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WCDMA RAN Protocols and ProceduresAgenda

WCDMA System Architecture Radio interfaceIUB ,IUR and Iu interface RRC (Radio Resource controller )ProtocolsRLC (Radio link controller) ProtocolsMAC and Physical layer function

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BTSGSM BSSNode-bRNCWCDMA Systems RANMSC / VLRGMSCOther PLMNFixed NetworkMGWSGSNGGSNIP NetworkAbisGbIubIuIu-PsIu-CSSGSN Handle the PS services to and from the UE. Forwards incoming and outgoing IP packets addressed to/from an UE that is attached within the SGSN SA Provides functions such as ciphering and authentication, session management and mobility managementGGSNInterface to the external IP packet network

MGW Connects the Core Network to the RNC CS traffic. Cross connection between the RNC and the SGSN.WCDMA System ArchitecturePCUBSC3

RNCRNCUEWCDMA RANCore NetworkMSCMGWSGSNGGSNEvery interface contains protocols used over it.Protocol used over the Iub interfaceNode B Application Part Protocol (NBAP).Protocol used over the Iur interfaceRadio Network Subsystems Application Part (RNSAP).Protocol used over the Iu interfaceRadio Access network application part(RNAP)NAS MessagesSignaling between the UE and CN directly

UuIubIURWCDMA RAN Interfaces.IuNAS messages4RNCCS DomainMGWMSCGGSNWCDMA RANIu-BcSGSNCBCPS DomainBroadcast domainCell Broadcast centerWCDMA RAN Interfaces (Contd).The Iu interface to the circuit switched domain, i.e. to the MSC, is referred to as Iu-CS.

The Iu interface to the packet switched domain, i.e. to the SGSN, is referred to as Iu-PS.

Iu-PSIn band SignalingDirect tunnelingdataSignalingCore NetworkIu-CSProtocols in WCDMA RAN

UE needs to contact the network which can be triggered either by:System information (Location Area Updating or Routing Area Updating)Timer expiring (Periodic Registration)Paging message received UE wants to initiate a call setup (Mobile Originating)

Exchange of signals between two entities. What nodes are involved ? What kind of information needs to be exchanged over the different interfaces?

Why protocol ?To be able to understand the kind of signaling messages that need to be sent and how they are transmitted over the interfacesProtocols in WCDMA RAN(Contd)Location UpdateUE performs location updating To keep the network up to date with the subscribers location .UE doesnt miss incoming calls

How the UE gets information regarding the Location Area Identity (LAI) of the serving cell ?When the UE is idle, it listens to the system information on BCCH.

11-UE reads from system information that the LAI is not the same as that stored in the USIM. This triggers the UE to update the location area.

2-UE tries to access the network and sends a request message to the RNC, via the RBSThe RNC checks if it is possible to allocate a dedicated channel to the UE.

3- Resources in the RBS and over the Iub interface are reserved by the RNC and are ACK by the RBS

4. Information about the new channel is sent to the UE with a setup message.

5. Synchronization is achieved between the UE and the RBS, and the UE sends a complete message.

22345RNCExample :LOCATION UPDATING

122345VLRRNCMSC66-The UE sends the request to update the location information to the CN.This message also carries the IMSI and LAI. Iu signaling bearer is set up between the RNC and the CN. There is now a signaling connection between the UE and the CN. As this is the first time the UE accesses this service area the subscriber is unknown in the VLR.

7-The VLR sends a request to the subscribers HLR for Authentication Information.

8- The HLR sends this information to the VLR.

9-MSC/VLR starts to authenticate the subscriber. This message is transparent over WCDMA RAN.

10-After Authentication, the VLR asks the HLR to update its Location information for the IMSI and with thenew VLR address

11- VLR receives an acknowledgement from the HLR.

12-The MSC/VLR transmits an acceptance to the UE, UE updates the location information in the USIM.

13- The signaling connection is released. First the UE is told to release the connection then the RBSHLR78910111213Location Update and Routing area update(Contd)LAYERED STRUCTURE OF PROTOCOLSLAYERED STRUCTURE OF PROTOCOLSSignaling message travels down in the protocol stack of the sending node.The layers on the way add their specific information to the original message.Message arrives at a receiving node. Handled upwards in the protocol stack, each layer in the receiving node analyzing information added by the peer protocol. 1100101100101001010010010010Peer layersUser DataCorrectionaddressingINTRODUCTION TO RADIO INTERFACE (Uu)

UEINTRODUCTION TO RADIO INTERFACE, UUThe interface is layered into three protocol layers:The physical layer (L1);The data link layer (L2); Network layer (L3)Layer 3Layer 2Layer 1Physical layer (L1)Data link layer (L2) Network layer (L3)Layer 3 (Network layer )Layer 3 consists of one protocol, called Radio Resource Control (RRC), which belong to the control plane. Function of RRC is to establish Signaling Radio Bearers between the UE and the RNC to handle most of the control signals. RRC controls the lower layers

