Reconfigurable Radio Systems E-Book

Maria Stella Iacobucci

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

Seitenzahl: 356

Veröffentlichungsjahr: 2013

Beschreibung

Covers the state of the art of the technology and standards for reconfigurable radio systems, from self organizing networks and cognitive radio, through to reconfigurable architectures for networks and terminals

This timely book provides a standards-based view of the development, evolution, techniques and potential future scenarios for the deployment of reconfigurable radio systems. 

After an introduction to radiomobile and radio systems deployed in the access network, the book describes cognitive radio concepts and capabilities, which are the basis for reconfigurable radio systems.  The self-organizing network features introduced in 3GPP standards are discussed and  before IEEE 802.22, the first standard based on cognitive radio, is described. Then the ETSI reconfigurable radio systems functional architecture and the IEEE 1900.4 standard for reconfigurable radio are examined. Finally, the author presents new scenarios and future visions that reconfigurable radio systems may bring.

Key features:-

• Examines the current standards based on cognitive and reconfigurable radio, and analyses future scenarios
• Includes a general overview of radiomobile (i.e. GSM, UMTS, HSPA, LTE) and wireless (i.e. WLAN, WPAN, WiMAX) network architectures
• Features an accompanying website features links and white papers

Leseprobe

Contents

Cover

Title Page

Copyright

Preface

Acknowledgements

List of Abbreviations

Chapter 1 The Multiradio Access Network

1.1 Introduction

1.2 Radiomobile Networks

1.3 Wireless Networks

References

Chapter 2 Cognitive Radio: Concept and Capabilities

2.1 Cognitive Systems

2.2 Spectrum Sensing Cognitive Radio

2.3 Introduction to the Full Cognitive Radio

References

Chapter 3 Self-Organizing Network Features in the 3GPP Standard

3.1 Self-Organizing Networks

3.2 LTE Overview

3.3 LTE Home eNB

3.4 LTE and Self-Organizing Networks

References

Chapter 4 IEEE 802.22: The First Standard Based on Cognitive Radio

4.1 White Spaces

4.2 IEEE 802.22

4.3 IEEE 802.22.1

References

Chapter 5 ETSI Standards on Reconfigurable Radio Systems

5.1 Introduction

5.2 ETSI Reconfigurable Radio Systems

5.3 Summary

References

Chapter 6 IEEE 1900.4

6.1 Introduction

6.2 IEEE Dynamic Spectrum Access Networks Standards Committee (DySPAN-SC)

6.3 IEEE 1900.4 Functional Architecture

6.4 IEEE 1900.4a Functional Architecture

6.5 Summary

References

Chapter 7 Regulatory Challenges of Reconfigurable Radio Systems

7.1 Introduction

7.2 Spectrum Management

7.3 Impacts of Reconfigurable Radio Systems to Spectrum Governance

7.4 Summary

References

Index

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Preface

Network evolution in the past decade involved the introduction of new access technologies, both fixed and wireless, using an IP backbone for all originating and terminating services. The evolution of the fixed access network mainly concerned the introduction of the optical fibre, with point-to-point or passive optical network (PON) architectures.

The next generation access network (NGAN) also includes radiomobile and wireless access technologies that, thanks to the adoption of advanced radio features, reach a maximum bit rate of hundreds of Mbps. The different access networks, which collect all originating and terminating services, are connected to an IP-based backbone, offering a transport service with quality of service (QoS).

The radio access technologies (RATs) are often managed by ‘manually’ configuring the radio parameters. Recently, some common radio resource management (CRRM) features have been introduced in the multi-RAT network in order to optimize the performances of the overall radio access network. The evolution of CRRM adds more intelligence to the access network, with self-organizing networks (SONs) and cognitive radio (CR). SONs are networks able to autoconfigure, self-manage and self-heal. This concept has been pushed by the industry forum of the next generation mobile network (NGMN) and SON features have been introduced in 3GPP standards starting from release 8.

All over the world a refarming process of the radiomobile spectrum is going on. In the near future, radiomobile frequencies will not be strictly associated to a technology, but will be used depending on user terminals, service profiles, traffic requests and network optimization.

With spectrum sensing cognitive radio terminals and networks, spectrum usage will be optimized among different radio access technologies. In this context, new scenarios are opening up different degrees of freedom: from the case of a licensed operator using cognitive radio inside its network to increasing the efficient use of radio resources, through the coordination of licensed operators for the spectrum usage, to a scenario where unlicensed cognitive radio terminals operate in times and zones where a licensed spectrum is underutilized. Cognitive radio also opens up a scenario where the spectrum resource can be managed in an hour-to-hour market for spectrum exchange.

In December 2010 the FCC gave a green light for the use of ‘white spaces’, that is the vacant spectrum in TV bands. White space transmissions are based on spectrum sensing and a geo-detecting database system to protect TV signals from interference. This is the first example of cognitive radio usage, which implies the deployment of the first wireless standard based on cognitive radio, IEEE 802.22. Full cognitive radio, in which every possible parameter observable by a wireless node or network is taken into account for adaptation and network optimization, evolves towards reconfigurable radio systems (RRSs), in both the network and terminal sides.

