Mobile Backhaul E-Book

Juha T. T. Salmelin

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 739

Veröffentlichungsjahr: 2012

Beschreibung

Comprehensive coverage of IP/MPLS/Ethernet backhaul technologies and solutions for 3GPP mobile network systems such as LTE, HSPA and GPRS Focusing on backhaul from a radio network viewpoint, Mobile Backhaul combines perspectives on mobile networks and transport network technologies, focusing on mobile backhaul specific functionalities, which are essential in building modern cost efficient packet networks for mobile systems, IP, MPLS and Carrier Ethernet. The key functions required for this process, Synchronization, Resiliency, Quality of Service and Security, are also explained. The reader benefits from a view of networking technology from a radio network viewpoint, which is specific to this application, as well from a data centre and more IT-oriented perspective. The book bridges the gap between radio and backhaul viewpoints to provide a holistic understanding. Organized into two parts, the book gives an advanced introduction to the principles of the topic before moving on to more specialized areas. Part 1 gives a network level overview, with the purpose of presenting the mobile network application, its protocols, interfaces and characteristics for the backhaul. This section also presents the key packet networking technologies that are most relevant for the radio network. Part 2 offers selected case studies in Synchronization, Resiliency, QoS and Security and gives example solutions for mobile operator owned and leased mobile backhaul cases building on the network view given in Part 1. Both radio network experts and IP networking experts will benefit from the treatment of essential material at the borderline between the radio and backhaul technologies. Key features: * Unique view and coverage of both the radio network and the packet mobile backhaul * Includes a view into the economic motivation for a packet based mobile backhaul and discusses scenarios of a migration to the new technology * Covers 2G, 3G, HSPA, HSPA+ and LTE in radio technologies as well as MWR, Sonet/SDH, Ethernet, Carrier Ethernet, MPLS and IP in networking technologies

