E1 1 UMTS Signaling Flow

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E1 1 UMTS Signaling Flow

Transcript of E1 1 UMTS Signaling Flow

  • UMTS Signaling FlowZTE University

  • ContentUE State transitionSignaling flow

  • Classification of FlowsIn terms of protocol stack, signaling flows can be access layer signaling flows or non-access layer signaling flows. In terms of network composition, signaling flows can be categorized as circuit-switched or packet-switched. Access layer and non-access layer signaling flows are actually so named from the perspective of protocol stack.

  • Classification of FlowsThe flows at the access layer include PLMN selection, cell selection, and radio resource management flows. The radio resource management flows are the flows at the RRC layer, including the RRC connection setup flow, flow of the signaling setup between UEs and CNs, RAB setup flow, call release flow, handover flow, and SRNS redirection flow.

  • UE Working ModesThere are two basic working modes:IdleUE stands by without any service. Theres no connection between UE and UTRAN.ConnectedUE transferred to the connected mode after accomplishing RRC Connection Setup.UE has 4 states under the connected mode:Cell-DCH, Cell-FACH, Cell-PCH, URA-PCH

  • UE State

  • UE States Under the Connected ModeCell-DCHUE is activated, and in service using its dedicated channels.There are dedicated channels in both uplink and downlink.UTRAN knows exactly which cell the UE is in.Cell-FACHUE is activated, but without too much date to transmit, so theres no need to assign dedicated channels to it.Downlink data transmitted in FACH, while uplink in RACH.UTRAN knows exactly which cell the UE is in.

  • UE States Under the Connected ModeCell-PCHThere is no data transmitted in both uplink and downlink.UE needs to listen to PICH for paging information.UE works in discrete receiving, which saves the power effectively.UTRAN knows exactly which cell the UE is in.UE needs to do cell update procedure when it passes cells.URA-PCHThere is no data transmitted in both uplink and downlink.UE needs to listen to PICH for paging information and receive discretely.UTRAN only knows which URA (UTRAN Registration Area) UE exists.UE updates its location information only when its URA changes, which further reduces the signaling saves resource.

  • RRC State Transition (I)After RRC Connection Setup, UE will transit to CELL_FACH or CELL_DCH.CN indicates UE using dedicated channel (CELL_DCH) or common channel (CELL_FACH) according to the service request.If there is no service right now, UE will be indicated into PCH mode or release RRC connection back to IDLE mode.URA_PCHCELL_DCHCELL_FACHCELL_PCHIDLEDEADIDLEDEADCELL_DCHCELL_FACHIDLESketch of RRC State Transition Transit from IDLE Mode

  • URA_PCHCELL_DCHCELL_PCHIDLEDEADIDLEDEADCELL_FACHIDLERRC State Transition (II)UE do not occupy dedicated channels In the mode of CELL_FACH.UE receives downlink data through FACH(S-CCPCH).UE transmits uplink data through RACH(PRACH).Transit from CELL_FACH ModeSketch of RRC State Transition

  • URA_PCHCELL_DCHCELL_FACHCELL_PCHIDLEDEADIDLEDEADCELL_DCHIDLEURA_PCHCELL_PCHCELL_DCHRRC State Transition (III)UE transceives uplink and downlink data through dedicated channels (DPDCHs and DPCCHs).During the time when there is no data transmitted, CN may indicate UEs transiting to URA_PCH or CELL_PCH.Transit from CELL_DCH ModeSketch of RRC State Transition

  • URA_PCHCELL_DCHCELL_FACHCELL_PCHIDLEDEADIDLEDEADCELL_DCHIDLECELL_DCHURA_PCHCELL_PCHCELL_FACHCELL_PCHURA_PCHRRC State Transition (IV)UE has no activated uplink.Paging Information makes UE back to CELL_FACH or CELL_DCH mode.In CELL_PCH, UE should transit to CELL_FACH first to finish cell updating, and go back if no service request.In URA_PCH, if URA changes, UE also transits to CELL_FACH to finish cell updating first before it goes back to URA_PCH.System resource can be saved in these two modes.Sketch of RRC State Transition

  • ContentUE State transitionSignaling flow

  • Basic Conception (1)RRC (Radio Resource Control)provides information transfer service to the NAS (Non Access Stratum).responsible for controlling the configuration of UMTS radio interface Layers 1 and 2.RRC ConnectionA point to point bi directional connection between the RRC (Radio Resource Control) entities on the UE (User Equipment) and UTRAN (UMTS Terrestrial Radio Access Network). The UE requires an RRC connection to access the services of the UMTS network.

  • Basic Conception (2)RAB -Radio Access BearerIdentify the service the AS (Access Stratum) provides to the NAS (Non Access Stratum) for transfer of user data between the UE (User Equipment) and the CN (Core Network). RB -Radio BearerThe service provided by the Layer 2 for the transfer of user data between UE (User Equipment) and UTRAN (UMTS Terrestrial Radio Access Network).

