MME vs PGW vs SGW in LTE | MME,PGW,SGW functions in LTE
This page compares MME vs PGW vs SGW used in LTE architecture and mentions functional difference between MME,PGW and SGW. MME stands for Mobility Management Entity, PGW stands for PDN gateway and SGW stands for Serving Gateway.
The figure depicts LTE EPS architecture. In the figure, UE refers to User Equipment. It is the mobile phone device used to access the LTE network. It can also be tablet, USB dongle which is LTE compliant to have access to 4G LTE internet. The eNodeB or eNB is the formal name which refers to LTE base station or cell tower. eNB provides radio access to the UEs using Uu air interface. Multiple eNBs talk to each other using X2 interface when UE moves through the LTE network. The tunneling of data happens between UE and IP network using S1-U interface. Tunneling of control information from UE toward network happens using S1-MME interface.
LTE MME | Mobility Management Entity
Following are the functions of MME (Mobility Management Entity):
• It keeps track of UEs which are registered on LTE network.
• It takes care of user requests for network access. It helps in setting up and tearing down the data sessions.
• It authenticates and authorizes users on the network.
• It does selection of S-GW and P-GW to be used for given session.
• A user can be registered or located with only one MME at a time.
• HSS acts as database of subscriber information which can be queried by MMEs to determine permitted services. Moreover it holds primary security key information for all SIM cards in a mobile network.
LTE SGW | Serving Gateway
Following are the functions of SGW (Serving Gateway) :
• One or more SGWs will serve given group of eNBs for user plane data.
• Single UE is served by one S-GW at any time.
• It receives instructions from MME to set up and tear down sessions for particular UE.
• It acts as interface module for signalling between PGW and MME.
• It takes care of user IP packets between P-GW and eNB.
• SGW functions as IP router with GTP support and charging functionality.
LTE PGW | PDN Gateway | Packet Data Network Gateway
Following are the functions of PGW (Packet Data Network Gateway):
• It provides access to external PDNs (Packet Data Networks).
• If UE has multiple data sessions to multiple PDNs. In this case, UE can be connected with multiple PGWs but it will still be served by only one SGW.
• It is also known by name PCEF as it is responsible for dictating QoS and BW parameters for subscriber's session.
• PGW acts as IP router with support for mobile specific tunneling and signaling protocols.