UMTS: Alive and Well - 4G Americas

• Mobility Management Entity (MME): The MME manages mobility, UE identities and securityparameters. MME functions include:oNAS signaling and related securityo Inter CN node signaling for mobility between 3GPP access networks (terminating S3)oooooIdle mode UE Tracking and Reachability (including control and execution of pagingretransmission)Tracking Area list managementRoaming (terminating S6a towards home HSS)GW selections (Serving GW and PDN GW selection)MME selection for handovers with MME changeooooooSGSN selection for handovers to 2G or 3G 3GPP access networksHRPD access node (terminating S101 reference point) selection for handovers to/fromHRPDAuthenticationBearer management functions including dedicated bearer establishmentLawful Interception of signaling trafficSupport for Single Radio VCC and CS Fallback for 2G/3G and 1xRTT CDMA• Serving GW: The Serving GW is the node that terminates the interface towards E-UTRAN. Foreach UE associated with the EPS, at a given point of time, there is a single Serving GW. ServingGW functions include:ooooooooThe local Mobility Anchor point for inter-eNodeB handoverMobility anchoring for inter-3GPP mobility (terminating S4 and relaying the trafficbetween 2G/3G system and PDN GW)E-UTRAN idle mode downlink packet buffering and initiation of network triggered servicerequest procedureTransport level packet marking in the uplink and the downlink, e.g. setting the DiffServCode Point, based on the QCI of the associated EPS bearerAccounting on user and QCI granularity for inter-operator chargingLawful InterceptionPacket routing and forwardingSome charging support• PDN GW: The PDN GW is the node that terminates the SGi interface towards the PDN. If a UE isaccessing multiple PDNs, there may be more than one PDN GW for that UE. PDN GW functionsinclude:oooPolicy enforcementPer-user based packet filtering (by e.g. deep packet inspection)Charging supportwww.3GAmericas.org February 2010 Page 146