EPC (EVOLVED PACKET CORE)

                                    EPC (EVOLVED PACKET CORE)

Background— in 1990’s the various standards of cellular system e.g GSM, CDMA etc. were based on circuit switching and the services which were developed were specially concentrated on typical applications of telecommunications. Mobile internet proved a revolutionary change in telecommuncation.

In Nov 2004, 3GPP started its work on 4G technologies that was like a successor of UMTS, particularly a work item named system architecture evolution (SAE) along with LTE which is responsible for evolution of Evolved Packet Core, which support the high bandwidth services at high data rates. In the standardization process of the EPC, various bodies like 3GPP2 (Third generation partnership project 2), Internet engineering task force (IETF), WiMAXforum and open mobile alliance (OMA) took part very actively.”3GPP ‘owns’ the EPS specifications and refers to IETF and occasionally OMA specifications where necessary, while 3GPP2 complements these EPS specifications with their own documents that cover the impact on EPS and GPP2-based systems. WiMAX forum also refers to 3GPP documentation where appropriate for their specification work”

OBJECTIVES SET BY 3GPP for EPC:

The objectives set by 3GPP for development of SAE and EPC were to deliver:

1.   Network architecture to support high data rates.

2.   It should support mobility between multiple heterogenous access systems like 3GPP and 3GPP2 or between 3GPP and WIMAX.

3.   All IP architecture to enhance its capabilty to cope up with high growth in IP data traffic.

EPC ARCHITECTURE:

EPS is Evolved Packet System , which represents all IP network and contains both EPC and LTE. It consists of different domains and each domain again consists of logical nodes. These nodes are interworked with each other to perform any specific set of functions.        

                                                

1.   GSM/GPRS represents 2G technology domain.

2.     WCDMA/HSPA (Wide CDMA/ High speed packet Access) represents 3G or 3.5G RAN (Radio access network).

3.    LTE (Long term evolution) is the latest domain specified by 3GPP and the fourth, Non-3GPP domain consists of access networks, e.g. WiMAX and WLAN, Which are not specified by 3GPP but actually provided by other standardization bodies like 3GPP2, IEEE.

 All four domains are connected to packet core domain (EPC). The core domain also consists of four basic domains. These are Circuit core domain, User domain, IMS (IP multimedia subsystem) and Packet core domain. The circuit core domain is linked to GSM/GPRS and WCDMA/HSPA. It supports and provides the circuit switch services in 2G and 3G technologies. The packet core domain provides IP services over GSM, WCDMA/HSPA,LTE and Non-3GPP technologies while the user domain provides the complete updated information of users on request. It maintains the database to support roaming mobility of the subscriber whether they are moving in a single network or in between different network. The IMS provides support to services based on Session initiation protocol (SIP). Since IMS supports IP services so it uses the IP connectivity with packet core domain to use its function provided by its node.Now we will turn our attention to the EPC architecture. The EPC architecture consists of packet core domain and user domain.

Mobility Management Equipment:

It is the node which is responsible for signal exchanges between base stations and core networks and between the subscriber and the core network.MME doesnot involve in air interface matters so it is non access stratum signaling which is exchanged between MME and radio network. Basic tasks which MME can perform are:

1.   Authentication

2.   Establishment of bearers

3.   NAS mobility management

4.    

External

HSS

Networks

GGSN

HLR

Gn

SGi

Gr

Gn

S6a

PDN

SGSN

Gn

Gn

Gb   Iu

S5/S8

MME

S11

SGW

S10

GSM

WCDMA

S1-MME

LTE

eNODEB

 

                   

Signalling

Voice/Data

The EPC supports IP session which is established over any network.it is also referred as session continuity.