Leseprobe

Contents

Cover

Title Page

Copyright

Foreword

Acknowledgements

List of Abbreviations

List of Contributors

Chapter 1: Introduction

1.1 Why Read This Book

1.2 What is ‘Mobile Backhaul’

1.3 Targets and Scope of the Book

1.4 Organization of the Book

Part I: Mobile and Packet Networks

Chapter 2: Mobile Backhaul and the New Packet Era

2.1 Backhaul Network, Tiers and Costs

2.2 Legacy Backhaul Networks

2.3 Drivers for the MBH Network Change

2.4 Packet Based Backhaul Networks

2.5 Making Transition to Packet Technology Networks

Chapter 3: 3GPP Mobile Systems

3.1 3GPP

3.2 2G

3.3 3G

3.4 LTE

3.5 Summary

Chapter 4: Packet Networks

4.1 Mobile Backhaul Application

4.2 Standardization

4.3 Physical Interfaces

4.4 PPP and ML-PPP

4.5 Ethernet and Carrier Ethernet

4.6 IP and Transport Layer Protocols

4.7 MPLS/IP Applications

4.8 Summary

Chapter 5: Backhaul Transport Technologies

5.1 Transport Systems

5.2 Wireless Backhaul Technology

5.3 Wire-Line Backhaul Technology

5.4 Aggregation and Backbone Tiers

5.5 Leased Line Services for Mobile Backhaul

5.6 Summary

Part II: Mobile Backhaul Functionality

Chapter 6: Synchronization

6.1 Cellular Networks Synchronization Requirements

6.2 Frequency Synchronization in TDM Networks

6.3 Frequency Synchronization in Packet Networks

6.4 Synchronization Metrics for TDM and Synchronous Ethernet

6.5 Packet Synchronization Fundamentals and Metrics

6.6 Rules of Thumb for Packet Timing Network Implementation

6.7 Time Synchronization

6.8 Conclusions

Chapter 7: Resilience

7.1 Introduction

7.2 Native Ethernet and Resilience

7.3 Carrier Grade Ethernet

7.4 IP Layer

7.5 MPLS Resilience

7.6 Resilience in the BTS Access

7.7 Resilience in the Controllers and the Core Interface

7.8 Summary

Chapter 8: QoS

8.1 End User Service, Radio Network Layers and the Transport Layer Service

8.2 TCP and UDP as End User Transport Layer Protocols

8.3 DSCP, Traffic Class, and Priority Bits

8.4 Ingress and Egress Functions

8.5 2G

8.6 3G/HSPA

8.7 LTE

8.8 Summary

Chapter 9: Security

9.1 Security in 3GPP Mobile Networks

9.2 Protection of the Backhaul

9.3 IP Layer Protection

9.4 IP Sec VPN Deployment

9.5 Summary

Chapter 10: Packet Backhaul Solutions

10.1 Creating a Packet Based MBH Solution

10.2 MBH Solution Starting Points

10.3 MBH Optimization Considerations

10.4 MBH Solution Alternatives

10.5 Outsourcing the MBH Network or Parts of it

10.6 Selecting MBH Access Solution for a Particular Case

10.7 From the Selected MBH Solution to Detailed Network Plans

10.8 Summary

Chapter 11: Summary

Index

This edition first published 2012

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Library of Congress Cataloging-in-Publication Data

Mobile backhaul / editors, Juha Salmelin, Esa Markus Metsala.

p. cm.

Includes bibliographical references and index.

ISBN 978-1-119-97420-8 (cloth)

1.Mobile communication systems.I.Salmelin, Juha.II.Metsala, Esa Markus.

TK5103.2.M577 2012

621.39′81—dc23

2011051682

A catalogue record for this book is available from the British Library.

ISBN: 978-1-119-97420-8

Foreword

In the last few years we have seen an explosion of traffic on mobile networks as more and more of our communication has become mobile. Today, many of the world's most advanced mobile networks struggle to meet the performance and cost requirements placed on them and they typically respond by investing heavily in technologies such as HSPA+ and LTE to increase the capacity of the air interface. What cannot be ignored in the end-to-end architecture of mobile networks is the transport that plays a major role in determining the overall performance and cost of such networks. It is in this context that hardly any title could be more topical than Mobile Backhaul.

The natural cycle of technology evolution and rapid replacement of legacy networks by more capable and efficient packet networks further complicate the transport strategies employed by service providers. As the benefits of past investments compete with the capacity and efficiency of new investments, the result is an environment where multiple technologies co-exist.

In addition, packet based communication poses technical challenges that are not straight forward to overcome. Not all packet technologies can be applied to mobile backhaul and a careful examination of the underlying technology is required to ensure the integrity of the overall system and its ability to meet specific requirements. Two relevant examples are quality of service and security. IP networks behave very differently in these two domains when compared with the legacy networks based on E1's. Additionally, mobile networks create specific issues for the backhaul. A relevant example here is the need for synchronization in a mobile environment in order to enable handover of users from one base station to another and prevent interference, however, IP networks were not originally designed with these requirements in mind and need modifications to handle such requirements appropriately. Similarly, in an IP environment the delivery of all packets is not guaranteed and this lack of guarantee poses challenges for mobile communication. Other technical and non-technical challenges also exist in building backhaul networks which when taken together, lead us to conclude that a common rule for building advanced backhaul networks capable of adequately handling many simultaneous requirements is impossible to find. At the end, every network has to be specified and deployed as a unique solution.

The book you're holding now does a great job in discussing these topics and reviewing and assessing technologies and possible solutions that are available either in the mobile network or in the packet network domains. Many innovations are known to be the result of combining multiple disciplines and this is exactly what the authors and editors of this book have done.

Hossein MoiinChief Technology and Strategy OfficerNokia Siemens NetworksEspoo, Finland

Acknowledgements

The editors would like to acknowledge the great contribution of authors from our colleagues at Nokia Siemens Networks: Thomas Deiß, Jouko Kapanen, José Manuel Tapia Pérez, Antti Pietiläinen, Jyri Putkonen, Csaba Vulkán and, last but not least, Erik Salo, ‘the great old transport guru’ who has already fully served his official work career.

Especially great thanks to Esa Törmä, the other grand old man in the mobile backhaul area for his insight and thinking, which has served us for laying the foundation and structure for many of the topics we have addressed in this book.

For specific review comments and suggestions we would like to thank Heikki Almay, Damian Dalgliesh, Joachim Eckstein, Carl Eklund, Timo Liuska, Sanna Mäenpää, Olli Pekka Mäkinen, Jukka Peltola, Mehammedneja Rahmato, Konstantin Shemyak, Antti Toskala, Jouko Törmänen, Eugen Wallmeier and Roland Wölker.

