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OWA210001 WCDMA UTRAN Interface and Signaling Procedure

ISSUE 1.0

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HUAWEI TECHNOLOGIES CO., LTD. Page 1All rights reserved

� Upon completion of this course, you will be able to:

�Understand UTRAN interface and structure

�Understand the definitions about UTRAN network elements

�Understand UTRAN signaling procedure

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Chapter 1 UTRAN Network OverviewChapter 1 UTRAN Network Overview

Chapter 2 Basic Concepts about UTRANChapter 2 Basic Concepts about UTRAN

Chapter 3 UTRAN Signaling ProcedureChapter 3 UTRAN Signaling Procedure

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The Position of UTRAN in WCDMA Network

Service manager layer

Service convergence layer

Radio access layer

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UMTS Construction

UTRANUTRAN UMTS Terrestrial Radio Access NetworkUMTS Terrestrial Radio Access NetworkCNCN Core NetworkCore NetworkUEUE User EquipmentUser Equipment

Iu

UTRAN

UE

Uu

CN

WCDMA network architecture shown in slide aboveUE (User Equipment)The User Equipment (UE) consists of two parts:1.The mobile equipment (ME) is the radio terminal used for radio communication over the Uu interface2. The UMTS Subscriber Identity Module (USIM) is the equivalent smartcard to SIM in GSM. It hold the subscriber identity , performs authentication algorithm , stores authentication and encryption keys ,etc.UTRAN (UMTS Terrestrial Radio Access network) The UTRAN consists of one or several Radio Network Subsystem ( RNS ) ,each containing one RNC and one or several NodeB1.NodeBThe NodeB is the correspondent element to the BTS in GSM. 2.RNCThe Radio Network Controller (RNC) owns and controls the radio resources of the connected NodeBCN (Core Network)Core network (CN) includes a lot of equipments such as MSC ,HLR, SGSN,GGSN,AUC,VLR etc.InterfaceIu interfaceThe Iu interface connects the UTRAN to the CN and is split in two parts. The Iucs is the interface between the RNC and the circuit switched domain of the CN. The Iups interface is the interface between the RNC and the packet switched domain of the CNUu interfaceThe Uu interface is the WCDMA radio interface with in UMTS. It is the interface through which the UE accesses the fixed part of the network.

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UMTS Structure

RNS

RNC

RNS

RNC

Core Network

Node B Node B Node B Node B

Iu Iu

Iur

Iub IubIub Iub

UTRAN (UMTS Terrestrial Radio Access network) struc ture

The UTRAN consists of one or several Radio Network Subsystem ( RNS ) ,each containing one RNC and one or several NodeB

Interface

Iu interface

The Iu interface connects the UTRAN to the CN and is split in two parts. The Iucsis the interface between the RNC and the circuit switched domain of the CN. The Iups interface is the interface between the RNC and the packet switched domain of the CN

Uu interface

The Uu interface is the WCDMA radio interface with in UMTS. It is the interface through which the UE accesses the fixed part of the network.

Iub interface

The Iub interface connects the NodeB and the RNC. Contrarily to GSM, this interface is fully open in UMTS and thus more competition is expected

Iur interface

This RNC-RNC interface was initially designed in order to provide inter RNC soft handover, but more features were added during the development

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Uu Interface

L3

cont

rol

cont

rol

cont

rol

LogicalChannels

TransportChannels

C-plane signalling U-plane information

PHY

L2/MAC

L1

RLC

DCNtGC

L2/RLC

MAC

RLCRLC

RLCRLC

RLCRLC

RLC

Duplication avoidance

UuS boundary

BMC L2/BMC

control

PDCPPDCP L2/PDCP

DCNtGC

RadioBearers

RRC

cont

rol

The radio interface (Uu) is layered into three protocol layers:

the physical layer (L1)the data link layer (L2)the network layer (L3).

The layer 1 supports all functions required for the transmission of bit streams on the physical medium. It is also in charge of measurements function consisting in indicating to higher layers, for example, Frame Error Rate (FER), Signal to Interference Ratio (SIR), interference power, transmit power, … It is basically composed of a “layer 1 management”entity, a “transport channel” entity, and a “physical channel” entity.The layer 2 protocol is responsible for providing functions such as mapping, ciphering, retransmission and segmentation. It is made of four sublayers: MAC (Medium Access Control), RLC (Radio Link Control), PDCP (Packet Data Convergence Protocol) and BMC (Broadcast/Multicast Control). The layer 3 is split into 2 parts: the access stratum and the non access stratum. The access stratum part is made of “RRC (Radio Resource Control)” entity and “duplication avoidance” entity. The non access stratum part is made of CC, MM parts.Not shown on the figure are connections between RRC and all the other protocol layers (RLC, MAC, PDCP, BMC and L1), which provide local inter-layer control services.The protocol layers are located in the UE and the peer entities are in the node B or the RNC.`

The radio interface (Uu) is spitted into 2 plane, left is control plane ,right is user plane ,control plane transfer control massage such as signalling, measurement control. User plane transfer user data such as speech ,packet data etc.

Many functions are managed by the RRC layer . Here is the list of the most important:

Establishment, re-establishment, maintenance and rel ease of an RRC connection between the UE and UTRAN : it includes an optional cell re-selection, an admission control, and a layer 2 signaling link establishment. When a RNC is in charge of a specific connection towards a UE, it acts as the Serving RNC.Establishment, reconfiguration and release of Radio Bearers : a number of Radio Bearers can be established for a UE at the same time. These bearers are configured depending on the requested QoS. The RNC is also in charge of ensuring that the requested QoS can be met.Assignment, reconfiguration and release of radio re sources for the RRC connection : it handles the assignment of radio resources (e.g. codes, shared channels). RRC communicates with the UE to indicate new resources allocation when handovers are managed.Paging/Notification : it broadcasts paging information from network to UEs.Broadcasting of information provided by the non-access stratum (Core Network) or access Stratum. This corresponds to “system information” regularly repeated.

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The radio interface (Uu) is layered into three protocol layers:

UE measurement reporting and control of the reportin g: RRC indicates what to measure, when and how to report.Outer loop power control : controls setting of the target values.Control of ciphering : provides procedures for setting of ciphering.

The RRC layer is defined in the 25.331 specification from 3GPP.

The RLC’s main function is the transfer of data from either the user or the control plane over the Radio interface. Two different transfer modes are used: transparent and non-transparent. In non-transparent mode, 2 sub-modes are used: acknowledged or unacknowledged .RLC provides services to upper layers:

data transfer (transparent, acknowledged and unacknowledged modes),QoS setting : the retransmission protocol (for AM only) shall be configurable by layer 3 to provide different QoS,notification of unrecoverable errors : RLC notifies the upper layers of errors that cannot be resolved by RLC.

