LTE/EPS Network
Architecture
LTE/EPS Fundamentals Course
Module Objectives
• After completing this module, the participant should be able to:
•
Briefly explain the Network Architecture evolution from HSPA to LTE.
•
Identify the major subsystems on an LTE/EPS network
•
Name the defined Network Elements in an LTE network.
•
List the key functionalities for every LTE Network Element.
•
Name the standardised interfaces for LTE and understand the protocol stack
implemented in each of them.
•
Discuss the different Roaming cases in LTE
•
Underline the inter-working principles of LTE with 2G/3G networks,
•
Explain the inter-working with non-3GPP networks, in particular cdma2000
HRPD
Module Contents
•
Network Architecture Evolution
•
LTE/EPS Network Subsystems
•
LTE/EPS Networks Elements
•
LTE/EPS Network Interfaces
•
LTE/EPS Roaming Architecture
•
LTE/EPS inter-working with 2G/3G networks
•
LTE/EPS inter-working with Non-3GPP access technologies
Module Contents
•
Network Architecture Evolution
•
LTE/EPS Network Subsystems
•
LTE/EPS Networks Elements
•
LTE/EPS Network Interfaces
•
LTE/EPS Roaming Architecture
•
LTE/EPS inter-working with 2G/3G networks
•
LTE/EPS inter-working with Non-3GPP access technologies
System Architecture Evolution
(SAE) in 3GPP
• The 3GPP system architecture evolution (SAE) framework is
concerned with the evolved packet core network
architecture.
• Targets for System Architecture Evolution:
• Optimization for PS services, No longer CS Core network
• Support for higher throughput (more capacity, higher data
rates)
• Decrease the response time for activation and bearer setup (Control plane latency)
• Decrease packet delivery delay (User plane latency)
• Architecture simplification when comparing with existing
cellular networks
• Inter-working with 3GPP access networks
• Inter-working with other wireless access networks
Network Architecture Evolution
User plane
Control
LTE Plane
HSPA
Direct tunnel
I-HSPA
HSPA R6
HSPA R7
HSPA R7
LTE R8
GGSN
GGSN
GGSN
SAE GW
SGSN
RNC
Node B
(NB)
SGSN
SGSN
MME/SGSN
RNC
Node B
(NB)
Node B +
RNC
Functionality
Evolved
Node B
(eNB)
Module Contents
•
Network Architecture Evolution
•
LTE/EPS Network Subsystems
•
LTE/EPS Networks Elements
•
LTE/EPS Network Interfaces
•
LTE/EPS Roaming Architecture
•
LTE/EPS inter-working with 2G/3G networks
•
LTE/EPS inter-working with Non-3GPP access technologies
What is EPS?
EPS architecture is driven by the goal to
optimize the system for packet data transfer.
The Evolved Packet Core (EPC)
The EPC provides access to external
packet IP networks and performs a
number of CN related functions (e.g. QoS,
security, mobility and terminal context
management) for idle (camped) and
active terminals
The Evolved UTRAN (eUTRAN)
•The eUTRAN performs all radio
interface related functions
Module Contents
•
Network Architecture Evolution
•
LTE/EPS Network Subsystems
•
LTE/EPS Networks Elements
•
LTE/EPS Network Interfaces
•
LTE/EPS Roaming Architecture
•
LTE/EPS inter-working with 2G/3G networks
•
LTE/EPS inter-working with Non-3GPP access technologies
LTE/EPS Network Elements
Main references to architecture in 3GPP specs.:
TS23.401,TS23.402,TS36.300
Evolved UTRAN (E-UTRAN)
Evolved Packet Core (EPC)
HSS
MME: Mobility Management Entity
S6a
Evolved
Node B
(eNB)
LTE-UE
PCRF:Policy & Charging Rule Function
MME
X2
Gx or S7
S1-MME
PCRF
S11
S5/S8
S1-U
SGi
IMS/PDN
cell
LTE-Uu
Rx
Serving
Gateway
PDN
Gateway
SAE
Gateway
Evolved Node B (eNB)
eNB Functions
LTE-UE
LTE-Uu
cell
•
Evolved
Node B
(eNB)
It is the only network element defined
as part of EUTRAN.
