figure 6 - The 7670 RSP in a Centralized Mobile Aggregation Role

spread across the IMA bundle of T1s or E1s that havebeen provisioned for this site. The multiservice nodeterminates the ATM IMA protocol and switches the VP towards the appropriate RNC in the MTSO. Twoimportant things have happened in this process:1) The ATM traffic is presented to the RNC via a fat

pipe (i.e., a simple, relatively inexpensive non-channelized port). The capacity of this connection can be OC-3/STM-1 or even OC-12/STM-4 or greater.

2) The traffic has been aggregated and statisticallymultiplexed so that the utilization of this fat pipe is very efficient.

The total bandwidth required between the multiservicenode(s) and the Node Bs can exceed the bandwidthbetween the multiservice node(s) and the RNC by asignificant factor. This is known as the statistical gainallowing for significant savings in RNC port costs.

A number of attributes of the 7670 RSP in combinationwith the ESC contribute to the success of this centralizedaggregation arrangement. These attributes are exploredin later sections of this document.

Powerful and scalable architectureThe combination of the Alcatel 7670 RSP and the ESCallows massive scaling in a centralized aggregation roleand greatly simplifies the operational processes as the RAN grows and is constantly re-engineered toaccommodate that growth.

As shown in Figure 8, growth and change in the RANcan be easily accommodated. The traffic from any T1/E1in any IMA bundle from any cell site can be connected toany RNC. This can be accomplished via simple point-and-click provisioning where the use of a less scalable devicewould actually require physical connectivity reconfigura-tion. The flexibility of the Alcatel multiservice nodesolution results in significant OPEX savings. Even if OPEXis not a major constraint, this capability ensures that re-engineering is rapid and not prone to errors, resulting in better overall availability for the mobile network.


6 < A L C AT E L

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NBAP (AAL5)ALCAP (AAL5)OAM (AAL5)Sync (AAL2)

n*User Data (AAL2)

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Figure 7 - 3G UTRAN Iub Aggregation Solution

Cell Site

Cell Site

Cell Site

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Figure 8 - Any T1/E1 in Any Bundle to Any RNC

The Alcatel 7670 RSP offers scalability to 320 Gb/sbidirectional user I/O. Full automatic protection switching(APS) is supported for rapid recovery under failure con-ditions. Interfaces from T1/E1 to OC-48/STM-16 and GigabitEthernet can be supported with full IP/MPLS for bothUTRAN and core evolution if needed. This offers tremen-dous insurance against future anticipated growth in theUTRAN. Some equipment vendors may try to emulatethis scalability by meshing platforms together in clusters.This approach has a number of disadvantages includingthe waste of bandwidth and ports in supporting meshinglinks. Also, element management systems will usually seethese discrete meshed nodes as multiple individual devices,adding to management and engineering complexity.

The Edge Services CardWhen it comes to high-density aggregation of Node B(Iub traffic) over ATM, the Alcatel 7670 RSP offersunprecedented density, scalability and future-readinessin its Edge Services Card (ESC). The ESC was created to meet the most stringent criteria for cost-effectivenessby offering the best price/bandwidth ratio on the marketwhile addressing the very important issue of being future-ready, with support for feature evolution towards IP. The ESC uses an 8-port OC-3/STM-1 I/O card, andsupports both unchannelized and channelized interfaces.With channelization supported down to the T1/E1 leveland the ability to fully and flexibly support 672 DS1s(504 E1s in SDH version) and up to 336 IMA groups on a single card (336 HSPA Node Bs), the ESC deliversindustry-leading scalability, delivering more than 16,000DS1s per system.

In cases where centralized aggregation needs toencompass more than six to eight OC-3s/STM-1s, thedeployment of the Alcatel 7670 RSP and the ESC providestangible and measurable benefits versus competing solu-tions. High-aggregation ESC deployment scenarios inwhich the role of the 7670 RSP is augmented with furtheroptimization of bandwidth utilization on OC-3/STM-1interfaces towards RNCs (Iub and Iur) can result incombined savings up to 25 percent on transport costsand RNC interfaces over non-optimized scenarios.

In Figure 8, one such example of centralized mobilehigh aggregation is shown with the illustration of theflexibility of Node B to RNC assignment control. TheAlcatel 7670 RSP and its ESCs terminate VPs from alarge number of Node Bs and deliver the traffic to adjacentRNCs via a smaller number of interfaces. In addition toIMA/ATM traffic coming from Node Bs (see Figure 7), the ESC can support feature evolution towards scenarios

in which Node Bs are IP-capable and are encapsulatingtraffic in IP for transport purposes.