Special thanks to Harri Holma and Antti Toskala for a very useful guideline, example, and hints on how to proceed with writing a technical book and for informing of the practicalities involved in this type of a project.

Also we like to thank the team at John Wiley & Sons and the co-operators for an easy editing process, and for the flexibility which we believe we used up to its full quota; and especially Mark Hammond, Sandra Grayson, Richard Davies, Sophia Travis, Prachi Sinha Sahay, Prakash Naorem and Sara Barnes.

We appreciate the patience and support of our families and our authors' families during the writing periods, which often extended into late night and weekend time.

Yet, despite all the hours consumed, we very much enjoyed writing this book. We are grateful for comments and suggestions for improvements or changes that could be implemented in forthcoming editions of this book. The feedback is welcome at editors' email addresses: [email protected] and [email protected].

List of Abbreviations

10GE10 gigabit Ethernet1GEGigabit Ethernet (IEEE 802.3 standard interface)1x(CDMA2000) 1 times Radio Transmission Technology2G2nd generation mobile system, GSM3G3rd generation mobile system, WCDMA3GPP3rd Generation Partnership Project64-QAM64-level Quadrature Amplitude ModulationAAL2ATM Adaptation Layer 2AAL2SIGAAL2 SignalingAAL5ATM Adaptation Layer 5ACAttachment CircuitACAdmission ControlACHAssociated Channel HeaderACKAcknowledgmentACRAdaptive Clock RecoveryACRAdaptive clock recoveryADMAdd-drop MultiplexingADSLAsymmetric Digital Subscriber LineAFAssured ForwardingA-GPSAssisted GPSAHAuthentication HeaderAIMDAdditive Increase Multiplicative DecreaseAISAlarm Indication SignalAKAAuthentication and Key AgreementAMAcknowledged ModeAMBRAggregate Maximum Bit RateAMRAdaptive Multi-RateANSIAmerican National Standards InstituteAPAccess PointAPSAutomatic Protection SwitchingARIBThe Association of Radio Industries and BusinessesARPAllocation and Retention PriorityARPAddress Resolution ProtocolARQAutomatic Repeat RequestASAutonomous SystemATISThe Alliance for Telecommunications Industry SolutionsATMAsynchronous Transfer ModeATMAsynchronous Transfer ModeAUAdministrative UnitBCBoundary ClockBCHBroadcast ChannelBCPBest Current PracticeBEBest EffortBFDBidirectional Forwarding DetectionBGPBorder Gateway ProtocolBPDUBridge Protocol Data UnitBSBase stationBSCBase Station ControllerBSSBase Station SubsystemBTSBase StationBWBandwidthBWPBandwidth ProfileC/ICarrier/InterferenceCACertificate AuthorityCAPEXCapital ExpenditureCBRConstant Bit RateCBSCommitted Burst SizeCBWFQClass-Based Weighted Fair QueuingCCCongestion ControlCCConnectivity CheckCCCable Cut (metric)CCMConnectivity Check MessageCDMACode Division Multiple AccessCECustomer EdgeCEPTEuropean Conference of Postal and Telecommunications AdministrationsCESCircuit emulation serviceCESoPCircuit Emulation Service over PacketCESoPSNStructure-aware time division multiplexed circuit emulation service over packet switched networkCFCoupling FlagCFMConnectivity Fault ManagementCFNConnection Frame NumberCHAPChallenge Handshake Authentication ProtocolCIRCommitted Information RateCMColor ModeCMPCertificate Management ProtocolCNCore NetworkCoSClass of ServiceCPControl PlaneCRCCyclic Redundancy CheckCRLCertificate Revocation ListCRNCControlling RNCCSCircuit