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Table of Contents
Chapter 1 UTRAN Interface Protocols and Functions............................................................... 1-1 1.1 Overview ............................................................................................................................ 1-1 1.2 Uu Interface ....................................................................................................................... 1-2
1.2.1 Uu Protocol Structure.............................................................................................. 1-2 1.2.2 RRC Functions........................................................................................................ 1-4 1.2.3 L2 Functions............................................................................................................ 1-5 1.2.4 L1 Functions............................................................................................................ 1-6
1.3 Iub Interface....................................................................................................................... 1-6 1.3.1 Iub Protocol Structure ............................................................................................. 1-6 1.3.2 NBAP Functions...................................................................................................... 1-7 1.3.3 NBAP Procedures ................................................................................................... 1-9 1.3.4 Iub FP for Common Transport Channel Data Transfer......................................... 1-10 1.3.5 Iub FP for Dedicated Transport Channel Data Transfer ....................................... 1-14
1.4 Iur Interface...................................................................................................................... 1-18 1.4.1 Iur Protocol Structure ............................................................................................ 1-18 1.4.2 RNSAP Functions ................................................................................................. 1-19 1.4.3 RNSAP Procedures .............................................................................................. 1-20 1.4.4 Iur FP for Transport Channel Data Transfer ......................................................... 1-22
1.5 Iu Interface ....................................................................................................................... 1-22 1.5.1 Iu Protocol Structure ............................................................................................. 1-22 1.5.2 RANAP Functions ................................................................................................. 1-25 1.5.3 RANAP Procedures .............................................................................................. 1-27 1.5.4 Iu UP Functions..................................................................................................... 1-29 1.5.5 GTP-U Functions................................................................................................... 1-34 1.5.6 SABP Functions .................................................................................................... 1-34
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Chapter 1 UTRAN Interface Protocols and
Functions
1.1 Overview
Figure 1-1 UTRAN interfaces
As shown in Figure 1-1, UTRAN interfaces in the UMTS system include Iub, Iur, Iu and Uu interfaces. See Table 1-1 for the description of the interfaces.
Table 1-1 UTRAN interfaces
Interface Description
Uu Logical interface between UTRAN and UE
Iub Logical interface between RNC and NodeB
Iur Logical interface between RNCs
Iu Logical interface between RNC and CN
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Iub, Iur, Iu and Uu interfaces are standard interfaces and can be used to connect different network elements (NEs) from different providers. Iub, Iur and Iu interfaces are also called UTRAN terrestrial interfaces.
According to the type of CN entity connected to RNC, the Iu interface can be classified as Iu-CS interface, Iu-PS interface and Iu-BC interface. The Iu-CS interface is used to connect RNC and MSC. The Iu-PS interface is used to connect RNC and SGSN. The Iu-BC interface is used to connect RNC and CBC.
1.2 Uu Interface
1.2.1 Uu Protocol Structure
Uu interface is the interface between User Equipment (UE) and UMTS Terrestrial Radio Access Network (UTRAN) and it is the most important interface in the UMTS system.
As shown in Figure 1-2, the Uu interface includes three protocol layers, physical layer (L1), data link layer (L2) and network layer (L3).
L1 provides the radio physical channels for the transmission of the traffic from upper layers. The functions of L1 are implemented by NodeB.
L2 includes four sublayers, Medium Access Control (MAC), Radio Link Control (RLC), Broadcast/Multicast Control (BMC) and Packet Data Convergence Protocol (PDCP). The functions of L2 are implemented by RNC.
L3 includes the Radio Resource Control (RRC) sublayer in the access stratum, the Mobility Management (MM) and Call Control (CC) in the non-access stratum (NAS). The RRC functions of L3 are implemented by RNC, and the MM and CC functions of L3 are implemented by CN.
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L3
co
ntr
co
ntr
co
ntr
co
ntr
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
Figure 1-2 Uu interface protocol stack
The technical specifications of Uu interface are shown in Figure 1-3.
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L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
TS25.211~TS25.215
L2/MAC
L1
RLC
DCNtGC
L2/RLC
TS25.321
RLCRLC
RLCRLC
RLCRLCTS25.322
Duplication avoidance
UuS boundary
TS25.324 L2/BMC
TS25.331
control
TS25.323 L2/PDCP
DCNtGC
Figure 1-3 Uu interface technical specifications
1.2.2 RRC Functions
The RRC performs the functions listed below:
Broadcast of information related to the non-access stratum (Core Network) Broadcast of information related to the access stratum Establishment, maintenance and release of an RRC connection between the UE
and UTRAN Establishment, reconfiguration and release of Radio Bearers Assignment, reconfiguration and release of radio resources for the RRC
connection RRC connection mobility functions Route selection for the Protocol Data Unit (PDU) of upper layers Control of requested QoS UE measurement reporting and control of the reporting Outer loop power control Control of ciphering Paging Initial cell selection and cell re-selection
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Arbitration of radio resources on uplink DCH RRC message integrity protection CBS control
1.2.3 L2 Functions
L2 includes four sublayers, Medium Access Control (MAC), Radio Link Control (RLC), Broadcast/Multicast Control (BMC) and Packet Data Convergence Protocol (PDCP).
