View
4
Download
2
Category
Preview:
Citation preview
UMTS Terrestrial Radio Access Network (UTRAN)
• UMTS Terrestrial Radio Access (UTRA) • UTRAN Architecture
Focus on FDD only
Cellular Communication Systems 2Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
UMTS Terrestrial Radio Access (UTRA)Radio Interface Protocols
• Air interface protocol architecture• Layer 1, 2 and 3 protocols• Mapping between logical, transport and
physical channels
Cellular Communication Systems 3Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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 (user plane)– RRC (control plane)
Layer 2– PDCP (user plane)– BMC (user plane)– RLC – MAC
Layer 1– PHY
See 3GPP 25.301 andUMTS Networks book, ch. 9
Control plane
User plane
Cellular Communication Systems 4Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Source: 3GPP 25.301
Radio Protocol ArchitectureRadio Access BearersAS control plane SAPs
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
Cellular Communication Systems 5Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
L3
cont
rol
cont
rol
cont
rol
cont
rol
Logical Channel
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
Duplication avoidance
UuS boundary
BMC L2/BMC
control
PDCP PDCP L2/PDCP
DC Nt GC
Radio Bearers
RRC
Radio Access BearersAS control plane SAPsPhysical Layer – Services
Transport channels do not define whatis transported (which is defined by logical channels)Example: DCH offers the same type of service for control and user data
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
Cellular Communication Systems 6Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Radio Access BearersAS control plane SAPs
L3
cont
rol
cont
rol
cont
rol
cont
rol
Logical Channel
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
Duplication avoidance
UuS boundary
BMC L2/BMC
control
PDCP PDCP L2/PDCP
DC Nt GC
Radio Bearers
RRC
Physical Layer – Channel Types (R99)• Common transport channels: with inband identification of the UEs
– BCH for broadcast information (DL)– PCH for paging information (DL)– RACH for contention-based access by UEs (UL)– FACH for data to individual UEs (DL)
• Dedicated transport channels where UEs are identified by the code – DCH for individual UE (UL &DL)
Cellular Communication Systems 7Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Common Transport Channels - Details
Random Access Channel (RACH)• Contention-based UL 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 DL channel for relatively small amount of data• no closed-loop power control
High-Speed Downlink Shared Channel (HS-DSCH)• High-speed DL channel shared by several UEs
Broadcast Channel (BCH)• DL channel used for broadcast of system information into an entire cell
Paging Channel (PCH)• DL channel used for broadcast of control information into an entire cell
allowing efficient UE sleep mode procedures • Information types are paging and notification
Cellular Communication Systems 8Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Dedicated Transport Channels & Transport Formats
Dedicated Channel (DCH)Channel dedicated to one UE used in UL or DL
Enhanced Dedicated Channel (E-DCH)• Channel dedicated to one UE used in UL 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
Cellular Communication Systems 9Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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
Cellular Communication Systems 10Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
L3
cont
rol
cont
rol
cont
rol
cont
rol
Logical Channel
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
Duplication avoidance
UuS boundary
BMC L2/BMC
control
PDCP PDCP L2/PDCP
DC Nt GC
Radio Bearers
RRC
Radio Access BearersAS control plane SAPsMedium 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– 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
Reporting of measurements– Local measurements such as
traffic volume and quality indication (reported to RRC)
Cellular Communication Systems 11Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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
• 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
Cellular Communication Systems 12Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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)
Cellular Communication Systems 13Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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)
Cellular Communication Systems 14Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Mapping between Logical, Transport & PhysicalChannels
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(MAC SAP)
Transport Channels(PHY SAP)
Physical Channels
DPCHKey: Uplink
DownlinkBidirectionalData TransferAssociation
Control ChTraffic Ch
Common Ch (no FPC)Common Ch (FPC)Dedicated Ch (FPC) Info Channels
Assoc Channels
Fixed Channels
Notes:• Figure describes a subset of possible mappings only! See 25.301, sc. 5.6
for complete list of possible mappings.• FPC denotes Fast Power Control
Cellular Communication Systems 15Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
L3
cont
rol
cont
rol
cont
rol
cont
rol
Logical Channel
