Evolving the LTE packet core

Long-Term Evolution isn’t just a crazy notion anymore. Verizon Wireless is deploying the first full-fledged LTE networks in North America this year and going live in 2010. AT&T and T-Mobile are starting to solidify their LTE rollout plans in the coming decade, while carriers worldwide are making commitments to future deployments. With LTE on the near horizon, operators are now starting to discuss the practicalities of building and operating these mobile broadband networks, and they’re starting with the network core.

The evolved packet core (EPC) will be a completely new architecture for wireless operators, one that that emulates the IP world of data communications rather than the voice-centric world of wireless. Gone are the network controllers, mobile switching centers and assorted gateways of 2G and 3G networks. Instead the EPC will have a simplified and collapsed structure, called service architecture evolution (SAE), consisting of only a few elements: the mobility management entity (MME), the control-node that authenticates and tracks a user across the network; the serving gateway (S-gateway) that routes data packets through the access network; and the packet data node gateway (PDN gateway or P-gateway), which acts as the on-ramp and off-ramp to the Internet and other IP networks.

Unlike its predecessors, the LTE network will be IP from handset to P-gateway, and voice -- instead of being the key service the network is designed for -- will become another IP application on the network. The problem is, no one is building LTE in a vacuum—at least not yet. Operators have legacy voice networks and legacy data networks, all with their dedicated legacy cores, that must interoperate with the new LTE network. These aren’t just GSM operators either. CDMA operators like Verizon are jumping from one standards path to the next to deploy LTE. Telus and Bell Mobility will have to integrate both high-speed packet access and CDMA networks with their future LTE architecture. Linking the old networks to the new won’t be the only task. The networks must be able to manage customers between them, hand off from one to the other and eventually bridge voice calls between circuit-switched and VoIP networks.

Verizon looks to Starent
When Verizon announced its LTE vendor selections at Mobile World Congress last month, the attention centered on Alcatel-Lucent and Ericsson and their key radio access network wins, but Verizon’s chief technology officer Dick Lynch was key to stress the importance of the core network to Verizon’s network plans.