I. MAC
The functions of MAC include:
Mapping between logical channels and transport channels Selection of appropriate transport format for each transport channel Priority handling between data flows of one UE Priority handling between UEs by means of dynamic scheduling Priority handling between data flows of several UEs on FACH Identification of UEs on common transport channels Multiplexing/demultiplexing of upper layer PDUs into/from transport blocks
delivered to/from the physical layer on common transport channels Traffic volume measurement Transport channel type switching Ciphering for transparent mode RLC Access Service Class selection
II. RLC
The functions of RLC include:
Segmentation, reassembly, concatenation, padding and transfer of user data Flow control Error correction, in-sequence delivery of upper layer PDUs and duplicate
detection Sequence numbers check Protocol error detection and recovery Ciphering Suspend/resume function
III. PDCP
The functions of PDCP include:
Header compression and decompression of IP data streams at the transmit and receive entities respectively
Transfer of user data
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Forwarding of PDCP-SDUs from NAS to RLC, and multiplexing of different RBs to the same RLC entity
IV. BMC
The functions of BMC include:
Storage of cell broadcast messages Traffic volume monitoring and radio resource request for CBS Scheduling of BMC messages Transmission of BMC messages to UE Delivery of cell broadcast messages to upper layer (NAS)
1.2.4 L1 Functions
The functions of L1 (physical layer) mainly includes:
Provision for higher layers with measurements and indications (such as FER, SIR, interference power, and transmission power)
Macro-diversity distribution/combination and soft handover execution Frequency and time (chip, bit, slot, frame) synchronization Closed-loop power control RF processing Multiplexing of transport channels and demultiplexing of coded composite
transport channels Mapping of coded composite transport channels onto physical channels Modulation/demodulation and spreading/despreading of physical channels
The detailed functions and relevant specifications of L1 are involved with the basic principles of WCMDA. They are out of the range of this manual. Refer to relevant protocols and documents for details.
1.3 Iub Interface
1.3.1 Iub Protocol Structure
Iub interface is the interface between RNC and NodeB. The protocol stack of Iub interface is illustrated in Figure 1-4.
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Node BApplication Part (NBAP)
TransportLayer
ATM
Physical Layer
Radio NetworkControl Plane
User Plane
Transport Network Control Plane
RadioNetwork
Layer
Q.2630.1
Q.2150.2
ALCAP
SSCF-UNI
SSCOP
AAL Type 5
SSCF-UNI
SSCOP
AAL Type 5 AAL Type 2
PC
H FP
FAC
H FP
RA
CH
FPD
CH
FP
Figure 1-4 Iub interface protocol stack
The technical specifications of Iub interface are shown in Figure 1-5.
NBAPTS 25.433
Transport Layer
Physical Layer TS 25.431
Radio Network Layer
Radio NetworkControl Plane
TransportNetwork
Control Plane
NBAP Transport
TS 25.432
User Plane
DedicatedChannels
TS 25.427
CommonChannels
TS 25.435
DedicatedChannel
Transport
TS 25.426
CommonChannel
Transport
TS 25.434
Transport Signaling
TS 25.426(Dedicated ChannelTransport)
TS 25.434(Common ChannelTransport)
Figure 1-5 Iub interface technical specifications
1.3.2 NBAP Functions
NodeB Application Part (NBAP) is the signalling protocol of the control plane of the radio network layer on the Iub interface, which provides the following functions:
Cell Configuration Management
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This function gives the controlling RNC (CRNC) the possibility to manage the cell configuration information in a NodeB.
Common Transport Channel Management
This function gives the CRNC the possibility to manage the configuration of common transport channels in a NodeB.
System Information Management
This function gives the CRNC the ability to manage the scheduling of System Information to be broadcast in a cell.
Resource Event Management
This function gives the NodeB the ability to inform the CRNC about the status of NodeB resources.
Configuration Alignment
This function gives the CRNC and the NodeB the possibility to verify and enforce that both nodes have the same information on the configuration of the radio resources.
Measurements on Common Resources
This function allows the NodeB to initiate measurements in the NodeB. The function also allows the NodeB to report the result of the measurements.
Radio Link Management
This function allows the CRNC to manage radio links using dedicated resources in a NodeB.
Radio Link Supervision
This function allows the CRNC to report failures and restorations of a radio link.
Compressed Mode Control
This function allows the CRNC to control the usage of compressed mode in a NodeB.
Measurements on Dedicated Resources
This function allows the CRNC to initiate measurements in the NodeB. The function also allows the NodeB to report the result of the measurements.
DL Power Drifting Correction
This function allows the CRNC to adjust the DL power level of one or more radio links in order to avoid DL power drifting between radio links.
Reporting of General Error Situations
This function allows reporting of general error situations.
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1.3.3 NBAP Procedures
NBAP procedures are divided into common procedures and dedicated procedures.
NBAP common procedures are procedures that request initiation of a UE context for a specific UE in NodeB or are not related to a specific UE. NBAP common procedures also incorporate logical O&M procedures.
NBAP dedicated procedures are procedures that are related to a specific UE context in NodeB. This UE context is identified by a UE context identity.
The two types of procedures may be carried on separate signalling links.
I. NBAP Common Procedures
The NBAP functions and corresponding NBAP elementary procedures (EPs) are shown in the Table 1-2.
Table 1-2 NBAP functions and corresponding elementary procedures
Function Elementary procedure
Cell Configuration Management Cell Setup Cell Reconfiguration Cell Deletion
Common Transport Channel Management
Common Transport Channel Setup Common Transport Channel Reconfiguration Common Transport Channel Deletion
System Information Management System Information Update
Resource Event Management Block Resource Unblock Resource Resource Status Indication
Configuration Alignment Audit Required Audit
Reset
Measurements on Common Resources
Common Measurement Initiation Common Measurement Reporting Common Measurement Termination Common Measurement Failure
Radio Link Management. Radio Link Setup
II. NBAP Dedicated Procedures
The NBAP functions and corresponding NBAP dedicated procedures are shown in Table 1-3.