switchedCSClass SelectorCWDMCoarse Wavelength Division MultiplexingCWNDCongestion WindowDCHDedicated ChannelDEIDrop Eligible IndicatorDelay_ReqDelay request (message used in PTP)Delay_RespDelay response (message used in PTP)DHCPDynamic Host Configuration ProtocolDiffServ, DSDifferentiated ServicesDLDownlinkDoSDenial Of ServiceDPDDead Peer DetectionDRNCDrift RNCDSCPDS Code PointDSLDigital Subscriber LineDWDMDense Wavelength Division MultiplexingE1Basic bit rate of European PDH; 2,048 Mbit/sE-BGPExternal BGPEBSExcess Burst SizeECMEPS Connection ManagementECMPEqual Cost MultipathECNExplicit Congestion NotificationE-DCHEnhanced DCHEDGEEnhanced Data rates for Global EvolutionEECSynchronous Ethernet equipment clockEFExpedited ForwardingEGPExterior Gateway ProtocolEIGRPEnhanced Interior Gateway ProtocolEIRExcess Information RateE-LSPExplicitly TC (Traffic Class)-encoded PSC (PHB Scheduling Class) LSPEMMEPS Mobility ManagementeNB, eNodeBE-UTRAN NodeBEoCEthernet over CopperEPLEthernet Private LineEPLANEthernet Privat LANEP-LANEthernet Private LANEPSEvolved Packet SystemEP-TreeEthernet Private TreeE-RABE-UTRAN Radio Access BearerESMCEthernet synchronization messaging channelESPEncapsulating Security PayloadEthEthernetETSIEuropean Telecommunications Standards InstituteE-UTRANEvolved UTRANEVCEthernet Virtual ConnectionEV-DOEvolution-Data OptimizedEVPLEthernet Virtual Private LineEVPLANEthernet Virtual Private LANEVP-LANEthernet Virtual Private LANEVP-TreeEthernet Virtual Private TreeFACHForward Access ChannelFCSFrame Check SequenceFDFrame DelayFDDFrequency Division DuplexFDMAFrequency Division Multiple AccessFDVFrame Delay VariationFECForwarding Equivalence ClassFLRFrame Loss RateFLRFrame Loss RateFPFrame ProtocolFRRFast RerouteFSNFrame Sequence NumberFTPFile Transfer ProtocolG-ACHGeneric Associated ChannelGALGeneral Associated LabelGBRGuaranteed Bit RateGERANGPRS/Edge Radio Access NetworkGFPGeneral Framing ProcedureGGSNGateway GPRS Support NodeGLONASSGlobalnaya navigatsionnaya sputnikovaya sistema or Global Navigation Satellite SystemGMGrandmaster clock (used in PTP)GMPLSGeneralized MPLSGNSSGlobal navigation satellite systemGPRSGeneral Packet Radio ServiceGPSGlobal positioning systemGSMGlobal System for Mobile communications, originally Groupe Spécial MobileGTP-CGPRS Tunneling Protocol Control PlaneGTP-UGPRS Tunneling protocol User PlaneGWGatewayH-ARQHybrid Automatic Repeat RequestH-BWPHierarchical Bandwidth ProfileHDLCHigh Level Data Link ControlHRM-1Hypothetical reference model 1HSCSDHigh Speed Circuit Switched DataHSDPAHigh Speed Downlink Packet AccessHS-DSCHHigh Speed Downlink Shared ChannelHSPAHigh Speed Packet AccessHSSHome Subscriber ServerHSUPAHigh Speed Uplink Packet AccessHTTPHypertext Transfer ProtocolHWHardwareIANAInternet Assigned Numbers AuthorityI-BGPInternal BGPICMPInternet Control Message ProtocolIEInformation ElementIEEEInstitute of Electrical and Electronics EngineersIETFInternet engineering task forceIGPInterior Gateway ProtocolIKEInternet Key ExchangeIMSIP Multimedia SubsystemIMSIInternational Mobile Subscriber IdentityIPInternet ProtocolIP-CANIP Connectivity Access NetworkIS-95Interim standard 95IS-ISIntermediate System - Intermediate SystemISOInternational Organization for StandardizationITUInternational Telecommunications UnionL1Layer 1 (in the OSI