LTE Signaling Flow
Dec 16, 2015
LTE Signaling Flow
Content
Interface and protocol Signaling Flow of S1 Interface Signaling Flow of X2 Interface Signaling Flow of Basic Service
Network architecture and interfaces
eNB
MME / S-GW MME / S-GW
eNB
eNB
S1
S1
S1 S
1X2
X2X2
E-UTRAN
Functional division of EPC and E-UTRAN
internet
eNB
RB Control
Connection Mobility Cont.
eNB MeasurementConfiguration & Provision
Dynamic Resource Allocation (Scheduler)
PDCP
PHY
MME
Serving Gateway
S1MAC
Inter Cell RRM
Radio Admission Control
RLC
E-UTRAN EPC
RRC
Mobility Anchoring
SAE Bearer Control
Idle State Mobility Handling
NAS Security
Control Plane Protocol
SCTP
L2
L1
IP
L2
L1
IP
SCTP
S1-MME eNodeB MME
S1-AP S1-AP
NAS
MAC
L1
RLC
PDCP
UE
RRC
MAC
L1
RLC
PDCP
RRC
LTE-Uu
NAS Relay
User Plane Protocol
Serving GW PDN GW
S5/S8a
GTP-U GTP-U
UDP/IP UDP/IP
L2
Relay
L2
L1 L1
PDCP
RLC
MAC
L1
IP
Application
UDP/IP
L2
L1
GTP-U
IP
SGi S1-U LTE-Uu
eNodeB
RLC UDP/IP
L2
PDCP GTP-U
Relay
MAC
L1 L1
UE
Signaling and data flow
Signaling flow
eNB
PHY
UE
PHY
MAC
RLC
MAC
MME
RLC
NAS
NAS
RRC RRC
PDCP PDCP
APP
UDP
GTPU
IP
S1AP
SCTP
SGW
IP
UDP
GTPU
IP
SCTP
S1AP
X2AP
Data flow
What is bearer ?
An EPS bearer uniquely identifies traffic flows that receive a common QoS treatment between a UE and a PDN GW
EPS Bearer Service Architecture
P-GWS-GW PeerEntity
UE eNB
EPS Bearer
Radio Bearer S1 Bearer
End-to-end Service
External Bearer
Radio S5/S8
Internet
S1
E-UTRAN EPC
Gi
E-RAB S5/S8 Bearer
Concept of Connection
Content
Interface and protocol Signaling Flow of S1 Interface Signaling Flow of X2 Interface Signaling Flow of Basic Service
S1 Setup
eNB MME
S1 SETUP REQUEST
S1 SETUP RESPONSE
eNB Configuration Update
eNB MME
ENB CONFIGURATION UPDATE ACKNOWLEDGE
ENB CONFIGURATION UPDATE
MME Configuration Update
MME eNB
MME CONFIGURATION UPDATE
MME CONFIGURATION UPDATE ACKNOWLEDGE
Content
Interface and protocol Signaling Flow of S1 Interface Signaling Flow of X2 Interface Signaling Flow of Basic Service
X2 Setup
Source eNB Neighbour eNB
X2 SETUP REQUEST
X2 SETUP RESPONSE
eNB Configuration Update
Neighbour eNBSource eNB
ENB CONFIGURTION UPDATE
ENB CONFIGURATION UPDATE ACKNOWLEDGE
Load Indication
Neighbour eNBSource eNB
LOAD INFORMATION
Resource Status Request
Neighbour eNB
Source eNB
RESOURCE STATUS REQUEST
RESOURCE STATUS RESPONSE
RESOURCE STATUS UPDATE
Resource Status Reporting Initiation
Neighbour eNB
Source eNB
RESOURCE STATUS REQUEST
RESOURCE STATUS RESPONSE
Content
Interface and protocol Signaling Flow of S1 Interface Signaling Flow of X2 Interface Signaling Flow of Basic Service
PLMN selection and cell selection
System Information Broadcast
eNBUE
Master Information Block
System Information Block Type1
System Information
Random access procedureUE eNB
Random Access Preamble1
Random Access Response 2
Scheduled Transmission3
Contention Resolution 4
L2/ L3 indicates "Random Access Preamble" transmission
L1 transmits "Random Access Preamble"
L2/ L3 procedure
L1 procedure
ACK ("Random Access Response" reception)
DTX reception (No "Random Access Response" reception)
L2/ L3 receives indication from L1
L2/ L3 receives indication from L1
L2/ L3 indicates "RRC Connection Request" transmission
L2/ L3 indicates "Random Access Preamble" transmission
UE AttacheNB MMEUE
Identity/Authentication/Security
INITIAL CONTEXT SETUP REQUEST(include Attach Accept,Activate default EPS bearer context
request message)
MSG1
MSG2-Random Access Response
RRC Connection Request
RRC Connection Setup
RRC Connection Setup Complete(include Attach request message) INITIAL UE MESSAGE(include Attach
request message)
UE Capability Enquiry
UE CAPABILITY INFO INDICATION
UE Capability Information
Security Mode Command
Security Mode Complete
RRCConnectionReconfiguration(include Attach accept,Activate default EPS bearer context
request message)
RRC Connection Reconfiguration Complete
ULInformationTransfer(include Attach Complete, Activate default EPS bearer context accept)
INITIAL CONTEXT SETUP RESPONSE
UPLINK NAS TRANSPORT(include Attach Complete, Activate default EPS bearer context accept)
UE Detach( power off in idle)eNB MMEUE
