1CN Core Network
UE User Equipment
Service manager layer
Service convergence layer
Radio access layer
Common Protocol Model of UTRAN Interfaces
The principle of interface protocol architecture is the logical mutual-independence between layers and planes. Protocol layers of a specified protocol version, or even all layers in a plane can be modified if required in the future.
Protocols of the terrestrial interfaces follow a general protocol model, based on the principle that the layers and planes of the protocols are logically independent of each other. So, the radio network layer and the transport network layer are independent of each other and the control plane and the user plane are independent of each other. Therefore, the protocol stacks and planes can be easily altered as and when required to fit future requirements.
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UMTS Rel99:
WCDMA L1
RRC :Radio Resource Control
Chapter 2 UTRAN Interface Protocol and Functions
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Iu Interface
Iur Interface
Iub Interface
Uu Interface
1,Physical Layer:
The physical layer provides transport channels for ATM cells. It adds transport overheads to the ATM cells from the upper ATM layer to form consecutive bit stream. It also extracts the valid ATM cells from the consecutive bit stream received from the physical media and transports them to the ATM layer.
The physical layer comprises two sublayers: Transmission Convergence (TC) sublayer and Physical Media (PM) sublayer.
2,ATM Layer:
Asynchronous Transfer Mode (ATM) layer is above the physical layer and communicates with its peer layer by utilizing services provided by the physical layer. The communication unit is cell. The ATM layer is independent of the type of the physical medium, the actual implementation of the physical layer and the type of the services transported. It only identifies and processes cell headers. That is to say, the ATM layer inserts a 5-byte header to the 48-byte cell payload transported from its upper layer, or removes the header from the cells transported from the physical layer and transports it to the upper layer.
3,AAL2:
AAL2 focuses on VBR (low rate) services with specific timing requirements, for example, compression voice service. In this kind of services, the data packets generated are too small to fill a cell, but to wait for enough data packets to fill the cell will surely lead to great delay. Therefore, AAL protocol multiplexes multiple users in one ATM channel, i.e., it fills a cell with the data packets from multiple users and adds a header to each packet to indicate which user it comes from.
4,AAL5:
AAL5 protocol is an AAL protocol especially made for Category-C connection oriented services for the purpose of efficiency improvement on the basis of AAl3/4. AAL5 protocol includes two sublayers: Segment And Reassemble (SAR) and Common part Convergence Sublayer (CPCS). The Segment And Reassemble (SAR) sublayer in the AAL5 segments the CPCS-PDU into 48-byte SAR-PDU without any overheads. Reassembly function is achieved during PDU receiving.
5,SSCOP:
6,SSCF:
The SSCF functions as the adaptation layer of the SSCOP and the upper layer applications. Upper layer applications refer to NBAP, MTP3-B and Signal Transporter (STC). The MTP3-B is used for NNI, which has higher link quality. SAAL is required to support link quality check and to help the MTP3-B with link switchover. But, NBAP is used for User Network Interface (UNI), which has poorer link quality and greater delay. Therefore, SSCF is divided into SSCF-NNI and SSCF-UNI to cater to different upper layer applications.
7,MTP3-B:
Based on Message Transfer Part Layer 3 (MTP3), MTP3-B is the protocol specification aiming at ATM features. As the signaling transport layer, MTP3-B is responsible for transferring signaling messages, managing signaling networks and signaling links. It performs message exchange via the services provided by SAAL.
8,ALCAP:
Access Link Control Application Part (ALCAP), also called Q.AAL2 protocol, complies with ITU-T Q.2630.1 and resides in the user plane of the Iub/Iur/Iu-CS transport network layer with the signaling bearers of SAAL UNI type and MTP3-B type. ALCAP consists of a Q.AAL2 protocol processing layer (one plane) and two STC adaptation layers (the other plane) in which the former plane performs all protocol functions while the latter one adapts primitives and shield bottom-layer differences (SAAL, MTP3-B).
The basic function of ALCAP is establishing and releasing AAL2 connection between two SPs. Besides, it also maintains and manages such resources as path, tunnel in the micro cell of the signaling system. The AAL2 connections controlled by ALCAP shall be regarded as the transmission bearer for the control plane and user plane of the radio network layer.