Radio Resource Management (RRM)
Radio Bearer Control: setup, modifications and
release of Radio Resources
Connection Mgt. Control: UE State Mgmt. MME-UE
Connection
Radio Admission Control
•
It replaces the old Node B / RNC
combination from 3G.
eNode B Measurements
Collection and evaluation
•
It terminates the complete radio
interface including physical layer.
Dynamic Resource
Allocation (Scheduler)
•
It provides all radio management
functions
IP Header Compression/ de-compression
•
An eNB can handle several cells.
•
To enable efficient inter-cell radio
management for cells not attached to
the same eNB, there is a inter-eNB
interface X2 specified (optional). It will
allow to coordinate inter-eNB
handovers without direct involvement
of EPC during this process.
Access Layer Security: ciphering and integrity
protection on the radio interface
MME Selection at Attach of the UE
User Data Routing to the SAE GW.
Transmission of Paging Message coming from MME
Transmission of Broadcast Info (System info, MBMS)
Mobility Management Entity (MME)
Evolved
Node B
(eNB)
S1-MME
HSS
MME
Control plane NE in EPC
S6a
S11
S1-U
Serving
Gateway
•
It is a pure signaling entity inside the EPC.
•
SAE uses tracking areas to track the position of idle
UEs. The basic principle is identical to 2G/3G LA or
RA.
•
MME handles attaches and detaches to the EPS
system, as well as tracking area updates.
•
Therefore it possesses an interface towards the HSS
(Home Subscriber Server) which stores the
subscription relevant information and the currently
assigned MME in its permanent data base.
•
MME Functions
A second functionality of the MME is the signaling
coordination to setup transport bearers (SAE bearers)
through the EPC for a UE.
•
MMEs can be interconnected via the S10 interface.
•
It generates and allocates temporary ids for UEs.
•
VLR-like functionality
Non-Access-Stratum (NAS)
Signalling
Idle State Mobility Handling
Tracking Area updates
Subscriber attach/detach
signaling coordination for
SAE Bearer Setup/Release & HO
Security (Authentication,
Ciphering, Integrity protection)
Trigger and distribution of
Paging Messages to eNB
Roaming Control (S6a interface
to HSS)
Inter-CN Node Signaling
(S10 interface), allows efficient
inter-MME tracking area updates
and handovers
Serving SAE Gateway (S-GW)
Evolved
Node B
(eNB)
S1-MME
MME
Gxc
(PMIP S5/S8)
S11
S5/S8
S1-U
Serving SAE
Gateway
•
PDN
Gateway
The S-GW and PDN Gateway provide the user plane
connectivity between the access network and the
external packet data network (PDN)
•
It connects towards the eNB via the S1-U interface
•
The S-GW has some kind of distribution and packet
data anchoring function within EPC.
•
•
•
PCRF
It relays the packet data within EPC via the S5/S8
interface to or from the PDN gateway.
A serving gateway is controlled by one or more
MMEs via S11 interface.
At a given time, the UE is connected to the EPC via a
single Serving-GW
Serving Gateway Functions
Local Mobility Anchor Point:
Switching the User plane to a new
eNB in case of Handover
Mobility anchoring for inter-3GPP
mobility. This is sometimes referred
to as the 3GPP Anchor function
Packet Buffering and notification to
MME for UEs in Idle Mode
Packet Routing/Forwarding
between eNB, PDN GW and SGSN
It support Lawful Interception and
Charging functionalities
Packet Data Network (PDN) SAE Gateway
(P-GW)
Gx
MME
Rx
PCRF
S6a
S11
S5/S8
PDN Gateway Functions
SGi
IMS/PDN
Serving
Gateway
•
PDN SAE
Gateway
The PDN gateway (or P-GW or PDN-GW)
provides the connection between the EPC and a
number of external data networks.