The RLC functions are:

mapping between higher layer PDUs and logical channels,ciphering : prevents unauthorized acquisition of data; performed in RLC layer for non-transparent RLC mode,segmentation/reassembly : this function performs segmentation/reassembly of variable-length higher layer PDUs into/from smaller RLC Payload Units. The RLC size is adjustable to the actual set of transport formats (decided when service is established). Concatenation and padding may also be used,error correction : done by retransmission (acknowledged data transfer mode only),flow control : allows the RLC receiver to control the rate at which the peer RLC transmitting entity may send information.

MAC services include:

Data transfer : service providing unacknowledged transfer of MAC SDUs between peer MAC entities.Reallocation of radio resources and MAC parameters : reconfiguration of MAC functions such as change of identity of UE. Requested by the RRC layer.Reporting of measurements : local measurements such as traffic volume and quality indication are reported to the RRC layer.

The functions accomplished by the MAC sublayer are listed above. Here’s a quick explanation for some of them:

Priority handling between the data flows of one UE : since UMTS is multimedia, a user may activate several services at the same time, having possibly different profiles (priority, QoS parameters...). Priority handling consists in setting the right transport format for a high bit rate service and for a low bit rate service.Priority handling between UEs : use for efficient spectrum resources utilization for bursty transfers on common and shared channels.Ciphering: to prevent unauthorized acquisition of data. Performed in the MAC layer for transparent RLC mode.Access Service Class (ACS ) selection for RACH transmission : the RACH resources are divided between different ACSs in order to provide different priorities on a random access procedure.

PDCPUMTS supports several network layer protocols providing protocol transparency for the users of the service.Using these protocols (and new ones) shall be possible without any changes to UTRAN protocols. In order to perform this requirement, the PDCP layer has been introduced. Then, functions related to transfer of packets from higher layers shall be carried out in a transparent way by the UTRAN network entities.PDCP shall also be responsible for implementing different kinds of optimization methods. The currently known methods are standardized IETF (Internet Engineering Task Force) header compression algorithms.Algorithm types and their parameters are negotiated by RRC and indicated to PDCP.Header compression and decompression are specific for each network layer protocol type.In order to know which compression method is used, an identifier (PID: Packet Identifier) is inserted. Compression algorithms exist for TCP/IP, RTP/UDP/IP, …Another function of PDCP is to provide numbering of PDUs. This is done if lossless SRNS relocation is required.To accomplish this function, each PDCP-SDUs (UL and DL) is buffered and numbered. Numbering is done after header compression. SDUs are kept until information of successful transmission of PDCP-PDU has been received from RLC. PDCP sequence number ranges from 0 to 65,535.

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BMC (broadcast/multicast control protocol)The main function of BMC protocol are:Storage of cell broadcast message. the BMC in RNC stores the cell broadcast message received over the CBC-RNC interface for scheduled transmission.Traffic volume monitoring and radio resource reques t for CBS. On the UTRAN side, the BMC calculates the required transmission rate for the cell broadcast service based on the messages received over the CBC-RNC interface, and requests appropriate .CTCH/FACH resources from from RRCScheduling of BMC message. The BMC receives scheduling information together with each cell broadcast message over the CBC-RNC interface. Based on this scheduling information, on the UTRAN side the BMC generates schedule message and schedules BMC message sequences accordingly. On the UE side ,the BMC evaluates the schedule messages and indicates scheduling parameters to RRC, which are used by RRC to configure the lower layers for CBS discontinuous reception. Transmission of BMC message to UE. The function transmits the BMC messages according to the scheduleDelivery of cell broadcast messages to the upper la yer. This UE function delivers the received non-corrupted cell broadcast messages to the upper layer

The layer 1 (physical layer) is used to transmit information under the form of electrical signals corresponding to bits, between the network and the mobile user. This information can be voice, circuit or packet data, and network signaling.The UMTS layer 1 offers data transport services to higher layers. The access to these services is through the use of transport channels via the MAC sublayer. These services are provided by radio links which are established by signaling procedures. These links are managed by the layer 1 management entity . One radio link is made of one or several transport channels, and one physical channel.The UMTS layer 1 is divided into two sublayers: the transport and the physical sublayers. All the processing (channel coding, interleaving, etc.) is done by the transport sublayer in order to provide different services and their associated QoS. The physical sublayer is responsible for the modulation, which corresponds to the association of bits (coming from the transport sublayer) to electrical signals that can be carried over the air interface. The spreading operation is also done by the physical sublayer. These sublayers are well described in chapters 6 and 7.These two parts of layer 1 are controlled by the layer 1 management (L1M) entity. It is made of several units located in each equipment, which exchange information through the use of control channels.

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General Protocol Mode for UTRAN Terrestrial Interface

� The structure is based on the principle that the layers and planes are logically independent of each other.

ApplicationProtocol

DataStream(s)

ALCAP(s)

TransportNetwork

Layer

Physical Layer

SignallingBearer(s)

TransportUser

NetworkPlane

Control Plane User Plane

TransportUser

NetworkPlane

Transport NetworkControl Plane

RadioNetwork

Layer

SignallingBearer(s)

DataBearer(s)

Protocol structures in UTRAN terrestrial interfaces are designed according to the same general protocol model. This model is shown in above slide. The structure is based on the principle that the layers and planes are logically independent of each other and, if needed, parts of the protocol structure may be changed in the future while other parts remain intact.

Horizontal Layers

The protocol structure consists of two main layers, the Radio Network Layer (RNL) and the Transport Network Layer (TNL). All UTRAN-related issues are visible only in the Radio Network Layer, and the Transport Network Layer represents standard transport technology that is selected to be used for UTRAN but without any UTRAN-specific changes.

Vertical Planes

Control Plane

The Control Plane is used for all UMTS-specific control signalling. It includes the Application Protocol (i.e. RANAP in Iu, RNSAP in Iur and NBAP in Iub), and the Signalling Bearer for transporting the Application Protocol messages. The Application Protocol is used, among other things, for setting up bearers to the UE (i.e. the Radio Access Bearer in Iu and subsequently the Radio Link in Iur and Iub). In the three plane structure the bearer parameters in the Application Protocol are not

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directly tied to the User Plane technology, but rather are general bearer parameters. The Signalling Bearer for the Application Protocol may or may not be of the same type as the Signalling Bearer for the ALCAP. It is always set up by O&M actions.

User Plane

All information sent and received by the user, such as the coded voice in a voice call or the packets in an Internet connection, are transported via the User Plane. The User Plane includes the Data Stream(s), and the Data Bearer (s) for the Data Stream(s). Each Data Stream is characterized by one or more frame protocols specified for that interface.

Transport Network Control Plane

The Transport Network Control Plane is used for all control signalling within the Transport Layer. It does not include any Radio Network Layer information. It includes the ALCAP protocol that is needed to set up the transport bearers (Data Bearer) for the User Plane. It also includes the Signalling Bearer needed for the ALCAP. The Transport Network Control Plane is a plane that acts between the Control Plane and the User Plane. The introduction of the Transport Network Control Plane makes it possible for the Application Protocol in the Radio Network Control Plane to be completely independent of the technology selected for the Data Bearer in the User Plane.