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Table 1-3 NBAP functions and corresponding dedicated procedures
Function Dedicated procedure
Radio Link Management. Radio Link Addition Radio Link Deletion Unsynchronized Radio Link Reconfiguration Synchronized Radio Link Reconfiguration Preparation Synchronized Radio Link Reconfiguration Commit Synchronized Radio Link Reconfiguration Cancellation
Radio Link Pre-emption
Radio Link Supervision. Radio Link Failure Radio Link Restoration
Compressed Mode Control Radio Link Setup Radio Link Addition Compressed Mode Command Unsynchronized Radio Link Reconfiguration Synchronized Radio Link Reconfiguration Preparation Synchronized Radio Link Reconfiguration Commit Synchronized Radio Link Reconfiguration Cancellation
Measurements on Dedicated Resources
Dedicated Measurement Initiation Dedicated Measurement Reporting Dedicated Measurement Termination Dedicated Measurement Failure
DL Power Drifting Correction Downlink Power Control
Reporting of General Error Situations
Error Indication
1.3.4 Iub FP for Common Transport Channel Data Transfer
Iub frame protocol (FP) for common transport channel data transfer is the protocol of the user plane of the radio network layer on the Iub interface, which provides the following services:
Transport of Transport Block Set (TBS) between the NodeB and the CRNC for common transport channels (including RACH, FACH, and PCH)
Support of transport channel synchronization mechanism Support of Node Synchronization mechanism
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I. RACH Data Transfer
RACH Data Transfer procedure is to transfer RACH Data Frame from NodeB to CRNC, as shown in Figure 1-6.
RACH Data Frame
NodeB CRNC
Figure 1-6 RACH data transfer procedure
II. FACH Data Transfer
FACH Data Transfer procedure is to transfer FACH Data Frame from CRNC to NodeB, as shown in Figure 1-7.
FACH Data Frame
NodeB CRNC
Figure 1-7 FACH data transfer procedure
III. PCH Data Transfer
PCH Data Transfer procedure is to transfer PCH Data Frame from CRNC to NodeB, as shown in Figure 1-8.
PCH Data Frame
NodeB CRNC
Figure 1-8 PCH data transfer procedure
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IV. Node Synchronization
Node synchronization is to obtain the round trip delay (RTD) of transmission over the Iub interface.
In the Node Synchronization procedure, the RNC sends a DL Node Synchronization control frame to the NodeB containing the parameter T1. Upon reception of the frame, the NodeB shall respond with a UL Node Synchronization control frame, indicating T2 and T3, as well as T1 that was indicated in the initiating DL Node Synchronization control frame, as shown in Figure 1-9.
DL Node Synchronization
NodeB CRNC
UL Node Synchronization
Figure 1-9 Node synchronisation procedure
Parameters T1, T2, and T3 are defined as follows:
T1: RNC specific frame number (RFN) that indicates the time when the RNC sends the DL Node Synchronization control frame through the service access point (SAP) to the transport network layer.
T2: NodeB specific frame number (BFN) that indicates the time when the NodeB receives the correspondent DL Node Synchronization control frame through the SAP from the transport network layer.
T3: NodeB specific frame number (BFN) that indicates the time when the NodeB sends the UL Node Synchronization control frame through the SAP to the transport network layer.
V. DL Transport Channels Synchronization
DL transport channel synchronization procedure is used to synchronize the transport channel after the transport channel has been set up or used to maintain the synchronization of the transport channel when there is no DL data frame.
In the DL transport channel synchronization procedure, the CRNC sends a DL Synchronization control frame to the NodeB. This message indicates the target Connection Frame Number (CFN). Upon reception of the frame, the NodeB shall immediately respond with a UL Synchronization control frame indicating the Time of Arrival (ToA) for the DL Synchronization frame and the CFN indicated in the received message, as shown in Figure 1-10.
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DL Synchronization
NodeB CRNC
UL Synchronization
Figure 1-10 FACH and PCH transport channels synchronization procedure
VI. DL Timing Adjustment
Timing Adjustment procedure is used for a NodeB to indicate the CRNC the incorrect ToA of downlink data to the NodeB.
Timing adjustment procedure is initiated by the NodeB if a DL frame arrives outside of the defined arrival window. If the DL frame has arrived before the ToAWS or after the ToAWE, the NodeB will include the ToA and the target CFN in the Timing Adjustment control frame, as shown in Figure 1-11.
Timing Adjustment
NodeB CRNC
.
Figure 1-11 FACH and PCH Timing Adjustment procedure
The arrival window and the ToA are defined as follows:
Time of Arrival Window Endpoint (ToAWE): ToAWE represents the time point by which the DL data shall arrive at the NodeB from Iub. ToAWE is defined as the amount of milliseconds before the last time point from which a timely DL transmission for the identified CFN would still be possible taking into account the NodeB internal delays. ToAWE is set via control plane. If data does not arrive before ToAWE, a Timing Adjustment control frame shall be sent by NodeB.
Time of Arrival Window Startpoint (ToAWS): ToAWS represents the time after which the DL data shall arrive at the NodeB from Iub. ToAWS is defined as the amount of milliseconds from ToAWE. ToAWS is set via control plane. If data arrives before ToAWS, a Timing Adjustment control frame shall be sent by NodeB.
Time of Arrival (ToA): ToA is the time difference between the end point of the DL arrival window (ToAWE) and the actual arrival time of DL frame for a specific CFN. A positive ToA means that the frame is received before ToAWE. A negative ToA means that the frame is received after ToAWE.