Starting from 2009, ETSI published deliverables on RRS and a series of recommendations for standardization. The ETSI RRS functional architecture proposes single operator and multioperator scenarios, with new entities for dynamic spectrum management, dynamic self-organizing network planning and management, joint radio resource management and configuration control. The new entities bidirectionally communicate through standard interfaces and with their corresponding parts in the radio terminal. On February 2009, the IEEE 1900.4 standard for reconfigurable radio systems was published. IEEE 1900.4 is a standard for architectural building blocks enabling network-device distributed decision making for optimized radio resource usage in heterogeneous wireless access networks.

From April 2009, the IEEE 1900.4 Working Group has been working on two projects: 1900.4a, an amendment to IEEE 1900.4 defining architecture and interfaces for dynamic spectrum access networks in white space frequency bands, and 1900.4.1, a standard for interfaces and protocols enabling distributed decision making for optimized radio resource usage in heterogeneous wireless networks.

The IEEE 1900.4 standard proposed architecture introduces new entities in both the terminal and network sides. In the network side, the new entities are the operator spectrum manager, the RAN measurement collector, the network reconfiguration manager and the RAN reconfiguration controller. All those blocks, except the operator spectrum manager, have pairs in the terminal side and standardized interfaces.

The book is structured as follows.

Chapter 1 presents an overview of the principal radiomobile and wireless systems, like GSM/GPRS/EDGE, UMTS/HSPA/HSPA+, LTE/LTE advanced, wireless LANs, wireless MANs and wireless PANs, and describes the performances, the network architectures and the radio access technologies.

In Chapter 2, the spectrum sensing cognitive radio and the related features at the transmitter and receiver sides are introduced. The techniques used at the physical layer to avoid interference to primary users, like spectrum sensing at the receiver side and adaptive modulation, coding and power control at the transmitter side, are described. At the end of the chapter full cognitive radio, more extensively covered in other chapters of the book, is introduced.

Chapter 3 introduces self-organizing networks and presents the self-organizing network features introduced in the 3GPP standard, like self-establishment, self-optimization and self-healing of the LTE access network.

Chapter 4 presents the concept of ‘white space’ and describes coexistence issues in TV bands. IEEE 802.22, the first standard based on cognitive radio, is described in terms of architecture and the principal features at the physical and MAC layers are shown. At the end of the chapter the IEEE 802.22.1 beaconing system for incumbent interference protection is introduced.

Chapter 5 presents the ETSI Functional Architecture (FA) for Reconfigurable Radio Systems (RRSs). Reconfigurable radio base stations and reconfigurable radio devices architectures are described, with related use cases. The concept of cognitive pilot channel, which conveys the necessary information from the network to the terminal in the cognition cycle, is introduced in both in-band and out-band possibilities, and related examples are given. The entities of the functional architecture in both the network and terminal sides together with the connecting interfaces are described.

Chapter 6 introduces the IEEE 1900.4 standard for reconfigurable radio systems. IEEE 1900.4 entities in both the network and terminal sides with the connecting interfaces are described and examples of procedures are given. The IEEE 1900.4a standard, which introduces new entities for dynamic spectrum access networks in white space frequency bands is presented, with its entities in both the network and terminal sides with connecting interfaces.

The last chapter of the book (Chapter 7) presents, without pretending to be exhaustive, the evolution from an exclusive usage of a spectrum regulated by individual licenses to the dynamic spectrum management and discusses how the systems described in the book enable dynamic spectrum management approaches.

Disclaimer

This text was prepared entirely on the author's personal time and with personal resources.

The author's affiliation with HRS Telecom Italia is provided for identification purposes only.

The opinions expressed in this text are those of the author and do not necessarily reflect the views of the author's affiliation company or of the standardization bodies.

Acknowledgements

My first acknowledgement is to my mentor, Prof. Maria Gabriella Di Benedetto. Some years ago, she taught me the method of scientific research and supported me during all of my PhD period. I would like to thank Domenico Di Giancristofaro and Giovanni Lofrumento for having read and commented on some parts of the book. I would also like to thank my colleagues from HRS for valuable discussions about some of the topics treated in the book: Giuliano Paris, Sandro Pileri, Italo Tobia, Giulio Di Vitantonio, Osvaldo Prosperi, Stefania Pace, Benvenuto Ioannucci and Santino Paciotti.

I appreciated the kind support provided by John Wiley & Sons, Ltd, in particular Tom Carter, Claire Foo, Sandra Grayson, Susan Barclay, Sophia Travis and Mark Hammond. I also appreciated the work of Patricia Bateson and Sharma Shalini during the editing process.

I thank my husband Silvio and my sons Raffaele and Maria because of the constant support they have given me during the writing of the book.