9,SCCP:
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1,Iu-PS Data Bearer:
The structure of Iu-PS user-plane data bearer is shown in slide. Working in IP over ATM (IPoA) bearing mode, the AAL layer takes AAL5 as the ATM adaptation type.
2,IP:
Internet Protocol (IP) provides a globally unified addressing mode to shield the differences between physically network addresses, thus enabling route search. Besides, it also provides a globally unified packet format to shield the differences between network link layers, thus enabling network interconnection.
3,UDP:
Providing connectionless service, User Datagram Protocol (UDP) increases port addresses based on IP to distinguish different applications on a host. For example, the destination port number used by GTP-U is 2152 and the source port number is an arbitrary value distributed by the transmitting end.
4,GTP-U
*
*
Physical (Full Rate E1 or STM1 Optical)
ATM Lower Layers
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Radio Access BearerRABManagement
Establishment, Modification and Release of RAB
Iu data transmission
normal data transmission
abnormal data transmission
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Iu Signaling Trace Management
Iu Interface Abnormality Management
CBS(Cell Broadcast Service) Control
Iu Interface
Iur Interface
Iub Interface
Uu Interface
1,Physical Layer:
The physical layer provides transport channels for ATM cells. It adds transport overheads to the ATM cells from the upper ATM layer to form consecutive bit stream. It also extracts the valid ATM cells from the consecutive bit stream received from the physical media and transports them to the ATM layer.
The physical layer comprises two sublayers: Transmission Convergence (TC) sublayer and Physical Media (PM) sublayer.
2,ATM Layer:
Asynchronous Transfer Mode (ATM) layer is above the physical layer and communicates with its peer layer by utilizing services provided by the physical layer. The communication unit is cell. The ATM layer is independent of the type of the physical medium, the actual implementation of the physical layer and the type of the services transported. It only identifies and processes cell headers. That is to say, the ATM layer inserts a 5-byte header to the 48-byte cell payload transported from its upper layer, or removes the header from the cells transported from the physical layer and transports it to the upper layer.
3,AAL2:
AAL2 focuses on VBR (low rate) services with specific timing requirements, for example, compression voice service. In this kind of services, the data packets generated are too small to fill a cell, but to wait for enough data packets to fill the cell will surely lead to great delay. Therefore, AAL protocol multiplexes multiple users in one ATM channel, i.e., it fills a cell with the data packets from multiple users and adds a header to each packet to indicate which user it comes from.
4,AAL5:
AAL5 protocol is an AAL protocol especially made for Category-C connection oriented services for the purpose of efficiency improvement on the basis of AAl3/4. AAL5 protocol includes two sublayers: Segment And Reassemble (SAR) and Common part Convergence Sublayer (CPCS). The Segment And Reassemble (SAR) sublayer in the AAL5 segments the CPCS-PDU into 48-byte SAR-PDU without any overheads. Reassembly function is achieved during PDU receiving.
5,SSCOP:
6,SSCF:
The SSCF functions as the adaptation layer of the SSCOP and the upper layer applications. Upper layer applications refer to NBAP, MTP3-B and Signal Transporter (STC). The MTP3-B is used for NNI, which has higher link quality. SAAL is required to support link quality check and to help the MTP3-B with link switchover. But, NBAP is used for User Network Interface (UNI), which has poorer link quality and greater delay. Therefore, SSCF is divided into SSCF-NNI and SSCF-UNI to cater to different upper layer applications.
7,MTP3-B:
Based on Message Transfer Part Layer 3 (MTP3), MTP3-B is the protocol specification aiming at ATM features. As the signaling transport layer, MTP3-B is responsible for transferring signaling messages, managing signaling networks and signaling links. It performs message exchange via the services provided by SAAL.
8,ALCAP:
Access Link Control Application Part (ALCAP), also called Q.AAL2 protocol, complies with ITU-T Q.2630.1 and resides in the user plane of the Iub/Iur/Iu-CS transport network layer with the signaling bearers of SAAL UNI type and MTP3-B type. ALCAP consists of a Q.AAL2 protocol processing layer (one plane) and two STC adaptation layers (the other plane) in which the former plane performs all protocol functions while the latter one adapts primitives and shield bottom-layer differences (SAAL, MTP3-B).
