LTE Architecture

Architecture

• The S1-C, S6a, S11, S7 interfaces in the above diagram represents the Control Plane signaling between the entities in LTE. 
• The S1-U, S5/S8, SGi interfaces in the above diagram represents the User Plane between the entities in LTE.

UE: (User Equipment) (Mobile Phone, Data device, Laptop etc.)

 eNodeB:  (Evolved NodeB) RRM (Radio Resource Management) functions, selection of MME, routing of user plane data to S-GW, IP header compression, encryption of user data, scheduling and transmission of paging message.

MME: (Mobility Management Entity) NAS signaling and security, tracking area list management, bearer management, DN GW and S-GW selection, handovers (intra- and inter-LTE), authentication

HSS: (Home Subscriber Server) server which holds user records and is also responsible for Authentication

S-GW: (Serving Gateway) The local mobility anchor point for inter-eNodeB handover; downlink packet buffering and initiation of network-triggered service requests, lawful interception, accounting on user and QCI granularity, UL/DL charging per UE

P-GW: (Packet Gateway) UE IP address allocation, packet filtering and PDN connectivity, UL and DL service-level charging, gating and rate enforcement.

PCRF: (Policy Charging and Rules Function) Takes care of resource allocation to the UE

The next post will describe the function in detail of each elements in the LTE Architecture. One significant point to know about LTE is that it is all IP. The UE is allocated an IP address by the Network Element (P-GW) and with this IP, it communicates with the world.