About AAl2 and AAL5

Above the ATM layer we usually find an ATM adaptation layer (AAL). Its function is to process the data from higher layers for ATM transmission.

This means segmenting the data into 48-byte chunks and reassembling the original data frames on the receiving side. There are five different AALs (0, 1, 2, 3/4, and 5). AAL0 means that no adaptation is needed. The other adaptation layers have different properties based on threeparameters:

• Real-time requirements;

• Constant or variable bit rate;

• Connection-oriented or connectionless data transfer.

The usage of ATM is promoted by the ATM Forum. The Iu interface uses two AALs: AAL2 and AAL5.

AAL2 is designed for the transmission of connection oriented, real-time data streams with variable bit rates.

AAL5 is designed for the transmission of connection less data streams with variable bit rates.

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RNL Control Plane Application Protocol

NBAP ：Node B Application PartRANAP：Radio Access Network Application PartRNSAP：Radio Network Subsystem Application PartRRC ：Radio Resource Control

Node B

RNC

CN

UE

RANAP

NBAP

RNSAPRRCRNC

RANAP is the signalling protocol in Iu that contains all the control information specified for the Radio Network Layer.

RNSAP is the signalling protocol in Iur that contains all the control information specified for the Radio Network Layer.

NBAP is the signalling protocol in Iub that contains all the control information specified for the Radio Network Layer.

RRC is the signalling protocol in Uu that locate in the Uu interface layer 3

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Iu-CS Interface

Q.2150.1

Q.2630.1

RANAPIu UP Protocol

Layer

TransportNetwork

Layer

Transport NetworkUser Plane


Transport Network User Plane


RadioNetwork

Layer

SSCOP

AAL5

SSCOP

SSCF-NNI

AAL2AAL5

MTP3bMTP3b

SCCP

SSCF-NNI

Physical Layer

ATM

Protocol Structure for Iu CS

The Iu CS overall protocol structure is depicted in above slide. The three planes in the Iu interface share a common ATM (Asynchronous Transfer Mode) transport which is used for all planes. The physical layer is the interface to the physical medium: optical fibre, radio link or copper cable. The physical layer implementation can be selected from a variety of standard off-the-shelf transmission technologies, such as SONET, STM1, or E1.

Iu CS Control Plane Protocol Stack

The Control Plane protocol stack consists of RANAP, on top of Broadband (BB) SS7 (Signalling System #7) protocols. The applicable layers are the Signalling Connection Control Part (SCCP), the Message Transfer Part (MTP3-b) and SAAL-NNI (Signalling ATM Adaptation Layer for Network to Network Interfaces). SAAL-NNI is further divided into Service Specific Coordination Function (SSCF), Service Specific Connection Oriented

Protocol (SSCOP) and ATM Adaptation Layer 5 (AAL) layers. SSCF and SSCOP layers are specifically designed for signalling transport in ATM networks, and take care of such functions as signalling connection management. AAL5 is used for segmenting the data to ATM cells.

Iu CS Transport Network Control Plane Protocol Stac k

The Transport Network Control Plane protocol stack consists of the Signalling Protocol for setting up AAL2 connections (Q.2630.1 and adaptation layer Q.2150.1), on top of BB SS7 protocols. The applicable BB SS7 are those described above without the SCCP layer.

Iu CS User Plane Protocol Stack

A dedicated AAL2 connection is reserved for each individual CS service.

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Iu-PS Interface

SSCF-NNI

SSCOP

AAL5

IP

SCTP

SCCP

SSCF-NNI

MTP3-BM3UA

Physical Layer


ATM

AAL5

IP

UDP

GTP-U

Physical Layer

ATM

TransportNetwork

Layer


RadioNetwork

LayerRANAP Iu UP Protocol

Layer



Protocol Structure for Iu PSThe Iu PS protocol structure is represented in above slide. Again, a common ATM transport is applied for both User and Control Plane. Also the physical layer is as specified for Iu CS.Iu PS Control Plane Protocol StackThe Control Plane protocol stack again consists of RANAP, and the same BB SS7-based signalling bearer as described in Section 5.4.1.1. Also, as an alternative, an IP-based signalling bearer is specified. The SCCP layer is also used commonly for both. The IP based signalling bearer consists of M3UA (SS7 MTP3 – User Adaptation Layer), SCTP (Simple Control Transmission Protocol), IP (Internet Protocol), and AAL5 which is common to both alternatives. The SCTP layer is specifically designed for signalling transport in the Internet. Specific adaptation layers are specified for different kinds of signalling protocol, such as M3UA for SS7-based signalling.

Iu PS Transport Network Control Plane Protocol Stac kThe Transport Network Control Plane is not applied to Iu PS. The setting up of the GTP tunnel requires only an identifier for the tunnel, and the IP addresses for both directions, and these are already included in the RANAP RAB Assignment messages.

Iu PS User Plane Protocol StackIn the Iu PS User Plane, multiple packet data flows are multiplexed on one or several AAL5 PVCs. The GTP-U (User Plane part of the GPRS Tunneling Protocol) is the multiplexing layer that provides identities for individual packet data flow. Each flow uses UDP connectionless transport and IP addressing.

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Iub Interface

Node BApplication Part

(NBAP)

AAL Type 2

ALCAP

TransportLayer

RadioNetwork

Layer

Radio NetworkControl Plane

TransportNetwork

Control Plane

DC

H F

P

RA

CH

FP

ATM

DS

CH

FP

AAL Type 5

User Plane

SSCF-UNI

SSCOP

AAL Type 5

SSCF-UNI

SSCOP

Q.2630.1

Q.2150.2

FA

CH

FP

PC

H F

P

US

CH

FP

CP

CH

FP

Physical Layer

The Iub interface is the terrestrial interface between NodeB and RNC. The protocol stack for the Iub is shown in the above slide. The Radio Network Layer defines procedures related to the operation of the NodeB. The transport Network Layer defines procedures for establishing physical connections between the NodeB and the RNC.

The Iub application protocol, NodeB application part ( NBAP ) initiates the establishment of a signaling connection over Iub . It is divided into two essential components, NBAP common for defining the signalling procedures across the common signalling link and NBAP dedicated for the dedicated signalling link. This split is due to the fact that the NodeB is defined as having a common part and a number of dedicated parts (each controlling a traffic connection) .

NBAP-C is used for signaling that initiates a UE context for a dedicated UE or signals that is not related to specific UE. Example of NBAP-C procedure are cell configuration , handling of common channels and radio link setup

NBAP-D signalling is used for signaling relating to a specific UE context. The initial request to NodeB from the RNC such as Radio link setup for a context activation uses NBAP-C ,but once the context has been set up ,NBAP-D is used from then. Example of NBAP-D functions are addition, reconfiguration and release of radio links for one UE context

SAAL is an ATM Adaptation Layer that supports communication between signalling entities over an ATM link.