The basic function of ALCAP is establishing and releasing AAL2 connection between two SPs. Besides, it also maintains and manages such resources as path, tunnel in the micro cell of the signaling system. The AAL2 connections controlled by ALCAP shall be regarded as the transmission bearer for the control plane and user plane of the radio network layer.
9,SCCP:
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Physical (Full Rate E1 or STM1 Optical)
ATM Lower Layers
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Support SRNC relocation
Paging between RNCs
Protocol Error Report
Dedicated Channel Functions
Establish, Modify or Release Dedicated Channels in DRNC during handover
Transmission of DCH TB(Transmission Block) on Iur
Management of RL(Radio Link) in DRNS by Dedicated Measurement Procedure and Filter Control
RL ManagementCompressed Mode Management
In order to support soft handover between RNCs, Iur interface was introduced. With the development of the standard, more functions are introduces.
1.Support basic mobility functions between RNCs;
2.Support dedicated channel services;
3.Support common channel services;
4.Support global resource management.
Iur Interface Functions
Common Channel Functions
Establishment, Deletion of Common transport Channels on IurOccupation of Common Transport Channels for Transmit UE information which is in Common Channel state in DRNC
Separate MAC-d From MAC-c
Global Resource Management
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Iu Interface
Iur Interface
Iub Interface
Uu Interface
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1,Physical Layer:
The physical layer provides transport channels for ATM cells. It adds transport overheads to the ATM cells from the upper ATM layer to form consecutive bit stream. It also extracts the valid ATM cells from the consecutive bit stream received from the physical media and transports them to the ATM layer.
The physical layer comprises two sublayers: Transmission Convergence (TC) sublayer and Physical Media (PM) sublayer.
2,ATM Layer:
Asynchronous Transfer Mode (ATM) layer is above the physical layer and communicates with its peer layer by utilizing services provided by the physical layer. The communication unit is cell. The ATM layer is independent of the type of the physical medium, the actual implementation of the physical layer and the type of the services transported. It only identifies and processes cell headers. That is to say, the ATM layer inserts a 5-byte header to the 48-byte cell payload transported from its upper layer, or removes the header from the cells transported from the physical layer and transports it to the upper layer.
3,AAL2:
AAL2 focuses on VBR (low rate) services with specific timing requirements, for example, compression voice service. In this kind of services, the data packets generated are too small to fill a cell, but to wait for enough data packets to fill the cell will surely lead to great delay. Therefore, AAL protocol multiplexes multiple users in one ATM channel, i.e., it fills a cell with the data packets from multiple users and adds a header to each packet to indicate which user it comes from.
4,AAL5:
AAL5 protocol is an AAL protocol especially made for Category-C connection oriented services for the purpose of efficiency improvement on the basis of AAl3/4. AAL5 protocol includes two sublayers: Segment And Reassemble (SAR) and Common part Convergence Sublayer (CPCS). The Segment And Reassemble (SAR) sublayer in the AAL5 segments the CPCS-PDU into 48-byte SAR-PDU without any overheads. Reassembly function is achieved during PDU receiving.
5,SSCOP:
6,SSCF:
The SSCF functions as the adaptation layer of the SSCOP and the upper layer applications. Upper layer applications refer to NBAP, MTP3-B and Signal Transporter (STC). The MTP3-B is used for NNI, which has higher link quality. SAAL is required to support link quality check and to help the MTP3-B with link switchover. But, NBAP is used for User Network Interface (UNI), which has poorer link quality and greater delay. Therefore, SSCF is divided into SSCF-NNI and SSCF-UNI to cater to different upper layer applications.
7,ALCAP:
Access Link Control Application Part (ALCAP), also called Q.AAL2 protocol, complies with ITU-T Q.2630.1 and resides in the user plane of the Iub/Iur/Iu-CS transport network layer with the signaling bearers of SAAL UNI type and MTP3-B type. ALCAP consists of a Q.AAL2 protocol processing layer (one plane) and two STC adaptation layers (the other plane) in which the former plane performs all protocol functions while the latter one adapts primitives and shield bottom-layer differences (SAAL, MTP3-B).