Note :Messages that are not meant for the RAN but for the CN are called Non Access Stratum (NAS) Transferred transparently over the WCDMA RAN. INTRODUCTION TO RADIO INTERFACE, UuLayer 3RRCNASControl PlaneNAS includes Mobility Management (MM), ConnectionManagement (CM), Session Management (SM) and Short MessageServices (SMS).13INTRODUCTION TO RADIO INTERFACE, Uu (Contd)Layer 2 (Data link layer) Layer 2 is split into different sub layers. A- Radio Link Control (RLC) B-Medium Access Control (MAC)Layer 3RRCNASControl PlaneLayer 2RLCMACUser Plan (User data)Signaling Radio BearersRadio BearersRLC layer (Radio Link Control)RLC layer provides service in both A-Control plane is called Signaling Radio Bearer (SRB) B-User plane it is called a Radio Bearer (RB).

Signaling Radio Bearer, SRB Signaling messages between the UE and the RNC.Radio Bearer, RB. User data transport between the UE and the RNC.

RB Part of the Radio Access Bearer (RAB).Each RAB is mapped onto one or more Radio Bearers.

14RLC make sure the messages have correct lengthLong messages convert them to segmentsShort messages add padding bits to them

RLC instance is configured by RRC to operate in one of three modes depending on the service : Acknowledged Mode (AM),Unacknowledged Mode (UM) Transparent Mode (TM).

RLC map messages on different logical channels.

Control ChannelsBroadcast Control Channel (BCCH, DL)Downlink channel for broadcasting system information. Paging Control Channel (PCCH, DL)Downlink channel that transfers paging informationCommon Control Channel (CCCH, DL & UL)Used by the UE needs to access the network. Dedicated Control Channel (DCCH, DL & UL)Point-to-point bi-directional channel Transmits dedicated control information between UE and network. Traffic ChannelsDedicated Traffic Channel (DTCH, DL & UL)Point-to-point channel, dedicated to one UE, Transferring user Information.Common Traffic Channel (CTCH, DL)Traffic channel for sending traffic to a group of UEslogical channelsINTRODUCTION TO RADIO INTERFACE, Uu (Contd)RLCSRBLogical ChannelsRBLogical ChannelsControl PlaneUser Plan (User data)In Acknowledged Mode an Automatic Retransmission Request(ARQ) mechanism is used for error correction.15MAC layer Medium Access Control Logical channels received from the RLC layer are mapped onto the transport channels.Multiplex signaling and data to transport channels INTRODUCTION TO RADIO INTERFACE, Uu (Contd)Common transport channel(Several users use the same channel)Broadcast Channel (BCH) (DL)Continuous transmission of system and cell information- Paging Channel (PCH) (DL)When the network wants to initiate communication with the terminal.Random Access Channel (RACH) (UL)The RACH is an uplink transport channel used to make requests to set up a connectionForward Access Channel (FACH) (DL)Control signaling during call setupPacket data transmission in low ratesHigh Speed Downlink Shared Channel (HS-DSCH)(DL)HSDPATransport channels Dedicated transport channel(For exclusive use of one user) Dedicated Channel (DCH) (UL & DL)Service data, such as speech frames

Layer 2RLCRLCLogical ChannelsLogical ChannelsMACTransport ChannelsBCCHBroadcast Control Ch.PCCHPaging Control Ch.CCCHCommon Control Ch.CTCHCommon Traffic Ch.DCCHDedicated Control Ch.DTCHDedicated Traffic Ch.Logical ChannelBCHBroadcast Ch.PCHPaging Ch.FACHForward Access Ch.DCHDedicated Ch.HS-DSCHHigh Speed DLShared Ch.DCHDedicated Ch.HSDPACPICHCommon Pilot Channel (Aids channel estimation )P-CCPCH(*)Primary Common Control Physical Ch.S-CCPCHSecondary Common ControlPhysical Ch.DPDCH (one or more per UE)Dedicated Physical Data Ch.

DPCCH (one per UE)Dedicated Physical Control Ch.Pilot /TPC /TFCIAICH Acknowledges that RBS has acquired a UE Random Access attempt(Acquisition Indicator Channel)PICH(Paging Indicator Channel )HS- PDSCH (one or more per UE)High Speed Physical Downlinkshared ChHS-SCCH ( 0 and Srxlev > 0RRC (Radio Resource Controller) ContdCell selection occurs whenUE is switched onUE goes from common channel(cellFACH) to idle modeUE goes from connected mode (cellDCH) to idleUE goes to idle mode after an emergency call on any PLMNUE in idle mode has had a number of failed RRC connection request

Cell reselection procedureWhen it occursWhen cell on which it is camping is no longer suitableWhen there is any neighbor with better quality than the selected oneWhen the UE in the limited service state on an acceptable cellWhen the UE is in cell _FACH state3G F13G F2GSM3G F12- INITIAL CELL SELECTION AND CELL RESELECTION (Contd)RRC (Radio Resource Controller) Contd1- Intra frequency measurements starts when

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