The user plane Iub Frame Protocol ( FP ), defined the structure of the frames and the basic in band control procedure for every type of transport channel. There are DCH-FP,RACH-FP,FACH-FP,HS-DSCH FP and PCH FP

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Iur Interface

SSCF-NNI

SSCOP

MTP3-B

AAL5

IP

SCTP

SCCP

AAL5

STC (Q.2150.1)

RNSAPIur Data

Stream(s)

Physical Layer


ATM

ALCAP(Q.2630.1)

AAL2

SSCF-NNI

SSCOP

MTP3-B

IP

SCTP

M3UAM3UA

TransportNetwork

Layer


RadioNetwork

Layer



Iur interface connects two RNCs. The protocol stack for the Iur is shown in above slide.

The RNSAP protocol is the signalling protocol defined for the Iur interface.

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SRNC/DRNC

� SRNC and DRNC are on per connection basis between a UE and the UTRAN

� The SRNC handles the connection to one UE, and may borrow radio resources of a certain cell from the DRNC

� Drift RNCs support the Serving RNC by providing radio resources

� A UE in connection state has at least one and only one SRNC, butcan has 0 or multiple DRNCs

CN

SRNC DRNC

IuIur

Inside the UTRAN, the RNCs of the Radio Network Subsystems can be interconnected together through the Iur. Iu(s) and Iur are logical interfaces. Iur can be conveyed over direct physical connection between RNCs or virtual networks using any suitable transport network .

For each connection between User Equipment and the UTRAN, One RNC is the Serving RNC. When required, Drift RNCs support the Serving RNC by providing radio resources. The role of an RNC (Serving or Drift) is on a per connection basis between a UE and the UTRAN.

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CRNC

� The CRNC owns the radio resources of a cell

� Dynamical control of power for dedicated channels, within limitsadmitted by CRNC, is done by the SRNC.

� Scheduling of data for dedicated channels is done by the SRNC, while for common channels it is done by the CRNC

Iub

Node B

Cell Cell Cell

Node B

...

Iu

CRNC

CN

Then what is CRNC? CRNC is related to a specific NodeB (or Cell)

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RAB, RB and RL

RAB

RB

RLNodeB

RNC CNUE

UTRAN

RAB: The service that the access stratum provides to the non-access stratum for transfer of user data between User Equipment and CNRB: The service provided by the layer2 for transfer of user data between User Equipment and Serving RNC

RL: A "radio link" is a logical association between single User Equipment and a single UTRAN access point. Its physical realization comprises one or more radio bearer transmissions

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UE Working Modes and States

� Idle mode

� Connected mode

�Cell_DCH

�Cell_FACH

�Cell_PCH

�URA_PCH

The connected mode is entered when the RRC connection is established. The UE leaves the connected mode and returns to idle mode when the RRC connection is released or at RRC connection failure.

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Idle Mode

� The UE has no relation to UTRAN, only to CN. For data transfer, a signalling connection has to be established.

� UE camps on a cell

� It enables the UE to receive system information from the PLMN

�When registered and if the UE wishes to establish an RRC connection, it can do this by initially accessing the network on the control channel of the cell on which it is camped

�UE can receive "paging" message from common channels of the cell.

� It enables the UE to receive cell broadcast services.

� The idle mode tasks can be subdivided into three processes:

�PLMN selection and reselection;

�Cell selection and reselection;

�Location registration.

When a UE is switched on, a public land mobile network (PLMN) isselected and the UE searches for a suitable cell of this PLMN to camp on.

The NAS shall provide a list of equivalent PLMNs, if available, that the AS shall use for cell selection and cell reselection.

The UE searches for a suitable cell of the chosen PLMN and chooses that cell to provide available services, and tunes to its control channel. This choosing is known as "camping on the cell". The UE will, if necessary, then register its presence, by means of a NAS registration procedure, in the registration area of the chosen cell.

If the UE finds a more suitable cell, it reselects onto that cell and camps on it. If the new cell is in a different registration area, location registration is performed .

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Connected Mode

� When at least one signalling connection exists, the UE is in connected mode and there is normally an RRC connection between UE and UTRAN. The UE position can be known on different levels:

�UTRAN Registration Area (URA) levelThe UE position is known on URA level. The URA is a set of cells

�Cell levelThe UE position is known on cell level. Different transport channel types can be used for data transfer:

�Common transport channels (RACH / FACH)

�Dedicated transport channels (DCH)

In connected mode, the UE is assigned a Radio Network Temporary Identity (RNTI) to be used as UE identity on common transport channels. Two types of RNTI exist. The Serving RNC allocates an s-RNTI for all UEs having an RRC connection. The combination of s-RNTI and an RNC-ID is unique within a PLMN. c-RNTI is allocated by each Controlling RNC through which UE is able to communicate on DCCH. c-RNTI is always allocated by UTRAN when a new UE context is created to an RNC, but the UE needs its c-RNTI only for communicating on common transport channels.

Within connected mode the level of UE connection to UTRAN is determined by the quality of service requirements of the active radio bearers and the characteristics of the traffic on those bearers.

The UE-UTRAN interface is designed to support a large number of UEs using packet data services by providing flexible means to utilize statistical multiplexing. Due to limitations, such as air interface capacity, UE power consumption and network h/w availability, the dedicated resources cannot be allocated to all of the packet service users at all times.

Variable rate transmission provides the means that for services of variable rate the data rate is adapted according to the maximum allowable output power.

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The UE state in the connected mode defines the level of activityassociated to the UE. The key parameters of each state are the required activity and resources within the state and the required signalling prior to the data transmission. The state of the UE shall at least be dependent on the application requirement and the period of inactivity.

Common Packet Channel (CPCH) uplink resources are available to UEs with an access protocol similar to the RACH. The CPCH resources support uplink packet communication for numerous UEs with a set of shared, contention-based CPCH channels allocated to the cell.

Assuming that there exists an RRC connection, there are two basic families of RRC connection mobility procedures, URA updating andhandover. Different families of RRC connection mobility procedures are used in different levels of UE connection (cell level and URA level):

-URA updating is a family of procedures that updates the UTRAN registration area of a UE when an RRC connection exists and the position of the UE is known on URA level in the UTRAN;

-Handover is a family of procedures that adds or removes one or several radio links between one UE and UTRAN when an RRC connection exists and the position of the UE is known on cell level in the UTRAN.

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� Cell-DCH

� In active state

�Communicating via its dedicated channels

�UTRAN knows which cell UE is in.

Connected Mode

If there is huge data to be transmitted, it must allocate dedicated channel. Thus UE will be in Cell-DCH. UE in Cell-DCH state is communicating via DCH (downlink and uplink) with UTRAN

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�Cell-FACH

� In active state

� Few data to be transmitted both in uplink and in downlink. Thereis no need to allocate dedicated channel for this UE.

� Downlink uses FACH and uplink uses RACH.

� UE need to monitor the FACH for its relative information.

� UTRAN knows which cell UE is in.

