umts terrestrial radio access network (utran) · umts terrestrial radio access network (utran) ......

UMTS Terrestrial Radio Access Network (UTRAN)

• UTRAN Architecture and Protocols

• UMTS Terrestrial Radio Access (UTRA)

• UTRAN Procedures (see separate presentation)

Cellular Communication Systems 2 Andreas Mitschele-Thiel, Jens Mueckenheim Oct-15

Important References Books: • Kaaranen, Ahtiainen, Laitinen, Naghian, Niemi: UMTS Networks –

Architecture, Mobility and Services. 2nd edition, Wiley, 2005 • Holma, Toskala: WCDMA for UMTS. 4th edition, Wiley, 2007 • Walke, Althoff, Seidenberg: UMTS – Ein Kurs. 2. Auflage, J. Schlembach

Fachverlag, 2002 • T. Benkner, C. Stepping: UMTS – Universal Mobile Telecommunications

System. J. Schelmbach Fachverlag, 2002.

Central 3GPP Documents on UTRAN: • 25.401: UTRAN overview • 25.301: Radio link protocols (UTRA) • 25.931: UTRAN procedures


UTRAN Architecture

Part 1: • UTRAN Components and Interfaces • UTRAN Functions


UTRAN Components and Interfaces

RNS

RNC

RNS

RNC

Core Network

Node B Node B Node B Node B

Iu Iu

Iur

Iub Iub Iub Iub

UTRAN

Source: 3GPP 25.401

A Radio Network Subsystem (RNS) consists of a RNC and a number of Node B‘s


UTRAN Architecture Principles – User Plane

Source: 3GPP 25.401

Non-Access Stratum: • Protocols between UE and CN that are not

terminated in the UTRAN Access Stratum: • Provides UE-CN transport service to NAS services • AS protocols are closely linked to radio technology

UTRAN UE CN

Access Stratum

Non-Access Stratum

Radio (Uu)

Iu

Radio protocols (1)


Iu protocols (2)

Iu protocols (2)

radio access bearer SAPs (user plane)


UTRAN Architecture Principles – Control Plane

UTRAN UE CN

Access Stratum

Non-Access Stratum

Radio (Uu)

Iu



Iu protocols (2)

Iu protocols (2)

CM,MM,GMM,SM (3)

CM,MM,GMM,SM (3)

Source: 3GPP 25.401

Non-Access Stratum control plane functions: CM: Connection Management MM: Mobility Management GMM: GPRS MM SM: Session Management

signaling connection


UTRAN Functions (1) - Transfer of User Data - Functions related to overall system access control

- Admission Control - Congestion Control - System information broadcasting

- Radio channel ciphering and deciphering - Integrity protection - Functions related to mobility

- Handover - SRNS Relocation - Paging support - Positioning

- Synchronisation

Source: 3GPP 25.401, Ch 7


UTRAN Functions (2) - Functions related to radio resource management and control

- Radio resource configuration and operation - Radio environment survey - Combining/splitting control - Connection set-up and release - Allocation and deallocation of radio bearers - Radio protocols function - RF power control - Radio channel coding and decoding - Channel coding control - Initial (random) access detection and handling - CN distribution function for Non Access Stratum messages

- Functions related to broadcast and multicast services (broadcast/multicast interworking function BM-IWF)

- Broadcast/Multicast Information Distribution - Broadcast/Multicast Flow Control - Cell-based Services (CBS) Status Reporting

- Tracing - Volume reporting


Functions located inside/outside AS Source: 3GPP TS 23.110, Release 9

LOCATION\ FUNCTION Outside the Access Stratum Inside the Access Stratum

Call set up/release yes no

(Connection) Bearer Set-Up Release CN bearer [tbd] Radio Access Bearer [tbd]

Supplementary Services yes no

Location management yes (IWF/CN related) yes (Radio related)

Attach/ Detach yes FFS, Contr expected

Resource Management yes (for NAS resource) yes (for AS resource incl. radio)

Handover yes* yes

Macrodiversity [ffs] yes* yes

Encryption yes yes**

Authentication yes no

compression (non source dependent) yes yes

source dependent coding yes no

radio channel coding (could be many) no yes (could be many)

UE location identification may be supported yes

Charging yes no

NOTE *: Optionally execution. In some CNs, it may not be present but not full service will be supported (e.g. limited to RLL type of service).

