What is the Evolved Packet Core and why should you care?
Sep 4, 2013
Ever wondered what happens behind the scenes when you connect your smartphone to browse the web, get your email, watch a video or look at some photos? A lot. All that data traverses a complex network of cellular, data transport, and core network elements to bring you that amazing broadband experience. And the network is even more advanced now that we’re making the transition from 2G/3G to LTE.
That’s because the difference with LTE is that it’s all-IP. In its simplest terms, moving to LTE means moving away from a packet/ TDM network architecture to a simpler flatter all-IP packet-based infrastructure. This leads to blazingly fast speeds, impressive quality, and serious gains in efficiency – driving down the cost of sending a bit across the network.
As LTE grows, so does the market for the many elements of an LTE infrastructure. A recent report from analyst firm Dell’Oro showed a 20% growth in packet core revenue in 2Q’13 compared to the same period a year ago. Alcatel-Lucent is #1 in the segment, according to Dell’Oro.
So what exactly does “packet core” mean for LTE? For LTE, it’s the new Evolved Packet Core (EPC) and it’s comprised of three different platforms that are needed to connect the user to his or her mobile communication universe. The EPC is both the brains and the brawn of the LTE network: it provides much of the intelligence and does a lot of the heavy lifting required to make LTE networks work.
3GPP LTE System Architecture Evolution (SAE)
When you connect via your device to the network, your data is sent over the air from your handset to the cellular tower where it is then transported – via the backhaul network –into your mobile providers’ EPC. Here, your data is processed through the EPC where it then is forwarded from your mobile providers’ network to the Internet or another public or private data network.
So what happens inside the critical EPC?
LTE’s Private Highways: the Bearer Channels
Bearer channels in LTE are like individual private highways or delivery lanes dedicated to specific users and their data services. For example user John may have a dedicated bearer channel for his voice service and at the same time he may have another separate bearer channel for his video or Internet service. These bearer channels are critical as they are assigned specific parameters that correspond to performance expectations that are defined by the user or operator.
The PDN Gateway (PGW)
Before John can talk through his voice service or watch a movie through his video service, separate bearer channels are established at the PGW and this is where all of the required parameters that define these private highways are applied.
The PGW is also the IP anchor point. It provides the exit and entry point of traffic from the mobile provider’s network to the user equipment (UE), i.e. the user’s mobile device. The PGW provides connectivity from the UE to the Internet, the IP Multimedia Subsystem (IMS) Core, and other data networks. It represents the service edge of the mobile provider’s network where a lot of the processing of packets is performed. Some of these functions include for each UE and each service:
creation and termination of the bearer channels
packet inspection and filtering (determines which kind of service/application and thus which bearer channel should be used)
policy enforcement (Quality of Service and charging support assigned to each bearer as defined by the user’s individual package)
accounting and reporting
The Serving Gateway (SGW)
The SGW is critical to the user being “mobile”. The SGW routes and forwards user data packets through the bearer channels like the PGW. It also represents the “mobility” anchor where its job is to ensure that packets are continuously delivered even as the user changes location. The SGW also participates in setting up the bearer channel and manages and stores bearer channel information. Finally, the SGW is responsible for triggering paging (e.g. notifying and waking up radio resources) when downlink data arrives for the UE.
The Mobility Management Entity (MME)
While the PGW and SGW are the “brawn”, the MME may be thought of as the “brains”. It operates completely in the control plane where it issues and receives instructions related to the network, services and applications. It has some key responsibilities:
assigns each UE to the proper SGW
orchestrates the establishment of bearer channels in the network
tracks the UE and assigns/optimizes network resources as the user moves geographically
authenticates the user by interacting with the HSS (the Home Subscriber Server, which is like a giant database of information for the LTE network)
provides security management between the user device and the network
Find out More
Behind every successful LTE connection, there’s an EPC doing the heavy lifting of both user data traffic and control signaling. It may seem like magic, but it’s an intricate process that has been refined and optimized for the future of mobile communications.
You can find out more about Alcatel-Lucent’s EPC by talking to your account representative, or visit our EPC solution page.
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