I will be grateful to all readers who open discussions about the topics of the book and will also appreciate comments and suggestions that could be considered in forthcoming editions of this book. The feedback is welcome to my email address [email protected]. I will also be pleased to get in touch with readers through my LinkedIn account.

My last thought is not to a person, but to a beautiful historical city which on 6 April 2009 was destroyed by a tremendous earthquake: L'Aquila. This is the city where I was born, I grew up and where I actually live with my family. Its historical centre is now uninhabited, empty and lifeless. I hope to have the chance to see once more life inside the houses, the streets and the medieval churches.

With this hope, I wish you a pleasant reading.

List of Abbreviations

AASAAggregation aware spectrum assignmentADSLAsymmetric digital subscriber lineAGCHAccess grant channelAICHAcquisition indicator channelAICPCAcquisition indication CPCAIPAdministrative incentive pricingAMCAdaptive modulation and codingANRAutomatic neighbour relationAOAAngle of arrivalAPAccess pointAPACAsia PacificAPTAsia Pacific TelecommunityARQAutomatic repeat requestASAAuthorized shared accessASN-GWAccess service network gatewayATMAsynchronous transfer modeBCCHBroadcast control channelBCHBroadcast channelBERBit error rateBLM_REQBulk measurement requestBPSKBinary phase shift keyingBSBase stationBSCBase station controllerBSICBase station identity codeBSSBase station subsystemBTSBase transceiver stationBWBandwidthCACCommand and controlCAFCyclic autocorrelation functionCAPContention access periodCBPCoexistence beacon protocolCBSCognitive base stationCBSMCCBS measurement collectorCBSRCCBS reconfiguration controllerCBSRMCBS reconfiguration managerCCCall control (Chapter 1)CCChannel contention (Chapter 4)CCConfiguration control (Chapter 5)CCBConfiguration control blockCCCHCommon control channelCCHControl channelCCKComplementary code keyingCCMConfiguration control moduleCCNChannel contention numberCCNCTChannel contention number of credit tokenCCSChannellization code setCell-IdCell identifierCEPTEuropean Conference of Postal and Telecommunications AdministrationCFCognitive functionalityCFPContention free periodCGICell global identityCICell identityCIOCell individual offsetCITELInter-American Telecommunication CommissionCMConfiguration managerCMTRCoordinated multipoint transmission and receptionCPControl planeCPCyclic prefix (Chapter 5)CPCCognitive pilot channelCPECustomer premise equipmentCPSCommon part sublayerCQIChannel quality indicatorCRCognitive radioCRCCyclic redundancy checkCRRMCommon radio resource managementCRSCognitive radio systemCSCircuit switched (Chapter 1)CSCoding scheme (Chapter 1)CSDBCommunications Society Standards Development BoardCSFBCircuit switched fallbackCSGClosed subscriber groupCSIChannel state informationCSMA/CACarrier sense multiple access with collision avoidanceCTCredit tokenCTAPChannel time allocation periodCTSClear to sendCUSCollective use of spectrumCWContention windowCWMComposite wireless networkCWMPCPE WAN management protocolCWNComposite wireless networkDBCPCDownlink broadcast CPC channelDCCHDedicated control channelDCDDownstream channel descriptorDCFDistributed coordination functionDCHDedicated channelDFTDiscrete Fourier transformDIFSDistributed interframe spaceDODCPCDownlink on demand CPCDPCCHDedicated physical control channelDPCHDedicated physical channelDPDCHDedicated physical data channelDSDownstreamDSADynamic spectrum access (Chapter 7)DSADynamic spectrum allocation (Chapter 5)D-SCHDownlink shared channelDSMDynamic spectrum managementDS-MAPDownstream MAPDSONPMDynamic self-organizing network planning managementDSSSDirect sequence spread spectrumDTCHDedicated traffic channelDTVDigital televisionE-AGCHEnhanced absolute grant channelEBDEigenvalue-based detectionECCElectronic Communication CommissionECGIE-UTRAN cell global identityE-DCHEnhanced dedicated channelEDGEEnhanced data rates for GSM evolutionE-DPCCHEnhanced dedicated physical control channelE-DPDCHEnhanced dedicated physical data channelEGCEqual gain combiningE-HICHEnhanced HARQ indicator channelEIRPEffective isotropic radiated powerEMElement managerEMEAEurope, Middle East and AfricaEMSElement management systemeNBEvolved Node BEPCEvolved packet coreEPSEvolved packet systemE-RGCHEnhanced relative grant channelESEnergy savingESSExtended service setETSIEuropean