NOTE **: Contributions expected to clarify the role between encryption and subscriber data.

o


Radio Interface Protocols UMTS Terrestrial Radio Access (UTRA)

• Air interface protocol architecture

• Layer 1, 2 and 3 protocols

• Mapping between logical, transport and physical channels


Radio Protocols – Overview

RLC

RRC

L1

GMM /SM / SMS

RRC

MAC

ATM

RANAP

AAL5

Relay

ATM

AAL5

3G SGSNRNSMSIu-PsUu

RLC SCCP

SignallingBearer

MAC

L1

SignallingBearer

RANAP

SCCP

GMM /SM / SMS

L1

RLC

PDCP

MAC

E.g., IP,PPP

Application

L1

RLC

PDCP

MAC

ATM

UDP/IP

GTP-U

AAL5

Relay

L1

UDP/IP

L2

GTP-U

E.g., IP,PPP

3G-SGSNUTRANMSIu-PSUu Gn Gi

3G-GGSN

ATM

UDP/IP

GTP-U

AAL5

L1

UDP/IP

GTP-U

L2

Relay

Layer 3

– IP, PPP (user plane) – RRC (control plane)

Layer 2 – PDCP (user plane) – BMC (user plane) – RLC – MAC

Layer 1 – PHY

See 3GPP 25.301 and UMTS Networks book, ch. 9

Control plane

User plane


Source: 3GPP 25.301

Radio Access Bearers AS control plane SAPs

Radio Protocol Architecture

L3

cont

rol

cont

rol

cont

rol

cont

rol

Logical Channels

Transport Channels

C-plane signalling U-plane information

PHY

L2/MAC

L1

RLC

DC Nt GC

L2/RLC

MAC

RLC RLC

RLC RLC

RLC RLC

RLC

BMC L2/BMC

control

PDCP PDCP L2/PDCP

Radio Bearers

RRC


L3

cont

rol

cont

rol

cont

rol

cont

rol

Logical Channel

Transport Channels


PHY

L2/MAC

L1

RLC

DC Nt GC

L2/RLC

MAC

RLC RLC

RLC RLC

RLC RLC

RLC

Duplication avoidance

UuS boundary

BMC L2/BMC

control

PDCP PDCP L2/PDCP

DC Nt GC

Radio Bearers

RRC

Radio Access Bearers AS control plane SAPs Physical Layer – Services

Transport channels do not define what is transported (which is defined by logical channels)

Example: DCH offers the same type of service for control and user traffic

Physical layer offers information transfer services (transport channels) to MAC and higher layers Physical layer transport services define

–how and –with what characteristics data are transferred over the radio interface


Radio Access Bearers AS control plane SAPs

L3

cont

rol

cont

rol

cont

rol

cont

rol

Logical Channel

Transport Channels


PHY

L2/MAC

L1

RLC

DC Nt GC

L2/RLC

MAC

RLC RLC

RLC RLC

RLC RLC

RLC


UuS boundary

BMC L2/BMC

control

PDCP PDCP L2/PDCP

DC Nt GC

Radio Bearers

RRC

Physical Layer – Channel Types • common transport channels (there is a need for inband

identification of the UEs when particular UEs are addressed) • dedicated transport channels (the UEs are identified by the physical

channel, i.e. code and frequency for FDD (code, time slot and frequency for TDD))


Physical Layer – Common Transport Channels (1)

Random Access Channel (RACH) • Contention based uplink channel used for transmission of relatively

small amounts of data, e.g. for initial access or non-real-time dedicated control or traffic data

Forward Access Channel (FACH) • Common downlink channel for relatively small amount of data • no closed-loop power control

Downlink Shared Channel (DSCH) – TDD only • Downlink channel shared by several UEs carrying dedicated control or

traffic data Uplink Shared Channel (USCH) – TDD only

• Uplink channel shared by several UEs carrying dedicated control or traffic data


Physical Layer – Common Transport Channels (2)

Broadcast Channel (BCH) • Downlink channel used for broadcast of system information into an

entire cell Paging Channel (PCH)

• A downlink channel used for broadcast of control information into an entire cell allowing efficient UE sleep mode procedures

• Currently identified information types are paging and notification • Another use could be UTRAN notification of change of BCCH

information

High-Speed Downlink Shared Channel (HS-DSCH) – Rel. 5

• High-speed downlink channel shared by several UEs


Physical Layer – Dedicated Transport Channels & Transport Formats

Dedicated Channel (DCH) Channel dedicated to one UE used in uplink or downlink

Enhanced Dedicated Channel (E-DCH) • Channel dedicated to one UE used in uplink only • Subject to Node-B controlled scheduling and HARQ

Transport Formats and Transport Format Sets • A Transport Format or a Transport Format Set is associated with each

transport channel • A Transport Format defines the format offered by L1 to MAC (encodings, interleaving, bit rate and mapping onto physical channels) • A Transport Format Set is a set of Transport Formats • Example: a variable rate DCH has a Transport Format Set (one Transport

Format for each rate), whereas a fixed rate DCH has a single Transport Format

See 3GPP 25.302, ch. 7 and Walke, ch 5.10, for details on Transport Formats and Transport Format Sets


