Demystifying LTE’s evolved packet core

"Wireless networks" are named for the so-called "last mile," the portion that delivers the connection to a handset. For the rest of the information path, the normal practice is to carry wireless traffic on wireline facilities, often called "backhaul," to the wireless service centers.

Backhaul in 2G and 3G wireless networks has been based on time-division multiplexing (TDM) circuits because TDM is the voice path for early-generation wireless. But with 4G Long Term Evolution (LTE) technology, no TDM pathway is needed, and no explicit "backhaul" at all. What replaces it is the concept of the "evolved packet core."

The fact that an evolved packet core replaces backhaul may give the impression that LTE tower connections form a completely separate network. In some markets, that may well be; where wireless services are built because there is limited or no existing wireline infrastructure (the case in evolving economies, for example). In major industrial economies with mature wireline networks and evolving wireline consumer broadband deployment, however, it's far more likely that EPC will be intimately linked with metro/middle-mile deployments.

Almost all Tier 1 operators believe that to be true, and require such integration in their LTE planning. It is fortunate that, by design, EPC facilitates this integration with wireline infrastructure, though just how it comes about may be hard to wrestle from the standards.

For purposes of infrastructure planning, it's probably best to visualize an LTE deployment as being a radio network, a control layer and an evolved packet core layer.

The radio network consists of the LTE towers that create the subscriber coverage.
The control layer manages the registration of handsets, the identification of customers and the management of the handset relationship to the data infrastructure.

The evolved packet core layer is the link between a mobile user and the fixed metro/middle-mile transport facilities, and provides session, mobility and quality-of-service (QoS) management, enabling operators to connect users to applications in their service delivery environment, on the Internet and on corporate networks.