Connected Mode

If there is only few data to be transmitted,there is no need to allocate dedicated channel. Thus UE will be in Cell-FACH. UE in Cell-FACH state is communicating via FACH (downlink) and RACH (uplink) with UTRAN. UE need to monitor the FACH for its relative information because FACH is shared for all users in the cell.

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�Cell-PCH

� No data to be transmitted or received.

� Monitor PICH, to receive its paging.

� lower the power consumption of UE.

� UTRAN knows which cell UE is in.

� UTRAN have to update cell information of UE when UE roams to another cell

Connected Mode

If UE has no data to be transmitted or received, UE will be in Cell-PCH or URA-PCH. In these two states, UE needs to monitor PICH,to receive its paging. UTRAN knows which cell or URA UE is now in. The difference between Cell-PCH and URA-PCH is that UTRAN update UE information only after UE which is in URA-PCH state has roamed to other URA.

UTRAN have to update cell information of UE when UE roams to another cell. UE migrates to cell-FACH state to complete the cell update. If there is also no data to be transmitted or received, UE is back to CELL-PCH state after cell update. If the cell update times in a fixed time reach a preset value, UTRAN will let UE migrate to URA-PCH. URA is an area of several cells.

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�URA-PCH

� No data to be transmitted or received.

� Monitor PICH.

� UTRAN only knows which URA (UTRAN Registration Area, which consists of multiple cells) that UE is in.

� UTRAN updates UE information only after UE has roamed to other URA.

� A better way to reduce the resource occupancy and signaling transmission

Connected Mode

It is the same as the CELL-PCH state. UE should migrate to CELL-FACH state to complete the URA update.

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UE States

CELL_DCH CELL_FACH

CELL_PCHURA_PCH

IDLE

DEAD - Scanning networks (PLMN)- ”Camp on” cell

- Monitor paging channel- cell re-selection

- Dedicated Channel- Radio bearers Transmission Services

- upper layer Signalingtrigger (CN)

- Reduce action ，，，，DTX，，，，and save power

RRC connection

This is the UE states figure. These states are significant only for UTRAN and UE. They are transparent to CN. Let’s focus on the switch between the states.

29


RNTI - Radio Network Temporary Identifier

� Five Types of RNTI exist

�Serving RNC RNTI (S-RNTI)

�Drift RNC RNTI (D-RNTI)

�Cell RNTI (C-RNTI)

�UTRAN RNTI (U-RNTI)

�HS-DSCH RNTI (H-RNTI)

SRNTI

SRNTI is used by UE to identify itself to the serving RNC

SRNTI is used by SRNC to address the UE

SRNTI is used by DRNC to identify the UE to serving RNC

SRNTI is allocated for all UEs having a RRC connection, it is allocated by serving RNC and it unique within the SRNC.SRNTI is always reallocated when the SRNC for the RRC connection is changed.

DRNTI

DRNTI is used to SRNC to identify the UE to the DRNC

DRNTI is never used on Uu interface. DRNTI is allocated by DRNC upon drift UE contexts establishment and is unique within the DRNC. The SRNC knows the mapping between SRNTI and DRNTI is allocated by DRNC for the same UE. The DRNC shall know the SRNTI and SRNC ID related to existing DRNTI within the DRNC.

CRNTI

CRNTI is used by a UE to identify itself to the CRNC

CRNTI is used by CRNC to address the UE

CRNTI is allocated by CRNC when UE accessing a new cell. CRNTI is unique within the accessed cell.

URNTI

URNTI is consisted of SRNC identity and SRNTI

HRNTI

HRNTI is allocated by CRNC when UE establishing a HS-DSCH channel. HRNTI shall be unique within the cell carrying the HS-DSCH

30





31



Section 1 Cell SetupSection 1 Cell Setup

Section 2 System Information BroadcastSection 2 System Information Broadcast

SectionSection 3 Paging3 Paging

SectionSection 4 Call Process4 Call Process

SectionSection 5 Handover5 Handover

32


Cell Setup

NBAP

NBAP

NBAP

NBAP

NBAP

NBAP

NBAP

NBAP

NBAP

NBAP

NCP: Resource Status Ind

NCP: Audit Req

NCP: Cell Setup Req

NCP: Cell Setup Rsp

NBAPNBAP NCP: Comm TrCh Setup Req

NBAPNBAP NCP: Comm TrCh Setup Rsp

Q.AAL2

Q.AAL2

Q.AAL2

Q.AAL2

Est Req

Est Conf

RNC NodeB

NCP: Audit Rsp

NBAPNBAP NCP: Comm TrCh Setup Req

NBAPNBAP NCP: Comm TrCh Setup Rsp

Q.AAL2

Q.AAL2

Q.AAL2

Q.AAL2

Est Req

Est Conf

Setup NCP and CCP in SAAL link stratum, which NCP carries the NBAP public information and CCP carries the NBAP dedicated information. One NodeB only can setup one NCP, but can setup several CCP;

To prepare the cell setting up, the resource of Node B should be audited;

Logic cell setup

Setup the common transport channel for cell, including RACH, FACH and PCH.

33




Section 2 System Information BroadcastSection 2 System Information Broadcast




34


System Information Broadcast Flow

3.BCCH:System Information

1.System Information Update Request

UE Node B RNC CN

NBAPNBAP

RRCRRC

4.BCCH:System Information RRCRRC

5.BCCH:System Information RRCRRC

2.System Information Update ResponseNBAPNBAP

系统消息更新周期

35


Introduction of System Information

MIB：Contains PLMN tag and SB (scheduling information block) or the scheduling information for SIB (system info block)

SB1：Contains scheduling information for SIB

SB2：Contains scheduling information for SIB

SIB1：Contains the system information for NAS and the timer/counter for UE

SIB2：Contains the URA information

SIB3：Contains the parameters for cell selection and cell re-selection

36



SIB4：Contains parameters for cell selection and cell re-selection while UE is in connecting mode

SIB5：Contains parameters for the common physical channels of the cell

SIB6：Contains parameters for the common physical channels of the cell while UE is in connecting mode

SIB7：Contains the uplink interference level and the refreshing timer for SIB7

SIB8：Contains the CPCH static information

37



SIB9：Contains the CPCH dynamic information

SIB10：Contains information to be used by UEs having their DCH controlled by a DRAC procedureUsed in FDD mode onlyTo be used in CELL_DCH state onlyChanges so often, its decoding is controlled by a timer

SIB11：Contains measurement controlling information

SIB12：Contains measurement controlling information in connecting mode

SIB13：Contains ANSI-41 system information

38



SIB14:Contains the information in TDD mode

SIB15:Contains the position service information

SIB16:Contains the needed pre-configuration information for handover from other RAT to UTRAN

SIB17:Contains the configuration information for TDD

SIB18:Contains the PLMN identities of the neighboring cellsTo be used in shared networks to help with the cell reselection process

39


System Information Block Type 1

� System information type 1� The NAS system information� CS domain DRX：K ＝ 6，then DRX

period is 2^k = 2 ^ 6 = 64 TTI = 640 ms

� PS domain DRX：K ＝ 6，then DRX period is 2^k = 2 ^ 6 = 64 TTI = 640 ms

� The different timers for UE in connecting mode and idle mode.