Physical Layer Processing

DCH DCH DCH

DPCH DPCH

CRC attachment

Channel Coding

Rate Matching

CRC attachment

Channel Coding

Rate Matching

CRC attachment

Channel Coding

Rate Matching

Transport Channel Multiplexing

Physical Channel Mapping

Coded Composite Transport Channel (CCTrCH)

Data Data Data Data

Data Data

Transport Block Set

Transport Block Set

Transport Block

Note: Physical Channel Mapping is used to implement multicoding (more than one DPCH). This will usually only be used for high data rates

Note: Functional blocks which implement concatenation, segmentation, interleaving, discontinuous transmission (DTX) and macrodiversity distirbution/combining have been suppressed.

See 3GPP 25.302 for details

o


Physical Layer – Functions

• Macrodiversity distribution/combining and soft handover execution • Error detection on transport channels and indication to higher layers (CRC) • FEC encoding/decoding and interleaving/deinterleaving of transport channels • Multiplexing of transport channels and demultiplexing of coded composite

transport channels • Rate matching (fit bits into physical channel) • Mapping of coded composite transport channel on multiple physical channels • Power weighting and combining of physical channels • Modulation and spreading/demodulation and despreading of physical channels • Frequency and time (chip, bit, slot, frame) synchronisation • Measurements and indication to higher layers (e.g. frame error rate, signal-to-

interference ratio, interference power, transmit power, etc.) • Closed-loop power control • RF processing • Support of timing advance on uplink channels (TDD only) • Support of Uplink Synchronisation (TDD only)


L3

cont

rol

cont

rol

cont

rol

cont

rol

Logical Channel

Transport Channels


PHY

L2/MAC

L1

RLC

DC Nt GC

L2/RLC

MAC

RLC RLC

RLC RLC

RLC RLC

RLC


UuS boundary

BMC L2/BMC

control

PDCP PDCP L2/PDCP

DC Nt GC

Radio Bearers

RRC

Radio Access Bearers AS control plane SAPs Medium Access Control (MAC) – Services

Data transfer (logical channels SAPs) – Unacknowledged transfer of MAC SDUs between peer MAC entities – No data segmentation (performed by higher layers) in R.99

Reallocation of radio resources and MAC parameters – Execution of radio resource reallocation and change of MAC

parameters by request of RRC, i.e. change of transport format (combination) sets, change of transport channel type

– Autonomous resource allocation in TDD mode Reporting of measurements

– Local measurements such as traffic volume and quality indication (reported to RRC)


MAC – Logical Channels

• Control Channels (transfer of control plane information) – Broadcast Control Channel (BCCH) – DL – Paging Control Channel (PCCH) – DL – Common Control Channel (CCCH) – DL/UL – Dedicated Control Channel (DCCH) – DL/UL – Shared Channel Control Channel (SHCCH) – DL/UL (TDD)

• Traffic Channels (transfer of user plane information) – Dedicated Traffic Channel (DTCH) – DL/UL – Common Traffic Channel (CTCH) – DL/UL

Logical channels define what information is transported (transport channels (PHY SAP) define how data are transported)

o


MAC – Functions (1)

PHY PHY

ATM

DschFP

IubUE NodeB CRNCUu Iur SRNC

AAL2

ATM

DschFP

MAC-c/sh

ATM ATM

MAC-d

DCCH DTCH

AAL2

MAC-c/sh

MAC-d

DTCH DCCH

AAL2

DschFP

AAL2

DschFP

• Mapping between logical channels and transport channels • Selection of appropriate Transport Format for each Transport Channel

depending on instantaneous source rate • Priority handling (multiplexing) between data flows of one UE (MAC-d)

• Priority handling (scheduling) between different UEs (MAC-c/sh) • Identification of UEs on common transport channels

Example: DTCH/DCCH mapped on DSCH (TDD only)


MAC – Functions (2)

PHY PHY

ATM

DschFP

IubUE NodeB CRNCUu Iur SRNC

AAL2

ATM

DschFP

MAC-c/sh

ATM ATM

MAC-d

DCCH DTCH

AAL2

MAC-c/sh

MAC-d

DTCH DCCH

AAL2

DschFP

AAL2

DschFP

• Multiplexing/demultiplexing of upper layer PDUs on common transport channels

• Multiplexing/demultiplexing of upper layer PDUs on dedicated transport channels

• Traffic volume measurement • Transport channel type switching (controlled by RRC) • Ciphering for transparent RLC mode

Example: DTCH/DCCH mapped on DSCH (TDD only)


Logical/ Transport/ Physical Channels Mapping (excerpt, FDD)

