LTE network architecture and functional nodes/elements

Source: Ericsson, 2009

The following are the key functional nodes/network elements in the LTE architecture:

Evolved Node B (eNB)

• eNodeB is the entity that supports air interface and performs radio resource management
• Provides radio resource management functions such as IP header compression, user data encryption, and routing the user date to the Serving Gateway
• The radio interface provided by eNodeB can be shared by several operators by having separate MME, SGW & PDN Gateway.
  

Serving Gateway (SGW)

• It serves as the mobility anchor for the user plane.
• It takes care of inter-eNodeB handovers & User Equipment (UE) mobility between 3GPP networks.
• It is responsible for routing/forwarding data packets between the eNodeB & PDN Gateway
  

Packet Data Network Gateway (PDN GW)

• It provides the UE with connectivity to the external packet data networks such as Internet.
• It serves as the anchor point for intra-3GPP network mobility, as well as mobility between 3GPP and non-3GPP networks.
• It takes care of Policy and Charging Enforcement Function (PCEF), which includes Quality of Service (QoS), online/offline flow-based charging data generation, deep-packet inspection, and lawful intercept.
  

Mobility Management Entity (MME) 

• It manages mobility, UE identities and security parameters
• It operates in the Control plane and provides functions such as managing session states, authentication, mobility with 3GPP 2G/3G nodes, and roaming.