The basic function of ALCAP is establishing and releasing AAL2 connection between two SPs. Besides, it also maintains and manages such resources as path, tunnel in the micro cell of the signaling system. The AAL2 connections controlled by ALCAP shall be regarded as the transmission bearer for the control plane and user plane of the radio network layer.
8,Abbreviation:
PCH FP: Paging CHannel Frame Protocol
SSCOP:Special Service Connection Protocol
DCH FP: Dedicated CHannel Frame Protocol
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ATM Lower Layers
RRC: Radio Resource Control
RLC: Radio Link Control
MAC: Medium Access Control
Iub Common Channel Data Transmission
Logical O&M of Node Bmaintenance functions such as cell configuration ManagementFault ManagementBlock Management, etc.
System Information Management
Iub Dedicated Data transmission
Compressed Mode Control
Iu Interface
Iur Interface
Iub Interface
Uu Interface
Uu Interface Protocol Stack 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 WCDMA system.
The radio interface is layered into three protocol layers:
- the physical layer (L1);
- network layer (L3).
Layer 2 is split into following sublayers: Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP) and Broadcast/Multicast Control (BMC).
Layer 3 and RLC are divided into Control (C-) and User (U-) planes. PDCP and BMC exist in the U-plane only.
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Multiplexing of transport channels and de-multiplexing of encoded composite channels
Mapping of encoded composite transport channels on physical channels
Macro-diversity distribution/combining and soft handover execution
Error detection on transport channels and indication to higher layers
FEC encoding/decoding and interleaving/de-interleaving of transport channels
Rate matching of coded transport channels to physical channels
Power weighting and combining of physical channels
closed-loop power control
open-loop power control
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Modulation and spreading/demodulation and de-spreading of physical channels
Synchronization between frequency and time (chip, bit, slot, frame)
Radio characters measurements (FER, SIR, Interference power) and indication to higher layers
Compressed mode support
Diversity of Transmission/Receiving
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MAC Services to upper layers
- Data transfer. This service provides unacknowledged transfer of MAC SDUs between peer MAC entities. This service does not provide any data segmentation. Therefore, segmentation/reassembly function should be achieved by upper layer.
- Reallocation of radio resources and MAC parameters. This service performs on request of RRC execution of radio resource reallocation and change of MAC parameters, i.e. reconfiguration of MAC functions such as change of identity of UE, change of transport format (combination) sets, change of transport channel type. In TDD mode, in addition, the MAC can handle resource allocation autonomously.
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selection of appropriate Transport Format for each Transport Channel depending on instantaneous data rate
priority handling between data flows of one UE
priority handling between UEs by means of dynamic scheduling
identification of UEs on common transport channels
multiplexing/demultiplexing of higher layer PDUs into/from transport blocks delivered to/from the physical layer on common transport channels
multiplexing/demultiplexing of higher layer PDUs into/from transport block sets delivered to/from the physical layer on dedicated transport channels
traffic volume monitoring
ciphering for transparent RLC
The functions of MAC include:
- Mapping between logical channels and transport channels. The MAC is responsible for mapping of logical channel(s) onto the appropriate transport channel(s).
- Selection of appropriate Transport Format for each Transport Channel depending on instantaneous source rate. Given the Transport Format Combination Set assigned by RRC, MAC selects the appropriate transport format within an assigned transport format set for each active transport channel depending on source rate. The control of transport formats ensures efficient use of transport channels.
- Priority handling between data flows of one UE. When selecting between the Transport Format Combinations in the given Transport Format Combination Set, priorities of the data flows to be mapped onto the corresponding Transport Channels can be taken into account. Priorities are e.g. given by attributes of Radio Bearer services and RLC buffer status. The priority handling is achieved by selecting a Transport Format Combination for which high priority data is mapped onto L1 with a "high bit rate" Transport Format, at the same time letting lower priority data be mapped with a "low bit rate" (could be zero bit rate) Transport Format. Transport format selection may also take into account transmit power indication from Layer 1.
- Priority handling between UEs by means of dynamic scheduling. In order to utilise the spectrum resources efficiently for bursty transfer, a dynamic scheduling function may be applied. MAC realises priority handling on common and shared transport channels. Note that for dedicated transport channels, the equivalent of the dynamic scheduling function is implicitly included as part of the reconfiguration function of the RRC sublayer.