Telecommunication Standard InstituteE-UTRANEvolved UTRANFAFunctional architectureFACCHFast associated control channelFACHForward access channelFCFlow controllerFC_ACKFrame contention acknowledgementFC_DSTFrame contention destinationFC_RELFrame contention releaseFC_REQFrame contention requestFC_RESFrame contention responseFC_SRCFrame contention sourceFCCFederal Communication CommissionFCCHFrequency correction channelFCHFrame control headerFDDFrequency division duplexFDMAFrequency division multiple accessFECForward error correctionFEMFront end moduleFERFrame error rateFHFrequency hoppingFIRFinite impulse responseFRFull rateFSFixed stationFSKFrequency shift keyingFSMFrequency spectrum managementFTFourier transformFTPFile transfer protocolFTTBFibre to the buildingFTTCabFibre to the cabinetGERANGSM EDGE radio access networkGGSNGateway GPRS support nodeGLGeo-locationGMSKGaussian minimum shift keyingGPONGigabit passive optical networkGPRSGeneral packet radio serviceGPSGlobal positioning systemGSMGlobal system for mobile communicationsHARQHybrid ARQHCSHeader check sequenceHeMSHome eNB management systemHIIHigh interference indicatorHLRHome location registerHOHandoverHOMHandover hysteresis marginHPRHardware processing resourceHRHalf rateHS-DPCCHHigh speed dedicated physical control channelHS-DSCHHigh speed downlink shared channelHSNHopping sequence numberHSPAHigh speed packet accessHSSHome subscriber serverHS-SCCHHigh speed shared control channelIBSSIndependent basic service setICHIndicator channelICICIntercell interference coordinationIdIdentifierIEInformation elementIEEE DySPAN-SCIEEE Dynamic Spectrum Access Networks Standards CommitteeIETFInternet Engineering Task ForceIMIdentity managementIMSIP multimedia subsystemIMSIInternational mobile subscriber identityIMTInternational Mobile TelecommunicationsIPInternet protocolIRIncremental redundancyIRCInterference rejection combiningISMIndustrial, Scientific and MedicalITUInternational Telecommunication UnionJRRMJoint radio resource managementKPIKey performance indicatorLALocation areaLACLocation area codeLLCLogical link controlLSALicensed shared accessLTELong term evolutionM2MMachine to machineMACMedium access controlMANETMobile ad hoc networkMBMarginal benefitMBFEMMultiband front end moduleMBMSMultimedia Broadcast Multicast ServicesMCManagement centreMCCHMulticast control channelMCHMulticast channelMCSModulation and coding schemeMGWMedia gatewayMIBManagement information baseMIBMaster information blockMIMOMultiple input multiple outputMLMaximum likelihoodMMMobility managementMMEMobility management entityMRCMaximum ratio combiningMRCMultiradio controllerMSMobile stationMSAMaximum satisfaction algorithmMSCMobile switching centreMSDUMAC service data unitMSISDNMobile station ISDN numberMSKMinimum shift keyingMTCHMulticast traffic channelNASNonaccess stratumNAVNetwork allocation vectorNCINeighbour cell identityNCMSNetwork control and management systemNFCNear field communicationNGANNext generation access networkNISTNational Institute of Standards and TechnologyNMNetwork managerNMEANational Marine Electronic AssociationNMSNetwork management systemNONetwork operatorNPDNext-in-line protecting deviceNRNeighbour cell relationNRMNetwork reconfiguration managerNRTNeighbour relation tableO&MOperation and maintenanceOASOrganization of American StatesODFCOn demand frame contentionODSCOn demand spectrum contentionOFDMOrthogonal frequency division multiplexingOFDMAOrthogonal frequency division multiple accessOIOverload indicatorOLTOptical line terminationONUOptical network unitOQPSKOffset quadrature phase shift keyingOSAOpportunistic spectrum accessOSMOperator spectrum managerOSSOperational support systemOTAOver the airOVSFOrthogonal variable spreading factorPACCHPacket associated control channelPADPaddingPAGCHPacket access grant channelPAPRPeak-to-average power ratioPBCCHPacket broadcast control channelPBCHPhysical broadcast channelPCPoint coordinatorPCCCHPacket common control channelPCCHPaging control channelPCCPCHPrimary common control physical channelPCFPoint coordination functionPCFPolicy control functionPCFICHPhysical control format indicator channelPCHPaging channelPCIPhysical cell identityPCRFPolicy and charging resource functionPCSPersonal communications servicePCUPacket control unitPDProtecting devicePDAPersonal digital assistantPDCCHPacket dedicated control channel (Chapter 1)PDCCHPhysical downlink control channel (Chapter 1)PDCPPacket data convergence protocolPDSCHPhysical downlink shared channelPDTCHPacket dedicated traffic channelPDUPacket data unit (Chapter 1)PDUProtocol data unit (Chapter 4)PGWPacket gatewayPHICHPhysical hybrid ARQ indicator channelPHYPhysical layerPICHPaging indicator channelPIFSPCF interframe spacePLMNPublic land mobile networkPMCHPhysical multicast channelPNCPiconet controllerPNCHPacket notification channelPONPassive optical networkPPCHPacket paging channelPPDPrimary protecting devicePRACHPhysical random access channelPRMProtocol reference modelPSPacket switched (Chapter 1)PSPortable station (Chapter 4)PSDPower spectral densityPSKPhase shift keyingPSSPrimary synchronization signalPTCCHPacket timing advance control channelPTCHPacket traffic channelPTM-MPoint-to-multipoint multicastPUCCHPhysical uplink control channelPUSCHPhysical uplink shared channelQAMQuadrature amplitude modulationQoSQuality of serviceQPQuiet periodsQPSKQuadrature phase shift keyingRARouting areaRACHRandom access channelRACPCRandom access CPCRANRadio access networkRATRadio access technologyRBSRadio base stationRCMRadio connection managerREReconfiguration entityREG-REQRegistration requestREG-RESRegistration responseRFRadio frequencyRFBRadio frequency blockRLCRadio link controlRLC-PDURLC-packet data unitRLFRadio link failureRMCRAN measurement collectorRNCRadio network controllerRNC-IdRadio network control identifierRNSRadio network systemRNTPIRelative narrowband transmission power indicatorRRRadio regulationsRRCRadio resource controlRRCRAN reconfiguration controllerRRDReconfigurable radio deviceRRMRadio resource managementRSReference signal (Chapter 1)RSResource sharing (Chapter 4)RSRPReference signal received powerRSSReceived signal strengthRTSRequest to sendRTTRound trip timeRVCCRadio voice call continuitySACCHStandalone associated control channelSAE GWSystem architecture evolution gatewaySAESystem architecture evolutionSAPService access pointsSC_MMF_EMSelf-configuration monitoring and management function element managerSC_MMF_NMSelf-configuration monitoring and management function network managerSCCPCHSecondary common control physical channelSCFSpectral correlation functionSC-FDMASingle carrier – frequency division multiple accessSCHSuperframe control headerSCHSynchronization channelSCWSelf-coexistence windowSDCCHStandalone dedicated control channelSDRSoftware defined radioSFSpreading factorSGSNServing GPRS support nodeSGWServing gatewaySH_CO_FSelf-healing cell outage functionSH_MMFSelf-healing monitoring and management functionSH_MMF_EMSelf-healing monitoring and management function element managerSH_MMF_NMSelf-healing monitoring and management function network managerSICSuccessive interference cancellationSIFSShort interframe spaceSIGSpecial interest groupSIMSubscriber identity moduleSMSession management (Chapter 1)SMSpectrum manager (Chapter 7)SNMPSimple network management protocolSNRSignal to noise ratioSO_MMF_EMSelf-configuration monitoring and management function element managerSO_MMF_NMSelf-configuration monitoring and management function network managerSO-MMFSelf-optimization monitoring and management functionSONSelf-organizing networkSPDSecondary protecting deviceSSSpectrum sensingSSASpectrum sensing automationSSSSecondary synchronization signalSTMSynchronous transfer modeSWSoftwareTACSTotal access communication systemTBTransport blockTBSTransport block sizeTBTTTarget beacon transmission timeTCTechnical CommitteeTCHTraffic channelTCITarget cell identityTDDTime division duplexTDMATime division multiple accessTETerminal equipmentTFTransmission formatTMSITemporary Mobile Subscriber IdentityTMCTerminal measurement collectorTOATime of arrivalTRCTerminal reconfiguration controllerTRMTerminal reconfiguration managerTTGTransmit/receive transition gapTTITransmission time intervalTTTTime to triggerTVBDTelevision band deviceUCDUpstream channel descriptorUCSUrgent coexistence situationUEUser equipmentUMTSUniversal mobile telecommunication systemUPUser planeUSUpstreamUS-MAPUpstream MAPUTRANUMTS terrestrial radio access networkVLRVisitor location registerVoIPVoice over IPWAVEWireless access in vehicular environmentsWGWorking groupWLANWireless local area networkWMANWireless metropolitan area networkWPANWireless personal area networkWRANWireless regional area networksWSWhite space (Chapter 6)WSWireless station (Chapter 1)WSDWhite space deviceWSMWhite space manager