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1.3.5 Iub FP for Dedicated Transport Channel Data Transfer
Iub FP for dedicated transport channel data transfer is the radio network user plane of Iub interface which provides the following services:
Transport of TBS between Serving RNC (SRNC) and NodeB Transport of outer loop power control information between SRNC and NodeB Support of transport channel synchronization mechanism Support of Node Synchronization mechanism Transfer of radio interface parameters from SRNC to NodeB
I. Uplink Data Transfer
UL Data Frame
NodeB SRNC
Figure 1-12 Uplink data transfer procedure
Uplink Data Transfer procedure is to transfer UL Data Frame from NodeB to SRNC, as shown in Figure 1-12.
Two modes can be used for the UL transmission: normal mode and silent mode. The SRNC selects the mode when setting up the transport bearer and notifies the NodeB with the relevant control plane procedure.
In normal mode, the NodeB shall always send an UL Data Frame to the RNC for all the DCHs in a set of coordinated DCHs regardless of the number of Transport Blocks of the DCHs.
In silent mode and in case only one transport channel is transported on a transport bearer, the NodeB shall not send an UL Data Frame to the RNC when it has received a TFI indicating “number of TB equal to 0” for the transport channel during a TTI.
In silent mode and in case of coordinated DCHs, when the NodeB receives a TFI indicating “number of TB equal to 0” for all the DCHs in a set of coordinated DCHs, the NodeB shall not send an UL data frame to the RNC for this set of coordinated DCHs.
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II. Downlink Data Transfer
DL Data Frame
NodeB SRNC
Figure 1-13 Downlink data transfer procedure
Downlink Data Transfer procedure is to transfer DL Data Frame from SRNC to NodeB, as shown in Figure 1-13.
The NodeB shall consider a transport bearer synchronized only after it has received at least one data frame on this transport bearer before the latest time of arrival (LTOA).
The NodeB shall consider the DL user plane for a certain RL synchronized if all transport bearers established for carrying DL DCH data frames for this RL are synchronized.
Only when the DL user plane is considered synchronized, the NodeB shall transmit the data on the DL DPDCH.
When the DL user plane is considered synchronized and the NodeB does not receive a valid DL Data Frame in a TTI, it assumes that there is no data to be transmitted in that TTI for this transport channel, and shall act as one of the following cases:
If the NodeB is aware of a TFI value corresponding to zero bits for this transport channel, this TFI is assumed. When combining the TFI’s of the different transport channels, a valid TFCI might result and in this case data shall be transmitted on Uu.
If the NodeB is not aware of a TFI value corresponding to zero bits for this transport channel or if combining the TFI corresponding to zero bits with other TFI’s, results in an unknown TFI combination, the handling will be different. In the former case, at each radio frame, the NodeB shall build the TFCI value of each CCTrCH, according to the TFI of the DCH data frames multiplexed on this CCTrCH. In the latter case, the NodeB shall transmit only the DPCCH without TFCI bits.
III. Outer Loop Power Control Information Transfer
Outer loop power control information transfer procedure is to transfer Outer Loop PC control frame from SRNC to NodeB, as shown in Figure 1-14. The Outer Loop PC control frame can be sent via any of the transport bearers dedicated to one UE.
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Based, for example, on the CRC Indicator (CRCI) values and on the quality estimate in the UL frames, the SRNC modifies the SIR target used by the UL Inner Loop Power Control by including the absolute value of the new SIR target in the Outer Loop PC control frame sent to the NodeB's. Upon reception of the Outer Loop PC control frame, the NodeB shall immediately update the SIR target used for the inner loop power control with the specified value.
Outer Loop PC
NodeB SRNC
Figure 1-14 Outer loop power control information transfer procedure
IV. Radio Interface Parameter Update
Radio interface parameter update procedure is used to update radio interface parameters which are applicable to all RL’s for the concerning UE. Both synchronized and unsynchronized parameter updates are also supported.
The procedure is realized by a transmission of Radio Interface Parameter Update control frame from SRNC to the NodeB, as shown in Figure 1-15.
Radio Interface Parameter Update
NodeB SRNC
Figure 1-15 Radio interface parameter update procedure
V. Node Synchronization
Node synchronization procedure is to obtain the round trip delay (RTD) of transmission over the Iub interface.
In the Node Synchronization procedure, the SRNC sends a DL Node Synchronization control frame to the NodeB containing the parameter T1. Upon reception of the frame, the NodeB shall respond with a UL Node Synchronization control frame, indicating T2 and T3, as well as T1 that was indicated in the initiating DL Node Synchronization control frame, as shown in Figure 1-16.
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DL Node Synchronization
NodeB SRNC
UL Node Synchronization
Figure 1-16 Node synchronization procedure
Parameters T1, T2, and T3 are defined as:
T1: RNC specific frame number (RFN) that indicates the time when RNC sends the DL Node Synchronization control frame through the SAP to the transport network layer.
T2: NodeB specific frame number (BFN) that indicates the time when the NodeB receives the correspondent DL Node Synchronization control frame through the SAP from the transport network layer.
T3: NodeB specific frame number (BFN) that indicates the time when the NodeB sends the UL Node Synchronization control frame through the SAP to the transport network layer.
VI. DL Transport Channel Sychronization
DL transport channel synchronization procedure is used to achieve or restore the synchronization of the DCH data stream in DL direction, and as a keep-alive procedure in order to maintain activity on the Iur/Iub transport bearer.
In the DL transport channel synchronization procedure, the CRNC sends a DL Synchronization control frame to the NodeB. This message indicates the target Connection Frame Number (CFN). Upon reception of the frame, the NodeB shall immediately respond with a UL Synchronization control frame indicating the Time of Arrival (ToA) for the DL Synchronization frame and the CFN indicated in the received message, as shown in Figure 1-17.