BCCH

PCCH

CCCH

DCCH

DTCH

CTCH

BCH

DCH

RACH

FACH

PCH

P-CCPCH

S-CCPCH

P-CPICH

PRACH

DPDCH

DPCCH

PICH

P-SCH

S-SCH

AICH

S-CPICH

Logical Channels Transport Channels Physical Channels

DPCH Key: Uplink

Downlink Bidirectional Data Transfer Association

Control Ch Traffic Ch

Common Ch (no FPC) Common Ch (FPC) Dedicated Ch (FPC) Info Channels

Assoc Channels

Fixed Channels

o

Notes: • Figure deschribes a subset of the possible mappings only! See 25.301,

sc. 5.6 or following slides for the complete list of possible mappings. • FPC denotes Fast Power Control


L3

cont

rol

cont

rol

cont

rol

cont

rol

Logical Channel

Transport Channels


PHY

L2/MAC

L1

RLC

DC Nt GC

L2/RLC

MAC

RLC RLC

RLC RLC

RLC RLC

RLC


UuS boundary

BMC L2/BMC

control

PDCP PDCP L2/PDCP

DC Nt GC

Radio Bearers

RRC

• Transparent data transfer (TM) • Unacknowledged data transfer (UM) • Acknowledged data transfer (AM)

Radio Link Control (RLC)


RLC – Services (1) Transparent data transfer (TM) • Transmission of upper layer PDUs without adding any protocol information (no

RLC header) • Possibly including segmentation/reassembly functionality

Unacknowledged data transfer (UM) • Transmission of upper layer PDUs without guaranteeing delivery to the peer

entity – Error detection: 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 (AM) • Transmission of upper layer PDUs and guaranteed delivery to the peer entity • Notification of RLC user at transmitting side in case RLC is unable to deliver the

data correctly • in-sequence and out-of-sequence delivery • error-free delivery (by means of retransmission) • duplication detection


RLC – Services (2) Maintenance of QoS as defined by upper layers • retransmission protocol shall be configurable by layer 3 to provide

different levels of QoS

Notification of unrecoverable errors

• RLC notifies the upper layer of errors that cannot be resolved by RLC itself by normal exception handling procedures

There is a single RLC connection per Radio Bearer


RLC – Functions • Transfer of user data (AM, UM, TM) • Segmentation and reassembly (RLC PDU size adapted to transport

format) • Concatenation • Padding • Sequence number check (UM mode) • Duplicate RLC PDUs detection • In-sequence delivery of upper layer PDUs • Error correction (selective-repeat ARQ)

• Flow control between RLC peers • SDU discard • Protocol error detection and recovery • Exchange of status information between peer RLC entities • Ciphering (non-transparent mode) • Suspend/resume and stop/continue of data transfer • Re-establishment of AM/UM RLC entity

Convert variable-size higher layer PDUs into fixed-size

RLC PDUs (TBs)

Convert radio link errors into packet

loss and delay

Avoid Tx and Rx buffer overflows or

protocol stalling


Logical/Transport Channels Mapping Details UTRAN side

Broadcast Channel (BCH)

Paging Channel (PCH)

Forward Access Channel (FACH)

Random Access Channel (RACH)

Dedicated Channel (DCH)

BCCH-SAP

DCCH-SAP

CCCH- SAP

PCCH-SAP DTCH- SAP

Transport Channels

MAC SAPs

CTCH- SAP

To / From Physical Channels

Logical Channels

Broadcast Control Channel (BCCH)

Paging Control Channel (PCCH)

Dedicated Control Channel (DCCH)

Common Control Channel (CCCH)

Common Traffic Channel (CTCH)

Dedicated Traffic Channel (DTCH)

U D U/D Uplink / Downlink

Uplink Downlink

U D D D U/D

U/D D D U/D U/D D

Tr

Tr

Tr UM AM

UM AM

Tr

Tr UM AM

UM

UM AM

UM AM Tr

UM AM

UM

Control Plane

User Plane

RLC Modes Tr Transparent UM Unacknowledged AM Acknowledged

o


Control Plane Relationships

RLC

Call signalling: RLC Entities / Channels / Signaling Radio Bearers (SRB) Relationships

Abbr. Mode RLC Entities Tr Transparent mode 2 (one Tx and one Rx) UM Unacknowleged Mode 2 (one Tx and one Rx) AM Acknowleged Mode 1 (bi-directional for ARQ)

SRB1 SRB2 SRB3/4

Notes: This is for a single user and only shows the control plane. SRB0 is not shown as this is for the CCCH - i.e. not used for a dedicated call, only for establishment.