1

The Multiradio Access Network

1.1 Introduction

Network evolution in the past decade regarded the introduction of new access technologies, both fixed and wireless, using an Internet protocol (IP) backbone for all originating and terminating services. The evolution of the fixed access network mainly concerns the introduction of the optical fibre, with point-to-point or passive optical network (PON) architectures.

Gigabit passive optical network (GPON) architectures deal with fibre optic deployment up to different points in the access network:

Fibre to the cabinet (FTTCab), if the fibre stops at the cabinet,Fibre to the building (FTTB), if the fibre stops at the building, andFibre to the home (FTTH), if the fibre stops at the customer's home.

Figure 1.1 shows FTTCab, FTTB and FTTH network architectures. Such architectures reach a downstream bit rate per user in the order of magnitude respectively up to 50 Mbps, up to 100 Mbps and up to 1 Gbps. The optical network is called passive because of the splitters, which repeat the input signal. The outgoing bandwidth of an optical line termination (OLT) is shared among many optical network units (ONUs), and in FTTCab and FTTB architectures the existing copper cable pair is used in the connection from the ONU up to the end users, with very high digital subscriber line (VDSL) transmissions. If the optical fibre reaches the home, the architecture is FTTH and the user will be provided with an optical modem called network termination (NT).

Figure 1.1 FTTCab, FTTB and FTTH fixed access network architectures.

In the point-to-point architecture, there is one optical fibre connecting the end user to the central office, completely replacing the copper cable pair. In this case one fibre is dedicated to one user and therefore the provided bandwidth can be very high, even tens of Gbps. Figure 1.2 shows an example of the point-to-point fibre architecture in the access network.

Figure 1.2 Point-to-point fibre architecture in the access network.

The point-to-point architecture, handling much more fibre optics than GPON, requires more spaces in the central office and absorbs much more power. Because of that, most operators have chosen the GPON architecture for fixed access network evolution.

The next generation access network (NGAN) also includes radiomobile and wireless access technologies that, thanks to the adoption of advanced radio features, reach a maximum bit rate of hundreds of Mbps. Among radiomobile technologies, the global system for mobile communications (GSM) and its evolutions for data transmission, the general packet radio service (GPRS) and enhanced data rates for GSM evolution (EGDE), have been largely deployed all around the world. The third generation radiomobile system, the universal mobile telecommunication system (UMTS), with its evolutions, HSPA (high speed packet access) and HSPA+ for high bit rates data transmission, has been deployed with targeted coverage in high traffic areas, like major and minor cities. Long term evolution (LTE) is operating in many countries and is going to be deployed in others. Wireless local area networks (LANs) and WiMAX (see Section 1.3.2) are other existing technologies used mostly for data but also for voice transmission.

The different access networks, which collect all originating and terminating services, are connected to an IP-based backbone, offering a transport service with quality of service (QoS). Figure 1.3 shows the network with one core and many accesses.

Figure 1.3 Many accesses and one core.

1.2 Radiomobile Networks

Radiomobile networks were standardized with the aim of extending the services provided by the fixed network to mobile users, by means of a wireless terminal with the ability to move while the connection is in progress.

First generation systems, like the total access communication system (TACS), provided only the voice service, which was transmitted over the radio interface using frequency division multiple access (FDMA). The digital GSM system [1], initially standardized mainly for voice service, with its GPRS and EDGE evolutions, added new features in the access network and new nodes in the core in order to optimize data transmission.

The third generation system UMTS, standardized for multimedia, includes in its evolutions HSPA and HSPA+, which are able to reach higher bit rates and decrease latency. Finally, LTE reaches bit rates of hundreds of Mbps in downlink and lower latency times. The advanced version of LTE (LTE advanced) promises rates of Gbps.

In this section second, third and fourth generation radiomobile networks are described in terms of network architecture, access network and radio interfaces.

1.2.1 GSM/GPRS/EDGE Network Architecture

Figure 1.4 shows the GSM network architecture. The first network element is the mobile station (MS), which includes the mobile terminal (MT) and the subscriber identity module (SIM). Its principal functions are transmission and reception over the radio interface, radio channels supervision, cell selection, measurements of downlink radio parameters and execution of access, authentication and handover procedures. The MS communicates through a standardized radio interface with the base transceiver station (BTS), which is the network node that realizes one or more radio coverage cells, measures uplink radio parameters, broadcasts system information and executes procedures like paging. Each BTS is connected, through the Abis interface, to the base station controller (BSC), which controls the BTS radio resources. It assigns and releases the radio channels to the mobile users, receives uplink and downlink measurements, performs intra-BSC handover, handles power control, resolves cells congestions, etc.

Figure 1.4 GSM network architecture.

Because the Abis interface is not standardized, the BTSs and the connected BSCs must be from the same vendor. The BSC with its connected BTSs form a base station subsystem (BSS) and represent the GSM access network nodes. The BSSs are connected to the core network, which includes switching nodes like mobile switching centres (MSCs) and databases like the visitor location register (VLR) and home location register (HLR). BSCs are connected to the MSC through the standard A interface.

The principal functions of an MSC are: call handling, mobility handling (through interworking with VLR and HLR), paging, intra-MSC handover, inter-MSC handover, toll-ticket generation. Associated to the MSC is the VLR, which is a database containing a record for each user registered in the MSC/VLR area. Some of the MSCs are gateways (GMSC), because they are connected to the other mobile operator's networks and to the fixed network, in order to handle all the mobile–mobile, mobile–fixed and fixed–mobile calls.

The HLR is a register that stores, for each user of the mobile network, the service profile, the key for authentication and encryption, the international mobile subscriber identity (IMSI) and mobile station ISDN (MSISDN), as well as an identifier of the VLR where the user is registered. When an MS registers to the network, the VLR creates a new record with the user profile downloaded from the HLR and the MS position in terms of the location area (LA). In the HLR the identifier of the actual VLR is updated. The VLR also assigns the temporary IMSI (TMSI), which temporarily substitutes the IMSI.