The UL Synchronization control frame shall always be sent, even if the DL Synchronization control frame is received by the NodeB within the arrival window.
DL Synchronization
NodeB SRNC
UL Synchronization
Figure 1-17 DCH synchronization procedure
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VII. DL Timing Adjustment
Timing adjustment procedure is used to keep the synchronization of the DCH data stream in DL direction.
The timing adjustment procedure is initiated by the NodeB if a DL frame arrives outside of the defined arrival window. If the DL frame has arrived before the ToAWS or after the ToAWE, NodeB will include the ToA and the target CFN in the Timing Adjustment control frame, as shown in Figure 1-18.
Timing Adjustment
NodeB SRNC
Figure 1-18 Timing adjustment procedure
1.4 Iur Interface
1.4.1 Iur Protocol Structure
Iur interface is the interface between RNCs. The protocol stack of Iur interface is illustrated in Figure 1-19.
Iur DataStream(s)
ALCAP(Q.2630.1)TransportNetwork
Layer
ATM
SSCOP
Physical Layer
SCCP
TransportUser
NetworkPlane
Control Plane User Plane
TransportUser
NetworkPlane
STC (Q.2150.1)
Transport NetworkControl Plane
RadioNetwork
Layer RNSAP
MTP3-B
SSCF-NNI
SSCOP
AAL5
MTP3-B
SSCF-NNI
AAL5 AAL2
Figure 1-19 Iur interface protocol stack
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The technical specifications of the Iur interface are shown in Figure 1-20.
RNSAP
TS 25.423
TransportLayer
Physical Layer TS 25.421
RadioNetworkLayer
Radio NetworkControl Plane
TransportNetwork
Control Plane
SignallingTransport
TS 25.422
User PlaneDedicatedChannels
TS 25.427
CommonChannels
TS 25.425
DedicatedChannel
Transport
TS 25.426
CommonChannel
Transport
TS 25.424
Transport Signaling
TS 25.426(Dedicated Channel
Transport)
TS 25.424(Common Channel
Transport)
Figure 1-20 Iur interface technical specifications
1.4.2 RNSAP Functions
Radio Network Subsystem Application Part (RNSAP) is the signalling protocol of the control plane of the radio network layer on Iur interface, which provides the following functions:
Radio Link Management
This function allows the Serving RNC (SRNC) to manage radio links using dedicated resources in a Drift RNS (DRNS).
Physical Channel Reconfiguration
This function allows the Drift RNC (DRNC) to reallocate the physical channel resources for a radio link.
Radio Link Supervision
This function allows the DRNC to report failures and restorations of a radio link.
Compressed Mode Control
This function allows the SRNC to control the usage of compressed mode within a DRNS.
Measurements on Dedicated Resources
This function allows the SRNC to initiate measurements on dedicated resources in the DRNS. The function also allows the DRNC to report the result of the measurements.
DL Power Drifting Correction
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This function allows the SRNC to adjust the DL power level of one or more Radio Links in order to avoid DL power drifting between the radio links.
CCCH Signalling Transfer
This function allows the SRNC and DRNC to pass information between the UE and the SRNC on a CCCH controlled by the DRNS.
Paging
This function allows the SRNC to page a UE in a URA or a cell in the DRNS.
Relocation Execution
This function allows the SRNC to finalize a relocation previously prepared via other interfaces.
Reporting of General Error Situations
This function allows reporting of general error situations, for which function specific error messages have not been defined.
1.4.3 RNSAP Procedures
RNSAP procedures can be classified into class 1 and class2.
The procedures of class 1 have response messages including successful or unsuccessful outcome, as shown in Table 1-4.
The procedures of class 2 have no response message. The message is always assumed successful, as shown in Table 1-5.
Table 1-4 RNSAP class 1 elementary procedures
Response message Elementary procedure
Initiating message
Successful outcome
Unsuccessful outcome
Radio Link Setup
RADIO LINK SETUP REQUEST
RADIO LINK SETUP RESPONSE
RADIO LINK SETUP FAILURE
Radio Link Addition
RADIO LINK ADDITION REQUEST
RADIO LINK ADDITION RESPONSE
RADIO LINK ADDITION FAILURE
Radio Link Deletion
RADIO LINK DELETION REQUEST
RADIO LINK DELETION RESPONSE
Synchronised Radio Link Reconfiguration Preparation
RADIO LINK RECONFIGURATION PREPARE
RADIO LINK RECONFIGURATION READY
RADIO LINK RECONFIGURATION FAILURE
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Response message Elementary procedure
Initiating message
Successful outcome
Unsuccessful outcome
Unsynchronised Radio Link Reconfiguration
RADIO LINK RECONFIGURATION REQUEST
RADIO LINK RECONFIGURATION RESPONSE
RADIO LINK RECONFIGURATION FAILURE
Physical Channel Reconfiguration
PHYSICAL CHANNEL RECONFIGURATION REQUEST
PHYSICAL CHANNEL RECONFIGURATION COMMAND
PHYSICAL CHANNEL RECONFIGURATION FAILURE
Dedicated Measurement Initiation
DEDICATED MEASUREMENT INITIATION REQUEST
DEDICATED MEASUREMENT INITIATION RESPONSE
DEDICATED MEASUREMENT INITIATION FAILURE
Common Transport Channel Resources Initialisation
COMMON TRANSPORT CHANNEL RESOURCES REQUEST
COMMON TRANSPORT CHANNEL RESOURCES RESPONSE
COMMON TRANSPORT CHANNEL RESOURCES FAILURE
Table 1-5 RNSAP class 2 elementary procedures