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
Duplication avoidance
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)
Cellular Communication Systems 16Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
RLC – Services (1)Transparent data transfer (TM)• Transmission of upper layer PDUs without adding any protocol information (no
RLC header)• Possibly including segmentation/reassembly functionalityUnacknowledged 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
Cellular Communication Systems 17Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
RLC – Services (2)Maintenance of QoS as defined by upper layers• retransmission protocol configurable by layer 3 to provide different
levels of QoSNotification 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
Cellular Communication Systems 18Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
RLC – Functions • Transfer of user data (AM, UM, TM)• Segmentation and reassembly (RLC PDU size adapted to transport
format)• Concatenation• Padding• Error correction (selective-repeat ARQ) • Sequence number check (UM mode)• Duplicate RLC PDUs detection• In-sequence delivery of upper layer PDUs• 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 higherlayer PDUs into fixed-size
RLC PDUs (TBs)
Convert radio link errors into packet
loss and delay
Avoid Tx and Rxbuffer overflows or
protocol stalling
Cellular Communication Systems 19Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
RLC Modes during CS Voice Call R
LC
Call signalling: RLC Entities / Channels / Radio Bearers (RB) Relationships
Abbr. Mode RLC EntitiesTr. 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 EntityUM RLC EntityAM
MAC
DCCH DCCH DCCH DCCH
LAYER 1CCTrCH
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
DPDCHPhysicalChannels
RLC EntityAM
DCH DCH
CCTrCH
DPDCH
Cellular Communication Systems 20Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
L3
cont
rol
cont
rol
cont
rol
cont
rol
Logical Channel
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
Duplication avoidance
UuS boundary
BMC L2/BMC
control
PDCP PDCP L2/PDCP
DC Nt GC
Radio Bearers
RRC
Radio Access BearersAS control plane SAPsPacket Data Convergence Protocol (PDCP)
Service: PDCP SDU delivery PDCP is defined for PS domain only!
Cellular Communication Systems 21Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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
Cellular Communication Systems 22Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
L3
cont
rol
cont
rol
cont
rol
cont
rol
Logical Channel
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
Duplication avoidance
UuS boundary
BMC L2/BMC
control
PDCP PDCP L2/PDCP
DC Nt GC
Radio Bearers
RRC
Radio Resource Control (RRC)
Services Provided to Upper LayersGeneral Control (GC) – information broadcast serviceNotification (Nt) – paging and notification broadcast servicesDedicated Control (DC) – connection management and message transfer
Cellular Communication Systems 23Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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
Cellular Communication Systems 24Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
RRC – Functions RRC handles control plane signaling between the UEs and UTRAN:
- Broadcast of information provided by non-access stratum (Core Network) and access stratum (UTRAN)
- Establishment, re-establishment, maintenance and release of RRC connections- Establishment, reconfiguration and release of Radio Bearers (L2 SAPs)- Assignment, reconfiguration and release of radio resources for the RRC
connection- RRC connection mobility functions- Paging/notification- QoS control- UE measurement reporting- Outer loop power control- Arbitration of radio resources on uplink DCH- Initial cell selection and re-selection in idle mode- Control of ciphering- Integrity protection (message authentication for sensitive data)- Control of Cell Broadcast Service (CBS)
Cellular Communication Systems 25Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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
Cellular Communication Systems 26Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
UTRAN Registration Area (URA)
LA RA
RA
RA RA
RA
RA RA
RA
RA
URA
URAURA
URA URA
URA
URAURA
URA URA
URA
URAURA
URA URA
URA
URAURA
URA URA
URA
URAURA
URA URA
URA
URAURA
URA URA
URA
URAURA
URA URA
URA
URAURA
URA URA
URA
URAURA
URA URA
• URA is used to optimizetradeoff betweenpaging traffic andlocation update traffic
• URA is known to theUTRAN only
• URA is established in RRC connected mode
• URAs may overlap• URA usually in the
order of 10 cells
URA
URAURA UR
A
URA
URA
URA
URA
URA
URA
URA
Cellular Communication Systems 27Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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
RRCconnectionestablishment
URAConnected
RRCconnectionrelease
Enter URAconnected state
Enter cellconnected state
Connected mode
Cellular Communication Systems 28Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
RRC State Machine
Idle mode
CellConnected
RRCconnectionestablishment
URAConnected
RRCconnectionrelease
Enter URAconnected state
Enter cellconnected state
