LTE Radio Access Network PROTOCOLS & PROCEDURES

LTE Radio Access Network Protocols and ProceduresLZU 1088773 Overview text:Hi!The LTE Protocols and Procedures eLearning course gives a detailed description of the LTE RAN signaling. It covers the X2 and S1 interfaces and corresponding protocols X2AP and S1AP as well as the protocols used over these interfaces: RRC, PDCP, RLC, MAC and the physical layer for the radio interface.

Explain the RRC ProtocolExplain the PDCP ProtocolExplain the RLC and MAC ProtocolsExplain the X2/S1 Interface and the X2AP/S1AP ProtocolDescribe attach procedure and UE states and the difference between connected and idle modeDescribe call setupDescribe mobility over X2 and S1 Interfaces Describe IRAT HandoverObjectives

Why learn aboutUnderstand the protocols and procedures involved within the Evolved Packet System (EPS).

Understand how signaling is performed between the UE, eNodeB, MME, Serving-Gateway and Packet Data Network Gateway.

Introduction to LTE Protocols & procedures

Module Scope and ObjectivesDescribe the Evolved Packet System Architecture.List the Control and user plane protocols Explain the General Protocol model and Protocol interactionsDescribe the various traffic cases in EPSObjectivesScopeEvolved Packet System ArchitectureControl and user plane protocolsGeneral Protocol model and Protocol interactions

3GPP LTE and SAE Work Items LTE: Long Term EvolutionEUTRAN: Evolved UMTS Terrestrial Radio Access NetworkSAE: System Architecture EvolutionEPC: Evolved Packet Core

Evolved Packet System Architecture

EPS Protocol CategoriesL3 SignallingL2 Transport Non Access Stratum (NAS) Communication between UE and MME Radio Resource Control (RRC) Communication between UE and eNodeB Packet Data Convergence Protocol (PDCP) - Ciphering and integrity protection for RRC messages - IP header compression/decompression for user plane Radio Link Control (RLC) - Transfer of RRC messages and user data using: * Acknowledged Mode (AM) * Transparent Mode (TM) or * Unacknowledged Mode (UM) - Error Correction (ARQ) Medium Access Control (MAC) - Error Correction (HARQ) - Transfer of RRC messages and user data using: - Priority handling (scheduling) - Transport Format selection GPRS Tunneling Protocol Control (GTP-C) - Communication between MME and SGW - Communication between SGW and PGW - Communication between MME and MME S1 Application Protocol (S1AP) Communication between eNodeB and MME X2 Application Protocol (X2AP) Communication between eNodeB and eNodeB GPRS Tunneling Protocol User (GTP-U) Transfers data between GPRS tunneling endpoints

General Protocol ModelFor each layer the payload is called SDU (Service Data Unit)For each layer SDU+Protocol Header is called PDU (Packet Data Unit) Layer n PDU = Layer n+1 SDUE.g. A PDCP PDU = RLC SDU and RLC PDU = RLC Header+RLC SDUPayloadHeaderLayer n

EPS Bearer service and NAS Signalling ConnectionEPS Bearer Service (S1-UP)Transport Bearer (GTP)UERBSMMES/P-GWData Radio BearerTraffic ChannelRRC Signalling ChannelSignalling Radio Bearer NAS Signalling Connection S1 Signalling Bearer

UE Protocol StackHeader CompressionTMAM UMPhysical LayerL2PDCPRLCMACRRCNASIntegrity/ CipheringSystem Info AquisitionCell SelectionPaging ReceptionMobility ManagementSession ManagementConnected Mode MobilityNAS SecurityIPApplicationAS SecurityRRC ConnectionRB ManagementvMeasurement ReportingControl/Report SAPsRA ControlHARQControlRA ControlHARQControl

Segmentation, ARQCipheringHeader Compr.Hybrid ARQHybrid ARQMAC multiplexingAntenna and resrouce mappingCoding + RM Data modulation Antenna and resource mapping Coding Modulation Antenna and resource assignmentModulation schemeMAC schedulerRetransmission controlPriority handling, payload selectionPayload selectionRLC #iPHYPDCP #iUser #iUser #jMAC Concatenation, ARQDecipheringHeader Compr.Hybrid ARQHybrid ARQMAC demultiplexingAntenna and resrouce mappingCoding + RM Data modulation Antenna and resource demapping Decoding Demodulation RLCPHYPDCPMACeNodeBUERedundancy versionIP packetIP packetEPS bearersE-UTRAN Radio BearersLogical ChannelsTransport ChannelsPhysical ChannelsProtocol Interaction

UE MME Control PlaneL2L1IPSCTPS1-MMEMMES1-APNASSCTPL2L1IPeNodeBS1- APMACRLCPDCPRRCRelayMACL1RLCPDCPUERRCNASUuL1

UE Packet Data NW Gateway User PlaneServing GWPDN GWS5/S8 UDP/IPUDP/IP L2 L2L1L1 UDP/IP L2 L1 GTP-UIPSGiS1-UUueNodeBRLCL2 PDCPMACL1L1PDCPRLC MAC L1 IPApplicationUEUDP/IPGTP-URelayGTP-URelayGTP-U

Summary

SummaryUE control plane protocolsPDCPRLCMACL1IPApplicationUE user plane protocolsPDCPRLCMACL1RRCNASThe control signaling between the UE and the Evolved Packet Core is done with NAS protocol.

The control signaling between the UE and the E-UTRAN (eNodeB) is done with the RRC protocol.

Quiz

Quiz

Quiz1. The E-UTRAN consists of: eNodeBs and RNCs S-GW and P-GW eNodeBs eNodeBs and S-GW

2. The protocol used to send user data over the S1 interface is: S1AP SCTP GTP-UGTP-C

Quiz3. LTE is a work item under 3GPP which talks about the: EPC E-UTRAN EPS UTRAN4. SAE is a work item under 3GPP which talks about the : EPC E-UTRAN EPSUTRAN

Quiz5. Which protocol provides security for the RRC messages PDCP RLCMACGTP

Radio Resource Control protocol - RRC

Introduction

Scope and ObjectivesExplain the RRC idle and connected states and elaborate on mobility in each case;Mention the RRC Procedures and MessagesDescribe how System Information is transmittedExplain how the UE performs cell selection and reselection in idle mode. Describe the paging procedure and the RRC connection establishment procedureObjectivesScopeRRC States and mobilityRRC Procedures and MessagesSystem InformationIdle Mode behaviorPaging initiated by the Core Network and how it is forwarded to the UE.Signaling Radio Bearers and RRC Connection establishment

RRC ProceduresSystem informationCell Selection / ReselectionConnection controlRRC connection establishmentSecurity activationRRC connection re-establishmentRRC connection reconfigurationPagingRRC connection releaseRadio link failure related actionsMeasurement ControlMeasurement configurationMeasurement reporting

RRCRRC ConnectionRB ManagementvMeasurement ReportingAS SecurityConnected Mode MobilityPaging ReceptionCell SelectionSystem Info AquisitionMobility ManagementInter/Intra E-UTRAN mobilityMobility from E-UTRANHandover to E-UTRAN

Other proceduresTransparent transfer of NAS messages (DL/UL Direct Transfer)UE capability transferProtocol error handling

RRC MessagesCounterCheckCounterCheckResponseCSFBParametersRequestCSFBParametersResponseDLInformationTransferHandoverFromEUTRAPreparationRequest MasterInformationBlockMeasurementReportMobilityFromEUTRACommandPagingRRCConnectionReconfigurationRRCConnectionReconfigurationCompleteRRCConnectionReestablishmentRRCConnectionReestablishmentCompleteRRCConnectionReestablishmentRejectRRCConnectionReleaseRRCConnectionRequestRRCConnectionSetupRRCConnectionSetupCompleteSecurityModeCommandSecurityModeCompleteSecurityModeFailureSystemInformationSystemInformationBlockType1UECapabilityEnquiryUECapabilityInformationULHandoverPreparationTransferULInformationTransfer

RRC States

RRC StatesRRC-CONNECTED(EMM-REGISTERED)RRC-IDLE(EMM-REGISTERED)Connection Re-activationMME-initiated Connection ReleaseTracking Area UpdateTracking Area Update

Protocol States and Mobility

System Information

Example of mapping to channelsMIBSIB1SIB2SIB3SIB4SISISIB5BCCHBCHPBCHPDSCHBCCHDL-SCHPDSCHDL-SCHBCCHTTI=80TTI= 160TTI= 320TTI= 40

System Information BlocksSystem Information carried in System Information Blocks

System Parameters Related toMIBSIB 1SIB 2SIB 3SIB 4SIB 5SIB 6SIB 7SIB 8SIB 9SIB 10SIB 11Cell Selection InfoxPLMN-idxTracking Area CodexCell IdxCell BarredxFrequency Band IndicatorxSIB SchedulingxUL EARFCNxUL BandwithxDL BandwithxCommon Radio Resource ConfxPaging InfoxCell ReselectionxNeighbouring Cells -intra frequencyxNeighbouring Cells -inter frequencyxInter RAT reselection (UTRAN)xInter RAT reselection (GRAN)xInter RAT reselection (CDMA2000)xhome eNodeBxETWS notificationxx

Idle Mode

Idle Mode TasksPLMN Selection Location Registration PLMNs available PLMN selected Location Registration response Registration Area changes Indication to user Manual Mode Automatic mode Service requests NAS Control Radio measurements Cell Selection and Reselection Support for manual CSG ID selection Available CSG IDs to NAS CSG ID selected

RRC_IDLE Cell Selection Cell Reselection Stored Information Cell Selection Initial Cell SelectionConnected ModeAny Cell SelectionCamped on any cell Connected Mode (Emergency calls only) 2Camped Normallygo here whenever a new PLMN is selected no cell information stored for the PLMN cell information stored for the PLMNno suitable cell foundsuitable cell foundSelected PLMN is rejected suitable cell foundno suitable Cell foundreturn to Idle ModeLeave Idle Mode triggerSuitableCell found no suitableCell found go hereWhen no USIM in the UE USIM insertedAcceptableCell Found SuitableCell found no acceptable cell foundtriggerAcceptableCell found no acceptableCell Found leave Idle ModeAcceptableCell foundreturn toIdle Mode suitable cell found

Paging

CN Initiated Paging

LTE Paging - Initial Context SetupThe MME a paging message which is sent to all eNodeBs in a tracking area(s)UEs use the Random Access procedure to initiate access to the serving cellNAS messaging continues in order to set up the callS1-AP: INITIAL UE MESSAGE (FFS)+ NAS: Service Request+ eNB UE signalling connection IDRandom Access ProcedureNAS: Service RequestRRC PAGINGS1AP:PagingMME