- Identification of UEs on common transport channels. When a particular UE is addressed on a common downlink channel, or when a UE is using the RACH, there is a need for inband identification of the UE. Since the MAC layer handles the access to, and multiplexing onto, the transport channels, the identification functionality is naturally also placed in MAC.
- Multiplexing/demultiplexing of upper layer PDUs into/from transport blocks delivered to/from the physical layer on common transport channels. MAC should support service multiplexing for common transport channels, since the physical layer does not support multiplexing of these channels.
- Multiplexing/demultiplexing of upper layer PDUs into/from transport block sets delivered to/from the physical layer on dedicated transport channels. The MAC allows service multiplexing for dedicated transport channels. This function can be utilised when several upper layer services (e.g. RLC instances) can be mapped efficiently on the same transport channel. In this case the identification of multiplexing is contained in the MAC protocol control information.
- Traffic volume measurement. Measurement of traffic volume on logical channels and reporting to RRC. Based on the reported traffic volume information, RRC performs transport channel switching decisions.
- Transport Channel type switching. Execution of the switching between common and dedicated transport channels based on a switching decision derived by RRC.
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{XOR}
DTCH
DTCH
1,DCH: Support soft handover, fast power control; Support fast data rate change.
2,CCH: Don’t support soft handover; Support fast power control for several CCHs. (CCHBCH/FACH/PCH/RACH/CPCP/DSCH)
3,BCH: Transmit special information of UTRA network or specific cells, such as: random access code, access slot, or other channels’ transmission diversity types. BCH’s transmission power is high, so all UEs in the cell can receive the information. The data rate of BCH is slow and fixed in order to let the low classic UE can decoding.
4,FACH: a downlink channel; one cell can have several FACHs, but one channel must transmit with slow bit rate.
5,PCH: the paging mode influences the UE’s power consumption. If UE adjusts its receiver to intercept the paging information more less, the UE’s battery can use longer in idle mode.
6,RACH: transmit connection request and little packet data.
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MAC: Transport Formation Selection(1)
Contrl immediate bit rate by means of changing traffic per TTI(Transmission Time Interval, is multiple of 10ms)
Transport Block (TB): Bit series to be trasmited from logical channel
Transport Block Size: Size of TB
Transport Block Set: A group of TB transferred in a TTI (Multiplexed on logical channel)bb
Transport Block Set Size: Whole bit length contained in a TBS
Transport Block, TB#1
Transport Time Interval, TTI
3,PS services: 336
4,AMR services: 8 types TB Size with different AMR rates
5,CS Stream: different rates with different services (576(14.4k/28.8k/57.6k),640(32k/64k) etc.
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Transport Format (TF) defines Transport Block Set (Transport Block Size, Transport Block Set Size)
Transport Format Set (TFS): Possible TF combinations of a transport channel. MAC will chose a TF during every TTI
Transport Format Combination (TFC): Determined TF combination in each TTI, each transport channel
Transport Format Combination Set (TFCS): define all possible TFC combination method. Thus MAC can process dynamic transport rate control in different transport channels
TFCS
- Transparent data transfer. This service transmits upper layer PDUs without adding any protocol information, possibly including segmentation/reassembly functionality.
- Unacknowledged data transfer. This service transmits upper layer PDUs without guaranteeing delivery to the peer entity. The unacknowledged data transfer mode has the following characteristics:
- Detection of erroneous data: The RLC sublayer shall deliver only those SDUs to the receiving upper layer that are free of transmission errors by using the sequence-number check function.
- Immediate delivery: The receiving RLC sublayer entity shall deliver a SDU to the upper layer receiving entity as soon as it arrives at the receiver.
- Acknowledged data transfer. This service transmits upper layer PDUs and guarantees delivery to the peer entity. In case RLC is unable to deliver the data correctly, the user of RLC at the transmitting side is notified. For this service, both in-sequence and out-of-sequence delivery are supported. In many cases a upper layer protocol can restore the order of its PDUs. As long as the out-of-sequence properties of the lower layer are known and controlled (i.e. the upper layer protocol will not immediately request retransmission of a missing PDU) allowing out-of-sequence delivery can save memory space in the receiving RLC. The acknowledged data transfer mode has the following characteristics:
- Error-free delivery: Error-free delivery is ensured by means of retransmission. The receiving RLC entity delivers only error-free SDUs to the upper layer.