The LA is a logical concept including a certain number of cells. The location area identifier (LAI) is broadcasted from the BTSs in all the cells belonging to the LA. When an MS moves from one LA to another, it performs the LA updating procedure. If the new LA belongs to a new MSC, then the new VLR downloads the user profile from the HLR and registers the new user with its LA. The HLR updates the VLR identifier and instructs the old VLR to delete the record of the user.

A GSM network with its core based on circuit-switching nodes, the MSCs, is well suited for voice but it is not for data. GSM data transmission is possible, but at a fixed bit rate of 9.6 kbps and using a voice-equivalent channel for all the duration of the call. Billing is based on the call duration and not on the amount of the exchanged data.

GPRS is the GSM evolution for data transmission. It introduces new features in the access network nodes in order to enhance data transmission speed and optimize resource allocation. In particular, GPRS needs new encoders in the BTSs and a new module, the packet control unit (PCU), in the BSC. The PCU implements radio resource management (RRM) algorithms for data transmission. GPRS also introduces new core network nodes: the serving GPRS support node (SGSN) and the gateway GPRS support node (GGSN).

The SGSN is responsible for the delivery of data packets from and to the mobile stations within its service area. Its tasks include packet routing and transfer, mobility management (attach/detach and location management), logical link management, authentication and charging functions. The location register of the SGSN stores location information and user profiles used in the packet data network of all GPRS users registered with this SGSN.

The GGSN is the node having connections with the other packet data networks. It contains routing information for the connected GPRS users. The routing information is used to tunnel packet data units (PDUs) to the MS's current point of attachment, that is the SGSN.

The BSC is connected to the SGSN through the standard Gb interface; the connection between SGSN and GGSN is the Gn interface; SGSN and GGSN are connected to the HLR through respectively the Gr and Gc interfaces; SGSN and MSC/VLR can see each other through the Gs interface. Gs and Gc interfaces are not mandatory. If Gs is present, an association between MSC/VLR and GGSN is created and it is possible to jointly handle a mobile station with packet switched and circuit switched services. Gs was introduced in order to reduce signalling over the radio interface. In fact, it is possible to carry out procedures like registration (IMSI attach) through the SGSN, combined LA and routing area (RA) updates, IMSI detach, etc. The RA is the equivalent of the LA in the GPRS domain; in general an LA contains an integer number of RAs.

A GPRS data transmission reaches a maximum download bit rate of about 50 kbps. EDGE, also called enhanced GPRS (EGPRS), is an evolution of GPRS allowing downlink bit rates up to about 240 kbps. EDGE adds new radio features to the GSM/GPRS access network nodes, and reuses the GPRS core network nodes: SGSN and GGSN. In particular, new modulators and encoders are added in the BTSs and new software in the PCU, in order to manage higher bit rate data connections.

Figure 1.5 shows the GSM/GPRS/EDGE network architecture. The access network, with its BSCs and BTSs, is shared among GSM and GPRS. The MSC-based core transports voice services and the SGSN/GGSN-based core transports data services.

Figure 1.5 GSM/GPRS/EDGE network architecture.

1.2.2 GSM/GPRS/EDGE Access Network

The GSM/GPRS/EDGE access network, also called the GERAN (GSM EDGE radio access network), includes MSs, BTSs, BSCs, and related interfaces. The radio interface is based on frequency division duplex (FDD) and FDMA/TDMA (time division multiple access). Table 1.1 shows GSM/GPRS/EDGE working frequencies in different countries of the world.

Table 1.1 GSM working frequencies in different countries of the world

BandUplink (MHz)Downlink (MHz)GSM 900 880–915  925–960 GSM 18001710–17851805–1880PCS (personal communication service) 19001850–19101930–1990Cellular 850 824–849  869–894 

In Europe, Africa, the Middle East and Asia most of the providers use 900 MHz and 1800 MHz bands. In North America, GSM operates on the bands of 850 MHz and 1900 MHz. GSM at 850 and 1900 MHz is also used in many countries of South and Central America.

All over the world, a refarming process of the radiomobile spectrum is going on, which is a rearrangement of the frequencies used for mobile services. For example, the 900 MHz band used for GSM is now available also for third generation (UMTS) services. FDMA in GSM contemplates the division of the assigned spectrum into carriers spaced 200 MHz apart. Figure 1.6 shows the division of the GSM 900 band into 200 kHz carriers.

Figure 1.6 Division of the GSM 900 band into 200 kHz carriers.

The theory of GSM frequency planning introduces the concept of cluster, which is a group of cells using all the available carriers. Cellular coverage is based on the repetition of the cluster. Figure 1.7 shows an example with the cluster and the relative theoretical frequency planning.