RLC Entity RLC Entity UM RLC Entity AM RLC Entity AM

MAC

Logical Channels DCCH DCCH DCCH DCCH

DCH

LAYER 1 CCTrCH

DCH

CCTrCH

DPDCH DPDCH

o


Circuit Switched Voice Call Relations R

LC

Call signalling: RLC Entities / Channels / Radio Bearers (RB) Relationships

Abbr. Mode RLC Entities Tr. Transparent mode 2 (one tx. and one rx.) UM Unacknowleged Mode 2 (one tx. and one rx.) AM Acknowleged Mode 1 (bi-directional for ARQ)

SRB1 SRB2 SRB3/4

Notes: This is for a single user. SRB0 is not shown as this is for the CCCH - i.e. not used for a dedicated call, only for establishment.

RLC Entity RLC Entity UM RLC Entity AM

MAC

DCCH DCCH DCCH DCCH

LAYER 1 CCTrCH

RLC

RLC

RLC

RLC

RLC

RLC

Cla

ss A

(81b

its)

Cla

ss B

(103

bits

)

Cla

ss C

(60b

its)

AMR

VO

ICE

CO

DEC

DL

Cla

ss A

(81b

its)

Cla

ss B

(103

bits

)

Cla

ss C

(60b

its)

AMR

VO

ICE

CO

DEC

UL

Tr

RB

RB

RB

RB

RB

RB

DTCH DTCH

Control Plane

Use

r Pla

ne

DCH DCH

DPDCH Physical Channels

RLC Entity AM

DCH DCH

CCTrCH

DPDCH

o


L3

cont

rol

cont

rol

cont

rol

cont

rol

Logical Channel

Transport Channels


PHY

L2/MAC

L1

RLC

DC Nt GC

L2/RLC

MAC

RLC RLC

RLC RLC

RLC RLC

RLC


UuS boundary

BMC L2/BMC

control

PDCP PDCP L2/PDCP

DC Nt GC

Radio Bearers

RRC

Radio Access Bearers AS control plane SAPs Packet Data Convergence Protocol (PDCP)

Service: PDCP SDU delivery PDCP is defined for PS domain only!


PDCP – Functions

Header compression and decompression • Header compression and decompression of IP data streams (e.g.

TCP/IP and RTP/UDP/IP headers) Header compression method is specific to the upper layer protocol

combinations, e.g. TCP/IP or RTP/UDP/IP (RFC 2507 & RFC 3095) Transfer of user data • PDCP receives PDCP SDU from the NAS and forwards it to the RLC layer

and vice versa Support for lossless SRNS relocation • Maintenance of PDCP sequence numbers for radio bearers that are

configured to support lossless SRNS relocation


L3

cont

rol

cont

rol

cont

rol

cont

rol

Logical Channel

Transport Channels


PHY

L2/MAC

L1

RLC

DC Nt GC

L2/RLC

MAC

RLC RLC

RLC RLC

RLC RLC

RLC


UuS boundary

BMC L2/BMC

control

PDCP PDCP L2/PDCP

DC Nt GC

Radio Bearers

RRC

Broadcast/Multicast Control (BMC)

Functions: • 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) in the UE

Service: • broadcast/multicast transmission service in the user plane

for common user data in unacknowledged mode

o


L3

cont

rol

cont

rol

cont

rol

cont

rol

Logical Channel

Transport Channels


PHY

L2/MAC

L1

RLC

DC Nt GC

L2/RLC

MAC

RLC RLC

RLC RLC

RLC RLC

RLC


UuS boundary

BMC L2/BMC

control

PDCP PDCP L2/PDCP

DC Nt GC

Radio Bearers

RRC

Radio Resource Control (RRC)

Services Provided to Upper Layers

General Control (GC) – information broadcast service

Notification (Nt) – paging and notification broadcast services Dedicated Control (DC) – connection management and message transfer


RRC – Interaction with Lower Layers

R R C R R C

R L C R L C

Radio Resource Assignment [Code, Frequency, TS, TF Set, Mapping, etc.]

Measurement Report

RLC retransmission control

L 1 L 1

U T R A N U E

Con

trol

Mea

sure

men

ts

Con

trol

Mea

sure

men

ts

Con

trol

Mea

sure

men

ts

Con

trol

Mea

sure

men

ts

M A C M A C

Con

trol

Con

trol


RRC – Functions RRC handles the control plane signaling of layer 3 between the UEs and UTRAN:

- Broadcast of information provided by the non-access stratum (Core Network) - Broadcast of information related to the access stratum - Establishment, re-establishment, maintenance and release of RRC

connections - Establishment, reconfiguration and release of Radio Bearers - Assignment, reconfiguration and release of radio resources for the RRC

connection - RRC connection mobility functions - Paging/notification - Routing of higher layer PDUs - Control of requested QoS - UE measurement reporting and control of the reporting - Outer loop power control - Control of ciphering - Slow DCA (TDD) - Arbitration of radio resources on uplink DCH - Initial cell selection and re-selection in idle mode - Integrity protection (message authentication for sensitive data) - Control of Cell Broadcast Service (CBS) - Timing advance control (TDD)