Paging and DRX cyclePaging channel (PCH) uses PDSCH transmissionPaging indicated on PDCCHDRX cycle definedSpecial paging MAC ID indicating paging groupIf ID matches UE reads PDSCH to find which UE that is pagedsubframeDRX cycleUE receiver circuitry switched offPossibility to page this terminalUE receiver circuitry switched offPDCCH

SRBs and RRC Connection

Signaling Radio Bearers (SRBs)Signaling Radio Bearers (SRBs) are offered by the PDCP layer to the RRC layer for transport of RRC (and NAS) messages

SRB0: Used for RRC messages on the CCCHSRB1: Used for RRC and NAS messages on the DCCHSRB2 (optionally configured): Used for low-priority NAS messages on DCCHPDCPRRCSRB0SRB1SRB2

RRC Connection Establishment RRC Connection Request is initiated by the higher layers in the UEA unique UE identity S-TMSI is used in the request message

RRC Connection Setup

RRC connection establishment procedure creates the signaling radio bearer SRB1RRC Connection Request CCCH/ULSCHRRC Connection Setup CCCH/DLSCHRRC Connection Setup Complete DCCH/ULSCHIdle ModeConnected Mode

Security Related ProceduresMMEINITIAL CONTEXT SETUP REQUEST (Integrity Protection Algorithm EIA; Ciphering Algorithm EEA;Security Key)SECURITY MODE COMMAND (EEA;EIA)SECURITY MODE COMPLETE2. Decide Algorithms, Derive Keys Activate Security for SRBINITIAL CONTEXT SETUP RESPONSE

Summary

summary RRC Connection Request is initiated by the higher layers in the UE RRC Connection Setup (C-RNTI is allocated) RRC connection establishment procedure creates the signaling radio bearer RB#1,RRC Connection Request CCCH/ULSCHDLSCH RRC Connection SetupRRC Connection Setup Complete DCCH/ULSCHRRC IDLERRC CONNECTEDMaster Information BlockSystem Information Block

Quiz

Quiz

Quiz1. The control protocol between the UE and the eNodeB. S1AP X2AP RRC GTP-C

2. The radio bearer that carries the RRC messages in the radio interface. DRB SRB S1 BearerEPS Bearer

Quiz3. A UE in RRC_Idle state keeps its IP address in LTE True False

4. What are the services provided by the RRC protocol Broadcast of system information Paging and other idle mode behavior of the UE Radio resource establishment

Quiz5. What form/s of security is/are applicable for RRC messages? Ciphering Integrity checkBoth Ciphering and Integrity CheckNo security

Packet Data Convergence protocol - PDCP

Introduction

Scope and ObjectivesExplain what happens when a PDU arrives in the PDCP transmitting and receiving entityExplain what happens during Sequence numbering, header compression, integrity protection, ciphering and why we need themDescribe the PDCP data and control PDUSequence numbering Header compression Integrity protectionCipheringPDCP data and control PDUObjectivesScope

Packet Data Convergence ProtocolPDCP Functions Header compression/decompression of IP data flows using ROHC Transfer of data Maintenence of sequence numbers for radio bearers In sequence delivery of upper layer PDUs at re-establishment of lower layers Duplicate detection of lower layer SDUs at re-establishment Ciphering/deciphering of dataIntegrity protection/verification of Control Plane Timer based discard Duplicate discardingPDCP Services Transfer of user plane data Transfer of control plane data Header compression Integrity protection of control plane Ciphering both control and user plane

PDCP Entity and Functions

PDCP EntityRadio Interface (Uu)E-UTRAN/UETransmittingPDCP entityCipheringHeader Compression(user plane only) Receiving PDCP entitySequence numberingIntegrity Protection (control plane only)Add PDCP headerDecipheringRemove PDCP HeaderIn order delivery and duplicateDetection (U plane) Integrity Verification (control plane only)Packets associatedto a PDCP SDU Header Compression(user plane only) Packets associatedto a PDCP SDU Packets NOT associatedto a PDCP SDU Packets NOT associatedto a PDCP SDU UE/E-UTRAN

Sequence NumberingUEUE CtxSRB1_ULDRB_ULCOUNTCOUNTCOUNT-CCOUNT-CHOW: PDCP SN:Next_PDCP_TX_SNTX_HFNCOUNTWHY: Reordering Duplicate detection Integrity protection CipheringeNBSRB1_DLSRB1_DLSRB1_ULDRB_DLDRB_DLDRB_UL

Header CompressionSave the bandwith by: * Removing redundant info* Encoding important info* Hop by Hop* UnidirectionalRB_ULRB_ULPDCP PDUCRCchecksum covering the header before compression is included in the compressed headerCompressed HeaderContains encoded dataUE/UE ContextUE/UE Context

Integrity ProtectionEIACOUNTDirectionK_eNB_RRCIntPDCP PDUPDCP PDUHeaderPDCP SDUBearer IdMAC-IEIACOUNTDirectionK_eNB_RRCIntPDCP PDUPDCP PDUHeaderPDCP SDUBearer IdXMAC-IXMAC-IMAC-I=Sending SideUE/eNBReceiving SideUE/eNBWHY: To ensure data origin

CipheringPLAINTEXTBLOCK EEA COUNT-C/COUNTDIRECTION BEARER LENGTH KEYUPenc KEYSTREAM BLOCK CIPHERTEXT BLOCK EEA DIRECTION BEARER LENGTH KEYSTREAM BLOCK PLAINTEXTBLOCK Sender ReceiverEEA0 EEA1 EEA2COUNT-C/COUNTWHY: To protect the data over radioKEYUPenc

PDCP PDU

PDCP Data PDUThe PDCP Data PDU is used to convey:

A PDCP SDU SNUser plane data containing uncompressed PDCP SDUUser plane data containing compressed PDCP SDUControl plane dataMAC-I field (for SRB only)

PDCP Data PDU Format...PDCP SN(cont.)DataD/CPDCP SNRRROct 1Oct 2Oct 3...D/CPDCP SNOct 1Oct 2DataPDCP Data: PDU format SRBPDCP Data: PDU format DRB:SN 12 bits mapped to RLC AM/UM SN 7 bits mapped to RLC UM

PDCP Control PDU FormatPDCP Contorol: ROCH feedback...Interspersed ROHC feedback packetD/CPDU TypeRRRROct 1Oct 2PDCP Contorol: STATUS Report...Bitmap1 (optional)D/CPDU TypeBitmapN (optional)FMS (cont.)FMSOct 1Oct 2Oct 3Oct 2+ND/CData/ControlFMSFirst Missing PDCP SNROHCRObust Header Compression

Summary

SummaryData transfer addition of PDCP sequence number Ciphering and deciphering of user and control plane data Header compression and decompression with ROHC Integrity protection of control plane data

Quiz

Quiz

Quiz1. In sequence deliver may be performed by PDCP. True False

2. Which functions are provided by the PDCP layer? HARQ Radio Access Security ARQPower control

Quiz3. Service provided by PDCP to the RRC layer DRB SRBS1 BearerEPS Bearer4. Header compression is applicable for both UP and CP packets. True False5. A PDCP status PDU is a PDCP control PDU. a. True b.False

Quiz6. PDCP Sequence Numbering is used for:Re-orderingDuplicate DetectionIntegrity protectionChipering

7 Which protocol is responsible for encryption of user plane data.RLCRRCMACPDCP

Radio Link Control Protocol- RLC

Introduction

Scope and ObjectivesExplain why we need three RLC modesDescribe the RLC entities, their function and the RLC PDUs in each modeRLC transparent mode entityRLC unacknowledged mode entityRLC acknowledged mode entityRLC PDUsObjectivesScope

RLC Protocol EntityRLC FunctionsRLC ServicesIn-sequence deliveryDuplicate detectionFlow controlRLC Re-establishmentProtocol Error Detection and Recovery Segmentation and re-assemblyConcatenationPaddingTransfer of user data in TM, UM and AMError correction (ARQ) Provided to Upper Layers:Transparent data transferUnacknowledged data transferAcknowledged data transferExpected From Lower Layers:Data transferNotification of a transmission opportunityNotification of HARQ delivery failure from transmitting MAC entity

RLC Entities & Modes

RLC Entities

RLC Transparent Mode EntityTransmissionbufferTransmitting TM-RLC entityTM-SAPradio interfaceReceiving TM-RLC entityTM-SAPUE/ENBENB/UEBCCH/PCCH/CCCHBCCH/PCCH/CCCH

RLC unacknowledged Mode EntityTransmissionbufferSegmentation &ConcatenationAdd RLC headerTransmitting UM-RLC entityUM-SAPradio interfaceReceiving UM-RLC entityUM-SAPUE/ENBENB/UEDTCHDTCHReceptionbuffer & HARQ reorderingSDU reassemblyRemove RLC header

RLC AM EntityTransmissionbufferSegmentation &ConcatenationAdd RLC header Retransmission bufferRLC controlRoutingReceptionbuffer & HARQ reorderingSDU reassemblyDCCH/DTCHDCCH/DTCHAM-SAPRemove RLC header

RLC PDU

Protocol Data Units - PDURLC Data PDUTM PDU, UM PDU, AM PDU and AMD PDU Segment RLC Control PDUSTATUS PDU

The RLC TM PDU introduces no overhead TM is used for signaling on BCCH and PCCHRLC Transparent Mode PDU

Data

...

Oct 1

Oct N

Header: Fixed Part (FI, E, SN) + Extension Part (Es, LIs)UM RLC Entity configured by RRC to use either 5 bit SN or 10 bit SNRLC Unacknowledged Mode PDUUMD PDU with 5 bit SN (No LI )UMD PDU with 10 bit SN (No LI )

E

FI

SN

Data

...

Oct N

Oct 1

Oct 2

R1

R1

R1

FI

E

SN

SN

Data

...

Oct 3

Oct N

Oct 1

Oct 2

RLC Unacknowledged Mode PDU,5 bits SN, contUMD PDU with 5 bit SN (Odd number of LIs, i.e. K = 1, 3, 5, ) PDU with 5 bit SN (Even number of LIs, i.e. K = 2, 4, 6, )

LI2

E

LI2 (if K>=3)

E

LI1

LI1

E

FI

SN

Data

Oct N

Oct 1

Oct 2

Oct 3

Oct 4

...

LIK-1

E

LIK-1

E

LIK-2

LIK-2

...

Padding

E

LIK

LIK

Oct [2.5+1.5*K-1]

Oct [2.5+1.5*K-2]

Oct [2.5+1.5*K-3]

Oct [2.5+1.5*K-4]

Oct [2.5+1.5*K-5]

Oct [2.5+1.5*K]

Present if K >= 3

LI2

E

LI2

E

LI1

LI1

E

FI

SN

Data

Oct N

Oct 1

Oct 2

Oct 3

Oct 4

...

