1. SAE-EPC Inam Ullah Director Product Development EMI
Networks
2. Contents What is SAE/EPC SAE Advantages SAE Architecture
Description of SAE Components Services in EPS Networks
3. What is SAE/EPC System Architecture Evolution (aka SAE) is
the core network architecture of 3GPP's LTE wireless communication
standard SAE is the evolution of the GPRS Core Network, with some
differences: Simplified architecture All-IP Network (AIPN) Support
for higher throughput and lower latency radio access networks
(RANs) Support for, and mobility between, multiple heterogeneous
access networks, including E-UTRA (LTE and LTE Advanced air
interface), 3GPP legacy systems (for example GERAN or UTRAN, air
interfaces of GPRS and UMTS respectively), but also non-3GPP
systems (for example WiMAX or cdma2000)
4. SAE - Advantages Improved data capacity: With 3G LTE
offering data download rates of 100 Mbps, and the focus of the
system being on mobile broadband, it will be necessary for the
network to be able to handle much greater levels of data. To
achieve this it is necessary to adopt a system architecture that
lends itself to much grater levels of data transfer. All IP
architecture: When 3G was first developed, voice was still carried
as circuit switched data. Since then there has been a relentless
move to IP data. Accordingly the new SAE, System Architecture
Evolution schemes have adopted an all IP network configuration.
Reduced latency: With increased levels of interaction being
required and much faster responses, the new SAE concepts have been
evolved to ensure that the levels of latency have been reduced to
around 10 ms. This will ensure that applications using 3G LTE will
be sufficiently responsive. Reduced OPEX and CAPEX: A key element
for any operator is to reduce costs. It is therefore essential that
any new design reduces both the capital expenditure (CAPEX)and the
operational expenditure (OPEX). The new flat architecture used for
SAE System Architecture Evolution means that only two node types
are used. In addition to this a high level of automatic
configuration is introduced and this reduces the set-up and
commissioning time.
5. Description of SAE Components LTE SAE Evolved Packet Core,
EPC consists of four main elements as listed below: Mobility
Management Entity MME Serving Gateway SGW Packet Gateway PGW Policy
Charging and Rule Function -PCRF
6. Mobility Management Entity, MME The MME is the main control
node for the LTE SAE access network, handling a number of features:
Idle mode UE tracking Bearer activation / de-activation Choice of
SGW for a UE Intra-LTE handover involving core network node
location Interacting with HSS to authenticate user on attachment
and implements roaming restrictions It acts as a termination for
the Non-Access Stratum (NAS) Provides temporary identities for UEs
The SAE MME acts the termination point for ciphering protection for
NAS signaling. As part of this it also handles the security key
management. Accordingly the MME is the point at which lawful
interception of signaling may be made. Paging procedure The S3
interface terminates in the MME thereby providing the control plane
function for mobility between LTE and 2G/3G access networks. The
SAE MME also terminates the S6a interface for the home HSS for
roaming UEs. It can therefore be seen that the SAE MME provides a
considerable level of overall control functionality.
7. Serving Gateway, SGW: The Serving Gateway, SGW, is a data
plane element within the LTE SAE. Its main purpose is to manage the
user plane mobility and it also acts as the main border between the
Radio Access Network, RAN and the core network. The SGW also
maintains the data paths between the eNodeBs and the PDN Gateways.
In this way the SGW forms a interface for the data packet network
at the E-UTRAN. Routing and forwarding user data packets acts as
mobility anchor for the user plane during inter-eNB handovers and
for mobility between LTE and other 3GPP for idle state UEs,
terminates the DL data path and triggers paging when DL data
arrives for the UE performs replication of the user traffic in case
of lawful interception.
8. PDN Gateway, PGW: Like the SGW, the Packet Data Network
Gateway (PDN GW) is the termination point of the packet data
interface towards the Packet Data Network(s). As an anchor point
for sessions towards the external Packet Data Networks, the PDN GW
supports: Policy enforcement features (applies operator-defined
rules for resource allocation and usage) Packet filtering (for
example, deep packet inspection for application type detection)
Charging support (for example, per-URL charging) One bearer, a
datapath between a UE and a PDN, has three segments: Radio bearer
between UE and eNodeB Data bearer between eNodeB and SGW Data
bearer between SGW and PGW
9. Policy and Charging Rules Function, PCRF: the Policy and
Charging Enforcement Function(PCEF) is the generic name for the
functional entity that supports service data flow detection ,
policy enforcement and flow-based charging. The Application
Function (AF) represents the network element that supports
applications that require dynamic policy and/or charging control.
In the IMS model, the AF is implemented by the Proxy Call Session
Control Function (P-CSCF).