40



� System info type 2

�URA information

41



� The references for cell selection and re-selection

�Qhyst2s

�Sintrasearch

�Sintersearch

�SinterRatsearch

�Qqualmin

�Qrxlemin

�T reselection

�Max Allowed UE TX power

42



� The configuration information for

the following physical channels

and the counterpart transport

channels

�PICH

�AICH

�PCCPCH

�PRACH

�SCCPCH

43


System Information Block Type 7 and 11


� Including the UL interference level which is used for open loop power control:

�Preamble_Initial_Power=Primary CPICH DL TX power -CPICH_RSCP + UL interference + Constant Value

� Including the Expiration Time Factor which is used for refreshing the SIB7 periodically


�The neighbor cell information for cell re-selection in IDLE mode.

44



SectionSection 1 Cell Setup1 Cell Setup

SectionSection 2 System Information Broadcast2 System Information Broadcast

Section 3 PagingSection 3 Paging



45


Paging Caused by CN

The paging procedure is a procedure of paging initiated from the CN to the called party. When the CN needs to set up a connection with the called subscriber, it first needs to find the called subscriber via the paging procedure. The purpose of the paging procedure is just to enable the CN to page the called subscriber. The paging procedure is set up via connectionless signaling.

46


Paging Caused by CN

� The paging information type which is sent by UTRAN is

decided by UE mode.

� If UE is in the CELL_FACH or CELL_DCH，UTRAN send

paging type 2. In other modes, the paging information is

type 1 and UE can use DRX method to detecting PICH.

When the RRC is idle, the UE may receive paging from the CS or PS domain. Because the UE is now in the idle state, the CN can learn the Location Area Identification (LAI) or RAI information of the UE. The paging will be sent via this location area and the LA or RA in this example crosses two RNCs.

The above example shows the paging procedure of the UE in the RRC connected state (CELL_DCH or CELL_FACH), where the UTRAN coordinates the paging request over the DCCH in the RRC connected state.

Paging Type 1 is sent over the PCCH when the UE is idle while Paging Type 2 is sent over the DCCH when the UE is in the RRC connected state. The typical case is that the UE uses the Paging Type 2 to send the PAGING message of the CS domain in the PS service procedure. However, the Paging Type is controlled by the RNC and the CN does not need to know it.

47


Paging Caused by UTRAN

When the system information is modified, UTRAN will send the paging

information to tell UEs which are in IDLE, Cell_PCH or URA_PCH mode.

Then, UE will read the modified system information from BCH.

To change the state of UE which is in Cell_PCH or URA_PCH state,

UTRAN will start a paging flow. Then, UE will start a Cell-Update or URA

update flow for response.

48






Section 4 Call ProcessSection 4 Call Process


49


Introduction of Call Process

� In WCDMA system, a call process includes the following basic signaling flows:

� RRC connection flow

� Iu interface signaling flow

� Authentication flow (optional)

� Security flow (optional)

� RAB establish flow

� Call proceeding

� NAS signaling before correlative bearer release

�Correlative bearer release

50


RRC Connection Establishment Flow (DCH)

� When UE is in IDLE mode and the NAS of UE request the signaling connection, UE will send a RRC Connection Request.

Each UE only can have one RRC Connection. The main function is to configure the signaling channel of UTRAN.

1. CCCH : RRC Connection Request

5. Downlink Synchronisation

UE Node BServing RNS

Serving RNC

DCH - FP

Allocate RNTISelect L1 and L2parameters

RRCRRC

NBAPNBAP3. Radio Link Setup Response

NBAPNBAP2. Radio Link Setup Request

RRCRRC7. CCCH : RRC Connection Set up

Start RX description

Start TX description

4. ALCAP Iub Data Transport Bearer Setup

RRCRRC9. DCCH : RRC Connection Setup Complete

6. Uplink Synchronisation

NBAPNBAP8. Radio Link Restore Indication

DCH - FP

DCH - FP

DCH - FP

In the idle mode, when the non-access layer of the UE requests to establish a signaling connection, the UE will initiate the RRC connection procedure. Each UE has up to one RRC connection only.

Description:

1. The UE sends an RRC Connection Request message via the uplink CCCH to request to establish an RRC connection.

2. Based on the RRC connection request cause and the system resource state, the SRNC decides to establish the connection on the dedicated channel, and allocates the RNTI and L1 and L2 resources.

3. The SRNC sends a Radio Link Setup Request message to Node B, requesting the Node B to allocate specific radio link resources required by the RRC connection.

4. After successfully preparing the resources, the Node B responds to the SRNC with the Radio Link Setup Responsemessage.

5. The SRNC initiates the establishment of Iub user plane transport bearer with the ALCAP protocol and completes the synchronization between the RNC and the Node B.

6. The SRNC sends an RRC Connection Setup message to the UE in the downlink CCCH.

7. The UE sends an RRC Connection Setup Complete message to the SRNC in the uplink DCCH.

By now, the RRC connection setup procedure ends.

51


Iu Interface Signaling Connection Establish

� In Iu interface, radio network layer reports the

RANAP information and NAS information.

NAS information is taken as directed

message in RANAP information.

� And the process of Iu signaling connection is

to establish the Iu interface connection of

SCCP between RNC and CN.

UE Node B RNC CN

RRC RRC

SCCP SCCP

SCCP SCCP

Initial DT

Initial UE message (Connect Request)

Connect Confirm

RANAP


Control Plane

SSCOP

AAL5

MTP3b

SCCP

SSCF-NNI

After the RRC connection between the UE and the UTRAN is successfully set up, the UE sets up a signaling connection with the CN via the RNC for NAS information exchange between the UE and the CN, such as authentication, service request and connection setup. This is also called the NAS signaling setup procedure.

For the RNC, the signaling exchanged between the UE and the CN is a direct transfer message. After receiving the first direct transfer message, that is, the Initial Direct Transfer message, the RNC sets up a signaling connection with the CN on the SCCP. The procedure isshown in the above figure:

The specific procedure is given as follows:

1. After the RRC connection is established, the UE sends the Initial Direct Transfer message to the RNC via the RRC connection. This message carries the NAS information content sent to the CN by the UE.

2. After receiving the Initial Direct Transfer message from the UE,the RNC sends the SCCP Connection Request (CR) message to the CN via the Iu interface. The message content is the Initial UE Message sent from the RNC to the CN, and carries the message content sent from the UE to the CN.

52

3.If the CN is ready to accept the connection request, then it returns the SCCP Connection Confirm (CC) message to the RNC. The SCCP connection is successfully set up. The RNC receives the message and confirms the signaling connection setup success.