LIK

E

LIK

E

LIK-1

LIK-1

Oct [2+1.5*K-1]

...

Oct [2+1.5*K-2]

Oct [2+1.5*K-3]

Oct [2+1.5*K]

RLC Unacknowledged Mode PDU,10 bits SN, contUMD PDU with 10 bit SN (Odd number of LIs, i.e. K = 1, 3, 5, ) UMD PDU with 10 bit SN (Even number of LIs, i.e. K = 2, 4, 6, )

LI2

E

LI2 (if K>=3)

E

LI1

LI1

R1

R1

R1

FI

E

SN

SN

Data

Oct N

Oct 1

Oct 2

Oct 3

Oct 4

Oct 5

...

LIK-1

E

LIK-1

E

LIK-2

LIK-2

...

Padding

E

LIK

LIK

Oct [2.5+1.5*K]

Oct [2.5+1.5*K-1]

Oct [2.5+1.5*K-2]

Oct [2.5+1.5*K-3]

Oct [2.5+1.5*K-4]

Oct [2.5+1.5*K+1]

Present if K >= 3

LI2

E

LI2

E

LI1

LI1

R1

R1

R1

FI

E

SN

SN

Data

Oct [2+1.5*K-1]

Oct [2+1.5*K-2]

Oct [2+1.5*K+1]

...

Oct N

Oct 1

Oct 2

Oct 3

Oct 4

Oct 5

...

LIK

E

LIK

E

LIK-1

LIK-1

Oct [2+1.5*K]

AM RLC Entity uses10 bit SNHeader: Fixed Part (D/C, RF, P, FI, E, SN)RLC Acknowledged Mode PDUAMD PDU with 10 bit SN (No LI )+ Extension Part (E(s), LI(s))

D/C

RF

P

FI

E

SN

SN

Data

...

Oct 3

Oct N

Oct 1

Oct 2

RLC Acknowledged Mode PDU

SO

SO

LSF

Oct 3

Oct 4

LI2

E

LI2 (if K>=3)

E

LI1

LI1

D/C

RF

P

FI

E

SN

SN

Data

Oct N

Oct 1

Oct 2

Oct 5

Oct 6

Oct 7

...

LIK-1

E

LIK-1

E

LIK-2

LIK-2

...

Padding

E

LIK

LIK

Oct [4.5+1.5*K]

Oct [4.5+1.5*K-1]

Oct [4.5+1.5*K-2]

Oct [4.5+1.5*K-3]

Oct [4.5+1.5*K-4]

Oct [4.5+1.5*K+1]

Present if K >= 3

LI2

E

LI2

E

LI1

LI1

D/C

RF

P

FI

E

SN

SN

Data

Oct [4+1.5*K-1]

Oct [4+1.5*K-2]

Oct [4+1.5*K+1]

...

Oct N

Oct 1

Oct 2

Oct 5

Oct 6

Oct 7

...

LIK

E

LIK

E

LIK-1

LIK-1

Oct [4+1.5*K]

SO

SO

LSF

Oct 3

Oct 4

Information Element: E bit Extension bitFixed headerExtension part of the header

ValueDescription0Data field follows from the octet following the fixed part of the header1A set of E field and LI field follows from the octet following the fixed part of the header

ValueDescription0Data field follows from the octet following the LI field following this E field1A set of E field and LI field follows from the bit following the LI field following this E field

Information Element: Length Indicator, LILength Indicator (LI) field The LI field indicates the length in bytes of the corresponding data field element present in the RLC data PDU delivered/received by an UM or an AM RLC entity. The value 0 is reserved.

Information Element: Framing Information field, FI

Information Element: Segment Offset, SOThe Segment Offset field indicates the position of the AMD PDU segment in bytes within the original AMD PDU. The first byte in the Data field of the original AMD PDU is referred by the SO field value "000000000000000"

Information Element: Last Segment Flag, LSF Last Segment Flag field

Information Element:Resegmentation Flag, RF

Information Element: Poll, P Polling bit field

Information Element: Control Pdu Type, CPTControl PDU Type bit field

Summary

SummaryData transfer in Acknowledged, Unacknowledged and Transparent modeError correction by ARQ (AM)Concatenation, segmentation and reassembly of RLC SDUs (AM & UM)Examples VoIP: UM TCP-based traffic: AM TM is only used for SRBs when no RLC UM or AM entity is set up yet.

Quiz

Quiz

Quiz1. Is segmentation applicable for TM RLC? Yes No

2. Which mode of RLC is most suitable for VoIP services? TM RLC UM RLC AM RLC

Quiz3. All RLC modes are capable of error correction by ARQ. True False

4. Which RLC mode is most applicable for TCP services? TM RLC UM RLC AM RLC

Quiz5. RLC peers communicate thru : SRB DRBLogical channelTransport channel

Medium Access Control Protocol - MAC

Introduction

Scope and ObjectivesExplain how logical channels are mapped to transport channels and physical channelsDescribe the MAC PDU format, the Random access procedure, the HARQ mechanism, the DL and UL scheduling mechanism and UL time alignmentExplain the connection setup procedure.ObjectivesScopeMapping of channels MAC PDURandom access procedureHARQ mechanismDL / UL Scheduling mechanismUL Time AlignmentConnection Setup procedure

MAC ServicesData TransferReallocation of resourcesMAC FunctionsMapping between logical- and transport channelsMultiplexing of MAC SDUs Demultiplexing of MAC SDUsScheduling information reportingError CorrectionPriority handling between UEsPriority handling between logical channelsLogical channel prioritizationTransport Format selectionMAC Protocol Entity

Channels

Logical ChannelsControl:Broadcast Control Channel (BCCH)DL broadcast of system control information.Paging Control Channel (PCCH)DL paging information. UE position not known on cell levelCommon Control Channel (CCCH)UL/DL. When no RRC connection exists.Dedicated Control Channel (DCCH)UL/DL dedicated control information. Used by UEs having an RRC connection.

Traffic:Dedicated Traffic Channel (DTCH)UL/DL Dedicated Traffic to one UE, user information.

Transport ChannelsDownlink:Broadcast Channel (BCH)System Information broadcasted in the entire coverage area of the cell. Beamforming is not applied. Downlink Shared Channel (DL-SCH)User data, control signaling and System Info. HARQ and link adaptation. Broadcast in the entire cell or beamforming. DRX and MBMS supported.Paging Channel (PCH) Paging Info broadcasted in the entire cell. Uplink:Uplink Shared channel (UL-SCH)User data and control signaling. HARQ and link adaptation. Beamforming may be applied.Random Access Channel (RACH)Random Access transmissions (asynchronous and synchronous). The transmission is typically contention based. For UEs having an RRC connection there is some limited support for contention free access.

Physical Channels and SignalsPhysical channelsPhysical Downlink Shared Channel (PDSCH) transmission of the DL-SCH transport channelPhysical Uplink Shared Channel (PUSCH) transmission of the UL-SCH transport channelPhysical Control Format Indicator Channel (PCFICH) indicates the PDCCH format in DLPhysical Downlink Control Channel (PDCCH)DL L1/L2 control signalingPhysical Uplink Control Channel (PUCCH)UL L1/L2 control signalingPhysical Hybrid ARQ Indicator Channel (PHICH) DL HARQ infoPhysical Broadcast Channel (PBCH)DL transmission of the BCH transport channel.Physical Random Access Channel (PRACH) UL transmission of the random access preamble as given by the RACH transport channel

Physical signalsReference Signals (RS)support measurements and coherent demodulation in uplink and downlink.Primary and Secondary Synchronization signals (P-SCH and S-SCH)DL only and used in the cell search procedure. Sounding Reference Signal (SRS)supports UL scheduling measurements

UL-SCHChannel MappingDL-SCHLogical Channels type of information (traffic/control)Transport Channels how and with what characteristics (common/shared/mc/bc)DownlinkUplinkPhysical Channels bits, symbols, modulation, radio frames etcBCH-CQI -ACK/NACK -Sched req.-Sched TF DL -Sched grant UL -Pwr Ctrl cmd -HARQ infoMIB SIBACK/NACKPDCCH infoPhysical Signals only L1 info-meas for DL sched -meas for mobility -coherent demod-half frame sync -cell id -frame sync -cell id group -coherent demod-measurements for UL scheduling

MAC PDU

MAC PDULCIDLogical Channel IDEExtension BitRReservedFLength Flag LLengthMAC Control element 1...MAC headerMAC payload...R/R/E/LCID/F/L sub-headerMAC Control element 2MAC SDU MAC SDU Padding (opt)R/R/E/LCID/F/L sub-headerR/R/E/LCID/F/L sub-headerR/R/E/LCID/F/L sub-headerR/R/E/LCID/F/L sub-headerR/R/E/LCID padding sub-header

MAC Sub-headerLCIDRFLR/R/E/LCID/F/L sub-header with 7-bits L fieldR/R/E/LCID/F/L sub-header with 15-bits L fieldRELCIDRFLRELOct 1Oct 2Oct 1Oct 2Oct 3LCIDRR/R/E/LCID sub-headerREOct 1

MAC Procedures

MAC ProceduresRandom AccessMaintenance of Uplink Time AlignmentDL-SCH data transfer UL-SCH data transferPCH reception BCH reception Discontinuous Reception (DRX) MAC reconfiguration MAC Reset Semi-Persistent Scheduling

Random Access ProcedurePurposeInitial accessEstablish UL synchronizationIndicate presence of UL data Two typesCBRA Contention BasedCFRA Contention Free Consists of four phasesRandom Access PreambleRandom Access ResponseRRC Connection RequestRRC Connection Setup

Data Transfer using HARQ Number of HARQ processes tuned to match the RTT FDD 8 HARQ processes TDD depending on asymmetry Receiver processingTrBlk 1ACKReceiver processing1 ms TTITrBlk 0CFN0Hybrid ARQ processesFixed timing relationNACK Demultiplexed into logical channels and forwarded to RLC for reordering

DL Scheduling MechanismUE provides a Channel Quality Report (CQI) based on DL reference symbols Scheduler assigns resources per RB based on QoS, CQI etc. Resource allocation is transmitted in connection with data eNodeBDL schedulerUE

UL Scheduling MechanismUE requests UL transmission via scheduling request Scheduler assigns initial resources without detailed knowledge of buffer content More detailed buffer status report may follow in connection with data eNodeBUL schedulerMeasurementsUE

Maintenance of Uplink Time AlignmentWhen the UE gets Timing - Random Access Response - Piggy Backed together with dataTiming Advance CommandRROct 1UE 2UE 1