The ESC extends the robust set of carrier-gradefeatures of the 7670 RSP (full redundancy, non-stoprouting, non-stop switching) by offering three levels of protection: line protection (APS), card protection(EPS/LCR) and service-level protection (non-stop IMA)and thus makes availability targets of 99.999 percent an achievable reality.

Efficient and intuitive network managementMany network management tasks are simplified by thedensity and scalability of the Alcatel 7670 RSP multiservicenode in combination with the Alcatel 5620 NM. A singlemanageable element in most MTSOs (rather than a meshedcluster) lessens the burden on the operations supportsystem (OSS) and the operations staff. The Alcatel networkand service management portfolio enables the addition of new services while reducing network operations costs.Distinguished by its open architecture, scalability, reliability,and flexibility, the industry-leading Alcatel 5620 NMempowers network service providers to add new serviceofferings without the overhead of introducing new manage-ment systems and retraining staff. These capabilities alsolead to lower overall operating costs, reduced provisioningtimes and greater efficiency in the use of the networkinfrastructure. Management functions span fault, configu-ration and performance management, and accountingand security functions.

The 5620 NM platform provides clear and intuitivecapabilities for provisioning, troubleshooting, repair andreporting. The fully evolved multiservice capabilitiesdelivered by the 7670 RSP support all of the necessaryon-network operations, administration and maintenance(OAM) capabilities to allow efficient and responsivenetwork and service management. It is important to notethat network operations personnel do not need to possesa high-level knowledge of the protocols operating in thenetwork. The 5620 NM can abstract the ATM/IP/MPLSnetwork via powerful tools and interfaces into a simple,intuitive connectivity model that minimizes operatorerror and maximizes efficiency.

Full support for common management informationprotocol (CMIP), common object request broker architec-ture (CORBA) and simple network management protocol(SNMP), which is essential if a platform is to be managedwithin a carriers existing OSS environment, is also provided.

The Alcatel 5620 NM enables mobile carriers to cost-effectively provide a complete management solution for the network. It supports real-time provisioning,


A L C AT E L > 7

Scenarios in which all traffic is backhauled to from cell sites without aggregation and traffic optimization. Result based on internal business case study. Details available upon request.

centralization of management functions, network tuningto optimize the use of network resources, and rapid faultisolation to reduce network downtime.

Key benefits of the Alcatel 5620 NM include:> End-to-end visibility and control of the network> Manual and automated provisioning of connections

and services> Easy identification of available resources in the network> Visual representation of resources based on their

relationships and geographical locations> Auto-discovery of equipment changes and network

re-configuration> Equipment upgrades performed remotely via software

downloading> Manual and automated Node B to RNC re-parenting > Real-time equipment, network and statistics monitoring> Customized, graphical real-time reports> Fault reporting, isolation and recovery> Remote diagnostics and troubleshooting> Integration with third-party equipment and applications> Integration with other network and service management

systems > Open interfaces to OSS/BSS

MULTIPLE ROLES WITHIN THE MTSO Within the MTSO, the Alcatel 7670 RSP can carry out a number of other value-added functions in addition toits role in Iub aggregation. The platform is ideally suitedto the aggregation of various interfaces in the MTSOincluding the Iur (the interface between RNCs), the Iu-cs(the interface that carries circuit-switched voice) and theIu-ps (the interface that carries packet-switched data).The intent is to get a more efficient (higher) utilization of physical interfaces and ports on costly mobile equip-ment (e.g., RNCs and MSCs). This has the potential toreduce CAPEX in the MTSO as fewer ports are necessaryin all interconnected elements. Figure 9 shows the role of the 7670 RSP in carrying out these functions.

A COMPLETE VIEWA number of roles have been described for the Alcatel7670 RSP both in the RAN and deeper in the mobilenetwork. Figure 10 shows a graphical summary of thesecapabilities, illustrating clearly the versatility of the 7670 RSP multiservice node and emphasizing the reasonswhy it has been widely deployed in some of the worldsmost extensive mobile networks.

Hybrid Centralized/Distributed Aggregation

This paper deals primarily with Layer 2 centralizedaggregation Layer 2 aggregation via a platform locatedin the MTSO. This approach is generally well suited tocarriers who are not particularly constrained in theiraccess to backhaul bandwidth. However, some largecarriers operating over a diverse geographic and economiclandscape may have different operating environments indifferent parts of their network. While TDM bandwidth maybe plentiful in some areas, in others it may be expensiveand/or scarce. Alcatel has significant experience in atiered aggregation approach and has a number of productswell-suited to deployment both in the cell site and atintermediate hubbing points.