RRC State Machine

• RRC state machine exists as two peer entities (MS and UTRAN) • The two peer entities are synchronized (apart from transient situations

and error cases)

Idle mode

CellConnected

RRCconnectionestablishment

URAConnected

RRCconnectionrelease

Enter URAconnected state

Enter cellconnected state

Connected mode


UTRAN Registration Area (URA)

LA

RA

RA

RA RA

RA

RA RA

RA

RA

URA

URA URA

URA URA

URA

URA URA

URA URA

URA

URA URA

URA URA

URA

URA URA

URA URA

URA

URA URA

URA URA

URA

URA URA

URA URA

URA

URA URA

URA URA

URA

URA URA

URA URA

URA

URA URA

URA URA

• URA is known to the UTRAN only

• URA is established in RRC connected mode

URA is independent of RNC area

URA may cover

•part of an RNC area

•parts of several RNC areas

URAs may overlap

URA

URA URA U

RA

URA

URA

URA

URA

URA

URA

URA


RRC State Machine

Idle mode

CellConnected


URAConnected




Connected mode

RRC Idle mode: – no connection established between the MS and UTRAN – no signalling between UTRAN and the MS except for system

information sent from UTRAN on a broadcast channel to the MS – MS can only receive paging messages with a CN identity on the PCH – no information of the MS is stored in UTRAN


RRC State Machine

RRC Connected mode: – two main states

• Cell Connected: MS position is known at the cell level; RRC connection mobility is handled by handover and cell update procedures

• URA Connected: MS position is known at the URA level; URA updating procedures provide the mobility functionality; no dedicated radio resources are used in the state.

– there is one RNC that is acting as serving RNC, and an RRC connection is established between the MS and this SRNC

An UE has either zero or one RRC connection

Idle mode

CellConnected


URAConnected




Connected mode


UMTS RRC State Optimization (PS mode) Goal: Minimization of Radio Resource Consumption during Idle Times Tradeoff for idle periods • retaining in state => continuous state cost or • move to cheaper state => one time transition cost

Limited resources • radio resources (transmit power) • channelization codes • processing cost (signaling) • power consumption • transport resources (Iu, Iub, …) Find optimal timeout settings depending on • traffic model (distribution of idle times) • cost per state • cost per transition • user mobility • …

cell_DCH

URA_PCH

cell_PCH

idle

T1

T2

T3


UMTS RRC State Optimization O

ptim

izat

ion

of T

imeo

ut V

alue

s

sum

state cost

transition cost


UTRAN Architecture

Part 2: • Macro diversity: Serving and Drift RNC • UTRAN architecture details and protocols • AS and NAS services • RRC connection and signaling connection


Macro Diversity: Serving and Drift RNS

Serving RNS (SRNS)

Core Network

Iu

Drift RNS (DRNS) Iur

UE

Cells

Source: 3GPP 25.401

Each RNS is responsible for the resources of its set of cells For each connection between User Equipment (UE) and the UTRAN, one RNS is the Serving RNS (SRNS)

Drift RNSs (DRNS) support the Serving RNS by providing radio resources

Macro-diversity and handover is jointly supported by Node B(s) and RNC(s)


Serving, Drift and Controlling RNC

RNS

RNC

RNS

RNC

Core Network


Iu Iu

Iur

Iub Iub Iub Iub

UTRAN

UE

SRNC DRNC

Softer handover: maximum ratio combining in Node B

Soft handover: radio frame selection (layer 1) in SRNC (and DRNC)


Roles of RNSs/RNCs Serving RNS (SRNS) • A role an RNS can take with respect to a specific connection between a UE and

UTRAN • There is one Serving RNS for each UE that has a connection to UTRAN • The Serving RNS is in charge of the RRC connection between a UE and the

UTRAN • The Serving RNS terminates the Iu for this UE

Drift RNS (DRNS) • A role an RNS can take with respect to a specific connection between a UE and

UTRAN • An RNS that supports the Serving RNS with radio resources when the

connection between the UTRAN and the UE need to use cell(s) controlled by this RNS

Controlling RNC (CRNC) • A role an RNC can take with respect to a specific set of UTRAN access points (an

UTRAN access point is specific to a cell) • Exactly one Controlling RNC serves an UTRAN access point (i.e. each cell) • The Controlling RNC has the overall control of the logical resources of its UTRAN

access points

Source: 3GPP 21.905


Distribution of Functions between RNCs

Radio resource management: • CRNC owns the radio resources of a cell • SRNC handles the connection (RRC/RANAP) to one UE, and may

borrow radio resources of a certain cell from the CRNC • SRNC performs dynamical control of power for dedicated channels,

within limits admitted by CRNC Inner loop power control for some radio links of the UE connection may be done by the Node B Inner loop control is controlled by an outer loop, for which the SRNC has overall responsibility