•
It is comparable to GGSN in 2G/3G networks.
•
A major functionality provided by a PDN gateway
is the QoS coordination between the external
PDN and EPC.
•
•
Therefore the PDN gateway has to be connected
via S7 to a PCRF (Policy & Charging Rule
Function).
If a UE is connected simultaneously to several
PDNs this may involved connections to more
than one PDN-GW
Mobility anchor for mobility between
3GPP access systems and non-3GPP
access systems. This is sometimes
referred to as the SAE Anchor function
Policy & Charging Enforcement (PCEF)
Per User based Packet Filtering (i.e.
deep packet inspection)
Charging Support
Lawful Interception support
IP Address Allocation for UE
Packet Routing/Forwarding between
Serving GW and external Data Network
Packet screening (firewall functionality)
Policy and Charging Rule Function
(PCRF)
Rx
MME
S6a
S11
PCRF
Gxc
Gx
(PMIP S5/S8)
S5/S8
SGi
IMS/PDN
Serving
Gateway
PDN SAE
Gateway
PCRF: Policy & Charging
Rule Function
QoS policy negotiation with PDN
•
The PCRF major functionality is the Quality of
Service (QoS) coordination between the external
PDN and EPC.
•
Therefore the PCRF is connected via Rx+
interface to the external Data network (PDN)
•
This function can be used to check and modify
the QoS associated with a SAE bearer setup
from SAE or to request the setup of a SAE bearer
from the PDN.
•
This QoS management resembles the policy and
charging control framework introduced for IMS
with UMTS release 6.
Charging Policy: determines how
packets should be accounted
PCRF to provide Policy & Charging
Control (PCC) rules every time a
new bearer has to be set up.
Home Subscriber Server (HSS)
HSS
MME
S6a
•
•
The HSS functionality was already introduced by
UMTS release 5.
With LTE/EPS the HSS will get additionally data
per subscriber for mobility and service handling.
•
Some changes in the database as well as in the
HSS protocol (DIAMETER) will be necessary to
enable HSS for LTE/EPS.
•
The HSS can be accessed by the MME via S6a
interface.
•
The HSS knows where the attached subscribers
are located (MME accuracy)
HSS Functions
Permanent and central subscriber
database
Stores mobility and service data for
every subscriber
Contains the Authentication Center
(AuC) functionality.
Module Contents
•
Network Architecture Evolution
•
LTE/EPS Network Subsystems
•
LTE/EPS Networks Elements
•
LTE/EPS Network Interfaces
•
LTE/EPS Roaming Architecture
•
LTE/EPS inter-working with 2G/3G networks
•
LTE/EPS inter-working with Non-3GPP access technologies
LTE/EPS Network Interfaces
Evolved UTRAN (E-UTRAN)
User plane
Control Plane
Control Plane + User plane
Evolved Packet Core (EPC)
HSS
MME: Mobility Management Entity
S6a
Evolved
Node B
(eNB)
S10
MME
X2
MME
Rx
S1-MME
PCRF
Gxc
S11
LTE-UE
Gx
S5/S8
S1-U
SGi
PDN
cell
LTE-Uu
Serving
Gateway
SAE
Gateway
PDN
Gateway
LTE Radio Interface and the X2 Interface
LTE-Uu
Control Plane (CP) User Plane (UP)
TS 24.301
NAS Protocols
TS 36.331
(E)-RRC
•Air interface of EUTRAN
User PDUs
TS 36.323
PDCP
TS 36.322
RLC
TS 36.321
MAC
TS 36.2xx
LTE-L1 (FDD/TDD-OFDMA/SC-FDMA)
•Based on OFDMA in downlink and SCFDMA in uplink
TS 36.300
X2
•Inter eNB interface
User PDUs
TS 36.422
TS 36.421
X2-AP
GTP-U
SCTP
UDP
IP
IP
L1/L2
L1/L2
TS 36.420
[X2 general aspects & principles)
•Scalable bandwidth: from 1.4 up to 20 MHz
•Data rates up to 100 Mbps (DL), 50Mbps
(UL)
X2-CP
X2-UP
(Control Plane) (User Plane)
TS 36.423
•FDD and TDD duplex methods
TS 29.281
•Handover coordination without involving the
EPC
•X2AP: special signaling protocol
TS 36.424
TS 36.421
•During HO, Source eNB can use the X2
interface to forward downlink packets still
buffered or arriving from the serving gateway
to the target eNB.