Connection Setup

Connection Setup* The IMSI is provided in the Attach Request** eNB UE S1AP id is included in all UE-related DL S1AP messages*** MME UE S1AP id is included in all UE-related UL S1AP messages except for Initial UE messageeNodeBMMEBCCH: System InformationUL-SCH: RRC Connection Request (Initial UE identity, Cause)Cell Selection DL-SCH: RRC Connection Setup (SRB1 parameters)Initial UE Message (eNB UE S1AP id **,NAS:Attach Request,TAI)Initial Context Setup Request (MME UE S1AP id ***, NAS: Attach Accept, Security, Bearer params, e.g. TEID)DL-SCH: Security Mode Command(Security Configuration)UL-SCH: Security Mode CompleteInitial Context Setup Response (Bearer params, e.g. TEID)UL-SCH: RRC Connection Setup Complete (Selected PLMN id, NAS: Attach Request *)PRACH: RACH preambleDL-SCH: RACH responseDL-SCH: RRC Connection Reconfiguration (Intra-frequency measurement configuration, Bearer Setup, NAS: Attach Accept)UL-SCH: RRC Conn Reconf CompleteUplink NAS Transport (NAS: Attach Complete)UL Inform Transfer (NAS: Attach Complete)LTE activeLTE activeRRC connectedRandom AccessRRC Connection EstablishmentInitial Context SetupAdmission Ctrl Allocation of SRB resources in BBMME selection (based on S-TMSI)Allocation of payload bearer resourcesRRC_CONNECTED

Summary

SummaryRandom Access ProcedureHybrid automatic repeat request (HARQ)

Quiz

Quiz

Quiz1. Which of the following is not a MAC function? Random access UL time alignment DL-SCH data transfer Ciphering

2. HARQ provides quicker layer 2 retransmission than ARQ. True False

Quiz3. Type of Random Access performed after cell reselection. CBRA CFRANo need to perform Random Access

4. Maximum number of parallel HARQ processes allowed in FDD. 2 4 68

Quiz5. The CQI report is transmitted on which channel when the UE is not scheduled in the uplink but UL synchronized? PUSCH PUCCH PRACH

Mobility in RRC Connected State

Introduction

Scope and ObjectivesUnderstand the S1 and X2 Interfaces and the related protocols Describe the X2, S1 and IRAT MobilityUnderstand the CS Fallback concept.

ObjectivesScopeS1 Interface and S1- APX2 Interface and X2- APX2, S1 and IRAT MobilityCS Fallback

S1 Interface and S1 Application Protocol

S1 Interface

Functions of S1APE-RAB ManagementInitial Context Transfer Function Mobility Function for UEs in LTE_ACTIVE PagingNAS signaling Transport between UE and MMECommon ID managementUE Capability Info Indication FunctionS1 Interface Management FunctionsS1 UE Context Release FunctionUE Context Modification FunctionStatus TransferTrace FunctionLocation ReportingS1 CDMA 2000 Tunneling FunctionWarning Message Transmission Function

S1AP Elementary Procedures, class 1

Elementary Procedure, class 1Initiating MessageSuccessful OutcomeResponse MessageUnsuccessful outcome Response MessageHandover PreparationHANDOVER REQUIREDHANDOVER COMMANDHANDOVER PREPARATION FAILUREHandover Resource AllocationHANDOVER REQUESTHANDOVER REQUEST ACKNOWLEDGEHANDOVER FAILUREPath Switch RequestPATH SWITCH REQUESTPATH SWITCH REQUEST ACKNOWLEDGEPATH SWITCH REQUEST FAILUREHandover CancellationHANDOVER CANCELHANDOVER CANCEL ACKNOWLEDGEE-RAB SetupE-RAB SETUP REQUESTE-RAB SETUP RESPONSEE-RAB ModifyE-RAB MODIFY REQUESTE-RAB MODIFY RESPONSEE-RAB ReleaseE-RAB RELEASE COMMANDE-RAB RELEASE RESPONSEInitial Context SetupINITIAL CONTEXT SETUP REQUESTINITIAL CONTEXT SETUP RESPONSEINITIAL CONTEXT SETUP FAILURE

S1AP Elementary Procedures, class 1

Elementary Procedure, class 1Initiating MessageSuccessful OutcomeResponse MessageUnsuccessful outcome Response MessageResetRESETRESET ACKNOWLEDGES1 SetupS1 SETUP REQUESTS1 SETUP RESPONSES1 SETUP FAILUREUE Context ReleaseUE CONTEXT RELEASE COMMANDUE CONTEXT RELEASE COMPLETEUE Context ModificationUE CONTEXT MODIFICATION REQUESTUE CONTEXT MODIFICATION RESPONSEUE CONTEXT MODIFICATION FAILUREeNB Configuration UpdateENB CONFIGURATION UPDATEENB CONFIGURATION UPDATE ACKNOWLEDGEENB CONFIGURATION UPDATE FAILUREMME Configuration UpdateMME CONFIGURATION UPDATEMME CONFIGURATION UPDATE ACKNOWLEDGEMME CONFIGURATION UPDATE FAILUREWrite-Replace WarningWRITE-REPLACE WARNING REQUESTWRITE-REPLACE WARNING RESPONSE

S1AP Elementary Procedures, Class 2

Elementary procedure, class 2Initiating MessageHandover NotificationHANDOVER NOTIFYE-RAB Release IndicationE-RAB RELEASE INDICATIONPagingPAGINGInitial UE MessageINITIAL UE MESSAGEDownlink NAS TransportDOWNLINK NAS TRANSPORTUplink NAS TransportUPLINK NAS TRANSPORTNAS non delivery IndicationNAS NON DELIVERY INDICATIONError IndicationERROR INDICATIONUE Context Release RequestUE CONTEXT RELEASE REQUESTDownlink S1 CDMA 2000 TunnelingDOWNLINK S1 CDMA 2000 TUNNELINGUplink S1 CDMA2000 TunnelingUPLINK S1 CDMA2000 TUNNELINGUE Capability Info IndicationUE CAPABILITY INFO INDICATIONeNB Status TransferENB STATUS TRANSFERMME Status TransferMME STATUS TRANSFERDeactivate TraceDEACTIVATE TRACETrace StartTRACE START

S1AP Elementary Procedures, Class 2

Elementary procedure, class 2Initiating MessageTrace Failure IndicationTRACE FAILURE INDICATIONLocation Reporting ControlLOCATION REPORTING CONTROLLocation Reporting Failure IndicationLOCATION REPORTING FAILURE INDICATIONLocation ReportLOCATION REPORTOverload StartOVERLOAD STARTOverload StopOVERLOAD STOPeNB Direct Information TransferENB DIRECT INFORMATION TRANSFERMME Direct Information TransferMME DIRECT INFORMATION TRANSFEReNB Configuration TransferENB CONFIGURATION TRANSFERMME Configuration TransferMME CONFIGURATION TRANSFERCell Traffic TraceCELL TRAFFIC TRACE

X2 Interface and X2 Application Protocol

X2 InterfaceInter-connection of eNodeBs supplied by different manufacturers;Support of continuation between eNodeBs of the E-UTRAN services offered via the S1 interface;Separation of X2 interface Radio Network functionality and Transport Network functionality to facilitate introduction of future technology

The main purpose for X2 is to support the active mode UE mobility (Packet Forwarding).

X2 Protocol Model

Functions of X2AP

Setting up the X2Resetting the X2Mobility ManagementLoad ManagementReporting of General Error SituationseNodeB Configuration Update

X2AP Elementary Procedures, class 1

Elementary Procedure, class 1Initiating MessageSuccessful OutcomeResponse MessageUnsuccessful outcome Response MessageHANDOVER PREPARATIONHANDOVER REQUESTHANDOVER REQUEST ACKNOWLEDGEHANDOVER PREPARATION FAILURERESETRESET REQUESTRESET RESPONSEX2 SETUPX2 SETUP REQUESTX2 SETUP RESPONSEX2 SETUP FAILUREENB CONFIGURATION UPDATEENB CONFIGURATION UPDATEENB CONFIGURATION UPDATE ACKNOWLEDGEENB CONFIGURATION UPDATE FAILURERESOURCE STATUS REPORTING INITIATIONRESOURCE STATUS REQUESTRESOURCE STATUS RESPONSERESOURCE STATUS FAILURE

X2AP Elementary Procedures, Class 2

Elementary procedure, class 2Initiating MessageLOAD INDICATIONLOAD INFORMATIONHANDOVER CANCELHANDOVER CANCELSN STATUS TRANSFERSN STATUS TRANSFERUE CONTEXT RELEASEUE CONTEXT RELEASERESOURCE STATUS REPORTINGRESOURCE STATUS UPDATEERROR INDICATIONERROR INDICATION

> Ue initial attach procedure

UE AttachMME7. INITIAL UE MESSAGE (Attach Request)14. INITIAL CONTEXT SETUP REQUEST (EPS bearers, Attach Accept, Security)22. INITIAL CONTEXT SETUP RESPONSE(EPS bearers)1. SYSTEM INFORMATION4. RRC CONNECTION REQUEST5. RRC CONNECTION SETUP15. RRC SECURITY MODE COMMAND16.RRC SECURITY MODE COMPLETE6. RRC CONNECTION SETUP COMPLETE (Attach Request)2. RANDOM ACCESS PREAMBLE3. RANDOM ACCESS RESPONSE10.RRC DL INFORMATION TRANSFER (Authentication Request)11. RRC UL INFORMATION TRANSFER (Authentication Response)DL NAS TRANSPORT (Authentication)UL NAS TRANSPORT (Auth. Response)DL NAS TRANSPORT (NAS SMC)UL NAS TRANSPORT (NAS SMC)Cell Select *23. RRC UL INFORMATION TRANSFER (Attach Complete)) UL NAS TRANSPORT (Attach Complete)RRC IDLERRC IDLE8.RRC DL INFORMATION TRANSFER (UE Identity Request)9. RRC UL INFORMATION TRANSFER (UE Identity Response)DL NAS TRANSPORT (UE Identity Req)UL NAS TRANSPORT (UEid Response)17. RRC UE CAPABILITY ENQUIRY18. RRC UE CAPABILITY iNFORMATION19. UE CAPABILITY INFO INDICATION(UE Radio Capability)24. UE CONTEXT RELEASE COMMAND26. RRC CONNECTION RELEASE25. UE CONTEXT RELEASE COMPLETERRC CONNECTED12. RRC DL INFORMATION TRANSFER (Security Mode Command)13. RRC UL INFORMATION TRANSFER (Security Mode Complete)20. RRC CONNECTION RECONFIGURATION (Attach Accept, Bearer Setup)21. RRC CONNECTION RECONFIGURATION COMPLETE