4.If the CN cannot accept the connection request, then it returns the SCCP Connection Reject (CJ) message to the RNC. The SCCP connection setup fails. The RNC receives the message and confirms the signaling connection setup failure. Then it initiates the RRC release procedure.

After the signaling connection is successfully set up, the message sent by the UE to the CN is forwarded to the RNC via the Uplink Direct Transfer message, and the RNC converts it into the Direct Transfer message to send to the CN. The message sent by the CN to the UE is forwarded to the RNC via the Direct Transfer message, and the RNC converts it into the Downlink Direct Transfer to send to the UE.

53


Authentication and Security Flow

UE RNC CN

RRC Connection SetupInitial DT

Initial UE Message

DL DT (Authentication Request)DL DT (Authentication

Request)DL DT (Authentication

Request) DL DT (Authentication Request)

Common ID

Security Mode CommandSecurity Mode Command

Security Mode CommandSecurity Mode Command

RAB Assignment

Authentication is used for the validity of CN and UE. Security flow includes the encrypt process and integrity protection.

54


Common ID

Imsi 用来寻呼时使用，cn寻呼的时候。会带下用户的imsi，然后utran根据这个imsi和common id带下来的imsi比较，查询ue的状态

55


RAB Establishment Flow

NodeBUE CNRNC

RANAPRANAPRAB Ass Req

Q.AAL2 Q.AAL2

Q.AAL2Q.AAL2

NBAPNBAP

AAL2 Setup Req

RL Recfg Prep

AAL2 Setup Rep

NBAPNBAPRL Recfg Ready

Q.AAL2Q.AAL2AAL2 Setup Req

Q.AAL2Q.AAL2AAL2 Setup Rep

FPFPDL Sync

FPFPUL Sync

RRC RRCRB Setup

NBAPNBAPRL Recfg Commit

RRC RRCRB Setup Complete

RANAPRANAPRAB Ass Rep

RAB is the carrier which is provided by AS for NAS.

RAB is the carrier in user plane, which is for transferring the voice service, data service or multiple media service between UE and CN.

RAB establishment flow mainly includes the AAL2 PATH establishment of Iu and Iubinterface, also includes the reconfiguration process of radio resource.

The RAB refers to the user plane bearer that is used to transfer voice, data and multimedia services between the UE and the CN. The UE needs to complete the RRC connection establishment before setting up the RAB.

The RAB setup is initiated by the CN and executed by the UTRAN. The basic procedure is as follows:

1. First the CN sends the RAB assignment request message to the UTRAN, requesting the UTRAN to establish the RAB.

2. The SRNC in the UTRAN initiates the establishment of the data transport bearer between the Iu interface and the Iub interface (Iur interface).

3. The SRNC sends the RB setup request to the UE.

4. After completing the RB establishment, the UE responds to the SRNC with the RB setup complete message.

5. The SRNC responds to the CN with the RAB assignment response message and the RAB setup procedure ends.

When the RAB is successfully established, a basic call is set up and the UE enters the conversation process.

56


NAS Signaling (CS)

UE Terminating Call

UE MSC

CM Service Request

RRC and NAS signaling Connection Setup

Authentication Request

Authentication Response

Security Mode Command


RAB Assignment

Setup

Call Proceeding

Alerting

Connect

Connect ACK

Disconnect

Release

Release Complete

UE Outgoing Call

UE MSC

Paging Response

Authentication Request

Authentication Response



RAB Assignment

Setup

Call Confirmed

Alerting

Connect

Connect ACK

Disconnect

Release

Release Complete

Paging

RRC and NAS signaling Connection Setup

Authentication and security flow are optional.CN does not need to the CM Service Response if the security mode is used.

57


NAS Signaling (PS)

SGSN SGSN

RRC connection and NAS signaling connection establishment RRC connection and NAS signaling

connection establishment

Security ModeSecurity ModeSecurity ModeSecurity Mode

RAB establishmentRAB establishmentRAB establishmentRAB establishment

Authentication and security flow are optional.

CN does not need to the CM Service Response if the security mode is used.

58


UE to UE (1)

59


UE to UE (2)

60


UE to UE (4)

61


UE to UE (5)

62


UE to UE (6)

63


UE to UE (7)

64


UE to UE (8)

65


Activate PDP Context from UEActivate PDP Context from UE

66


Activate PDP Context from UEActivate PDP Context from UE

67


Activate PDP Context from NetworkActivate PDP Context from Network

68


Activate PDP Context from NetworkActivate PDP Context from Network

69







Section 5 HandoverSection 5 Handover

70


Concepts about Soft Handover

� Soft handover: the signals from different NodeBs are merged in RNC.

� Softer handover: the signals from different cells, but from the

same NodeB are merged in NodeB.

Soft handover:

Selection combination in uplink

Maximum combination in downlink

Softer handover

Maximum combination in uplink and downlink

71


Node B

RNC

AirBridgeAirBridge

AirBridgeAirBridge

AirBridgeAirBridge

Soft Handover Flow

Core NetworkCore Network

It is no handover in this slide, only one radio links is connected with UE.

72


Node B

RNC

AirBridgeAirBridge

AirBridgeAirBridge

AirBridgeAirBridge

Merged in NodeB

Soft Handover FlowCore NetworkCore Network

It is softer handover. During the handover, the cells in active set are belong to one NodeB. The NodeB uses the RAKE receiver to combine the data, and the UE also combines the data in RAKE receiver.

73


Merged in RNC

Node B

RNC

AirBridgeAirBridge

AirBridgeAirBridge

AirBridgeAirBridge

Soft Handover Flow


It is soft handover. During the handover, the cells in active set are belong to one RNC, but different NodeBs. So the UE can combine the data in RAKE receiver. But in uplink, the data are combined with selection combination in RNC.

74


Soft Handover Flow (SRNC-DRNC)

Merged in SRNC

Node B

AirBridgeAirBridge

AirBridgeAirBridge

AirBridgeAirBridge

Serving RNC

Drift RNC


It is soft handover. During the handover, the cells in active set are belong to different RNCs. So the UE can combine the data in RAKE receiver. But in uplink, the data are combined with selection combination in SRNC.

75


Soft Handover Flow (SRNC Relocation)

Node B

AirBridgeAirBridge

AirBridgeAirBridge

AirBridgeAirBridge

Serving RNC

RNC


It is no handover. The SRNC has changed.

76


Before Handover After Handover

SRNC

NodeBNodeB

SRNC

NodeBNodeB

SRNC

NodeBNodeB

During Handover

Soft Handover Flow（Intra-RNC）

CNCN CN

During the soft handover, two radio links are connected with UE, and data in each RL are same.