Elementary procedure Initiating message
Uplink Signalling Transfer UPLINK SIGNALLING TRANSFER INDICATION
Downlink Signalling Transfer DOWNLINK SIGNALLING TRANSFER REQUEST
Relocation Commit RELOCATION COMMIT
Paging PAGING REQUEST
Synchronised Radio Link Reconfiguration Commit
RADIO LINK RECONFIGURATION COMMIT
Synchronised Radio Link Reconfiguration Cancellation
RADIO LINK RECONFIGURATION CANCEL
Radio Link Failure RADIO LINK FAILURE INDICATION
Radio Link Restoration RADIO LINK RESTORE INDICATION
Dedicated Measurement Reporting
DEDICATED MEASUREMENT REPORT
Dedicated Measurement Termination
DEDICATED MEASUREMENT TERMINATION REQUEST
Dedicated Measurement Failure DEDICATED MEASUREMENT FAILURE INDICATION
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Elementary procedure Initiating message
Downlink Power Control DL POWER CONTROL REQUEST
Compressed Mode Command COMPRESSED MODE COMMAND
Common Transport Channel Resources Release
COMMON TRANSPORT CHANNEL RESOURCES RELEASE REQUEST
Error Indication ERROR INDICATION
Radio Link Pre-emption RADIO LINK PREEMPTION REQUIRED INDICATION
1.4.4 Iur FP for Transport Channel Data Transfer
Iur frame protocol (FP) is the protocol of the user plane of the radio network layer on the Iur interface. It includes Iur FP for common transport channel data transfer and Iur FP for dedicated transport channel data transfer.
Iur FP for common transport channel data transfer and Iub FP for common transport channel data transfer are both specified in 3GPP TS25.425 protocol. For details, refer to section 1.3.4 “Iub FP for Common Transport Channel Data Transfer”.
Iur FP for dedicated transport channel data transfer and Iub FP for dedicated transport channel data transfer are both specified in 3GPP TS25.427 protocol. For details, refer to section 1.3.5 “Iub FP for Dedicated Transport Channel Data Transfer”.
1.5 Iu Interface
1.5.1 Iu Protocol Structure
Iu interface is the interface between UTRAN and CN.
The Iu interface between UTRAN and CS domain of CN is called Iu-CS. The protocol stack is shown in Figure 1-21.
The Iu interface between UTRAN and PS domain of CN is called Iu-PS. The protocol stack is shown in Figure 1-22.
The Iu interface between UTRAN and BC domain of CN is called Iu-BC. The protocol stack is shown in Figure 1-23.
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Iu UP Protocol Layer
Q.2630.1TransportNetwork
Layer
ATM
SSCOP
Physical Layer
SCCP
TransportUser
NetworkPlane
Control Plane User Plane
TransportUser
NetworkPlane
Q.2150.1
Transport NetworkControl Plane
RadioNetwork
Layer RANAP
MTP3-B
SSCF-NNI
SSCOP
AAL5
MTP3-B
SSCF-NNI
AAL5 AAL2
Figure 1-21 Iu-CS interface protocol stack
Iu UP Protocol Layer
TransportNetwork
Layer
ATM
SSCOP
Physical Layer
SCCP
TransportUser
NetworkPlane
Control Plane User Plane
TransportUser
NetworkPlane
Transport NetworkControl Plane
RadioNetwork
Layer RANAP
MTP3-B
AAL5 AAL5
ATM
Physical Layer
IP
GTP-UUDPSSCF-NNI
Figure 1-22 Iu-PS interface protocol stack
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TransportNetwork
Layer
RadioNetwork
Layer SABP Protocol Layer
SA Broadcast Plane
TransportUser
NetworkPlane
AAL5
IP
TCP
Physical Layer
ATM
Figure 1-23 Iu-BC interface protocol stack
The technical specifications of Iu interface are shown in Figure 1-24.
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25.413 25.415
TransportNetwork
Layer
25.411
TransportUser
NetworkPlane
Control Plane User Plane
TransportUser
NetworkPlane
Transport NetworkControl Plane
RadioNetwork
Layer
25.412 25.414
25.419
SA Broadcast Plane
TransportUser
NetworkPlane
Figure 1-24 Iu interface technical specifications
1.5.2 RANAP Functions
Radio Access Network Application Part (RANAP) is the signalling protocol of the control plane of the radio network layer on the Iu interface, which provides the following functions:
Relocating SRNC
This function enables to change the SRNC functionality as well as the related Iu resources (RAB(s) and Signalling connection) from one RNC to another.
Overall RAB management
This function is responsible for setting up, modifying and releasing RABs.
Queuing the setup of RAB
The purpose of this function is to allow placing some requested RABs into a queue, and indicate the peer entity about the queuing.
Requesting RAB release
While the overall RAB management is a function of the CN, the RNC has the capability to request the release of RAB.
Release of all Iu connection resources
This function is used to explicitly release all resources related to one Iu connection.
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Requesting the release of all Iu connection resources
While the Iu release is managed from the CN, the RNC has the capability to request the release of all Iu connection resources from the corresponding Iu connection.
SRNS context forwarding function
This function is responsible for transferring SRNS context from the RNC to the CN for intersystem forward handover in case of packet forwarding.
Controlling overload in the Iu interface
This function allows adjusting the load in the Iu interface.
Resetting the Iu
This function is used for resetting an Iu interface.
Sending the UE Common ID (permanent NAS UE identity) to the RNC
This function makes the RNC aware of the UE's Common ID.