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 from a CN identity on the PCH – no information of the MS is
stored in UTRAN
Cellular Communication Systems 29Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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 => transition cost
Limited resources• radio resources (transmit power)• channelization codes• processing resources (signaling)• power consumption• transport resources (Iu, Iub, …)
Find optimal timeout settings depending on • traffic model (distribution of idle times)• cost per state and scarcity of allocated resources• cost per transition • user mobility• …
cell_DCH
URA_PCH
cell_PCH
idle
T1
T2
T3
Cellular Communication Systems 30Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
UTRAN Architecture
• UTRAN Components and Interfaces• Macro diversity: Serving and Drift RNC• UTRAN architecture details and protocols• AS and NAS services• RRC connection and signaling connection
Cellular Communication Systems 31Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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
Cellular Communication Systems 32Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
UTRAN Architecture Principles – User Plane
Source: 3GPP 25.401
Non-Access Stratum (NAS): • Protocols between UE and CN that are not
terminated in the UTRANAccess Stratum (AS): • 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 proto- cols (1)
Radio proto- cols (1)
Iu protocols (2)
Iu protocols (2)
radio access bearer SAPs (user plane)
Cellular Communication Systems 33Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
UTRAN Architecture Principles – Control Plane
UTRAN UE CN
Access Stratum
Non-Access Stratum
Radio (Uu)
Iu
Radio proto- cols (1)
Radio proto- cols (1)
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 ManagementMM: Mobility ManagementGMM: GPRS MMSM: Session Management
signaling connection
Cellular Communication Systems 34Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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 cellsFor 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 resourcesMacro-diversity and handover is jointly supported by Node B(s) and RNC(s)
Cellular Communication Systems 35Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Serving, Drift and Controlling RNC
RNS
RNC
RNS
RNC
Core Network
Node B Node B Node B Node B
Iu Iu
Iur
Iub Iub Iub Iub
UTRAN
UE
SRNCDRNC
Softer handover: maximum ratio combiningin Node B
Soft handover: radio frame selection (layer 1) in SRNC (and DRNC)
Cellular Communication Systems 36Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Roles of RNSs/RNCsServing RNS (SRNS)• A role an RNS can take with respect to a specific UE• There is one Serving RNS for each UE connected to the UTRAN• The Serving RNS is in charge of the RRC connection of the UE• The Serving RNS terminates the Iu for this UE
Drift RNS (DRNS)• A role an RNS can take with respect to a specific UE• An RNS supports the Serving RNS with radio resources when the UE uses cells
controlled by this RNS
Controlling RNC (CRNC)• A role an RNC can take with respect to a specific set of UTRAN access points,
i.e. the cells with its resources• Exactly one CRNC serves an UTRAN cell• CRNC has the overall control of the logical resources of its cells
Source: 3GPP 21.905
Cellular Communication Systems 37Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Distribution of RRM Functions between RNCs
• CRNC owns the radio resources of a cell
• SRNC handles the connection (RRC) to one UE, and may borrow radio resources from other CRNC
• SRNC performs dynamical control of power for dedicated channels, within limits admitted by CRNC
• Node B implements inner loop power control of its radio links
• SRNC has overall responsibility for outer loop power control
• SRNC schedules data on dedicated channels• CRNC schedules data on common channels (no macro diversity)
Source: 3GPP 25.401, Ch 6.3
Cellular Communication Systems 38Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Serving, Drift and Controlling RNC
RNS
RNC
RNS
RNC
Core Network
Node B Node B Node B Node B
Iu Iu
Iur
Iub Iub Iub Iub
UTRAN
UE 1
SRNCDRNC
UE 2
Dedicated channel with single link
SRNC
Dedicated channel in macro-diversity mode with multiple links
Cellular Communication Systems 39Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
UTRAN Architecture: Functional Split
Control plane
Bearer plane
Core Network
Node-B
Paging
Com./ SharedChannel
Processing
Cell Control
DedicatedChannel
Processing
Mobile Control (RRC state)
Broadcast
CRNC/DRNC SRNC
Cellular Communication Systems 40Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Serving and Controlling RNCExample: 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)
Combine links served by the same node B
Combine links served by the same
CRNC (optional)
Combine links served by different RNCs
Cellular Communication Systems 41Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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)
• General Control (GC) – general network-specific broadcasts• Notification (Nt) – UE-specific infos, e.g. paging• Dedicated Control (DC) – connected mode• User data transfer (RAB) – connected mode