- Unique delivery: The RLC sublayer shall deliver each SDU only once to the receiving upper layer using duplication detection function.
- In-sequence delivery: RLC sublayer shall provide support for in-order delivery of SDUs, i.e., RLC sublayer should deliver SDUs to the receiving upper layer entity in the same order as the transmitting upper layer entity submits them to the RLC sublayer.
- Out-of-sequence delivery: Alternatively to in-sequence delivery, it shall also be possible to allow that the receiving RLC entity delivers SDUs to upper layer in different order than submitted to RLC sublayer at the transmitting side.
- Maintenance of QoS as defined by upper layers. The retransmission protocol shall be configurable by layer 3 to provide different levels of QoS. This can be controlled.
- Notification of unrecoverable errors. RLC notifies the upper layer of errors that cannot be resolved by RLC itself by normal exception handling procedures, e.g. by adjusting the maximum number of retransmissions according to delay requirements.
There is a single RLC connection per Radio Bearer.
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In-sequence delivery of higher layer PDUs, duplicate detection
Flow control
Protocol error detection and recovery
Ciphering
Suspend/resume function
RLC Functions:
- Segmentation and reassembly. This function performs segmentation/reassembly of variable-length upper layer PDUs into/from smaller RLC PDUs. The RLC PDU size is adjustable to the actual set of transport formats.
- Transfer of user data. This function is used for conveyance of data between users of RLC services. RLC supports acknowledged, unacknowledged and transparent data transfer. QoS setting controls transfer of user data.
- Error correction. This function provides error correction by retransmission (e.g. Selective Repeat, Go Back N, or a Stop-and-Wait ARQ) in acknowledged data transfer mode.
- In-sequence delivery of upper layer PDUs. This function preserves the order of upper layer PDUs that were submitted for transfer by RLC using the acknowledged data transfer service. If this function is not used, out-of-sequence delivery is provided.
- Duplicate Detection. This function detects duplicated received RLC PDUs and ensures that the resultant upper layer PDU is delivered only once to the upper layer.
- Flow control. This function allows an RLC receiver to control the rate at which the peer RLC transmitting entity may send information.
- Sequence number check. This function is used in unacknowledged mode and guarantees the integrity of reassembled PDUs and provides a mechanism for the detection of corrupted RLC SDUs through checking sequence number in RLC PDUs when they are reassembled into a RLC SDU. A corrupted RLC SDU will be discarded.
- Protocol error detection and recovery. This function detects and recovers from errors in the operation of the RLC protocol.
- Ciphering. This function prevents unauthorised acquisition of data. Ciphering is performed in RLC layer for non-transparent RLC mode.
- Suspend/resume function. Suspension and resumption of data transfer.
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BMCBroadcast/Multicast Control
The BMC-SAP provides a broadcast/multicast transmission service in the user plane on the radio interface for common user data in unacknowledged mode.
2,PDCP Services provided to upper layers:
PDCP SDU delivery.
Mapping of network PDU from network protocol to RLC protocol
header compression and de-compression in order to reduce the redundant control information in higher layer data, thus enhance the transport efficiency in air interface
TCP/IP (RFC2507) - Non-realtime IP
support of Loss-less SRNS Relocation
buffering and retransmit of higher layer data
PDCP Functions:
- Header compression and decompression. Header compression and decompression of IP data streams (e.g., TCP/IP and RTP/UDP/IP headers) at the transmitting and receiving entity, respectively. The header compression method is specific to the particular network layer, transport layer or upper layer protocol combinations e.g. TCP/IP and RTP/UDP/IP.
- Transfer of user data. Transmission of user data means that PDCP receives PDCP SDU from the NAS and forwards it to the RLC layer and vice versa.
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Storage of cell broadcast message
Monitoring of traffic volume and CBS (Cell Broadcast Service) radio resource request
BMC message dispatching
Transport BMC message to higher layer
BMC Functions:
- Storage of Cell Broadcast Messages.
The BMC stores the Cell Broadcast messages received over the CBC-RNC interface for scheduled transmission.
- Traffic volume monitoring and radio resource request for CBS.