Intra lte handover

X2 Handover

DL Data Forwarding S-GW Transmitter State 5 6 4 X2APNext SN = 7 PDCP SN is continuous through Handoverend marker Source forwards outstanding un-ACK:ed SDUs to target with their SN attached. Source tells Target what PDCP SN to allocate next. Non-outstanding SDUs are forwarded (in order) without SN Target prioritizes forwarded SDUs. UE re-orders PDCP SDUs based on the SN. UE may submit a PDCP Status to guide Target re-Tx NO Data forwarding for SRBs; PDCP SN and HFN are reset @ target Source eNBTarget eNB

S1 HandoverRRC CONNECTEDRRC CONNECTED

Irat mobility

Interworking with 2G/3GHandover CELL_PCHURA_PCHCELL_DCH UTRA_Idle E-UTRA RRC_CONNECTED E-UTRARRC Idle GSM_Idle/ GPRS Idle GPRS Packet transfer modeGSM_Connected Reselection Reselection Reselection Connection establishment/release CCO, ReselectionCCO with NACC CELL_FACH CCO, Reselection +PDP context est* PMM_CONNECTED PMM_IDLE * PDP Context establishment is needed if no PDP context existsReselection +PDP context est* ECM-CONNECTEDECM-IDLE PMM_DETACHEDEMM-DEREGISTERED Idle Cell change without signalingCell change without signalingHandoverConnection establishment/releaseConnection establishment/releaseRelease with Redirect

LTE to 3G HandoverMMEsourceS-GWSGSNRNCPDN-GWtarget S-GW

Cs fallback

Why CS Fallback? The alternative if investment in IMS should be avoided

Based on reuse of legacy CS access

CS Fallback may be used as a generic telephony fallback method.E.g. secure functionality for incoming roamers.Terminals are expected to support it even if IMS/MMtel is supported

CS Fallback - ConceptSubscribers roaming with preference on LTE access, no CS-voice service available (i.e. IMS is not used as voice engine)

Fallback triggered to overlapping CS domain (2G/3G) whenever voice service is requested

Resumed LTE access for PS services after call completion (cell reselection)LTELTELTELTEGERAN/UTRANLTE island

CS FallbackMSS as voice engine for LTE subscribersMSS MSC-SM-MGwMGCFIM-MGwMRFPPacket CoreGSM / WCDMA RANLTE RANRCMMESAE GwGGSNSGSN4. Page over SGs-interfaceCSFB Terminal1. Subscriber registered in MSC but roam in LTE3. Incoming call to subscriber in LTECSFB Terminal5. RAN triggers an release with redirect

Attach Procedure CS FallbackMMELOCATION UPDATE ACCEPTRRC CONNECTION SETUP COMPLETE (Attach Request)LOCATION UPDATE REQRRC Connection Set up ProcedureEPS attach type IE: 001 EPS attach 010 combined EPS/IMSI attach 110 EPS emergency attach 111 reservedMSC Server/VLRHSSEPS Attach Procedure - initiatedUpdate Location in CS domainEPS Attach Procedure completedDerive VLR number;Allocate default LAI

Summary

Summary

More Information3GPP Technical Specifications 36-series3GPP TS 36.331E-UTRA; RRC Protocol specification 3GPP TS 36.323E-UTRA; Packet Data Convergence Protocol (PDCP) specification3GPP TS 36.322E-UTRA; Radio Link Control (RLC) protocol specification3GPP TS 36.321E-UTRA; Medium Access Control (MAC) protocol specification3GPP TS 36.300E-UTRA; Overall description

Quiz

Quiz

Quiz1. The application protocol between the eNodeB and the MME. S1AP X2AP RRC GTP-C

2. An X2 interface can be configured between eNodeBs belonging to different MME pool. True False

Quiz3. DL packet forwarding can be done in the X2 UP. True False

4. IRAT mobility may be executed using the X2 interface. True False

Quiz5. Handover decision in EPS is done by: UE eNodeBMMESGW

*Welcome to this eLearning LTE Radio Access Network Protocols and Procedures course.

Hi!The LTE Protocols and Procedures eLearning course gives a detailed description of the LTE RAN signaling. It covers the X2 and S1 interfaces and corresponding protocols X2AP and S1AP as well as the protocols used over these interfaces: RRC, PDCP, RLC, MAC and the physical layer for the radio interface.The objectives are to:Explain the RRC ProtocolExplain the PDCP ProtocolExplain the RLC and MAC ProtocolsExplain the X2/S1 Interface and the X2AP/S1AP ProtocolDescribe attach procedure and UE states and the difference between connected and idle modeDescribe call setupDescribe mobility over X2 and S1 Interfaces Describe IRAT Handover

*The course provides in-depth understanding of the protocols and procedures involved within the Evolved Packet System, EPS, in order to establish, maintain and release subscriber IP sessions. Are you a Systems Engineer, Service Engineer, Network Design Engineer, or are you just interested in learning how the latest technology in telecommunication works?This course will give you the knowledge you need in order to understand how signaling is performed between the UE, eNodeB, MME, Serving-Gateway and Packet Data Network Gateway. You will learn how the protocols communicate with each other, the functions and services that each one is responsible for and you will be able to follow the call flows in LTE. *Introduction to LTE Protocols & Procedures*The scope of this module includes:Evolved Packet System ArchitectureControl and user plane protocols andGeneral Protocol model and Protocol interactions

After the completion of this module you will be able to:Describe the Evolved Packet System ArchitectureList the control and user plane protocols Explain the General Protocol model and the interactions between protocolsDescribe the various traffics cases in EPS

LTE and SAE are work items or project names under 3GPP. LTE describes the new radio network, E-UTRAN. SAE is all about the new core network, the EPC. EPC is PS domain only.The whole network, E-UTRAN + EPC is known as the EPS, Evolved Packet System.*E-UTRAN, EPC and the UE together form the Evolved Packet System. An overview of the EPC architecture and its nodes are presented in this figure.The nodes within EPC are MME (Mobility Management Entity), S-GW (Serving Gateway), P-GW (Packet Data Network Gateway) and the HSS (Home Subscriber Server).In E-UTRAN, which is the radio access network, only one node exists, the eNodeB. The interface between the eNodeBs is called X2 and the interface between the EPC and the E-UTRAN is S1.

L3 signaling protocols are used to communicate between nodes using various messages with a defined structure. NAS, Non Access Stratum, messages are signaling messages between UE and MME which are always transparent in the eNodeB. RRC is the control plane connection between UE and eNodeB. S1AP is the application protocol in the S1 CP. X2 is the application protocol in the X2 CP. GTP-C is the control plane protocol in the S11, S5 CP, and S10 interfaces.

L2 transport protocols are used to carry signaling and user data across the EPC interfaces. PDCP, RLC and MAC are the 3 sublayer protocols in the CP and UP between the UE and the eNodeB. GTP-U transfers the user plane data in the S1 UP and the S5 UP. *This picture shows the general concept of SDUs (Service Data Units) and PDUs (Packet Data Units).For each layer, the payload is called SDU (Service Data Unit). whereas, for each layer, the payload plus the protocol header is called PDU (Packet Data Unit). For layer n, the PDU, when it is forwarded to the layer n+1, is considered payload for layer n+1 and thus it is called layer n+1 SDU. Then layer n+1 adds the protocol header for layer n+1 and the new layer n+1 PDU is created. For example, an RRC PDU is carried in a PDCP SDU. The PDCP SDU plus the PDCP header becomes the PDCP PDU. This PDCP PDU is carried in the RLC SDU, and so on...

EPS Bearer is the user plane connection between the UE and PGW.The NAS, Non Access Stratum, Signaling Connection is the control plane connection between the UE and the MME. It consist of the RRC connection or SRB between the UE and the eNodeB and the S1 control plane between the eNodeB and the MME.A UE having an RRC connection with the eNodeB is said to be in RRC_connected state.There is no soft or softer handover for the UE in LTE.

EPS Bearer is the user plane connection between the UE and PGW. Within the EPS bearer is an ERAB between the UE and the SGW and the DRB between the UE and eNodeB.EPS bearer can be default or dedicated.Default EPS bearer has no QoS defined and is always NonGBR. There is always one default EPS bearer for a UE attached to a PDN.This gives the UE the paradigm of an always on or always ready IP connectivity.Dedicated EPS bearer can be GBR or NonGBR.A UE can have a maximum of 8 EPS bearers, 1 default and up to 7 dedicated.

*In this figure we see the UE protocol stack and the main functionality that each layer is responsible for. The Non Access Stratum, NAS, protocols are responsible for Mobility management for idle UEs, NAS Security and Session Management. The NAS messages are transported by the RRC layer either concatenated with other RRC messages, or encapsulated in dedicated RRC messages.

The Radio Resource Control, RRC layer and protocol are responsible for :Broadcast of System Information,Paging,Establishment, maintenance and release of an RRC connection between the UE and E-UTRAN,Establishment, maintenance and release of point to point Radio Bearers.Also RRC is responsible for Mobility functions including: UE measurement reporting and control of the reporting for inter-cell and I-RAT mobility, UE cell selection and reselection and UE Context transfer between eNodeBs. On the network side, the RRC layer is terminated by the eNodeB.

Packet Data Convergence Protocol, PDCP provides its services to the NAS and RRC layers at the UE or the relay at the evolved Node B. It supports the following functions:header compression and decompression of IP data flows, transfer of data,maintenance of PDCP sequence numbers for radio bearers mapped on Radio Link Control, RLC, acknowledged mode,in-sequence delivery of upper layer PDUs at Handover,duplicate elimination of lower layer SDUs at Handover for radio bearers mapped on RLC acknowledged modeciphering and deciphering of user plane data and control plane data integrity protection of control plane data.PDCP uses the services provided by the RLC layer.

Radio Link Control, RLC, protocol is responsible for data transfer in unacknowledged, acknowledged or transparent mode. For example, unacknowledged mode could be used for Voice over IP while acknowledged mode is used to carry TCP-based traffic. The transparent mode shall be only used to send RRC messages when no RLC unacknowledged or acknowledged mode entity is set up yet.