•This will avoid loss of packets during intereNB handover.
S1-MME & S1-U Interfaces
TS 36.410
[S1 general aspects & principles]
S1-MME
S1-MME
(Control Plane)
•Control interface between eNB and MME
•MME and UE will exchange non-access
stratum signaling via eNB through this
interface.
•E.g.: if a UE performs a tracking area
update the TRACKING AREA UPDATE
REQUEST message will be sent from UE
to eNB and the eNB will forward the
message via S1-MME to the MME.
•S1AP:S1 Application Protocol
TS 24.301
NAS Protocols
TS 36.413
S1-AP
TS 36.412
MME
SCTP
IP
eNB
TS 36.411
L1/L2
S1-U
(User Plane)
User PDUs
TS 29.281
GTP-U
UDP
TS 36.414
IP
S1-U
•User Plane interface between eNB and serving
gateway.
•It is a pure user data interface
•Which Serving GW a user’s SAE bearer will
have to use is signaled from the MME of this
user.
TS 36.411
L1/L2
TS 36.410
[S1 general aspects & principles]
Serving
Gateway
EUTRAN & EPC connected with
S1-flex
Several cases
1
eNB 1 Single S1-MME
Single S1-U
eNB 2 Single S1-MME
Multiple S1-US1Flex-U
2
eNB 3 Multiple S1-MMES1Flex
Single S1-U
3
eNB 4 (Not shown in picture)
- Multiple S1-MMES1Flex
- Multiple S1-US1Flex-U
S10 & S6a Interfaces
S10
(Control Plane)
TS 29.274
MME
S6a Appl.
GTP-C
UDP
S6a
(Control Plane)
DIAMETER
MME
TCP/SCTP
IP
IP
L1/L2
L1/L2
TS 29.272
HSS
S10
•Interface between different MMEs
•Used during inter-MME tracking area
updates (TAU) and handovers
•Inter-MME TAU: The new MME can
contact the old MME the user had been
registered before to retrieve data about
identity (IMSI), security information
(security context, authentication vectors)
and active SAE bearers (PDN gateways
to contact, QoS, etc.)
•Obviously S10 is a pure signaling
interface, no user data runs on it.
S6a
•Interface between the MME and the HSS
•The MME uses it to retrieve subscription
and authentication information from HSS
(handover/tracking area restrictions,
external PDN allowed, QoS, etc.) during
attaches and updates
•The HSS can during these procedures
also store the user’s current MME address
in its database.
S11 Interface
MME
S11
S11
(Control Plane)
TS 29.274
•Interface between MME and a Serving
GW
•A single MME can handle multiple Serving
GW each one with its own S11 interface
GTP-C
UDP
•Used to coordinate the establishment of
SAE bearers within the EPC
IP
L1/L2
•SAE bearer setup can be started by the
MME (default SAE bearer) or by the PDN
Gateway.
Serving
Gateway
S5/S8 Interface (3GPP Candidate based on
GTP)
S5/S8 3GPP Alternative
Control
Plane
User
Plane
User PDUs
Serving TS 29.274
Gateway
GTP-C
GTP-U
UDP
TS 29.281
PDN
Gateway
SGi
IP
PDN
L1/L2
S5/S8 (3GPP candidate)
•Interface between Serving GW and PDN GW
•S5: If Serving GW and PDN GW belong to the same network (non-roaming case)
•S8:If this is not the case (roaming case)
•S8 = S5 + inter-operator security functions
•Mainly used to transfer user packet data between PDN GW and Serving GW
•Signaling on S5/S8 is used to setup the associated bearer resources
•S5/S8 can be implemented either by reuse of the GTP protocol from 2G/3G or by using
Mobile IPv6 with some IETF enhancements.