At the UTRAN side, the BMC calculates the required transmission rate for Cell Broadcast Service based on the messages received over the CBC-RNC interface, and requests for appropriate CTCH/FACH resources from RRC.
- Scheduling of BMC messages.
The BMC receives scheduling information together with each Cell Broadcast message over the CBC-RNC-interface. Based on this scheduling information, at the UTRAN side, BMC generates schedule messages and schedules BMC message sequences accordingly. At the UE side, 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 messages to UE.
This function transmits the BMC messages (Scheduling and Cell Broadcast messages) according to schedule.
- Delivery of Cell Broadcast messages to upper layer (NAS).
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- General Control
The GC SAP provides an information broadcast service. This service broadcasts information to all UEs in a certain geographical area.
- Notification
The Nt SAP provides paging and notification broadcast services. The paging service sends information to a specific UE(s). The information is broadcast in a certain geographical area but addressed to a specific UE(s).
- Dedicated Control
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Paging/Notification
Radio Bearer (RB) Managementestablish, reconfig and release, support NAS services
RRC connection mobility management
Routing of higher layer PDUs
Control of requested QoS and map into different resources of Access Stratum
Management and control of radio resources
The Radio Resource Control (RRC) layer handles the control plane signalling of Layer 3 between the UEs and UTRAN. The RRC performs the following functions:
- Broadcast of information provided by the non-access stratum (Core Network). The RRC layer performs system information broadcasting from the network to all UEs. The system information is normally repeated on a regular basis. The RRC layer performs the scheduling, segmentation and repetition. This function supports broadcast of higher layer (above RRC) information. This information may be cell specific or not. As an example RRC may broadcast Core Network location service area information related to some specific cells.
- Broadcast of information related to the access stratum. The RRC layer performs system information broadcasting from the network to all UEs. The system information is normally repeated on a regular basis. The RRC layer performs the scheduling, segmentation and repetition. This function supports broadcast of typically cell-specific information.
- Paging/notification. The RRC layer can broadcast paging information from the network to selected UEs. Higher layers on the network side can request paging and notification. The RRC layer can also initiate paging during an established RRC connection.
- Establishment, re-establishment, maintenance and release of an RRC connection between the UE and UTRAN. The establishment of an RRC connection is initiated by a request from higher layers at the UE side to establish the first Signalling Connection for the UE. The establishment of an RRC connection includes an optional cell re-selection, an admission control, and a layer 2 signalling link establishment. The release of an RRC connection can be initiated by a request from higher layers to release the last Signalling Connection for the UE or by the RRC layer itself in case of RRC connection failure. In case of connection loss, the UE requests re-establishment of the RRC connection. In case of RRC connection failure, RRC releases resources associated with the RRC connection.
- Establishment, reconfiguration and release of Radio Bearers. The RRC layer can, on request from higher layers, perform the establishment, reconfiguration and release of Radio Bearers in the user plane. A number of Radio Bearers can be established to an UE at the same time. At establishment and reconfiguration, the RRC layer performs admission control and selects parameters describing the Radio Bearer processing in layer 2 and layer 1, based on information from higher layers.
- Assignment, reconfiguration and release of radio resources for the RRC connection. The RRC layer handles the assignment of radio resources (e.g. codes, CPCH channels) needed for the RRC connection including needs from both the control and user plane. The RRC layer may reconfigure radio resources during an established RRC connection. This function includes coordination of the radio resource allocation between multiple radio bearers related to the same RRC connection. RRC controls the radio resources in the uplink and downlink such that UE and UTRAN can communicate using unbalanced radio resources (asymmetric uplink and downlink). RRC signals to the UE to indicate resource allocations for purposes of handover to GSM or other radio systems.
- RRC connection mobility functions. The RRC layer performs evaluation, decision and execution related to RRC connection mobility during an established RRC connection, such as handover, preparation of handover to GSM or other systems, cell re-selection and cell/paging area update procedures, based on e.g. measurements done by the UE.
- Initial cell selection and re-selection in idle mode. Selection of the most suitable cell based on idle mode measurements and cell selection criteria.