Medium Access Control, MAC, layer is responsible for Uplink/Downlink Scheduling, Link Adaptation, Preamble based Random Access, Mapping between Logical channels to Transport channels, Error Correction by means of The Hybrid ARQ (HARQ) protocol.The Physical Layer is responsible for the actual transmission over the radio interface. It is also responsible for channel coding, Modulation and the mapping between Transport Channels to Physical Channels.*The protocol interaction and main functionality is illustrated in this picture. At the left side, there is the eNodeB and to the right there is the UE.Starting from top in the eNodeB, we see that PDCP performs header compression, ciphering. It also adds sequence numbers to the PDCP PDUs which are used for security algorithms and to guarantee in-sequence delivery at handovers. PDCP also provides ciphering and integrity functions. The RLC protocol may perform segmentation of large packets or concatenation of small packets. Also, ARQ (Automatic Repeat Request) is performed by this protocol. ARQ performs retransmissions of erroneously received blocks. A block is erroneous when the CRC (Cyclic Redundancy Check) at the receiver indicates an error.The MAC protocol handles scheduling of radio resources. The scheduler informs RLC of the amount of data to be sent, so that the RLC protocol can make decisions whether to perform segmentation or concatenation. MAC multiplexing is done in order to multiplex several logical channels onto transport channels.HARQ (Hybrid ARQ) is used in order to enable very rapid retransmissions over the radio interface. The scheduler controls both initial transmissions and retransmissions. The retransmissions are combined with the initial transmission. This is referred to as soft combining.Part of MAC protocol functionality is also transport format selection and link adaptation, which dynamically adapts the transport block size and modulation scheme to the current radio channel conditions. The physical layer adds the CRC to the transport block and performs Forward Error Correction, coding, modulation and the mapping of the transport block onto the physical resource blocks and mapping onto 1, 2 or 4 antennas.At the receiver side everything is done approximately in the reverse order.

*The control plane signaling between the UE and the network is handled by the RRC and the NAS, Non Access Stratum, protocols.The NAS protocol is responsible for the signaling between the UE and the core network node MME. The RRC protocol is responsible for the signaling between the UE and the eNodeB, but also carries the NAS signaling over the radio interface, Uu.The control plane signaling is carried by PDCP, RLC, MAC and the physical layer over the radio interface and by the S1 Application Protocol, Stream Control Transmission Protocol (SCTP), Internet Protocol (IP) and, typically, Ethernet (layer1/layer2) over the S1 interface.

*Over the air interface, the user plane between the UE and the packet gateway is carried by the PDCP, RLC, MAC protocols. Over S1, the user plane is carried by GTP-U (Gateway Tunneling Protocol- User plane), UDP (User Datagram Protocol), IP (Internet Protocol) and typically Ethernet (Layer1/Layer2). The end-to-end application is carried transparently in EPS over IP.In order to transmit information between the UE and the EPS, each layer sends packets to the lower layer or forwards data received from the lower layer to the upper layer. The next figure explains how each layer sends a packet to the next layer.

*Summary*The control signaling between the UE and the Evolved Packet Core is done with NAS protocol. The control signaling between the UE and the E-UTRAN is done with the RRC protocol. NAS is carried by RRC which is carried by PDCP, RLC, MAC and the physical layer in the UE side. RRC and NAS are not involved during data transfer in user plane. In the following modules we will explain each one of these protocols in detail. *Quiz **Answers: eNodeBsGTP-U*Answers: 3. E-UTRAN4. EPC*Answer:5. PDCP *Radio Resource Control protocol - RRC *RRC is the protocol responsible for signaling between the UE and the E-UTRAN. When the UE is powered on, it needs to select a PLMN and camp on a cell. The next step is to register to the network and to be prepared to receive paging messages and to establish calls. These are, among others, subjects that will be analyzed in this module. *The scope of this module includes:RRC States and mobilityRRC Procedures and MessagesSystem InformationIdle Mode behaviorPaging initiated by the Core Network and how it is forwarded to the UESignaling Radio Bearers and RRC Connection establishmentAfter this module you will be able to :Explain the RRC idle and connected states and elaborate on mobility in each case;Mention the RRC Procedures and MessagesDescribe how System Information is transmittedExplain how the UE performs cell selection and reselection in idle mode. Describe the paging procedure and the RRC connection establishment procedure*The RRC protocol is responsible for the following functions:Broadcasting of system information.Cell selection and reselection in idle mode based on measurements and system information. Connection Control, which includes : RRC connection establishment at call setup, the security functions, such as integrity check and ciphering. RRC connection re-establishmentRRC connection reconfiguration when the user plane service is established.Paging connected UEs in a tracking areaRRC connection releaseRRC connection supervision and release due to bad quality or radio link failure.Also, Connected mode mobility is carried out by RRC procedures, like Measurement configuration and measurement reporting. RRC protocols is responsible for coordinating intra-LTE and inter-Radio Access Technology handover. Other functions that RRC is responsible for is transparent transfer of NAS messages, UE capability transfer and protocol error handling.

*The RRC signaling is carried out by a number of RRC messages, which are listed in the slide.Click next to continue *Before we continue, we should explain the RRC States.*There are two RRC states: idle and connected.In RRC-IDLE state:The UE acquires the system information.It performs cell selection, neighboring cell measurements and cell reselectionIt monitors a Paging channel to detect incoming calls and system information changes. The ETWS capable UEs detect in addition Earthquake Tsunami Warning System notifications over the paging channels.In RRC-CONNECTED state there is transfer of unicast data to and from the UE.The UE monitors a Paging channel and/ or System Information Block Type 1 contents in order to detect system information change, and for ETWS capable UEs, ETWS notification;It monitors control channels associated with the shared data channel to determine if data is scheduled for it;It provides channel quality and feedback informationIt performs neighboring cell measurements and measurement reporting. Note that in connected state, mobility is network controlled.

*In Idle mode, the UE is not allocated any radio resources. This means that there is no user plane nor control plane connection established. The UE is responsible for the idle mode mobility. The UE measures neighboring cells and decides whether to make cell reselection to a new better cell or not.In order to support paging of idle mode UEs, the MME keeps track of the UEs locations, on a Tracking Area level. A Tracking Area, TA, consists of a number of cells, configured by the operator to belong to the same Tracking Area. The MME is informed about the UE position by Tracking Area Update messages. A UE sends a Tracking Area Update message when it enters a cell belonging to different tracking area.In connected mode the mobility is handled by the eNodeB, which makes all the handover decisions. The UE assists the eNodeB by sending measurement reports.*System information*The UEs read the system information in RRC_IDLE and RRC_CONNECTED mode.System information consists of the MasterInformationBlock, MIB, a number of SystemInformationBlocks,SIBs and a Scheduling Block, SB that indicates where and when the SIBs are transmitted.The MIB includes a limited number of the most essential and most frequently transmitted parameters and is transmitted on BCH. The SIBs and the Scheduling Block are grouped into Scheduling Units, SUs, mapped on the Downlink Shared Channel. The Scheduling Unit 1 that contains the Scheduling Block has a fixed scheduling.SIBs other than SystemInformationBlockType1 are carried in SystemInformation messages. The mapping of SIBs to System information messages is flexibly configurable by SchedulingInfoList included in SystemInformationBlockType1, with certain restrictions.

*In this table you can see the main content of the different System Information Blocks. Click on the play button to continue.*Idle mode behavior*The idle mode tasks can be divided into four processes:PLMN selection; Cell selection and reselection; Location registration;Support for manual CSG ID selection.

The relationship between these processes is illustrated in this figure.If necessary, the UE shall perform location registration in the tracking area of the chosen cell. The selected PLMN becomes the registered PLMN.If the UE finds a more attractive cell according to the cell reselection criteria, it reselects that cell and camps on it. If the new cell belongs to a different tracking area, location registration is performed. Search of available CSG IDs may be triggered by NAS to support manual CSG ID selection within the registered PLMN.

*The UE shall use one of the following two cell selection procedures:Initial Cell SelectionThis procedure requires no prior knowledge of which RF channels are E-UTRAN carriers. The UE shall scan all RF channels in the E-UTRAN bands according to its capabilities in order to find a suitable cell. On each carrier frequency, the UE need only search for the strongest cell. Once a suitable cell is found this cell shall be selected.Stored Information Cell SelectionThis procedure requires stored information of carrier frequencies and optionally also information on cell parameters, from previously received measurement control information elements or from previously detected cells. If no suitable cell is found the Initial Cell Selection procedure shall be started.

For normal service, the UE shall camp on a suitable cell, tune to that cell's control channel(s) so that it can receive system information from the PLMN and if registered, the UE can receive paging and notification messages from the PLMN and initiate transfer to connected mode.

*Paging*During Core Network initiated paging, the MME sends a paging message to all eNodeBs in the Tracking Area. Then the eNodeBs issue an RRC paging message in all the cells in the Tracking Area.*UEs use DRX, Discontinous Reception, when in idle mode in order to save battery. They do not check for paging messages continuously, but at regular intervals. When a UE receives a paging message, it sends, where necessary, a paging response back to the MME via the eNodeB and sets up the initial context. *With DRX the UE sleeps and it wakes up in regular intervals called paging occasions in order to check for a paging message. A paging occasion is a sub frame within a paging frame. The interval between the paging frames is called a DRX cycle. The DRX cycle is configurable by the operator.

The paging is indicated on PDCCH in the beginning of the paging occasion. There, the UE is informed that the group to which it belongs is paged. Also, it is informed about where to find the actual paging message in the time-frequency grid in this sub frame on the PDSCH.*Signaling Radio Bearers and RRC Connection

*Signalling Radio Bearers (SRBs) are defined as Radio Bearers that are used only for the transmission of RRC and NAS messages. More specifically, the following three SRBs are defined:SRB0 is for RRC messages using the CCCH logical channel.SRB1 is for RRC messages as well as for NAS messages on the DCCH only prior to the establishment of SRB2.SRB2 is for NAS messages, using DCCH logical channel. SRB2 has a lower-priority than SRB1 and is always configured by E-UTRAN after security activation.In downlink, piggybacking of NAS messages is used only for one dependant (i.e. with joint success/ failure) procedure: bearer establishment/ modification/ release. In uplink NAS message piggybacking is used only for transferring the initial NAS message during connection setup.Once security is activated, all RRC messages on SRB1 and SRB2 are integrity protected and ciphered by PDCP. NAS independently applies integrity protection and ciphering to the NAS messages.*RRC connection establishment involves SRB1 establishment. The procedure is also used to transfer the initial NAS dedicated information/ message from the UE to E-UTRAN.The UE will, after successful Random Access procedure, send RRC Connection Request on the Uplink shared channel to the eNodeB. The UE will identify itself with the Random Access Radio Network Temporary Identity in the random access procedure. However, in the RRC Connection Request the UE uses S-TMSI, SAE Temporary Mobile Subscriber Identity.The eNodeB answers with an RRC Connection Setup message on the Downlink shared channel and then the UE confirms the RRC connection setup with an RRC Connection Setup Complete message on the Uplink shared channel.Security Mode Command (click) and Security Mode Complete (click) activates security for the RRC messages.RRC Security Mode Command is triggered by the EPC (MME) at Initial Context Setup Request (click). This message includes all security setting needed to start Integrity Protection of the control plane signaling and Encryption of the both user plane and control plane signaling. Security setting includes Integrity Algorithm (EIA) Ciphering Algorithm (EEA) and Security key. Integrity check is mandatory while ciphering is optional.