protocol stack)L2Layer 2 (in the OSI protocol stack)L2VPNLayer 2 virtual private networkL3Layer 3 (in the OSI protocol stack)L4Layer 4 (in the OSI protocol stack)LACPLink Aggregation Control ProtocolLAGLink Aggregation GroupLANLocal Area NetworkLCPLink Control ProtocolLDPLabel Distribution ProtocolLEDLight Emitting DiodeLLCLogical Link ControlLLQLow Latency QueuingL-LSPLabel-only-inferred PSC (PHB Scheduling Class) LSPLOSLoss of Signal; Line of SightLSALink State AdvertisementLSDBLink State DatabaseLSPLabel Switched PathLSRLabel Switch RouterLTELong Term Evolution (3GPP mobile network standard)MMasterM3UAMessage Transfer Part 3 (MTP3) User Adaptation LayerMACMedia Access ControlMAFEMaximum average frequency errorMATIEMaximum average time interval errorMBHMobile BackhaulMBMSMultimedia broadcast multicast serviceMBRMaximum Bit RateMDEFModified Allan DeviationMDEVModified Allan deviationMEFMetro Ethernet ForumMEPMaintenance End PointMGWMedia GatewayMIBManagement information baseMIMOMultiple Input Multiple OutputMIPMaintenance Intermediate PointML-PPPMulti Link-Point-to-Point ProtocolMMEMobility Management EntityMPManagement PlaneMP-BGPMulti Protocol BGPMPLSMulti Protocol Label SwitchingMPLS-TEMPLS Traffic EngineeringMPLS-TPMPLS Transport ProfileMRUMaximum Receive UnitMSPMultiplex Section ProtectionMSPPMultiservice Provisioning PlatformMSSMaximum Segment SizeMSTPMultiple Spanning Tree ProtocolMTBFMean Time Between FailureMTIEMaximum Time Interval ErrorMTTRMean Time To RepairMTUMaximum Transfer UnitMWRMicrowave RadioNATNetwork Address TranslationNDSNetwork Domain SecurityNENetwork ElementNG-SDHNext Generation Synchronous Digital HierarchyNICNetwork Interface CardNIDNetwork interface deviceNLRINetwork Level Reachability InformationNMSNetwork Management SystemN-PENetwork-PE (Provider Edge)NPVNet Present ValueNRINetwork Resource IdentifierNTPNetwork time protocolO&MOperation and MaintenanceOAMOperation, Administration and MaintenanceOC1Optical carrier 1, 51.84 Mbit/sOC3Optical carrier 3, 155.52 Mbit/sOCSPOnline Certificate Status ProtocolOFDMOrthogonal frequency-division multiplexingOFDMAOrthogonal Frequency Division Multiple AccessOHOverheadOPEXOperational ExpenditureopexOperating expendituresOSIOpen System InterworkingOSPFOpen Shortest Path FirstOSSPOrganization specific slow protocolOTDOAObserved time difference of arrivalOTHOptical Transport HierarchyOTNOptical transport networkOUIOrganizationally Unique IdentifierOWAMPOne-way Active Measurement ProtocolPAPPassword Authentication ProtocolPBProvider BridgingPBBProvider Backbone BridgingPCCPolicy and Charging ControlPCEFPolicy and Charging Enforcement FunctionPCHPaging ChannelPCMPulse code modulationPCPPriority Code PointPCRFPolicy and Charging Rules FunctionPDCPPacket Data Convergence ProtocolPDHPlesiochronous Digital HierarchyPDNPacket Data NetworkPDUProtocol Data UnitPDVPacket delay variationPEProvider EdgePEC-BCombined packet slave clock and packet master clockPEC-MPacket master clockPEC-SPacket slave clockPFSPerfect Forward SecrecyP-GWPDN Gateway (PDN GW)PHBPer-Hop BehaviourPHPPenultimate Hop PoppingPKIPublic Key InfrastructurepktfilteredMTIEPacket-filtered MTIE (maximum time interval error)PLLPhase-locked loopPMPerformance MonitoringPMIPProxy Mobile IPPMPPoint-to-MultipointPMTUDPath MTU DiscoveryPONPassive optical networkPoSPacket