Post on 05-Aug-2015
1
LTE Network Architecture
2
LTE Network Architecture
LTE Network architecture is structured to provide:
� “Smart platform for 4G services and applications”
� “Natural” IP connectivity to IP based networks,
services and applications
� Easy integration of network elements from
different vendors
� Easy integration of third party services and
applications
� Allows sophisticated charging schemes
� Scalability
� Tight QoS control
� “Build in” QoS mechanisms and interfaces
3
3G Vs. LTE Network Architecture
NodeB
Radio Network Controller
Packet Switch Core
CircuitSwitch Core
NodeB
Packet Data
Networks
3rd Generation
Circuit
Switch
Networks
eNodeB
Packet Switch Core
eNodeB
Packet Data
Networks
IMS
Radio Access Network - RAN
LTE
Circuit
Switch
Networks
4
The Bigger Picture
The LTE-EPS is part of a bigger picture of next generation network architecture
for IP based services and call control where the IMS plays a central role:
�Common authentication, authorization and accounting framework
�Common media control and network management
- Common policy enforcement rules
�Can easily serve roaming subscribers
�Open application development framework
2G, 3G
Non 3GPPAccess
“IP networks”
CS networks
“User Mgmt”
Circuit Core
IMS Domain
Core Network
Applications
LTEeUTRAN
Evolved Packet Core
5
LTE/SAE Terminology
• EPS- Evolved Packet System
–The EPS provides access to external packet IP networks and performs CN (Core Network) related functions. The EPS is sometimes called: SAE – System Architecture Evolution
• EPC- Evolved Packet Core
–No circuit switched components
–Direct connection between the base station (eNB) and the Core Network (No RNC)
• eUTRAN – LTE Radio Access Network
• UE – User Equipment
eUTRAN
EPC
IMS/PDN
EPS/SAEUE
eNB eNB
UE
6
LTE Architecture Elements and Interfaces
E-UTRAN Evolved Packet Core-EPC
eNB
eNB MMEPCRF
X2
S1-U
S11
S5/S8 SGi
GxS1-MME
S6a
Rx+
Serving Gateway
PDN Gateway
HSSHome Subscriber Server
SAE Gateway
Uu
Uu
PDN
Separation between control and data entities and interfacesAllows separate scale up for data increase and for increase in subscriber numberAllows distribution of data supporting entities while centralizing control supporting entities
Policy and Charging Rule
Function
Packet Data Network
S1-UX2
SPRSp
Gxa
7
A UE May Connect to Multiple PDN’s
PDN Gateway
PDN# 1
Serving Gateway
PDN Gateway
PDN# 2
Internet
Operator Portal
YouTube
Others
Music
Video
Games
PDN Gateway
PDN# 3
IMS SMS
Voice
Others
IP Address #1
IP Address #2
IP Address #3
� A PDN is established when the UE attaches to the network
� The UE uses APN (Access Point Name) to define the required PDN
� Otherwise, the network assigns the default APN of the UE (stored in the HSS)
� For each APN connection the UE have different IP address
� Each PGW serves a single PDN
� A PDN may be served by multiple PGW’s
UE E-NodeB
8
LTE Architecture Elements and InterfacesE-UTRAN
eNB
MME
PCRF
X2
Serving Gateway
PDN Gateway
HSSHome Subscriber Server
Uu
Uu
PDN 1
Packet Data Network 1
eNB
eNB MME
Serving Gateway
PDN Gateway
PDN 2
Packet Data Network 2
AF
PCRF
AF
SPR
X2
X2
1. Most system elements are not “hard nailed“ to each other but can be routed to support different portions of the system.
2. Supports Pooling, weight factoring, load balancing
9
PDN
IP
IPIP IP
IP
Layer1Layer1Layer1
Layer2 Layer2Layer2
PDN GW
RouterServing GW
Application layer
UE IP Connection
Application layer
PDN Connection layer
Transport layer
UE
� Two IP layers:
� PDN connection IP layer (EPS entities as UE, PDN GW etc.)
� Transport IP layer (routers, switches etc.)
� The PDN connection is not aware to the transport IP layer network
techniques as required (Diffserv etc.)
PDN Connectivity and the Transport Layer
10
LTE Roaming – Home Routed Traffic
Case 1: Home Routed Traffic
Access of the UE to the PDN is routed through the Home
Network. Also called “Remote Breakout”.
CelleNBUE
MME
S-GW
S1-U
S1-MMES11
LTE-Uu
HSS
SGi
Gx
Rx+
PDN
P-GW
PCRF
S6a S8
Home NetworkhPLMN
Visited NetworkvPLMN
Home Network
Provides Data
connectivity
11
LTE Roaming - “Local Breakout”
Case 2: “Local Breakout”
UE can access the PDN network directly from the vPLMN rather than traffic being
routed through the hPLMN.
� The hPCRF communicates the allowed services and the authorization of
resources to the vPCRF.
� Th evPCRF may accept or reject but not change the hPCRF authorized services
HSS
Rx+
hPCRF
S6a S9
Home NetworkhPLMN
Visited NetworkvPLMN
CelleNBUE
MME
S-GWS1-U
S1-MMES11
SGi
Gx
Rx+
PDNP-GW
S5
vPCRFLTE-Uu
Home Network
Provides Policy
AF
AF may be associated with eithr the hPCRF or vPCRF