Paging the user
This function provides the CN for capability to page the UE.
Controlling the tracing of the UE activity
This function allows setting the trace mode for a given UE. This function also allows the deactivation of a previously established trace.
Transport of NAS information between UE and CN
This function has two sub-classes:
Sub-class1: Transport of the initial NAS signalling message from the UE to CN. This function transfers transparently the NAS information. After transmission, the Iu signalling connection is set up.
Sub-class2: Transport of NAS signalling messages between UE and CN, This function transfers transparently the NAS signalling messages on the existing Iu signalling connection. It also includes a specific service to handle signalling messages differently.
Controlling the security mode in the UTRAN
This function is used to send the security keys (ciphering and integrity protection) to the UTRAN, and setting the operation mode for security functions.
Controlling location reporting
This function allows the CN to operate the mode in which the UTRAN reports the location of the UE.
Location reporting
This function is used for transferring the actual location information from RNC to the CN.
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Data volume reporting function
This function is responsible for reporting unsuccessfully transmitted DL data volume over UTRAN for specific RABs.
Reporting general error situations
1.5.3 RANAP Procedures
RANAP procedures can be classified as class 1, class 2 and class 3.
The procedures of class 1 have response messages including successful or unsuccessful outcome, as shown in Table 1-6.
The procedures of class 2 have no response message. The message is always considered successful, as shown in Table 1-7.
The procedures of class 3 may have one or several response messages reporting both successful and unsuccessful outcomes of the requests as well as temporary status information about the requests, as shown in Table 1-8. This type of procedures only terminates through response(s) or EP timer expiry.
Table 1-6 NANAP class 1 elementary procedures
Response message Elementary procedure
Initiating message
Successful outcome Unsuccessful outcome
Iu Release IU RELEASE COMMAND
IU RELEASE COMPLETE
Relocation Preparation
RELOCATION REQUIRED
RELOCATION COMMAND
RELOCATION PREPARATION FAILURE
Relocation Resource Allocation
RELOCATION REQUEST
RELOCATION REQUEST ACKNOWLEDGE
RELOCATION FAILURE
Relocation Cancel
RELOCATION CANCEL
RELOCATION CANCEL ACKNOWLEDGE
SRNS Context Transfer
SRNS CONTEXT REQUEST
SRNS CONTEXT RESPONSE
Security Mode Control
SECURITY MODE COMMAND
SECURITY MODE COMPLETE
SECURITY MODE REJECT
Data Volume Report
DATA VOLUME REPORT REQUEST
DATA VOLUME REPORT
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Response message Elementary procedure
Initiating message
Successful outcome Unsuccessful outcome
Reset RESET RESET ACKNOWLEDGE
Reset Resource
RESET RESOURCE
RESET RESOURCE ACKNOWLEDGE
Table 1-7 NANAP class 2 elementary procedures
Elementary procedure Message
RAB Release Request RAB RELEASE REQUEST
Iu Release Request IU RELEASE REQUEST
Relocation Detect RELOCATION DETECT
Relocation Complete RELOCATION COMPLETE
SRNS Data Forwarding Initiation SRNS DATA FORWARD COMMAND
SRNS Context Forwarding from Source RNC to CN
FORWARD SRNS CONTEXT
SRNS Context Forwarding to Target RNC from CN
FORWARD SRNS CONTEXT
Paging PAGING
Common ID COMMON ID
CN Invoke Trace CN INVOKE TRACE
CN Deactivate Trace CN DEACTIVATE TRACE
Location Reporting Control LOCATION REPORTING CONTROL
Location Report LOCATION REPORT
Initial UE Message INITIAL UE MESSAGE
Direct Transfer DIRECT TRANSFER
Overload Control OVERLOAD
Error Indication ERROR INDICATION
Table 1-8 NANAP class 3 elementary procedures
Elementary procedure Initiating message Response message
RAB Assignment RAB ASSIGNMENT REQUEST RAB ASSIGNMENT RESPONSE x N (N>=1)
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1.5.4 Iu UP Functions
Iu UP is located in the user plane of the radio network layer on the Iu interface and used to convey user data associated to Radio Access Bearers (RABs). One Iu UP protocol instance is associated to one RAB only.
Iu UP protocol instances exist at Iu access point i.e. at CN and UTRAN. Whenever a RAB requires transfer of user data in the Iu UP, an Iu UP protocol instance exists at each Iu interface access points. These Iu UP protocol instances are established, relocated and released together with the associated RAB procedures.
The Iu UP includes two modes of operation: Transparent Mode (TrM) and Support Mode for predefined SDU size (SMpSDU).
Transparent mode (TrM)
The transparent mode is intended for those RABs that do not require any particular feature from the Iu UP protocol other than transfer of user data. Figure 1-25 illustrates the transparent mode of Iu UP protocol layer.
Iu UP layer(transparent mode)
TNL-SAP
RNL-SAP
TNL-SAP
CNUTRAN
R
adio
Inte
rface
P
roto
cols
Non AccessStratum
Access Stratum
Iu
Iu UP layer(transparent mode)
Figure 1-25 Transparent mode of Iu UP
In this mode, the Iu UP protocol instance does not perform any Iu UP protocol information exchange with its peer over the Iu interface. The Iu UP protocol layer is used for PDUs transfer between upper layers and transport network layer. For instance, Iu UP of Iu-PS adopts transparent mode.
Support mode
The support modes are intended for those RABs that require particular features from the Iu UP protocol in addition to transfer of user data. When operating in a support mode, the peer Iu UP protocol instances exchange Iu UP frames. Figure 1-26 illustrates the support mode of Iu UP protocol layer.