over SONETPOTSPlain Old Telephone ServiceppbParts per billionppmParts per millionPPPPoint-to-Point ProtocolppsPackets per second, pulse per secondPRCPrimary reference clockPRTCPrimary reference time clockPSPacket SwitchedPSKPre-Shared KeyPSNPacket Switched NetworkPSTNPublic Switched Telephone NetworkPTPPrecision time protocolPTPPoint-to-PointPWPseudowirePWEPseudowire EmulationPWE3Pseudo Wire Emulation Edge-to-EdgeQCIQoS Class IdentifierQoEQuality of ExperienceQoSQuality of ServiceQPSKQuadrature Phase Shift KeyingR&DResearch and DevelopmentRACHRandom Access ChannelRANRadio Access NetworkRBRadio BearerREDRandom Early DetectionRFRadio frequencyRFCRequest For CommentsRFQRequest for QuotationRIPRouting Information ProtocolRLCRadio Link ControlRNCRadio Network ControllerRRRoute ReflectorRRMRadio Resource ManagementRSTPRapid Spanning Tree ProtocolRSVPResource ReserVation ProtocolRSVP-TEResource ReserVation Protocol-Traffic EngineeringRTCPRTP Control ProtocolRTORetransmission Timeout TimerRTPReal Time Transport ProtocolRTTRound Trip TimeSSlaveSASecurity AssociationSACKSelective AcknowledgementSAESystem Architecture EvolutionSAKSecure Association KeySAToPStructure-agnostic time division multiplexing over packetSCCPSignalling Connection Control PartSC-FDMASingle Carrier FDMASCTPStream Control Transmission ProtocolSDFService Data FlowSDHSynchronous Digital HierarchySECSDH equipment clock, SDH equipment slave clockSEGSecurity GatewaySFNSingle-frequency networkSFPSmall Form PluggableSGSNServing GPRS Support NodeS-GWServing GatewaySIMSubscriber Identity ModuleSLAService Level AgreementSLSService Level SpecificationSONSelf Optimizing NetworksSONETSynchronous Optical NetworkSPFShortest Path FirstSPIScheduling Priority IndicatorSRBSignaling Radio BearerSRNCServing RNCSTMSynchronous transport moduleSWSoftwareSWSwitchSyncSynchronization (message used in PTP)T1Basic bit rate of US & Japanse PDH; 1,544 Mbit/sTCTraffic ClassTCTransparent clockTCOTotal costs of OwnershipTCPTransmission Control ProtocolTDDTime Division DuplexTDEVTime deviationTDMTime Division MultiplexingTDMATime Division Multiple AccessTD-SCDMATime division synchronous code division multiple accessTETraffic EngineeringTETerminal EquipmentTEIDTunnel Endpoint IdentifierTHPTraffic Handling PriorityTICTOCTiming over IP connection and transfer of clockTLSTransport Layer SecurityTLVType-Length-ValueToPTiming over PacketTOSType of ServiceTTITransport Time IntervalTTLTime To LiveTWAMPTwo-way Active Measurement ProtocolUDPUser Datagram ProtocolUEUser Equipment (mobile terminal)ULUplinkUNIUser-Network InterfaceUPUser PlaneU-PEUser-PE (Provider Edge)UTRANUniversal Terrestrial Radio Access NetworkWANWide Area NetworkVCVirtual ChannelVCVirtual ContainerWCDMAWideband CDMAWDMWavelength Division MultiplexingVDSLVery-high-bit-rate digital subscriber lineWFQWeighted Fair QueuingWiMAXWorldwide Interoperability for Microwave AccessVLANVirtual local area networkVLRVisitor Location RegisterVoDVideo on DemandVoIPVoice over IPVoLTEVoice over LTEVPLSVirtual Private LAN ServiceVPNVirtual Private NetworkVPWSVirtual Private Wire ServiceWREDWeighted REDVRFVirtual Routing and ForwardingWRRWeighted Round RobinVRRPVirtual Router Redundancy ProtocolVSIVirtual Switch InstanceX2Interface in a LTE networkXPICCross Polarisation Interference Cancellation