*SummaryIn RRC idle mode the UE reads the System information and it selects a PLMN and a cell to camp on. If it needs to connect, it establishes the RRC Connection and it gets in RRC Connected state. During the last procedure it establishes the SRB1. SRB2 is established after the security activation.

*Quiz **Answers: RRCSRB*Answers: 3. True4. All 3 answers are correct (a,b and c)*Answer:5. C Both Ciphering and Integrity Check *Packet Data Convergence protocol - PDCP *In this module we are going to describe the PDCP protocol, its functions, the PDCP transmitting and receiving entity and the possible PDCP PDU formats. *The scope of this module includes: Sequence numbering Header compression Integrity protection Ciphering PDCP data and control PDU

After the completion of this module you will be able to: Explain what happens when a PDU arrives in the PDCP transmitting and receiving entity Explain what happens during Sequence numbering, header compression, integrity protection, ciphering and why we need them Describe the PDCP data and control PDU*Packet Data Convergence Protocol, PDCP, provides its services to the NAS and RRC protocols at the UE or the relay at the evolved Node B.

The Packet Data Convergence Protocol supports the following functions:Header compression and decompression of IP data flows using the Robust Header Compression protocol, ROHC, at the transmitting and receiving entity, respectively Transfer of data, user plane or control plane. This function is used for conveyance of data between users of PDCP services. Maintenance of PDCP sequence numbers for radio bearers mapped on Radio Link Control, RLC, acknowledged mode In-sequence delivery of upper layer PDUs at Handover Duplicate elimination of lower layer SDUs at Handover for radio bearers mapped on RLC acknowledged mode Ciphering and deciphering of user plane data and control plane data Integrity protection of control plane data Timer based discard Duplicate discarding

PDCP offers these functions as services to the above layers. At the same time, it uses the services provided by the Radio Link Control sub layer.

*PDCP Entity and Functions*Each Data Radio Bearer and Signaling Radio Bearer, except for SRB0, is associated with one PDCP entity. Each PDCP entity is associated with one or two RLC entities, one for each direction, depending on the Radio Bearer characteristic and RLC mode. The PDCP entities are located in the PDCP sub-layer.

Each PDCP entity is carrying the data of one radio bearer. In the current version of the specification, only the robust header compression protocol, ROHC, is supported. Every PDCP entity uses at most one ROHC instance.

A PDCP entity is associated either with the control plane or the user plane depending on which radio bearer it is carrying data for.Packets NOT associated to a PDCP SDU are, for example, ROHC feedback.*Sequence numbering is the first PDCP task at reception of an IP package. There are several functions that use sequence number: Reordering of the PDCP PDUs at the receiver side Duplicate detection in case of packet forwarding at handover

Furthermore, the PDCP sequence number together with the Hyper Frame Number (HFN) is used to calculate the parameters COUNT and COUNT-C which are used for integrity protection and ciphering. *Header compression and decompressionIn many services and applications, e.g. Voice over IP, interactive games, messaging etc. the payload of the IP packet is sometimes even smaller than a header.

Over end-to-end connection, comprised of multiple hops, the content of the IP header is extremely important. However over just one link, UE to eNodeB, it is possible to omit some information that will never change, due to its static nature during the connection time. Thus, it is possible to compress those headers in many cases up to 90%. As a consequence link budget can be improved by several dB due to the decrease of the header size. In the low bandwidth networks, using header compression results in a better response time due to smaller packet sizes. Header Compression has to be negotiated at the time of the link set up. Both sides of the link need to be capable of running the same header compression algorithms.The header compression protocol specified in PDCP is based on the Robust Header Compression, ROHC, framework IETF RFC 3095. There are multiple header compression algorithms, called profiles, defined for the Robust Header Compression framework. Each profile is specific to the particular network layer, transport layer or upper layer protocol combination e.g. TCP/IP and RTP/UDP/IP.*The integrity protection function includes both integrity protection and integrity verification and is performed in PDCP for PDCP entities associated with SRBs. The data unit that is integrity protected is the PDU header and the data part of the PDU before ciphering. The integrity protection key to be used by the PDCP entity is generated during EPS Authentication and Key Agreement function. The UE Computes the KASME based on the parameters received in the Authentication Request message and the MME receives the KASME from HSS. KASME is further used to generate K_eNB. Using key derivation function K_RRCenc, K_RRCint and K_UPenc are derived from K_eNB. K_RRCint is used for integrity protection, while K_UPenc and K_RRCenc are used for ciphering.The algorithm to be used is decided by eNodeB during RRC security activation. The integrity protection function shall be applied to all control plane PDUs for the downlink and the uplink, respectively.

*The ciphering function in PDCP includes both ciphering and deciphering and is performed in PDCP. For the control plane, the data unit that is ciphered is the data part of the PDCP PDU and the MAC-I. For the user plane, the data unit that is ciphered is the data part of the PDCP PDU; ciphering is not applicable to PDCP Control PDUs.The encryption key to be used by the PDCP entity is generated during EPS Authentication and Key Agreement function. The ciphering function is activated by upper layers as defined in 3GPP technical specification 36.331. After security activation, the ciphering function shall be applied to all PDCP PDUs indicated by upper layers for the downlink and the uplink, respectively.The parameters that are required by PDCP for ciphering are defined in 3GPPTechnical Specification33.401 and are inputs in the ciphering algorithm. The required inputs to the ciphering function include the: COUNT or COUNT-C, DIRECTION, Downlink or Uplink the radio bearer identifier (BEARER) and the ciphering keys, KRRCenc for the control plane and KUPenc for the user plane.*PDCP PDU*There are two types of PDCP PDUs: PDCP Data PDUs and PDCP Control PDUs.

The PDCP Data PDUs carry a sequence number. They are used to convey both Control plane and User plane SDUs. The user plane data can be either compressed or uncompressed PDCP SDUs. When PDCP carries Signaling Radio Bearer, the MAC-I is also present for integrity protection. *At the left side you can see the format of a PDCP Data PDU carrying data for control plane SRBs.At the upper right side you can see the format of the PDCP Data PDU when a 12 bit sequence number length is used. This format is applicable for PDCP Data PDUs carrying data from Data Radio Bearers mapped on RLC Acknowledge mode or RLC Unacknowledged mode.The Lower right part of this figure shows the format of the PDCP Data PDU when a 7 bit Sequence number length is used. This format is applicable for PDCP Data PDUs carrying data from Data Radio Bearers mapped on RLC Unacknowledged mode.*The left part of this figure shows the format of the PDCP Control PDU carrying one interspersed ROHC feedback packet. This format is applicable for data radio bearers mapped on RLC acknowledged mode or RLC unacknowledged mode. The right part of this figure shows the format of the PDCP Control PDU carrying one PDCP status report. This format is applicable for Data radio bearers mapped on RLC acknowledged mode. *Summary*When an RRC PDU or an IP packet arrives in the PDCP transmitting entity, the PDCP sequence number is added for reordering and duplicate detection reasons. Then, header compression is performed in order to save some bandwidth. Last but not least, security functions like integrity protection and ciphering are performed. In the PDCP receiving entity, everything happens in the reverse order.

*QuizQuiz **Answers: TrueRadio access security*Answers: 3. SRB4. False. Only for UP packets.5. True

*Answer:6. all answer are corrrect (should be marked)7. PDCP *Radio Link Control Protocol- RLC *This module deals with the RLC protocol layer. We will talk about the three RLC modes: transparent, unacknowledged and acknowledged, and also about the RLC entities and the RLC PDUs in each case.

*The scope of this module includes:RLC transparent mode entityRLC unacknowledged mode entityRLC acknowledged mode entityRLC PDUs

After the completion of this module you will be able to: Explain why we need three RLC modes.Describe the RLC entities, their function and the RLC PDUs in each mode.