S5/S8 Interface (IETF Candidate based on
PMIPv6)
S5/S8 IETF Alternative
Control
Plane
User
Plane
User PDUs
Serving
Gateway
TS 29.275
MIPv6
Tunneling
Layer (GRE)
PMIPv6
TS 29.275
PDN
Gateway
SGi
PDN
IPv4/IPv6
IPv4/IPv6
L1/L2
S5/S8 (IETF candidate)
•Interface between Serving GW and PDN GW
•S5: If Serving GW and PDN GW belong to the same network (non-roaming case)
•S8:If this is not the case (roaming case)
•S8 = S5 + inter-operator security functions
•Mainly used to transfer user packet data between PDN GW and Serving GW
•Signaling on S5/S8 is used to setup the associated bearer resources
•S5/S8 can be implemented either by reuse of the GTP protocol from 2G/3G or by using
Mobile IPv6 with some IETF enhancements.
Gx (or S7) & Gxc Intefaces
Gx (Control Plane)
Gxc (Control Plane)
TS 29.212
Gx Application
Gx Application
DIAMETER
PCRF
DIAMETER
SCTP
SCTP
IP
IP
L1/L2
L1/L2
TS 29.212
SGi
S-GW
S5/S8
Gxc
•Interface between the S-GW and the PCRF
(Policy and Charging Rule Function)
• It is only needed in case the S5/S8 interface
is based on PMIP (IETF candidate)
•The reason is that only in this case the S-GW
will perform the mapping between IP service
flows in S5/S8 and GTP tunnels in the S1-U
interface. The information to do the mapping
comes from directly from the PCRF
IMS/PDN
P-GW
Gx (Also referred as S7)
•Interface between the PDN GW and the
PCRF (Policy and Charging Rule Function)
•It allows:
the PCRF to request the setup of a SAE
bearer with appropriate QoS
the PDN GW to ask for the QoS of an SAE
bearer to setup
to indicate EPC status changes to the
PCRF to apply a new policy rule.
Rx & SGi Interfaces
•Interface between PCRF (Policy & Charging
Rules Function) and the external PDN
network/operators IMS (in general, towards the
Service Domain)
Rx
(Control Plane)
RX Application
TS 29.214
DIAMETER
PCRF
Rx
SCTP
•Standardized in 3GPP TS 29.214: “ Policy and
Charging Control over the Rx reference point
(release 8)”
IP
L1/L2
SGi
•Interface used by the PDN GW to send and
receive data to and from the external data
network or Service Platform
SGi
(User Plane)
•It is either IPv4 or IPv6 based
Application
UDP or TCP
PDN
Gateway
IPv4/IPv6
L1/L2
PDN
TS 29.061
•This interface corresponds to the Gi interface
in 2G/3G networks
•Standardized in 3GPP TS 29.061:
“Interworking between the Public Land Mobile
Network (PLMN) supporting packet based
services and Packet Data Networks (PDN)
Module Contents
•
Network Architecture Evolution
•
LTE/EPS Network Subsystems
•
LTE/EPS Networks Elements
•
LTE/EPS Network Interfaces
•
LTE/EPS Roaming Architecture
•
LTE/EPS inter-working with 2G/3G networks
•
LTE/EPS inter-working with Non-3GPP access technologies
LTE/EPS Roaming Architecture –
Case 1
Rx+
PCRF
Gx
HSS
SGi
PDN
Gateway
Home PLMN
hPLMN
S6a
Visited PLMN
vPLMN
S8
Case 1:
Home Routed Traffic
•By connecting Serving GW
MME
Evolved
Node B
(eNB)
cell
LTE-Uu
Evolved UTRAN (E-UTRAN)
IMS/PDN
S1-MME
S11
S1-U
Serving
Gateway
Evolved Packet Core (EPC)
in vPLMN to PDN GW in
hPLMN
•GTP tunnel and MIPv6
options over the S8
interface
•Also called “Remote
Breakout”.