List of Contributors

Thomas Dei

Nokia Siemens Networks

Düsseldorf, Germany

Jouko Kapanen

Nokia Siemens Networks

Espoo, Finland

Esa Metsälä

Nokia Siemens Networks

Espoo, Finland

José Manuel Tapia Pérez

Nokia Siemens Networks

Espoo, Finland

Antti Pietiläinen

Nokia Siemens Networks

Espoo, Finland

Jyri Putkonen

Nokia Siemens Networks

Espoo, Finland

Juha Salmelin

Nokia Siemens Networks

Espoo, Finland

Erik Salo

Independent Consultant

Espoo, Finland

Csaba Vulkán

Nokia Siemens Networks

Budapest, Hungary

Chapter 1

Introduction

Esa Metsälä, Juha Salmelin and Erik Salo

1.1 Why Read This Book

Several textbooks exist either on mobile networks or on (packet) networking, but separately, and they usually consider their subjects in isolation from each other. However, no mobile network exists without a related transport network connecting the elements; and also, mobile networks are becoming more and more important ‘customers’ for many kinds of packet networks.

Therefore this book is about considering these two domains together, and about looking at mobile network and backhaul network interactions, and how these two domains should take each other into account, particularly in the new era of (fully) packet-based transport solutions.

Mobile backhaul, as shown in Figure 1.1, is at the intersection of a mobile network and a transport network. Some aspects are more closely related to the radio network. Another area originates from the transport and networking side.

Figure 1.1 Mobile backhaul.

Usually mobile networks, radio interfaces, and other radio related topics are discussed within a circle of radio communication experts, without considering so much the other parts of the whole network. As an example, the 3GPP view of the transport connection between any two mobile network elements is a single, straight line. This very high level of abstraction serves focusing on the mobile network specific issues. However, when transport connections in real life are more complex, and in the era of packet networks very much more complex, different types of issues start to appear; functionalities and especially performance of the mobile network are impacted. The influence can in some cases be significant.

Correspondingly, it is not that easy for a networking expert to delve into the details of mobile network – even the fundamental concepts may be hidden into a number of mobile network standards. Also, 3GPP mobile networks, and their radio interfaces are not at all like a wireless LAN: their protocols are not based on Ethernet (which one could feel familiar with), and there is more of protocol layering and a division of functionality between mobile elements; simply put, they are more complex.

Therefore, if your background is in radio communication and mobile network, you will benefit from having an understanding of how the backhaul is built and how it influences the actual behavior and performance of the mobile network. For example, end-user bit rates are not limited only by the radio interface, but also by backhaul links, and thus it is becoming more important to understand and take into account the backhaul solutions applied.

On the other hand, if you are an IP and networking expert, you can use your competence more effectively when you understand more of the internal workings of the radio network side, and the basic requirements of radio networks relating to connections. Even if mobile backhaul is not the main driver for the networking industry, innovative solutions are needed to provide economic connections for advanced mobile networks and their services and data volumes, for example to cope with the high peak rates of HSPA+ and LTE networks.

1.2 What is ‘Mobile Backhaul’

Figure 1.1 already provides the first answer: mobile backhaul unites a mobile network with transport/packet networks. Some elements and functions of the mobile network are within the scope, and the rest of functionality and characteristics are coming from the transport and packet networking side. Ultimately it is the mobile network that serves the end-users, however, the deployment and design of the mobile backhaul impacts not only the mobile element interfaces, but also contributes to mobile network's overall operation and performance.

Mobile networks themselves are already well established in very many parts of the world, and mobile networks continue to expand, covering wider and wider areas of the globe. They also develop at a rapid rate and offer more and more services, including many kinds of wideband services, and enable higher and higher bit rates between the terminals and the network. This means that especially the data traffic is growing very fast in many mobile networks. Therefore well-working inter-element connections are necessary for the mobile networks to operate properly, and the role of supporting transport and packet networks is increasing. These transport and packet networks serving mobile networks are called ‘mobile backhaul networks’, or often just ‘mobile backhaul’ (MBH), as they connect a large number of base station sites to a limited number of centralized sites (see Figure 1.2).

Figure 1.2 Mobile backhaul (MBH) network connects the sites of a mobile network.

The MBH networks are presently experiencing a big change, as the growth of mobile data traffic and development of packet transport technologies and equipment has created a strong push to use packet-based MBH solutions, both to increase feasible data throughputs and to improve the cost-efficiency of MBH networks.

Backhaul networks have always been an important part of the overall mobile network business case; connections to the base station sites are important, as their number is very high. These ‘last mile links’ (or ‘first mile links’, depending on your point of view) influence significantly the overall network costs. Now when network capacities increase and cell sizes decrease, transport share of the overall network costs tends to increase. Packet-based transport solutions help here, in keeping transport cost increase at a reasonable level.

1.3 Targets and Scope of the Book

This book is intended to give an overview of different aspects of mobile backhaul networks, and also provide a more detailed discussion on protocols, functionalities and technologies on both the radio network side and on the backhaul and networking technologies.