Evolution

The Alcatel 7670 RSP is in a powerful position in itsclass, with both a full-featured ATM capability as well asthe benefit of significant and continuing investment in IP,Ethernet and MPLS capabilities. The pace of innovationin mobile networking is rapid and any deployed productsmust carry the versatility and continued investmentrequired to remain a viable platform. Ethernet transporthas attractive price points and will increasingly be seenin various transport roles, particularly in metro areas.Alcatel is committed to converged, IP-centric networkingfor deployment where it is technically and economicallyadvantageous to the carrier. Investments continue toenable this in many product areas.


8 < A L C AT E L

RNC

RNC SGSN

MSC/MG

Iups

Iur

Iucs

Figure 9 - Additional Networking Capabilities within the MTSO

Summary and Conclusions

Mobile operators are seeing strong traffic growth. Constantre-engineering in the RAN is required and must be efficientfor business success as more radio cells (and more accessbandwidth per cell) are deployed. The Alcatel 7670 RSPscales to 320 Gb/s with best-in-class 5620 NM manage-ment for point-and-click adds, moves and changes, and also advanced diagnostic, accounting and servicemanagement tools. Capacity and topology changes thatwould be highly disruptive and potentially error-prone on other architectures and platforms can often be fullyaccomplished from an operator console in an accurateand timely fashion. Many equipment vendors requiremultiple node configurations to approach 7670 RSP scaling.This leads to complex management and wasted meshinglinks, where growth can often require new chassis andcomplex link reassignments.

Continuous investment in a modern multiserviceplatform has created the broadest and deepest protocolsupport in its class. Consolidation, grooming and trafficmanagement can be delivered across the range of intra-and inter-MTSO interfaces (e.g., Iur, Iu-cs, iu-ps, Gn, Gp,Gr, Nb).

Independent lab testing is available to demonstrate theclass-leading non-stop routing and signaling capabilitiesof the platform. Many competing platforms implementlink and equipment resiliency mechanisms such as APSbut their architecture often does not permit true, hitlessservice resiliency outages still happen under manyfailure conditions.

The flexibility of the Alcatel 7670 RSP is unrivalled in this space. As varying access media and mechanismsbecome technically and economically attractive, theplatform can adapt to support them. The dual controlplane architecture enables simultaneous Layer 2 andLayer 3 services support and is a major differentiator in this class.

The Alcatel 7670RSP is deployed with over 110 multi-service carriers globally and in the networks of manymajor carriers deploying the platform in a RAN aggrega-tion role. In these networks the platform interoperateswith radio network elements from Alcatel and from allother major wireless equipment vendors.

The experience gained in these deployments allowsAlcatel to be a strong business and technology partnerwhen deploying a successful end-to-end solution.


A L C AT E L > 9

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NodeB

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4. Iu-ps Switching

Figure 10 - Multiple Roles for the 7670 RSP

Abbreviations

APS automatic protection switchingARPU average revenue per userATM asynchronous transfer modeBSC base station controllerBTS base transceiver stationCAPEX capital expendituresCMIP common management information protocolCORBA common object request broker architectureEPS equipment protection systemESC Edge Services CardGPRS general packet radio serviceGSM global system for mobile communicationsHSDPA high-speed downlink packet accessIMA inverse multiplexing over ATMIMS IP multimedia subsystemIP Internet protocolLCR least cost routingMLPPP multilink point-to-point protocolMPLS multiprotocol label switchingMSC mobile switching centerMTSO mobile telephone switching officeNM Network ManagerOAM operations, administration and maintenanceOPEX operating expendituresOSS operations support systemQoS quality of serviceRAN radio access networkRNC radio network controllerRSP Routing Switch PlatformSDH synchronous digital hierarchySGSN serving GPRS support nodeSNMP simple network management protocolSONET synchronous optical networkTDM time division multiplexingUMTS Universal Mobile Telecommunications SystemUTRAN UMTS terrestrial radio access networkWDM wavelength division multiplexing


1 0 < A L C AT E L

www.alcatel-lucent.comAlcatel, Lucent, Alcatel-Lucent, the Alcatel-Lucent logo, are trademarks of Alcatel-Lucent.

All other trademarks are the property of their respective owners. Alcatel-Lucent assumes no responsibility for the accuracy of the information presented, which is subject to change without notice.

12 2006 Alcatel. All rights reserved. 3CL 00469 1021 TQZZA Ed.02 21343

IntroductionMarket Conditions and Busine...Mobile Operators Requiremen...Radio Access Network Archite...The Alcatel Solution for Cen...Centralized Aggregation of N...Multiple Roles within the MT...A Complete View

Hybrid Centralized/Distribut...Abbreviations

Mobile RAN v2 An

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