LTE Architecture Flashcards
EPS?
Evolved Packet System
EPS Components?
User Equipment
Evolved UTRAN
Evolved Packet Core
UE Components?
Mobile Terminal
Terminal Equipment
Universal Integrated Circuit Card
USIM?
Stores user-specific data such as
- User’s phone number
- Home network identity
Carries out various security-related calculations, using secure keys that the smart card stores
IP Support?
LTE UE Supports
- IPv4
- IPv6
- Duel Stack
A mobile receives one IP address for every Packet Data Network it is communicating from:
- Internet
- Private corporate network
What is E-UTRAN is made of?
Enhanced NodeB
Features of eNodeB?
Serving eNB
Hard Handover
Combines the functions of NodeB and RNC of UMTS
X2 Interface
Transport Network?
S1 and X2 Interfaces are not physical, rather logical interfaces.
Femto Cell
Smallest cell in LTE eNB is called Home eNB Closed Subscriber Group Home eNB Gateway S1 Interface in Femto cell
Architecture of the EPC?
Main components of the EPC
- HSS
- P-GW
- S-GW
- MME
HSS
Home Subscriber Server
P-GW
PDN Gateway
S-GW
Serving Gateway
MME
Mobility Management Entity
Home Subscriber Server?
Continued from UMTS
Central database
Contains information about all the subscribers
PDN Gateway?
EPC's gateway to the Packet Data Networks (PDN) Connects to one or more - Outside data networks - LTE Operator's servers - IP Multimedia Subsystem APN SGi
Serving Gateway?
Acts as a high-level router
Forwards data between the base station and the PDN gateway.
Mobility Management Entity?
Controls the high-level operation of the mobile
Sends signalling messages to mobiles about:
- Security
- Management of data streams
- Communicates with other elements of the network
- Using signalling messages that are internal to the EPC
One MME is responsible for?
For the mobiles in a certain geographical region
Each mobile is?
Assigned to a single MME
- Called its serving MME
- Serving MME will change if the mobile moves sufficiently far
Roaming Architecture?
Roaming allows a mobile to communicate with the Internet and the IP multimedia subsystem while visiting other network
Data traffic to PDN may go in two ways?
Home Routed Traffic
Local Breakout
Home Routed Traffic?
In which the PDN gateway lies in the home network
Local Breakout?
In which the PDN gateway lies in the visited network
EPC is divided into 3 types of geographic areas:
MME Pool Area
S-GW Service Area
Tracking Area
MME Pool Area?
Overlapping; mobile does not change MME in an area
S-GW Service Area?
Overlapping, mobile does not change S-GW with in the area
Tracking Area?
Non-overlapping; used to track the locations of mobiles that are on standby
Similar to location area in GSM/UMTS
GUMMEI?
Composition of Globally Unique MME Identifier
PLMN-ID?
Public Land Mobile Network Identifier
- MCC
- MNC
MMEI?
MME Identifier
- MMEGI
- MMEC
Tracking Area Identifiers?
TAC
TAI
TAC?
Tracking Area Code
- Identifies a tracking area within a network
TAI?
Tracking Area Identity
- Globally unique ID of a tracking area
Cell Identifiers?
E-UTRAN Cell Identity (ECI)
E-UTRAN Cell Global Identifier (ECGI)
Physical Cell Identity
Identities used by the mobile?
IMEI
IMSI
Temporary IDs mobile used in the air interface
High-Level Protocol Architecture of LTE?
User plane protocols
Control plane protocols
Transport protocols
User plane protocols?
Carries user traffic
TCp/IP-based
Control Plane Protocols?
Carries signalling
LTE/SAE Specific
Transport Protocols?
Provides transport for both user plane and control plane
TCP/IP and underlying transport protocol
Communication between mobile and MME?
No direct path between MME and a mobile
Non Access Stratum is carrier by Access Stratum
Air Interface Transport Protocols?
Physical Layer MAC (Media Access Control) RLC (Radio Link Control) PDCP (Packet Data Convergence Protocol) RRC (Radio Resource Control) IP (Internet Protocol)
Access Stratum?
Any layer 1 and layer 2 protocol Layer 3 is invariably IP Layer 4: - UDP for user traffic - TCP and SCTP for signalling
MME controls a mobile’s high-level behavior using two protocols
EPS Session Management
EPS Mobility Management