• SRNC handles scheduling of data for dedicated channels • CRNC handles scheduling of data for common channels (no macro

diversity on DL common channels)

Source: 3GPP 25.401, Ch 6.3


Serving, Drift and Controlling RNC

RNS

RNC

RNS

RNC

Core Network


Iu Iu

Iur

Iub Iub Iub Iub

UTRAN

UE 1

SRNC DRNC

UE 2

common/shared channel

SRNC

dedicated channel in macro-diversity mode


UTRAN Architecture: Functional Split

Control plane

Bearer plane

Core Network

Node-B

Paging

Com./ Shared Channel

Processing

Cell Control

Dedicated Channel

Processing

Mobile Control

Broadcast

CRNC/DRNC SRNC


Core Network

User plane Control plane

Iub Iurpaging (connected)

paging(connected,

PCCH)

MAC-b

RLC-b

RRC-b

BCCH

BCH

PHY

Softer HandoverSplitting / Combining

NBAP

IubCCHFP

Node-B

Iub/IurDCHFP

Iu

Soft HandoverSplitting / Combining

optional

CTCHPCCHBCCH

NBAP

RNSAP

IurCCHFP

IubCCHFP

Iub/IurDCHFP

Iub/IurDCHFP

RANAPCRNC

paging (idle)

DRNCBM-IWF

PCH RACHFACHDSCHCPCH

CCCH

RLC-c/sh

MAC-c/sh

BMC

RRC-c/sh

SABP

Iu

MAC-d

DCH

DTCH

RLC-d

PDCP

RRC-d

Soft Handover Splitting / Combining

DCCH

SRNC

RNSAP

RANAP

IurCCHFP

Iub/IurDCHFP

Iu-CS FP

Iu-PS FP

LOGICAL CHANNELS

TRANSPORT CHANNELS

UTRAN Protocol Architecture: Summary

o


Mapping of Layers to NodeB, CRNC and SRNC R

LC, e

tc.

PHY

MAC

Node B

CCCH DCCH, DTCH

MAC

-c/s

h

MAC

-d

MAC

-d

PHY-upper

RLC

, etc

.

RLC

, etc

. Controlling RNC Serving RNC

Iub Iur

PCH

FAC

H

RAC

H

DSC

H

USC

H

DC

H

FAC

H

RAC

H

DSC

H

USC

H

DC

H

Common Ch (no fast power control) Common Ch (fast power control) Dedicated Ch (fast power control)

Control Ch Traffic Ch

Logical Channels Transport Channels

o


Wrap-up: Why is UTRAN so complicated?

Some answers:

• Radio resources are the limiting factor

• CDMA macro-diversity mode – Single RLC/MAC entity required for synchronous delivery of radio

frames over all SHO legs – Splitting/combining of radio frames (multicast)

• Tight handover requirements esp. for voice

– Need for proactive handover initiation requires interaction between radio layers

• Designed for maximum functionality and flexibility

– Overdimensioned from the viewpoint of a single application


Serving and Controlling RNC Example: DCH (Dedicated Channel – UL&DL macro diversity)

PHY PHY

ATM

DchFP

ATM

MAC-d

Iub UE NodeB CRNC Uu SRNC

ATM ATM

Iur

MAC-d

DCCH DTCH

DchFP PHY-upper PHY

AAL2 AAL2

DTCH DCCH

AAL2 AAL2

DchFP DchFP PHY

Source: 3GPP 25.401, sc 11.2.4 (see also 25.301, sc 5.6.1)

Combining/ splitting of

phy. channels

Combining/splitting is supported for DCH only (no layer 2 processing in Node B and DRNC)

cells served by the same

node B

cells served by the same

CRNC (optional)

cells served by different

RNCs


PHY PHY

ATM

FachFP

Iub UE NodeB CRNC Uu Iur SRNC

AAL2

ATM

FachFP

MAC-c/ sh

ATM ATM

MAC-d

DCCH DTCH

AAL2

MAC-c/ sh

MAC-d

DTCH DCCH

AAL2

FachFP

AAL2

FachFP

Serving and Controlling RNC Example: FACH (Forward Access Channel – DL, no macro diversity)

Physical channel is terminated within node B (no support for combining/splitting)

Common MAC (MAC-c/sh) terminates in the CRNC

Dedicated MAC (MAC-d) terminates in the SRNC

Source: 3GPP 25.401, sc 11.2.3 (see also 25.301, sc 5.6.2)