  • Basic Conception (3)RL (Radio Link)RL is a logical association between single UE (User Equipment) and a single UTRAN (UMTS Terrestrial Radio Access Network) access point. Its physical realization comprises one or more radio bearer transmissions. It is possible for a UMTS mobile to have many radio links established, when this occurs the mobile is said to be in a soft handover.

  • Sketch of the basic conceptions

  • UE Calling FlowPower onCell selection

    Location Update

    Idle ModeRRCEstablishNASEstablishHand OverCell/URA updateChannelreconfigurationRB/RAB ModificationRAB EstablishRRCReleaseCallInitiate

  • UE in Idle Mode

  • What Information needed for UE?1 Strongest cell2 Slot boundary3Frame boundary4 Primary SC5 Information in broadcasts channel

  • 1st Step: Cell Selection and Slot Synchronization

  • DL Scrambling Code Rule218-1 DL Scrambling Codes in total(0..262142)The left 8192 Scrambling codes are used for compression modeThe left 8192 Scrambling codes are used for compression mode

    #0 Scrambling Code Cluster#63 Scrambling Code Cluster

    #511 Scrambling Code Group81768177


    #510 Scrambling Code Group81608161


    #504 Scrambling Code Group80648065


    #7 Scrambling Code Group112113


    #1 Scrambling Code Group1617


    #0 Scrambling Code Group01


  • 2rd Step: Frame synchronization and Scrambling code-group

  • Scrambling-code identificationCPICH is predefine sequenceSpreading Factor is 256 (Cch,256,0)Scrambling by P-scrambling codeUE identified through symbol-by-symbol correlation over the primary P-CPICH with all the scrambling codes within the code group.

  • Obtain broadcast information in P-CCPCHP-CCPCH contain the current SFN and system broadcast informationP-CCPCH SF=256 (Cch,256,1)P-CCPCH scrambling by primary scrambling codeUE can use obtained primary scrambling code to descrambling the P-CCPCH and obtain the BCH information

  • UE Calling FlowPower onCell selectionLocation UpdateIdle ModeRRCEstablishNASEstablishHand OverCell/URA updateChannelreconfigurationRB/RAB ModificationRAB EstablishRRCReleaseCallInitiate

  • UE Initiate Random Access

  • Establish Dedicated RRC ConnectionUENode BSRNC2.Allocate RNTIL1 and L2 Parameters1. RRC Connection Request5. ALCAP Establish and Synchronization3. NBAP RL Setup Request7. RRC Connection Setup Complete6. RRC Connection Setup4. NBAP RL Setup Response

  • RRC Connection RejectionIf the RNC determines that the RRC connection cannot be established (for example, due to insufficient resources), the RNC directly sends the UE an RRC CONNECTION REJECT message which contains the reason for the rejection of the RRC connection.

  • 1. RRC Initial Direct TransferEstablish Signaling Link with CNUESRNCCN3. SCCP CC(Success)2. RANAP Initial UE MessageSCCP Connect Request3. SCCP CJ(Failure)4. RRC Direct Transfer5. RRC Direct Transfer

  • 1.1 Send Authentication Info4. Security Mode Command5. Security Mode Complete6. Security Mode Complete3.Security Mode ControlAuthentication and Security ModeUERNSMSC Server/VLR1. Authentication Request2. Authentication ResponseHLR2.1 Send Authentication Info Ack

  • CS Location Update Process

  • UE Calling FlowPower onCell selectionRRCEstablishNASEstablishHand OverCell/URA updateChannelreconfigurationRB/RAB ModificationRAB EstablishRRCReleaseCallInitiate

    Location Update

    Idle Mode

  • UE Work Mode TransformingRRC connectionAll the Status exist in UTRAN and UE, and transparent for CNNetwork Selection (PLMN)Cell CampingProbe paging channelCell ReselectionHigh level Signaling Triger (CN)Dedicated ChannelRB Transport Service

  • UE Calling FlowPower onCell selection

    Location Update

    Idle ModeRRCEstablishNASEstablishHand OverCell/URA updateChannelreconfigurationRB/RAB ModificationRAB EstablishRRCReleaseCallInitiate

  • Procedure of Call Initiate

  • Call Setup FlowCN initiates a paging message to RNC. RNC judges the paging message from the CN and then sends a paging message to the corresponding UE. If no RRC connection is available, UE will send a RRC connection setup request message (RRC Connection Request) to RNC. RNC determines to set up a RRC connection according to the service request and system resource occupation then sends a RRC connection setup message (RRC Connection Setup) to UE. After signaling connection setup, the higher layer of UE (NAS) sends a service request message to CN through a directly transfer message. CN sends a RAB assignment message (RAB Assignment Request) to the RNC to allocate resource for UEs request.

  • 3. NBAP RL Reconfigure PrepareRAB Establish FlowUENode BSRNC1. RANAP RAB Assignment Request4. NBAP RL Reconfigure ReadyMSC2. ALCAP Establish and Sync