02 lte architecture summary 25min
TRANSCRIPT
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8/3/2019 02 LTE Architecture Summary 25min
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Eiko Seidel
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3GPP Network Evolution
Directions
Simple, flat, IP based architecture low complexity, low latency
IP based low cost network, reuse of backhaul
Separate control and user plane scalability, low latency
Move all radio into base station only very fast adaptations
LTE Architecture Summary2
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LTE Architecture/Terminology
MME Serving Gateway
S1- S1
S1-
S1-MME
S1-
S1-U
EPC
(Evolved packet Core)
MME
(Mobility Management
Entity)
LTE Architecture Summary3
eNB eNB
eNB
ME
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UME
X2
X2
X2
E-UTRAN
U
(Evolved UMTS Terrestrial
Radio Access Network)
EPS(Evolved Packet
System)
eNB(evolved Node B)
UE
User Equipment
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Logical and physical interfaces
X2 interface is a logical interface !
Physical path might look very different
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Topologies
Traditional 2G/3G hierarchy
One to many relation top down
Changed from UMTS Rel. 5
Iu Flex option
GGSN
PDN GW
Flexible topology
Avoids single point of failure
Load balancing and scalability
Reduction of relocations in ACTIVE
LTE Architecture Summary5
SGSN
NB
RNC
eNB
Serving GW
MME
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Pooling concept
Pools of nodes are created to have some centralized control Node selection is done at registration within the pool nodes
Stateful network elements with UE context in every node
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Overload protection
Active load balancing between network nodes possible Node specific weight factors also influence the node selection
LTE Architecture Summary8
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Overall LTE Architecture
LTE Architecture Summary9
HSS Home Subscriber ServerHLR Home Location RegisterAuC Authorization CenterPCRF Policy and Charging Rules FunctionPDN Packet Data Network
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PDNGW
ServingGW
PeerEntity
UE eNB
End-to-end Service
InternetE-UTRAN EPC
LTE/SAE QoS Architecture
Service Data
Flow(s)
Service Data
Flow(s)Application
EPS Bearer
Radio Bearer S1 Bearer
External Bearer
Radio S5/S8S1 Gi
S5/S8 Bearer
LTE Architecture Summary14
UL Packet
Filter(s) DL Packet
Filter(s)
Information about EPS Bearer Parameter from PCRF
(e.g. IP flows, QoS description, labels)
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User Plane Architecture
GTP-UGTP-U
UDP/IP UDP/IP
RelayPDCP
RLC
IP
Application
UDP/IP
GTP-U
IP
RLC UDP/IP
PDCP GTP-U
Relay
LTE Architecture Summary16
Serving GW PDN GW
S5/S8
22
L1 L1L1
2
L1
SGiS1-ULTE-Uu
eNodeB
2
L1 L1
UE
GTP GPRS Tunnel ProtocolPDCP Packet Data Convergence ProtocolRLC Radio Link ControlMAC Medium Access Control
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Control Plane Architecture
S1-AP S1-AP
NAS
RRCRRC
NASRelay
Constrained in terms of security, reliability and data
loss to provide reliable control procedures
LTE Architecture Summary18
SCTP
L2L1
IPL2L1
IPSCTP
S1-MMEeNodeB
MME
MAC
L1
RLCPDCP
UE
MAC
L1
RLCPDCP
LTE-Uu
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S1-MME Interface Procedures
SAE Bearer Service Management function Setup, release and modification
Mobility (handover) functions for UEs in LTE_ACTIVE
Intra-LTE Handover Inter-3GPP-RAT Handover
Paging function for UEs in LTE_IDLE Paging within the Tracking Area (set of cells)
NAS Signalling Transport function S1-interface management functions Other functions
Error indication Network Sharing Function
Roaming and Area Restriction Support Function NAS Node Selection Function Initial Context Setup Function MME Load Balancing Overload Function
LTE Architecture Summary19
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X2 Control Plane (X2-C)
Logical point to point interfacebetween eNBs
Interface between eNodeBmight not be a physical interface
Only point to pointSCTP
X2-AP
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Reliable transport (PER < 10-8)
Flow control
Typical delay ca. 5 ... 20ms
LTE Architecture Summary20
IP
Data link layer
Physical layer
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X2-C Interface Procedures
User specific procedures Mobility procedures to support handover
Handover request to prepare handover
PDCP status report during handover for lossless handoverDelete context after completion of the procedure
Global procedures Setting up X2 interfaces and resetting
Including security and exchange of eNB configuration data eNB configuration update
Change of the served cell IDs, global ID, group ID for pooling etc
Load management between eNBsRegular load measurement exchange
Support of intercell interference coordination
Handover procedures in active mode
Error indication
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Self-Organizing Networks
Term is used for many, many different things
LTE supports various SON functions to automate network configuration/optimization processes
reduce need for centralized planning and human intervention
SON functions are enabled by exchange of messages between neighbour eNBs (mostly X2)
exchange of messages between eNBs and MMEs (partly S1)
UE reporting measurements to the eNBs (partly Uu air)
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Standardised SON functions
Automatic Neighbor Relation (ANR) functioneNB automatically builds and maintains its neighbour relations based on
UE reports
Automatic Physical Cell Identity (PCI) selectioneNB automatically selects its own PCI based on UE reports and
information received from neighbour eNBs
Dynamic configuration of X2/S1 interfaceseNB dynamically configures the S1MME interface with the serving MMEs
and the X2 interface with neighbour eNBs
RACH parameters optimizationeNBs exchange information about their used PRACH resources to avoid
interference and RACH collisions
Mobility parameters optimization
eNBs automatically adapts mobilityrelated parameters to enhance mobility
robustness or for loadbalancing reasons
LTE Architecture Summary23