CCCH CCCH


Example: BCH (Broadcast Channel – DL, system information)

UE NodeB

RLC

MAC

PHY

RLC

MAC

PHY

RRC RRC

RRC

CRNC

Source: 3GPP 25.301, sc 5.6.7

RRC terminates in

• CRNC: provides broadcast information distributed by node B

• Node B: handles periodic repetition of broadcast information

Splitting of RRC eliminates repetition of broadcast data on Iub interface

o


Access Stratum Services Revisited

DC Nt GC

UTRAN UE Core Network

Access Stratum (AS)

Non-Access Stratum (NAS)

Radio (Uu) Iu

DC Nt GC

DC Nt GC DC Nt GC DC Nt GC DC Nt GC

end AS entity end AS entity

Relay/RNC functions

Uu Stratum (UuS)

Iu Stratum

L2/L1

RRC

L2/L1

RRC

Source: 3GPP 25.301 (see also 3GPP 23.110)

Services of Access Stratum: • General Control (GC) – idle mode • Notification (Nt) – idle mode • Dedicated Control (DC) – connected mode • User data transfer (RAB) – connected mode

Note: NAS signaling services are provided by RANAP


Services provided at AS SAPs – GC and Nt (UE in idle mode)

General Control SAPs (GC) – information broadcast service – Enable CN to provide information and to give commands that do not

relate to specific users or specific sessions (group calls, conference)

– Typically one GC SAP per AN/CN connection point (Iu) – Typically one GC SAP in MS

Notification SAPs (Nt) – paging and notification broadcast services

– SAPs are used to broadcast data to identified users – Typical use is for initiating paging in the AN

– Typically one Nt SAP per AN/CN connection point (Iu) – Typically one Nt SAP (a Paging SAP) in MS

Source: 3GPP 23.110, ch. 6; see also 25.301, ch 5.4

o


Services provided at AS SAPs – DC (conn. mode)

Dedicated Control SAPs (DC) – connection establishment/release and message transfer

• SAPs are used to establish and release connections with specific UEs, and to transfer information on these connections

• Several types of connections are identified, point connections (single user) and group connections

• SAPs are identified by a SAPI at the AS boundary • SAPI is valid for the lifetime of a connection • SAPI is used as a unambiguous connection identifier of the associated

SAP • Typically a great number of DC SAPs per AN/CN connection point • Typically a single DC SAP in MS

Source: 3GPP 23.110

o


UE mode

HLR

GGSN

Side note: modes, states and hierarchy (PS mode, AS and NAS)

SGSN

RNC

UE

RRC connection

Signaling connection

PMM state (detached, idle, connected)

SM: PDP context (active, inactive)


Radio Link, RRC Connection, Signaling Connection

RNS

RNC

RNS

RNC

Core Network


Iu Iu

Iur

Iub Iub Iub Iub

UTRAN

UE radio link

RRC connection -> connected mode


SRNC

RRC connections and signaling connections are logical links


Radio Link, RRC Connection & Signaling Connection

RNS

RNC

RNS

RNC

Core Network


Iu Iu

Iur

Iub Iub Iub Iub

UTRAN

UE radio link

SRNC DRNC

RRC connection



MSC/VLR or SGSN

SRNC UE

RRC Connection and Signaling Connection

RRC Connection RANAP Connection

RRC RANAP RRC RANAP

Signaling Connection

Radio Access Bearer

Signaling Radio Bearer Iu Signaling Bearer

Higher layer control

Higher layer control


Signaling Connection

• No signaling connection exist (idle state) – UE has no relation to UTRAN, only to CN – no data transfer – paging identification by IMSI, TMSI, P-TMSI

• Signaling connection exist (connected state) UE position can be known on different levels:

- URA level (UTRAN registration area): URA is a specified set of cells, which can be identified on the BCCH.

- Cell level: Different channel types can be used for data transfer:

- Common transport channels (RACH, FACH, DSCH, USCH) - Dedicated transport channels (DCH)

Source: 3GPP 25.301, ch 6.2


Recap on Important Vocabulary RRC connection • point-to-point bi-directional connection between RRC peer entities on the UE and

the UTRAN sides • UE has either zero or one RRC connection

Signaling connection • an acknowledged-mode link between the UE and the CN to transfer higher layer

information between the entities in the non-access stratum (via RRC and RANAP)

Radio link • a logical association between a single UE and a single UTRAN access point (cell) • its physical realization comprises one or more radio bearer transmissions

Radio bearer (compare signaling radio bearer)

• service provided by the RLC layer for transfer of user data between UE and SRNC

Radio interface • interface between UE and a UTRAN access point • radio interface encompasses all the functionality required to maintain the

interface

Source: 3GPP TR 21.905