Figure 1.7 Example of theoretical frequency planning with repetition of the cluster.

As very often happens, the reality is far from the theory. The goal of cell planning is to guarantee the availability of radio resources that satisfy QoS for the provision of a set of services in an area target. In general, forms and dimensions of each cell are different and in each cell one or more carriers are switched on, depending on the requirements of coverage, capacity and performances. When GSM 900 and GSM 1800 coexist, an overlay/underlay technique is used for coverage. The underlay coverage is in general at 900 MHz and covers a higher area than overlay cells working at 1800 MHz. Overlay and underlay cells share sites, antenna systems and control channels.

Among cells of different dimensions, there are the macro, micro and pico cells depending on the size. Micro and pico cells are used to solve traffic peaks in small areas. Figure 1.8 shows an example of macro and micro coverage.

Figure 1.8 Example of macro and micro coverage.

GSM multiple access is FDMA/TDMA and is based on a frame structure of eight time slots per carrier, as shown in Figure 1.9. The frame duration is 4.6 ms; the slot duration is 577 μs; the signal burst is contained in one time slot and lasts 546 μs.

Figure 1.9 FDMA/TDMA multiple access in GSM.

The transmission and reception frames are shifted by three time slots. This allows the mobile station transceiver to transmit over the uplink, move to the downlink frequency, receive the downlink signal and make measurements over the other radio channels. This process is shown in Figure 1.10.

Figure 1.10 GSM transmission and reception.

The GSM frames are grouped together to form multiframes, superframes and iperframes. This temporal structure allows the establishment of a time schedule for operation and network synchronization. In particular, one multiframe can be formed of 26 or 51 frames; one superframe lasts 6.12 s and is formed of 51 multiframes of 26 frames or 26 multiframes of 51 frames; one iperframe is formed of 2048 superframes and lasts 3 h, 28 min, 53 s and 760 ms.

GSM access includes, as an optional feature, frequency hopping (FH). The goal of frequency hopping in GSM is to obtain an intrinsic diversity in frequency that protects the transmission from effects like rapid fluctuations of the radio channel or cochannel interferences. There are a total of 63 different hopping algorithms available in GSM.

When the BTS orders the MS to switch to the frequency hopping mode, it also assigns a list of channels and the hopping sequence number (HSN), which corresponds to the particular hopping algorithm that will be used. Figure 1.11 shows the principle of frequency hopping.

Figure 1.11 Principle of frequency hopping.

1.2.2.1 GSM Physical and Logical Channels

A physical channel in the GSM access network is identified from the time slot in the frame, the frame number, an FH sequence (if FH is active). A logical channel is dedicated to the transmission of specific information, using a mapping over appropriate physical resources. Logical channels are divided into traffic channels (TCHs), carrying voice and data, and control channels (CCHs), carrying control information.

GSM TCHs are:

TCH/FS: full rate (FR) speechTCH/HS: half rate (HR) speechTCH/F9.6: data at 9.6 kbps (FR)TCH/F4.8: data at 4.8 kbps (FR)TCH/F2.4: data at 2.4 kbps (FR)TCH/F1.2: data at 1.2 kbps (FR)

Also half rate data channels at 4.8 and 2.4 kbps are defined.

Full rate traffic channels use one time slot per frame; half rate channels use one time slot each two frames, occupying half capacity. The gross bit rate of a full rate channel is 22.8 kbps; the gross bit rate of an half rate channel is 11.4 kbps.

CCHs are divided into broadcast channels (BCHs), carrying broadcast information, common control channels (CCCHs), carrying common signalling information, and dedicated control channels (DCCHs) carrying signalling information dedicated to a user.

Figure 1.12 shows control and traffic channel mapping.

Figure 1.12 GSM logical channels mapping.

In downlink, BCHs are:

FCCH: frequency correction channel, carrying a frequency reference signalSCH: synchronization channel, carrying a frame synchronization reference signal and a base station identity code (BSIC)BCCH: broadcast control channel, carrying a cell global identity (CGI), location area identity (LAI), frequency hopping algorithm, references for control channels of adjacent cells and other cell parameters

CCCHs are:

PCH: paging channel, where the downlink is sent to search for an MS having an incoming call and paging is broadcast over all the cells belonging to the MS location areaAGCH: access grant channel, where the downlink is used to allocate a standalone dedicated control channel (SDCCH) to the MSRACH: random access channel, where the uplink carries user access information and is used from the MS to request an SDCCH allocation

DCCHs are:

SDCCH: standalone dedicated control channel, which is bidirectional and uses to execute signalling procedure like location area updating, TMSI allocation, attach and detach and occupies an eighth of one slotSACCH: standalone associated control channel, which is bidirectional and carries control information related to an active connection like measurement reports in uplink and power control and timing advance in downlinkFACCH: fast associated control channel, which is bidirectional and uses one TCH by substituting signalling to the traffic (frame stealing), in general carrying handover information

Figures 1.13,