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Management and control of RB, transport channel and physical channel
open loop power control
Support of SRNS relocation
Ciphering control, protection of integrity
CBS related functionsBMC configurationCBS radio resource distribute request, support of CBS non-continuous receiving
RRC Functions (Continue)
- Outer loop power control. The RRC layer controls setting of the target of the closed loop power control.
- Control of requested QoS. This function shall ensure that the QoS requested for the Radio Bearers can be met. This includes the allocation of a sufficient number of radio resources.
- UE measurement reporting and control of the reporting. The measurements performed by the UE are controlled by the RRC layer, in terms of what to measure, when to measure and how to report, including both UMTS air interface and other systems. The RRC layer also performs the reporting of the measurements from the UE to the network.
- Control of ciphering. The RRC layer provides procedures for setting of ciphering (on/off) between the UE and UTRAN.
- Integrity protection. This function adds a Message Authentication Code (MAC-I) to those RRC messages that are considered sensitive and/or contain sensitive information.
- Initial Configuration for CBS
This function performs the initial configuration of the BMC sublayer.
- Allocation of radio resources for CBS
This function allocates radio resources for CBS based on traffic volume requirements indicated by BMC. The radio resource allocation set by RRC (i.e. the schedule for mapping of CTCH onto FACH/S-CCPCH) is indicated to BMC to enable generation of schedule messages. The resource allocation for CBS shall be broadcast as system information.
- Configuration for CBS discontinuous reception
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RAB, RB and RL
RABThe service that the access stratum provides to the non-access stratum for transfer of user data between User Equipment and CN
RBThe service provided by the layer2 for transfer of user data between User Equipment and Serving RNC
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Idle mode
Connected mode
Cell_DCH
Cell_FACH
Cell_PCH
URA_PCH
When a UE is switched on, a public land mobile network (PLMN) is selected 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.
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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 control 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) is selected 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.
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Connected Mode (Cell-DCH, Cell-FACH, Cell-PCH, URA-PCH)
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) level
The UE position is known on URA level. The URA is a set of cells
Cell level
The UE position is known on cell level. Different transport channel types can be used for data transfer:
Common transport channels (RACH / FACH, DSCH, CPCH)
Dedicated transport Channels (DCH)
The connected mode is entered when the RRC connection is established. 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. cRNTI 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.
The UE leaves the connected mode and returns to idle mode when the RRC connection is released or at RRC connection failure.
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.
The UE state in the connected mode defines the level of activity associated 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.
The different levels of UE connection to UTRAN are listed below:
- No signalling connection exists
The UE is in idle mode and has no relation to UTRAN, only to CN. For data transfer, a signalling connection has to be established.
- Signalling connection exists
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) level
The UE position is known on URA level. The URA is a set of cells
- Cell level
The UE position is known on cell level. Different transport channel types can be used for data transfer:
- Common transport channels (RACH / FACH, DSCH, CPCH)
- Dedicated transport CHannels (DCH)
Assuming that there exists an RRC connection, there are two basic families of RRC connection mobility procedures, URA updating and handover. 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;
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Cell-DCH
UTRAN knows which cell UE is in.
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In active state
Few data to be transmitted both in uplink and in downlink. There is 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.
Cell-PCH
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
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 FACHs is shared for all users in the cell.
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Monitor PICH.
UTRAN only knows which URA (UTRAN Registration Area, which consists of multiple cells) that UE is in.
UTRAN update UE information only after UE has roamed to other URA.
A better way to lower the resource occupancy and signaling transmission
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RRC connection
CELL_DCH
CELL_FACH
CELL_PCH
URA_PCH
IDLE
DEAD
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SRNC/DRNC
SRNC and DRNC are on a 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 RNSs support the Serving RNS by providing radio resources
A UE in connection state has at least one and only one SRNC, but can has 0 or multiple DRNCs
CN
SRNC
DRNC
Iu
Iur
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 .
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The CRNC owns the radio resources of a cell
Dynamical control of power for dedicated channels, within limits admitted 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
CRNC
Iub
CN
Iu
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Source RNC/Target RNC
The SRNS Relocation function coordinates the activities when the SRNS role is to be taken over by another RNS.
Source RNC is the SRNC before SRNs Relocation and Target RNC is the SRNC after SRNs Relocation
CN
CN
Target
RNC
Serving
RNC
Iu
Iu
Iur
RNC
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