LTE/SAE Roaming Architecture – Case 2
Case 2: “Local Breakout”
• UE can access the PDN network directly from
HSS
the vPLMN rather than traffic being routed through
the hPLMN.
•Breakout should depend on the service:
i.e.: internet access local breakout
i.e.: access to corporate VPN remote breakout
•S9: PCRF-to-PCRF interface: roaming controlled
by hPLMN policies
hPCRF
S6a
Visited PLMN
vPLMN
Home PLMN
hPLMN
S9
MME
Evolved
Node B
(eNB)
cell
LTE-Uu
Evolved UTRAN (E-UTRAN)
vPCRF
S1-MME
S11
Gx
S5
S1-U
Serving
Gateway
Rx+
SGi
PDN
Gateway
Evolved Packet Core (EPC)
IMS/PDN
S9 Interface
S9
(Control Plane)
S9 Application
TS 29.215
DIAMETER
hPCRF
SCTP
vPCRF
IP
L1/L2
S9
• Interfaces between the hPCRF and the vPCRF is used in roaming cases.
• It is used in the VPLMN for enforcement of dynamic control polices from the hPLMN.
• It is standardized in 3GPP TS 29.215: “ Policy and Charging Control over the S9
reference point (Release 8)”.
Module Contents
•
Network Architecture Evolution
•
LTE/EPS Network Subsystems
•
LTE/EPS Networks Elements
•
LTE/EPS Network Interfaces
•
LTE/EPS Roaming Architecture
•
LTE/EPS inter-working with 2G/3G networks
•
LTE/EPS inter-working with Non-3GPP access technologies
LTE/EPS Interworking with 2G/3G Networks
Gn
Gb
GERAN
Gi
PDN
SGSN
S6d: diameter Based
Gr: MAP Based
Iu-PS
UTRAN
GGSN
S3
S4
HSS
S6a
MME
Evolved
Node B
(eNB)
LTE-UE
cell
LTE-Uu
Evolved UTRAN (E-UTRAN)
Gx
S1-MME
Rx+
PCRF
S11
S5/S8
S1-U
Serving
Gateway
SGi
PDN
Gateway
Evolved Packet Core (EPC)
PDN
S3 & S4 Interfaces
S4
(Control Plane + User Plane)
S3
(Control Plane)
User PDUs
TS 29.274
GTP-C
TS 29.274
GTP-U
GTP-C
TS 29.281
UDP
UDP
IP
L1/L2
IP
2G/3G
SGSN
L1/L2
MME
Serving
Gateway
S3/S4
•Interfaces between EPC and 2G/3G packet switched core network domain
•They would allow inter-system changes between EPS and 2G/3G
•The S3 is a pure signaling interface used to coordinate the inter-system change between
MME and SGSN
•The S4 contains user plane and control plane interface and it is located between SGSN
and Serving SAE GW.
•These 2 interfaces are based on the Gn interface between the SGSN and the GGSN.
•This would allow to either forward packet data from EUTRAN via Serving SAE GW to
SGSN (and then to GGSN) or from 2G/3G RAN to SGSN to Serving SAE GW to PDN GW.