*Radio Link Control, RLC, Protocol Layer is a Layer 2 protocol. It is controlled and configured by RRC layer but it offers services both to RRC and PDCP protocols. RLC is responsible for providing data transfer to and from the upper layers in three different modes: Transparent Mode, TM, Unacknowledged Mode, UM, and Acknowledged Mode, AM. Apart from data transfer, it expects from the lower layer Notification of a transmission opportunity and notification of HARQ delivery failure from the transmitting MAC entity.An RLC entity can be configured to operate in TM, UM or AM mode. The functions that are performed by the RLC entities are concatenation, padding, data transfer, error correction, In-sequence delivery, Duplicate detection, Flow control, RLC Re-establishment, Protocol Error Detection and Recovery. *RLC Entities and Modes*This figure illustrates the RLC entities. The transmitting and receiving entities of Transparent and Unacknowledged mode are independent of each other in Uplink and Downlink. In Acknowledged mode there is a dependency between the transmitting and receiving entity that is related to the ARQ mechanism. *A Transparent mode RLC entity can be configured to deliver or receive RLC PDUs through the following logical channels: BCCH, Downlink/Uplink CCCH and PCCH.When a transmitting Transparent mode RLC entity forms the PDUs from RLC SDUs it will not:segment nor concatenate the RLC SDUsinclude any RLC headers. Remember that a PDU is an SDU with the header. In the Transparent mode case, there is no header, so RLC PDU is the same as the RLC SDUWhen a receiving Transparent mode RLC entity receives PDUs it will deliver the transparent mode data PDUs to the upper layer.*An unacknowledged mode RLC entity delivers or receives RLC unacknowledged mode data PDUs.In the transmitting unacknowledged mode RLC entity, the unacknowledged mode SDUs are put in the transmission buffer. Then there is segmentation and/or concatenation so they fit within the total size of RLC PDU. After the segmentation and concatenation the RLC header is added to the RLC SDU and the RLC PDU is created. When a receiving unacknowledged mode RLC entity receives unacknowledged mode data PDUs, it will:detect whether or not the PDUs have been received in duplication, and discard duplicated onesreorder the PDUs if they are received out of sequencedetect the loss of PDUs at lower layers and avoid excessive reordering delaysreassemble the SDUs from the reordered PDUs and deliver the RLC SDUs to upper layer in ascending order of the RLC sequence numberdiscard received unacknowledged mode data PDUs that cannot be re-assembled into an RLC SDU due to loss at lower layers of an unacknowledged mode data PDU which belonged to the particular RLC SDUAt the time of RLC re-establishment, the receiving unacknowledged mode RLC entity will:if possible, reassemble RLC SDUs from the PDUs that are received out of sequence and deliver them to upper layerdiscard any remaining PDUs that could not be reassembled into RLC SDUsinitialize relevant state variables and stop relevant timers*An acknowledged mode RLC entity can be configured to deliver and receive RLC PDUs through the logical channels Downlink/Uplink DCCH or Downlink/Uplink DTCH.An acknowledged mode RLC entity delivers and receives acknowledged mode data PDUs, data PDU segments and control STATUS PDUs. At the transmitting side of an acknowledged mode RLC entity, the RLC SDUs will be segmented and concatenated if necessary, so that the acknowledged mode data PDUs fit within the total size of RLC PDUs indicated by lower layer. Then the RLC header will be added to the RLC SDU so that the RLC PDU will be created. The transmitting side of an acknowledged mode RLC entity supports retransmission of RLC data PDUs.When the receiving side of an acknowledged mode RLC entity receives RLC data PDUs, it will:detect whether or not the RLC data PDUs have been received in duplication, and discard duplicated RLC data PDUsIt will reorder the RLC data PDUs if they are received out of sequencedetect the loss of RLC data PDUs at lower layers and request retransmissions to its peer acknowledged mode RLC entityreassemble RLC SDUs from the reordered RLC data PDUs and deliver the RLC SDUs to upper layer in sequenceDuring RLC re-establishment, the receiving side of an acknowledged mode RLC entity has the same tasks as the unacknowledged mode entity. *RLC PDU*There are two types of RLC PDUs:RLC Data PDUs carry both control plane and user plane signaling that origins from RRC or PDCP while RLC Control PDUs carry control information between RLC peers.*Transparent Mode PDU is illustrated in this figure and as already mentioned it does not introduce any overhead in terms of RLC header. It consists of Data field only and is octet aligned.*Unacknowledged Mode data PDU consists of a Data field and an Unacknowledged Mode data PDU header.Unacknowledged Mode PDU header consists of a standard part and an extension part.The fixed part of the UMD PDU header itself is byte aligned and consists of a Framing Info - FI, an extension - E and a Sequence number - SN. The extension part of the acknowledged mode data PDU header itself is byte aligned and consists of extensions and Length Indicators, LIs.An unacknowledged mode RLC entity is configured by RRC to use either a 5 bit Sequence number or a 10 bit Sequence numberWhen the 5 bit Sequence number is configured, the length of the fixed part of the unacknowledged mode data PDU header is one byte When the 10 bit Sequence number is configured, the standard part of the unacknowledged mode data PDU header is identical to the standard part of the acknowledged mode data PDU header. The difference is that the Data/Control, the re-segmentation flag and the Poll bit fields are here replaced with R1 fieldsThe extension part of the unacknowledged mode PDU header is identical to the extension part of the acknowledged mode PDU header, regardless of the configured Sequence number size.An unacknowledged mode PDU header consists of an extension part only when more than one Data field element is present in the unacknowledged mode PDU, in which case an extension and a Length indicator are present for every Data field element except the last. Furthermore, when an unacknowledged mode data PDU header consists of an odd number of Length indicators then four padding bits follow after the last length indicator.*Unacknowledged mode data PDU consists of a Data field and an Unacknowledged mode data PDU header.The header consists of a standard part and an extension part. The extension is present only when necessary. The standard part of the header itself is octet aligned and consists of a Framing Information - FI, an extension - E and a Sequence Number - SN. The extension part of the header consists of extensions, Es, and length indicators LIs.An Unacknowledged mode RLC entity is configured by RRC to use either a 5 bit Sequence number or a 10 bit Sequence number. When the 5 bit Sequence number is configured, the length of the standard part of the Unacknowledged mode data PDU header is one byte. Furthermore, when an Unacknowledged mode data PDU header consists of an odd number of length indicators then four padding bits follow after the last length indicator.

*When the 10 bit Sequence number is configured, the standard part of the unacknowledged mode data PDU header is identical to the standard part of the acknowledged mode data PDU header. The difference is that the Data/Control, the re-segmentation flag and the Poll bit fields are here replaced with R1 fields.The extension part of the Unacknowledged mode data PDU header is identical to the extension part of the Acknowledged mode data PDU header, regardless of the configured Sequence number size.The header consists of an extension part only when more than one Data field element is present in the PDU, in which case an extension and a length indicator are present for every Data field element except the last. Furthermore, when an Unacknowledged mode data PDU header consists of an odd number of length indicators, four padding bits follow after the last length indicator. *Acknowledged mode data PDU consists of a Data field and a header.The header consists of a fixed part and an extension part. The fixed part of the header itself consists of a Data/Control field, a Re-segmentation Flag field, RF, a Poll bit field, P, a Framing Info, FI, an extension, E, and a Sequence Number, SN. The extension part of the header consists of extensions, Es, and length indicators, LIs.*An Acknowledged mode data PDU header consists of an extension part only when more than one Data field element is present in the Acknowledged mode data PDU. In this case, an extension and a length indicator field are present for every Data field element except the last. Furthermore, when the header consists of an odd number of length indicators, four padding bits follow after the last length indicator.

The Extension may be found in both the fixed and the extension part of the header.The Extension field (E field) indicates whether the Data field or another set of E field and Length Indicator (LI) field follows this bit.The first LI present in the RLC data PDU header corresponds to the first Data field element present in the Data field of the RLC data PDU. The second LI present in the RLC data PDU header corresponds to the second Data field element present in the Data field of the RLC data PDU, and so on.More than one LI field indicates concatenation.The FI field is composed of 2 bits.This field indicates the position of this RLC SDU segment within the original RLC SDU after segmentation.This field is necessary during reassembly.Specifically, the SO field indicates the position within the Data field of the original AMD PDU to which the first byte of the Data field of the AMD PDU segment corresponds to.

SO start (SOstart) fieldLength: 15 bits.The SOstart field (together with the SOend field) indicates the portion of the AMD PDU with SN = NACK_SN (the NACK_SN for which the SOstart is related to) that has been detected as lost at the receiving side of the AM RLC entity. Specifically, the SOstart field indicates the position of the first byte of the portion of the AMD PDU in bytes within the Data field of the AMD PDU. The first byte in the Data field of the original AMD PDU is referred by the SOstart field value "000000000000001", i.e., numbering starts at one.

SO end (SOend) fieldLength: 15 bits.The SOend field (together with the SOstart field) indicates the portion of the AMD PDU with SN = NACK_SN (the NACK_SN for which the SOend is related to) that has been detected as lost at the receiving side of the AM RLC entity. Specifically, the SOend field indicates the position of the last byte of the portion of the AMD PDU in bytes within the Data field of the AMD PDU. The first byte in the Data field of the original AMD PDU is referred by the SOend field value "000000000000001", i.e., numbering starts at one. The special SOend value "111111111111111" is used to indicate that the missing portion of the AMD PDU includes all bytes to the last byte of the AMD PDU. The LSF indicates if this RLC PDU is the last segment of the corresponding original RLC SDU which is significant to commence reassembly.The RF field indicates whether the RLC PDU is an AMD PDU or AMD PDU segment.The RLC in the transmitter sets the Polling bit to a value of 1 whenever it requires a status report from the receiving RLC.The setting of this bit follows a window based timing and is only used by AM RLC for normal ARQ.This field indicates which type of RLC control PDU it is.There is only a status PDU type as of now indicated by 000 in the header.The status PDU contains the status report from the receiving RLC when the polling bit was set to 1. *Summary*The RLC protocol supports transparent, unacknowledged and acknowledged mode data transfer. In acknowledged and unacknowledged mode the RLC layer performs concatenation, segmentation and reassembly of RLC SDUs. The Unacknowledged mode is best effort. The acknowledged mode requires acknowledgement of reception of packets and offers error correction by means of ARQ mechanism. Whether Unacknowledged mode or Acknowledged mode is used is configured per radio bearer. For example, Unacknowledged mode could be used for Voice over IP while Acknowledged mode is used to carry TCP-based traffic. The RLC transparent mode shall only be used to send RRC messages when no RLC Unacknowledged mode or Acknowledged mode entity is set up yet. The transparent mode introduces no overhead as there is no RLC header. *Quiz **Answers: NoUM RLC*Answers: 3. False. Only AM RLC4. AM RLC*Answer:5. Logical channel *Medium Access Control protocol - MAC *The MAC layer for the LTE access can be compared to the Rel-6 MAC-hs/MAC-e and covers mainly similar functionality like Hybrid Automatic Repeat Request - HARQ, priority handling, transport format selection and DRX control.*The scope of this course includes:Mapping of channels MAC PDURandom access procedureHARQ mechanismDownlink/Uplink Scheduling mechanismUL time alignmentConnection Setup procedure

After the completion of this module you will be able to:Explain how logical channels are mapped to transport channels and then to physical channels;Describe the MAC PDU format, the Random access procedure, the HARQ mechanism, the Downlink and Uplink scheduling mechanism; Explain the connection setup procedure.

*This figure summarizes the Services and functions of the MAC protocol.The MAC Services includes Data Transfer and Reallocation of resources. The MAC Functions include:Mapping between logical channels and transport channelsMultiplexing of MAC SDUs from one or different logical channels onto transport block (TB) to be delivered to the physical layer on a transport channelDemultiplexing of MAC SDUs from one or different logical channels from transport block to be delivered from the physical layer on a transport channelScheduling information reportingError Correction (HARQ)Priority handling between UEs by means of dynamic schedulingPriority handling between logical channels of one UELogical channel prioritizationTransport Format selection *Channels*The following logical channels are supported for control signaling:Broadcast Control Channel for Downlink broadcast of system control information.Paging Control Channel for Downlink paging information when the position of the UE is not known on cell level.Common Control Channel for Uplink and Downlink signaling when no RRC connection exists.Dedicated Control Channel for Uplink and Downlink control information, used by UEs that do not have an RRC connection.

For uplink and downlink user plane traffic there is the Dedicated Traffic Channel.

*The following Transport channels are supported in the Downlink:Broadcast Channel for broadcast of System Information in the entire coverage area of the cell. Downlink Shared Channel for User data, control signaling and System Information. It uses MIMO with spatial multiplexing.Paging Channel for broadcast of Paging Info in the entire cell. In the uplink there is:The Uplink Shared channel for User data and control signaling and The Random Access Channel for Random Access transmissions, asynchronous and synchronous.

*The transport channels just mentioned are carried by physical channels in the physical layer. The physical channels are listed in this picture. The mapping between the transport channels and the physical channels is explained in the following slide.

Some of the physical channels do not carry transport channels. These are the PCFICH, PDCCH, PHICH and PRACH. The PCFICH is used to indicate the transmission format of the PDCCH.The PDCCH carries layer 1 and layer 2 control signaling in downlink, for instance scheduling assignments for downlink and scheduling grants for the uplink. The PUCCH carries layer 1 and layer 2 control signaling in uplink, for instance CQI information and acknowledgements. The PHICH carries acknowledgements and non-acknowledgements in Downlink for the Uplink data transmissions.

Transmissions that do not carry any information from higher layers (i.e. Layer 2 and above) are referred to as Physical Signals. This is pure layer 1 signaling, e.g. Reference Signals and Synchron