Cellular Communication Systems 42Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
MSC/VLRor SGSN
SRNCUE
RRC Connection and Signaling Connection
RRC Connection RANAP Connection
RRC RANAPRRC RANAP
Signaling Connection(provides DC SAP for SM, CM, MM)
Radio Access Bearer
Signaling Radio Bearer Iu Signaling Bearer
Higher layer control
Higher layer control
Cellular Communication Systems 43Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Radio Link, RRC Connection & Signaling Connection
RNS
RNC
RNS
RNC
Core Network
Node B Node B Node B Node B
Iu Iu
Iur
Iub Iub Iub Iub
UTRAN
UEradio link
RRC connection -> connected mode
signaling connection
SRNC
RRC connections and signaling connections are logical links
Cellular Communication Systems 44Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Radio Link, RRC Connection & Signaling Connection
RNS
RNC
RNS
RNC
Core Network
Node B Node B Node B Node B
Iu Iu
Iur
Iub Iub Iub Iub
UTRAN
UEradio link
SRNCDRNC
RRC connection
signaling connection
Cellular Communication Systems 45Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
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 cellsidentified on the BCCH
- Cell level: Different channel types can be used for data transfer:- Common transport channels (RACH, FACH)- Dedicated transport channels (DCH)
Source: 3GPP 25.301, ch 6.2
Cellular Communication Systems 46Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Recap on Important VocabularyRRC 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 connectionSignaling 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 SRNCRadio 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
Cellular Communication Systems 47Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
UTRAN ProceduresElementary procedures
– Paging– RRC connection setup– Transaction reasoning– Authentication and security control– Transaction setup with RAB allocation– Transaction clearing and RAB release– RRC connection release
RRM procedures– Radio link addition and deletion– Intersystem handover from UMTS to GSM (CS/PS)– UE state transitions/ bearer reconfiguration
MM and CM procedures -> see separate slides
Cellular Communication Systems 48Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Basic Model of UMTS Network TransactionsPaging
RRC Connection Establishment
Transaction Reasoning(Signaling conn. establishment)
Authentication andSecurity
Transaction Setup andRAB Allocation
Transaction(user or control plane)
Transaction Release andRAB Release
RRC Connection Release
UE indicates the CN the requested service
A transaction comprises all the elementary procedures required to enable
– the transport of user data (PS or CS mode) or
– the exchange of higher-layer signaling messages (e.g. MM or CM)
Allocation of bearers to support required UMTS bearer service
Transfer of data
Release of all bearers to support UMTS bearer service
Cellular Communication Systems 49Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Paging
Paging type 1:• UE idle mode (no RRC connection) or• RRC connected modes (cell_PCH or URA_PCH)
Example: paging for a UE in idle modeUE Node B
1.1Node B
2.1RNC
1RNC
2CN
RANAPRANAP 1. Paging
2. PCCH : Paging Type 1
RANAP RANAP1. Paging
3. PCCH : Paging Type 1
(Requesting CN domain, IMSI, ...)
Paging
RRC Connection Establishment
Transaction Reasoning(Signaling conn. establishment)
Authentication andSecurity
Transaction Setup andRAB Allocation
Transaction(user or control plane)
Transaction Release andRAB Release
RRC Connection Release
Paging type 2 (not shown here):• UE is in RRC connected mode (cell_DCH or cell_FACH)• Paging request from another CN domain
Cellular Communication Systems 50Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Initial Random Access on RACH
UE addressing• CCCH: UE ID embedded in the RRC message• DTCH/DCCH: UE ID included in MAC header
UE Node B Controlling RNC
Preamble
Preamble
Preamble
Acquisition Indication (AICH)
PRACH Message
Resourcing Node B Hardware
RACHFP
RACH Message [RRC Connection Request]
CRC Check
RACHFP
Persistency check before
Cellular Communication Systems 51Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
RRC Connection Setup
Establishment of a RRC connection in cell_DCH mode
Paging
RRC Connection Establishment
Transaction Reasoning(Signaling conn. establishment)
Authentication andSecurity
Transaction Setup andRAB Allocation
Transaction(user or control plane)
Transaction Release andRAB Release
RRC Connection Release
UE Node B RNC CN
UE_Idle
CELL_DCH
Initial Random Access
CCCH (TM)/ RACH: RRC Connection Request
RL Setup Request
RL Setup Response
ALCAP Iub Transport bearer Setup
UL/DL Synchronisation
CCCH (UM)/ FACH: RRC Connection Setup
DCCH (AM)/ DCH: RRC Connection Setup Complete • Addr.: by DCH • DCCH established • UE capabilities
known
• Addr.: Initial UE ID • Request for DCCH • Incl. Establishment
cause
Establishment of UTRAN DCH resources incl. CAC
Addr.: Initial UE ID
Cellular Communication Systems 52Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
RRC Connection SetupReasons for RRC connection setup:• Call setup (mobile-originated and mobile-terminated calls)
