LTE EPS (LTE/SAE) Architecture
The EPS architecture is made up of an EPC (Packet Core Network) and eUTRAN Radio Access Network.
EPC Key Network Elements
The core network (Evolved Packet Core in SAE) is responsible for the overall control of the UE and establishment of the bearers. The main logical nodes of the EPC are:
- Mobility Management Entity (MME)
- Serving Gateway (S-GW)
- PDN Gateway (P-GW)
Mobility Management Entity (MME)
This is a key control plane element. Among other functions, it is in charge of managing security functions (authentication, authorization, NAS signaling), handling idle state mobility, roaming, and handovers. Also selecting the Serving Gateway (S-GW) and Packet Data Network Gateway (PDN-GW) nodes is part of its tasks. The S1-MME interface connects the EPC with the eNodeBs.
Serving Gateway (S-GW)
The EPC terminates at this node, and it is connected to the E-UTRAN via the S1-U interface. Each UE is associated to a unique S-GW, which will be hosting several functions. It is the mobility anchor point for both local inter-eNodeB handover and inter 3GPP mobility. S-GW performs inter-operator charging as well as packet routing and forwarding.
PDN Gateway (P-GW)
This node provides the UE with access to a Packet Data Network (PDN) by assigning an IP address from the PDN to the UE, among other functions. Additionally, the evolved Packet Data Gateway (ePDG) provides security connection between UEs connected from an untrusted non-3GPP access network with the EPC by using IPSec tunnels.
SAI has developed MME, S-GW, P-GW which are fully compliant with 3GPP Release 8 and 9.0. SAI is working towards LTE Advanced (Release 10 and beyond).
With licensing UE or eNodeB software, SAI provides EPC software running on Intel Servers. These modules are validated with rigorous interoperability tests with other vendors.