By nature, some terminology will be more 3GPP and radio-oriented, while a part comes from the networking world.

The book covers the mobile backhaul networks from the base station sites up to the core sites; however, it puts more emphasis on network segments closer to the base station sites (access tier, see Figure 2.2), as these parts have more mobile specific characteristics and are also economically the most important part of the backhaul.

Upper MBH network tiers often serve a combination of mobile and fixed traffic, are more built based on fixed traffic requirements and have a smaller influence on the mobile network economy; however, it is important to take into account also their impact on mobile network performance. Backhauls for indoor solutions are often a mix of fixed and mobile traffic and are beyond the scope of this book.

Technically, the book covers networking (or transport and transmission) related functionalities. Radio network protocols and key functionalities are reviewed as the radio network is the client layer for the mobile backhaul. While reading the backhaul oriented chapters it is useful to keep the basic mobile network architecture and operation in mind as this helps to identify interactions that are of a more subtle nature.

1.4 Organization of the Book

The body of the book is organized in two parts.

Part I considers networks as entities, from needs and change drivers to network transitions and from mobile systems to packet networking and implementation aspects. Part II studies key functionalities in MBH: Synchronization, Resilience, Quality of Service, and Security, with the aim of going deeper into each of these topics.

The first chapter in Part I, Chapter 02, provides an introduction to the backhaul networks, to the needs and economic aspects of transport in mobile networks, and discusses the drivers for the packet-based MBH solutions as well as some transition issues. Part I continues with Chapter 03 describing mobile systems standardized by 3GPP. The emphasis is on logical interfaces and the related protocol stacks for the transport and for the end user service delivery. Radio network key functionality is introduced as well.

Chapter 04 in turn provides an overview of packet networks and networking technologies and protocols especially for readers who are already more familiar with the radio network technologies. Chapter 4 also discusses how the packet technologies are used in implementing a backhaul service for the radio network layer.

The last chapter of Part I, Chapter 05, discusses transport technologies and systems used in MBH networks, their main characteristics and briefly the services available for outsourcing MBH functionality; the focus in Chapter 05 is on the systems needed and used in the MBH access tier.

Part II starts with Chapter 06 discussing an important and very mobile network specific transport topic, namely provision of synchronization for mobile base stations over the transport network – a topic of increasing importance when we move towards packet-based MBH networks.

Chapter 07 addresses resilience. When moving to the packet network, carrier grade resilience is needed. Failure types in the packet network differ from those experienced in TDM networks, which easily causes a concern unless the topic is addressed. Recovery after a failure in the packet network as well typically relies on different methods than TDM does.

Chapter 08 is about quality of service (QoS) in the backhaul, focusing on QoS needs of all traffic types existing in the backhaul. Also, the role of transport in the overall end-to-end quality is discussed. QoS is one of the topics which directly and concretely links the radio network layer with the backhaul layers. It is often the first topic mentioned when discussing common areas between the radio network and backhaul experts.

And then Chapter 09 discusses security in the MBH networks and various networking solutions. With packet-based mobile backhaul, new types of threats emerge, and these need to be addressed. Cryptographic protection with IPsec is one of the tools for protecting the backhaul.

Chapter 10 provides an overview on how a packet-based MBH solution for a particular mobile network case is found and put together, including some examples of possible MBH solutions (solution types) for specific mobile network development cases.

Chapter 11 then contains a brief summary of the book.

Part I

Mobile and Packet Networks

Chapter 2

Mobile Backhaul and the New Packet Era

Erik Salo and Juha Salmelin

2.1 Backhaul Network, Tiers and Costs

Mobile backhaul (MBH) networks serve mobile networks by providing connections between mobile network elements located in different geographical sites; no mobile network exists without a related MBH network. The main task of a MBH network is to connect a very large number of mobile network base station sites to a relatively small number of central sites where the mobile network core elements are located.

Basically a MBH network transfers transparently mobile system internal traffic and signaling between the mobile system elements. Even if mobile traffic is not interpreted by the MBH network, its properties affect mobile traffic in several ways, and thus the MBH network has a significant influence on the mobile network end-to-end quality. It is important to take these dependencies and influence fully into account when designing mobile networks which are optimized in respect of total cost and end-to-end performance.