Evolved Packet Core primer

Learn about the Evolved Packet Core for 4G LTE networks that converges voice and data to run as packet-switched services with Quality of Service, session and policy management.

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Understanding the Evolved Packet Core

The Evolved Packet Core (EPC) is a new, end-to-end packet core architecture for 4G Long-Term Evolution (LTE) that provides a converged voice and data networking framework to connect users to an LTE network. EPC makes LTE more like traditional IP networks rather than previous generations of voice-centric wireless networks.

In a departure from 2G and 3G networks, which process and switch voice and data separately using TDM circuits for mobile backhaul, LTE's Evolved Packet Core unifies voice and data on an IP service architecture where voice is only one of many IP applications handled by the network.

The Evolved Packet Core is a "flatter" architecture with fewer elements than earlier wireless networks. Its three-layer architecture includes the radio network of LTE towers that create subscriber coverage, a control layer that manages handset registration and management, customer identification, and the packet core layer that links mobile users to fixed transport facilities.

Standards for EPC operation were specified by the Third Generation Partnership Project (3GPP) in early 2009. LTE/EPC has been deployed in only a few networks, and Tier 1 operators are in the LTE-migration planning stages.

Why do you need to know about the Evolved Packet Core?

Evolved Packet Core architecture was created to help wireless operators meet the hockey-stick growth of mobile broadband and multimedia services. If LTE is to meet subscriber needs, it must provide high-quality real-time and non-real-time mobile broadband access. Operators are counting on LTE to help usher in business models that accommodate revenue sharing with third-party content and application providers, as well as new services and new applications.

Evolved Packet Core architecture continues to develop to enable wireless operators to offer mobile broadband services whose quality rivals that of wireline. EPC provides session, mobility and Quality of Service (QoS) management to ensure that subscribers have high-performance access to real-time and non-real-time applications on the Internet and corporate networks.

EPC interacts with legacy networks and its architecture enables a common core network for convergence, which significantly reduces the cost of ownership for operators with fixed and mobile broadband services. EPC's simplified architecture is intended to make LTE more efficient, as well as offer higher throughput and reduced delays.

Most operators are in the planning phase of LTE evolution and network deployment. As they upgrade their networks, they need to be able to link their legacy networks to LTE to manage customers between them and hand off customers from one to the other. Eventually, operators will need to bridge voice calls between traditional circuit-switched networks and packet-switched LTE voice.

What do you need to know about Evolved Packet Core?

The technology needed to support EPC is challenging because of its flatter architecture, eliminating circuit-switched voice handling, and the need to guarantee delivery of real-time, low-latency services.

The Evolved Packet Core is a subset of the System Architecture Evolution (SAE) -- a 3GPP concept to help evolve LTE mobile architecture to handle multimedia and media-rich services. Within the overarching SAE concept, the Evolved Packet Core has the following three subcomponents:

  • Mobility Management Entity (MME): The control node related to subscriber and session management, including signaling and control functions to manage equipment access to network connections, assigns network resources, and manages mobility states to support tracking, paging, roaming and handovers. MMEs are homed to service gateways.
  • Serving gateway: The data connection between the towers and the network that routes and forwards user data packets through the access network. Serving gateways create tunnels for a call to a packet gateway (PGW) that is the edge of the next-generation network.
  • The packet data network (PDN) gateway: On and off ramps to IP networks. The PDN gateway performs policy enforcement, and packet filtering and filtering for each subscriber.

Evolved Packet Core products: EPC solutions are available from a variety of vendors, including Alcatel-Lucent, Cisco (which acquired Starent), Ericsson, Huawei, Juniper Networks, Motorola, Nokia Siemens Networks, NEC and Tellabs. Mobile packet core vendors expect a period of double-digit growth as LTE deployment speeds up. EPC can support multiple access technologies, which extends the life of GSM and CDMA equipment.

This was first published in May 2011

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