LTE Network Topology
EPC:
- Evolved Packet Core (EPC), also knows as the System Architecture Evolution (SAE) core.
- Its a simplified all-IP network architecture.
- It supports higher throughput and lower latency.
- It supports mobility between legacy 3GPP-based systems, but also non-3GPP systems like WiMax and CDMA2000.
MME:
- Mobility Management Entity (MME), It controls the signalling between the UE and the core network.
- It handles the establishment, maintenance and release of radio bearer services.
- It is also responsible for paging and tracking the UE between calls and selecting of proper S-GW upon connection.
- It acts as the termination point for ciphering protection, and is therefore the point of lawful interception of signalling.
S-GW:
- The serving gateway (S-GW), This routes data packets; maintains the data connection for inter eNodeB handovers, as well as, inter system handovers between LTE and GSM/UMTS networks.
- It stores UE contexts, for example bearer service parameters and routing information.
- It is the main junction between the radio access network (RAN) and the core network(CN).
P-GW:
- Packet-Data Network (PDN) Gateway, It provides connectivity for the UE to external packet data networks.
- It allocates IP addresses for the UE and enforces QOS(Quality of Service).
- It maintains the mobility connection between LTE/UMTS/GSM systems and non-3GPP systems like WiMax and CDMA2000.
eUTRAN:
- The enhanced UTRAN is simply a collection of eNodeBs networked together.
- It's responsible for radio resource management, header compression, security and connectivity to the evolved packet core.
eNodeB:
- The enhanced NodeB, contains the radio and antenna equipment to link the UE and the LTE core network via the RF air interface.
- It is practically equivalent to the BTS in GSM and the NodeB in UMTS, however functionality is more robust in LTE.
- The Radio Controller functionality now resides in the eNodeB resulting in a more efficient, less latent network... For example, mobility is governed by the eNodeB instead of the BSC or RNC.
HSS:
- Home Subscriber Service (HSS), is a database similer to HLR in GSM/UMTS core network that contains subscriber-related information supporting call control and session management.
- Its primarily involved in authentication, authorization, security ciphering and also can provide use location details.
PCRF:
- The Policy control and Charging Rules Function (PCRF), is responsible for policy control decision making.
- It provides the QOS authorization to decide how data will be treated with respect to the user's subscription.
SGSN:
- The Serving GPRS Support Node (SGSN), It interconnects the LTE, UMTS and GSM networks for increased mobility.