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TNL-SAP
Iu
TNL-SAP
Iu UP layer(support mode)
CNUTRAN
Rad
io In
terfa
ceP
roto
cols
RNL-SAPNon Access
Stratum
Access Stratum
Transfer of IuUP protocol
frames
Support ModeFunctions
Iu UP layer(support mode)
Support ModeFunctions
Figure 1-26 Support mode of Iu UP
The only support mode which has been defined is the support mode for predefined SDU size (SMpSDU). For instance, the transfer of AMR speech PDUs would utilize SMpSDU.
I. User Data Transfer
User data transfer procedure is to transfer Iu UP frames between the two Iu UP protocol layers on the Iu interface. Since an Iu UP instance is associated to an RAB and an RAB only, the user data being transferred only relate to the associated RAB.
As shown in Figure 1-27, the transfer of user data procedure is invoked whenever user data for that particular RAB needs to be sent across the Iu interface.
In SRNC, the upper layers may deliver frame quality classification information together with the RFCI.
CN/ RNC
RNC/ CN Transfer of User Data
(RFCI, payload)
Figure 1-27 Transfers of user data
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II. Initialization Procedure
Initialization procedure is to configure both termination points of the Iu UP with the RFCIs and associated RAB Sub Flows SDU sizes necessary during the transfer of user data phase. This procedure is mandatory for RABs using the support mode for predefined SDU size.
The RNC sends initialization frame to the CN, indicating the RFCIs and their corresponding RAB sub-flow SDU size, as shown in Figure 1-28.
If the CN receives the initialization frame and accepts the parameters, it will respond with an Initialization ACK frame. Otherwise, it will respond with an Initialization NACK frame.
*
Transfer Of User Data
Initialisation
((RFCI, SDU sizes ) m )
Initialisation ACK
* it can repeated n times
RNC CN/other
Figure 1-28 Initialization of Iu UP for m RFCIs
III. Iu Rate Control
Iu rate control procedure is to signal to the peer Iu UP protocol layer the permitted rate(s) over Iu in the reverse direction of the sent rate control frame.
The Iu rate control procedure is invoked whenever the SRNC/CN decides that the set of downlink/uplink permitted rates over Iu shall be modified, as shown in Figure 1-29. The permitted rate is given as RFCI indicators.
Rate Control(RFCI indicators,
[Downlink send intervals*])
* Optional
RNC/CN CN/RNC
Figure 1-29 Rate control
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IV. Time Alignment Procedure
Time alignment procedure is to minimize the buffer delay in RNC by controlling the transmission timing in the peer Iu UP protocol layer entity.
The time alignment procedure is invoked whenever the SRNC detects the reception of Iu UP PDU at an inappropriate timing that leads to an unnecessary buffer delay as shown in Figure 1-30. The Iu UP protocol layer entity in SRNC indicates the peer entity the necessary amount of the delay or advance adjustment in the number of 500 µs steps.
A supervision timer TTA is started after sending the Iu UP time alignment frame. This timer supervises the reception of the time alignment acknowledgement frame.
The requested Iu UP protocol layer entity in the peer node adjusts the transmission timing by the amount as indicated by SRNC. If the time alignment frame is correctly formatted and treated by the receiving Iu UP protocol layer and the time alignment is treated correctly by the upper layers, this latter sends a time alignment acknowledgement frame.
Upon reception of a time alignment acknowledgement frame, the Iu UP protocol layer in the SRNC stops the supervision timer TTA.
If the CN cannot handle the time alignment frame, it will send an NACK frame to the RNC, indicating the causes. The RNC will decide whether to send again the time alignment frame or not according to the causes and meanwhile stop the timer TTA.
Time Alignment
ACK
User data with bad timing
User data with adjusted timing
RNC CN
Figure 1-30 Time alignment
V. Error Event
Error event procedure is to handle the error reporting.
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Over the Iu UP protocol the error reports are made with Error event frames as shown in in Figure 1-31,The Error event procedure in the Iu UP can be triggered by:
An error detected by the Iu UP functions A request by the upper layers
When an Error event is reported by an Error event frame the following information shall be included:
A cause value Error distance (0: if Iu UP function detected; 1: if requested by upper layers).
CN or other/RNC
RNC/CN or other
Error event(Cause value,
Error distance)
Figure 1-31 Error event
VI. Frame Quality Classification
Frame quality classification (FQC) is used to classify the Iu UP frames depending on whether errors have occurred in the frame or not.
The FQC information is exchanged between RNC and CN through user data transfer procedure, as shown in Figure 1-32.
Transfer of User Data(FQC, RFCI, payload )
Transfer of User Data(FQC, RFCI, payload )
CN/RNCRNC/CN
Figure 1-32 Transfers of user data with FQC information
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1.5.5 GTP-U Functions
GPRS Tunnel Protocol User Plane (GTP-U) is to transfer Iu-PS user data through tunnel protocol. In addition, it also includes the user plane auxiliary signalling such as error indication of data transferring, handshaking message and supported extension head list.
1.5.6 SABP Functions
Service Area Broadcast Protocol (SABP) is the protocol of the radio network layer on the Iu-BC interface, which provides the following functions:
Message Handling
This function is to broadcast new messages, amend existing broadcasted messages, and stop the broadcasting of specific messages.
Load Handling
This function is responsible for determining the loading of the broadcast channels at any particular point in time.
Reset
This function permits the CBC to end broadcasting in one or more service areas.
Error Handling
This function allows the reporting of general error situations, for which function specific error messages have not been defined.