77


Decision to setupnew RL

7. DCCH : Active Set Update Complete

6.DCCH: Active Set Update

UE Node B(new) SRNC

NBAP1. Radio Link Setup RequestNBAP

NBAP2. Radio Link Setup ResponseNBAP

3 ALCAP Iub Data Transport Bearer Setup


DCH-FP4. Downlink SynchronisationDCH-FP

DCH-FP5.Uplink SynchronisationDCH-FP


RRC

RRC

RRC

RRC

Soft Handover Flow （Add Branch in RNC）

In the WCDMA system, since the intra-frequency exists among neighboring cells, the UE can communicate with the network via multiple radio links, and can select one with good signal quality by comparison when these radio links are merged, thus optimizing the communication quality. The soft handover can be conducted only in the FDD mode. The soft handover falls into the following cases according to the locations of the cells. The first case is the soft handover among difference cells of the Node B. In this case, the radio links can be merged within the Node B or the SRNC. If they are merged within the Node B, it is called softer handover. The second case is the soft handover among different Node Bs within the same RNC and among different RNCs.

An important issue during the soft handover is the merge of multiple radio links. In the WCDMA system, the MACRO DIVERSITY technology is adopted for the merge of the radio links, that is, the system compares the data from different radio links based on certain standards (such as BER), and selects the data with better quality to send to the upper layer.

The following are some key concepts about the neighboring cell in the soft handover:

1. Active set: The set of cells currently used by the UE. The execution result of the soft handover indicates the increase or decrease of the cells in the active set.

78

2. monitor set: The set of cells that are not in the active set but are being observed by the UE based on the neighboring cell information from the UTRAN. The UE measures the cells in the observation set. When the measurement results satisfy certain conditions, the cells may be added to the active set. Therefore,the observation set sometimes is also called the candidate set.

3. Detected set: The set of cells that have been detected by the UE but do not belong to the active set or the observation set. The UTRAN can request the UE to report the measurement result of the detected set. Since the cells in the detected set are not listed in the neighboring cell list, this set is also called the unlisted set.

The soft handover procedure comprises the following steps:

1. Based on the measurement control information from the RNC, the UE measures the intra-frequency neighboring cells, and reports the measurement result to the RNC after processing.

2. The RNC compares the reported measurement result with the set threshold to decide the cells to be added and deleted.

3. If some cells are to be added, the RNC notifies the Node B to get ready.

4. The RNC notifies the UE to add and/or delete cells via the active set update message.

5. After the UE successfully update the active set, if the cells are deleted, the Node B will be notified to release the corresponding resources.

The original communication is not affected during the soft handover procedure so that smooth handover from a cell to another can be successfully completed.

79


Decision to deletea RL

2. DCCH : Active Set Update Complete

1.DCCH: Active Set Update

UE Node B(old) SRNC

NBAP3. Radio Link Deletion RequestNBAP

NBAP4. Radio Link Deletion ResponseNBAP

RRC

RRC

RRC

RRC

Stop RX and Tx

5 ALCAP Iub Transport Bearer release

Soft Handover Flow （Del Branch in RNC）

80


Before HandoverBefore Handover After HandoverAfter Handover

Radio Link can not exist simultaneouslyRadio Link can not exist simultaneously

SRNC

NodeBNodeB

SRNC

NodeBNodeB

Hard Handover (Intra-RNC)

CNCN

It is hard handover. The UE disconnects the original radio link, then connects to the target cell. It happens in intra-frequency, inter-frequency and inter-RAT.

81


UE Node B Source Node B Target SRNC

8. DCCH : Physical Channel Reconfiguration Complete

6.DCCH : Physical Channel Reconfiguration

1. Radio Link Setup Request

2. Radio Link Setup Response

9. Radio Link Deletion Request

10. Radio Link Deletion Response

3 ALCAP ub Data Transport Bearer Setup

7. Radio Link Failure IndicationRRCRRC

NBAPNBAP

NBAP

RRCRRC

NBAP

NBAP

NBAP NBAP

Decide tohandover

Start Rx

Start Tx

DCH-FP4. Downlink SynchronisationDCH-FP

DCH-FP5.Uplink SynchronisationDCH-FP

NBAP

NBAP

NBAP

11. ALCAP Iub Data Transport Bearer Release

Hard Handover (Intra-RNC)

Description:

1. The SRNC sends the Radio Link Setup Request message to the Node B where the target cell is, requesting the Node B to establish a radio link.

2. The Node B where the target cell is sends the Radio Link Setup Response message to the SRNC, indicating the radio link is successfully established.

3. The SRNC adopts the ALCAP protocol to set up the Iub interface transport bearer between the SRNC and the target Node B, and synchronizes the FP.

4. The SRNC sends the Physical Channel Reconfiguration message carrying the target cell information to the UE via the downlink DCCH.

5. After the UE hands over from the source cell to the target cell,the Node B of the source cell detects the radio link communication failure and then sends the Radio Link Failure Indication message to the SRNC, indicating the radio link failure.

6. After successfully handing over to the target cell, the UE sendsthe Physical Channel Reconfiguration Complete message to the SRNC via the DCCH, notifying the SRNC that the physical cannel reconfiguration is complete.

82

7. The Node B where the source cell is deletes the radio link resources, and then responds to the SRNC with the Radio Link Deletion Response message.

8. The SRNC adopts the ALCAP protocol to release the Iub interface transport bearer of the SRNC and the Node B where the source cell is.

83


SRNC Relocation

SRNS

Core Network

Iu

DRNSIur

UE

RNS

Core Network

Iu

SRNS

UE

After SRNS RelocationBefore SRNS Relocation

Cells

The RNC relocation refers to that the SRNC of the UE changes from one RNC to another RNC. It is divided into two cases based on the UElocation at the time of relocation: Static relocation and associated relocation, or in other words, UE Not Involved and UE Involved.

The precondition for the static relocation is that the UE accesses the network from one and only one DRNC. Since the relocation procedure does not require the UE’s participation, it is also called the UE Not Involved relocation. The following is an example of two radio links. After the relocation, the original DRNC becomes the SRNC, the Iur interface connection is released, and the Iu interface migrates

Associated relocation refers to that the UE accesses the target RNC from the SRNC via hard handover, and the Iu interface changes at the same time. Since the relocation procedure requires the UE’s participation, it is also called the UE Involved relocation.

84


Hard Handover with Relocation (CS)

Associated relocation refers to that the UE accesses the target RNC from the SRNC via hard handover, and the Iu interface changes at the same time. Since the relocation procedure requires the UE’s participation, it is also called the UE Involved relocation.

85


Inter-System Handover Flow（UMTS->GSM）

86


Inter-System Handover Flow (GSM-UMTS)

87


Forward Handover

� Forward Handover is sponsored by UE, including cell update and

URA update. URA update is only used to make the URA re-selection

for the UE which is in URA_PCH state, and check the RRC

connection.

When UE is in Cell_FACH or Cell_PCH state

1. Cell reselection

2. In service area, the T304 timer is overdue.

When UE is in Cell_PCH or URA_PCH state:

1. UE is going to upload data (from Cell_PCH or URA_PCH to Cell_FACH)

2. After UE received the paging information from PCCH, UE sponsored cell update.

88


� This chapter mainly explains the

basic signaling flow in UTRAN. This

is very helpful for the CN signaling

flow.

SummarySummary

89

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