– Conversational call– Streaming call– Interactive call– Background call– Emergency call– Call re-establishment
• Exchange of signaling messages (low/high priority)
RRC connection request message contains, e.g.• IMSI, TMSI, IMEI• Location area, routing area identity, etc.• Other information: e.g. UE capabilities
Cellular Communication Systems 53Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
NAS Signaling Connection Establishment(Transaction Reasoning)
UE ServingRNC
CN
1. RRC Connection Establishment
RRCRRC2. DCCH : Initial Direct Transfer
RANAP RANAP3. Initial UE Message
Payload contains system network message: Information about the transaction initiated by the UE (IMSI, TMSI, location area, kind of requested transaction)
Paging
RRC Connection Establishment
Transaction Reasoning(Signaling conn. establishment)
Authentication andSecurity
Transaction Setup andRAB Allocation
Transaction(user or control plane)
Transaction Release andRAB Release
RRC Connection Release
Cellular Communication Systems 54Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Authentication and Security Control
Authentication request/response: mutual authentication of UE and networkSecurity mode command/complete: CN domain indicates to UTRAN and UE the encryption
details (method/algorithms and encryption keys)
Paging
RRC Connection Establishment
Transaction Reasoning(Signaling conn. establishment)
Authentication andSecurity
Transaction Setup andRAB Allocation
Transaction(user or control plane)
Transaction Release andRAB Release
RRC Connection Release
Cellular Communication Systems 55Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Transition Setup and RAB Establishment (CS Mode)
Paging
RRC Connection Establishment
Transaction Reasoning(Signaling conn. establishment)
Authentication andSecurity
Transaction Setup andRAB Allocation
Transaction(user or control plane)
Transaction Release andRAB Release
RRC Connection Release
Cellular Communication Systems 56Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Transition Setup and RAB Establishment (PS Mode)
Paging
RRC Connection Establishment
Transaction Reasoning(Signaling conn. establishment)
Authentication andSecurity
Transaction Setup andRAB Allocation
Transaction(user or control plane)
Transaction Release andRAB Release
RRC Connection Release
⇒ see next slide for details
Cellular Communication Systems 57Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Transaction Release and RAB Release (PS Mode)
Note: signaling connection and RRC connection remain
Paging
RRC Connection Establishment
Transaction Reasoning(Signaling conn. establishment)
Authentication andSecurity
Transaction Setup andRAB Allocation
Transaction(user or control plane)
Transaction Release andRAB Release
RRC Connection Release
Cellular Communication Systems 58Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
RRC Connection ReleasePaging
RRC Connection Establishment
Transaction Reasoning(Signaling conn. establishment)
Authentication andSecurity
Transaction Setup andRAB Allocation
Transaction(user or control plane)
Transaction Release andRAB Release
RRC Connection Release
Cellular Communication Systems 59Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Soft Handover – Radio Link Addition UE SRNC Target
Node B DRNC
ALCAP Iur bearer Setup
Active Set Update (Radio Link Addition)
ALCAP Iub Data Transport bearer Setup
RNC Decides to add a new Radio Link
Target Node B is ready
UE starts Rx on new radio link
E.g. new neighbour cell list
Radio Link Restore Indication Radio Link Restore Indication
Active Set Update Complete
Measurement Control
start Rx
start Tx
When RL Setup
Radio Link Add/ Setup Request
Radio Link Add/ Setup Response
Radio Link Add/ Setup Request
Radio Link Add/ Setup Response
Unsynchronized addition
Cellular Communication Systems 60Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
Soft Handover – Radio Link Deletion
Unsynchronized deletion
Cellular Communication Systems 61Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
SRNS Relocation (CS)
Cellular Communication Systems 62Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
UE RRC Connected States – Traffic Perspective
• Cell_DCH– Dedicated Traffic and Control carried over DCH
• Cell_FACH– Dedicated Traffic and Control carried over RACH/FACH
• URA_PCH– No air interface resources required, “dormant” RB– UE receives paging on UTRAN Routing Area (URA) basis rather than
standard routing area (RA)
Cell FACH
Cell DCHURA PCHNo data
No data
Data activity
Data activity
Low traffic
High trafficor CS call
Dynamic RBreconfigure
Cell FACH
Cell DCHURA PCHNo data
No data
Data activity
Data activity
Low traffic
High trafficor CS call
Dynamic RBreconfigure
optional
Cellular Communication Systems 63Andreas Mitschele-Thiel, Jens Mueckenheim Nov-18
ReferencesBooks:• Kaaranen, Ahtiainen, Laitinen, Naghian, Niemi: UMTS Networks –
Architecture, Mobility and Services. 2nd edition, Wiley, 2005• Cornelia Kappler: UMTS Networks and Beyond, Wiley, 2009• Holma, Toskala: WCDMA for UMTS. 4th edition, Wiley, 2007
Central 3GPP Documents on UTRAN:• 25.401: UTRAN overview• 25.301: Radio link protocols (UTRA)• 25.931: UTRAN procedures
Recommended