LTE/EPS Interworking with 2G/3G Networks
Gn
Gb
GERAN
GGSN
Gi
PDN
SGSN
S6d: diameter Based
Gr: MAP Based
Iu-PS
S3
S4
UTRAN
HSS
Direct Tunnels from
Serving GW to RNC
(User Plane)
S6a
S12
MME
Evolved
Node B
(eNB)
LTE-UE
cell
LTE-Uu
Evolved UTRAN (E-UTRAN)
Gx
S1-MME
Rx+
PCRF
S11
S5/S8
S1-U
Serving
Gateway
SGi
PDN
Gateway
Evolved Packet Core (EPC)
PDN
S12 Interface
S12
(User Plane)
User PDUs
TS 29.281
UTRAN
GTP-U
UDP
IP
Serving
Gateway
L1/L2
S12
•Interfaces between EPC and 3G Radio access network
•It would allow inter-system changes between LTE and 3G
•The S12 is the user plane interface used for tunneling user data directly between the
Serving GW and the UTRAN.
•This would allow to forward packet data from 3G RAN to Serving GW to PDN GW.
•It is based on the Gn interface between the SGSN and the GGSN and therefore uses the
GTP-U protocol.
Module Contents
•
Network Architecture Evolution
•
LTE/EPS Network Subsystems
•
LTE/EPS Networks Elements
•
LTE/EPS Network Interfaces
•
LTE/EPS Roaming Architecture
•
LTE/EPS inter-working with 2G/3G networks
•
LTE/EPS inter-working with Non-3GPP access technologies
LTE/EPS inter-working with Non-3GPP Access
Technologies
• Inter-working with non-3GPP Access Networks (ANs) was one
of the key design goals for LTE
• There is a separate architecture specification (3GPP TS
23.402: “Architecture enhancements for non-3GPP access
(Release 8)” to reach this goal.
There are 2 sets of LTE/EPS inter-working principles:
1.- Generic and loose Inter-working solution for any non-3GPP
Access Network (AN).
2.- Specific and tighter inter-working solution for cdma2000
HRPD
LTE/EPS Interworking with Non-3GPP Access
Evolved Packet Core (EPC)
Evolved UTRAN (E-UTRAN)
Evolved
Node B
(eNB)
The P-GW keeps
the role of mobility
anchor point
HSS
S6a
MME
cell
LTE-Uu
Gx
S1-MME
Rx+
PCRF
S1-U
S11
S5
Serving
Gateway
SGi
PDN
PDN
SAE
Gateway Gateway
• S2 interface provides
connectivity to a non-3GPP
access network (e.g.
WLAN, WiMAX, 3gpp2,
Fixed,…)
S2a
S2b
Trusted
Un-Trusted
Non-3GPP
Non-3GPP
Access
Access
S2a Interface
S2a based on:
Proxy Mobile(PM) IPv6
Trusted Non-3GPP
Gateway
User Plane
S2a based on:
Mobile IPv4 Foreign Agent (FA) Mode
Control Plane
User Plane
Control Plane
User PDUs
User PDUs
IPv4/IPv6
IPv4/IPv6
IPv4
Tunnelling layer
UDP
Tunneling layer
PMIPv6
IPv4/IPv6
IPv4
L1/L2
L1/L2
Serving
Gateway
(LTE)
TS 29.275
S2a
•It provides the user plane with related control and mobility support between trusted non3GPP IP access and the PDN Gateway.
•S2a is based on Proxy Mobile IP.
•To enable access via trusted non-3GPP IP accesses that do not support PMIP, S2a also
supports Client Mobile IPv4 FA mode.
•S2a is standardized in 3GPP TS 29.275: “ PMIP based Mobility and Tunneling Protocols
(Release 8)”.
Proxy Mobile IP(PMIP).
SAE/EPS Interworking with cdma2000 HRPD AN
E-HRPD AN
HSGW
A10/A11
PDN
PCF/
RNC
BTS
cdma2000 E-HRPD Network
STa
S101
S103
HSS
SWx
MME
Evolved
Node B
(eNB)
S6a
S1-MME
LTE-UE
cell
LTE-Uu
Evolved UTRAN (E-UTRAN)
3GPP
AAA
Server
Gx
Rx+
PCRF
S11
S5/S8
S1-U
Serving
Gateway
SGi
PDN
Gateway
Evolved Packet Core (EPC)
PDN