MSG1
MSG2-Random Access Response
RRC Connection Request
RRC Connection Setup
RRC Connection Setup Complete(include Detach request message)
INITIAL UE MESSAGE(include Detach request message)
UE CONTEXT RELEASE COMMAND
UE CONTEXT RELEASE COMPLETE
UE Detach( power off in connected)
eNB MMEUE
ULInformationTransfer(include Detach request message)
DLInformationTransfer(include Detach accept message)
UPLINK NAS TRANSPORT(include Detach request message)
DOWNLINK NAS TRANSPORT(include Detach accept message)
UE CONTEXT RELEASE COMMAND
UE CONTEXT RELEASE COMPLETE
UE Detach(no power off in idle)eNB MMEUE
RRC Connection Release
UE CONTEXT RELEASE COMPLETE
UE CONTEXT RELEASE COMMAND
DLInformationTransfer(include
Detach accept message)
DOWNLINK NAS TRANSPORT(include Detach accept message)
INITIAL UE MESSAGE(include Detach request
message)
RRC Connection Setup Complete(include Detach request message)
RRC Connection Setup
RRC Connection Request
MSG2-Random Access Response
MSG1
UE Detach(no power off in connected)eNB MMEUE
ULInformationTransfer(include
Detach request message)
DLInformationTransfer(include Detach
accept message)
UPLINK NAS TRANSPORT(include
Detach request message)
DOWNLINK NAS TRANSPORT(include Detach accept message)
UE CONTEXT RELEASE COMMAND
RRC Connection Release
UE CONTEXT RELEASE COMPLETE
Paging(system information changed)
MMEUE
Paging
Paging(MME trigger)
MMEUE
Paging
eNB
PAGING
Service Request(UE trigger)eNB MMEUE
INITIAL CONTEXT SETUP RESPONSE
RRC Connection Reconfiguration Complete
RRC Connection Reconfiguration
Security Mode Complete
Security Mode Command
UE Capability Information
UE Capability Enquiry
UE CAPABILITY INFO INDICATION
INITIAL CONTEXT SETUP REQUEST
Identity/Authentication/Security
INITIAL UE MESSAGE(include Service
request message)
RRC Connection Setup Complete( include Service request message)
RRC Connection Setup
RRC Connection Request
MSG2-Random Access Response
MSG1
TAU in Idle(no active identifier)
UE EPCeNB
1 . RA Preamble
7 . Authentication Security/
3 . RRC Connection Request
2 . RA Response
4 . RRC Connection Setup
5 . RRC Connection Setup Complete ( include TAU request )
13. UE CONTEXT RELEASE COMMAND
6 . Initial UE message (Include TAU request)
9 . DOWNLINK NAS TRANSPORT ( include TAU Accept)
10. DL Information Transfer ( include TAU Accept)
11. UL Information Transfer (include TAU Complete)
12. UPLINK NAS TRANSPORT (include TAU Complete)
Return to IDLE mode
15. UE CONTEXT RELEASE COMPLETE
14. RRC Connection Release
8 . Update UE context information between MME
In idle mode, UE into TAI is not within TAI list
TAU in Idle(setup active identifier)
UE EPCeNB
1. RA Preamble
First Downlink Data
7. Authentication/Security
3. RRC Connection Request
2. RA Response
4. RRCConnectionSetup
5. RRC Connection Setup Complete (include TAU Request )
First Uplink Data
6. Initial UE message (include TAU request)
9. Initial context setup request (include TAU Accept)
15. RRC Connection Reconfiguration (include TAU Accept)
16. RRC Connection Reconfiguration Complete 17. Initial context setup
response
19. UPLINK NAS TRANSPORT (include TAU Complete)
10. UE Capability Enquiry
11. UE Capability Information
13. SecurityModeCommand
14. SecurityModeComplete
12. UE Capability Info Indication
18. UL Information Transfer (include TAU Complete)
In idle mode, UE into TAI is not within TAI list
8. Update UE context
information between MME
20. Update RAB
TAU in Connected UE EPCeNB
In connected mode, UE into TAI is not
within TAI list
3. Update UE Context between MME
1. ULInformationTransfer(include TAU request message)
4. DOWNLINK NAS TRANSPORT(include TAU Accept message)
5. DLInformationTransfer(include TAU Accept message)
6. ULInformationTransfer(include TAU Complete message)
7. UPLINK NAS TRANSPORT
(include TAU Complete message)
2. UPLINK NAS TRANSPORT
(include TAU request message)
E-RAB Setup
E-RAB Release
RRC Connection Re-establishment
UE Handover between one eNB’s cellseNB
UE Handover between the different eNB’s cells(through X2 interface)
UE Handover between the different eNB’s cells(through S1 interface)