User Equipment (UE) functions
• Contains the Universal Subscriber Identity Module (USIM) which holds
authentication information
• Supports services and applications
• Monitors radios and conveys performance to the Evolved Node B (eNB) channel
quality indicator (CQI)
• Supports LTE uplink and downlink air interface
• Maps upstream traffic into traffic classes that are defined by upstream traffic
flow templates
Evolved Node B (eNB) functions
• Radio resource management: radio bearer control, radio admission control,
connection mobility control, uplink/downlink scheduling
• IP header compression and ciphering of user data stream
• Mobility management entity (MME) selection
• Forwarding uplink data to serving gateway
• Paging
• Scheduling and transmission of broadcast information, originated from the mobility
management entity (MME) or operations and maintenance (O&M)
• Measurement and measurement reporting configuration for mobility and scheduling
• Scheduling and transmission of Earthquake and Tsunami Warning System (ETWS)
messages, originated from the MME
Mobility Management Entity (MME) functions
• Non-Access Stratum (NAS) signaling (attachment, bearer setup/deletion)
• NAS signaling security
• Signaling for mobility between 3GPP access networks (S3)
• Idle mode user equipment reachability
• Tracking Area list management
• PDN gateway and serving gateway selection
• MME selection for handoffs with MME change
• Roaming - s6a to home subscriber server (HSS)
• Authentication
• Bearer management functions including dedicated bearer establishment
• Support for Earthquake and Tsunami Warning System (ETWS) message transmission
Serving Gateway (S-GW)
• Local mobility anchor for inter-evolved Node B (eNB) handover
• Mobility anchor for inter-third-generation partnership project (3GPP) mobility
• Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) idle-mode downlink
packet buffering and initiation of network triggered service request procedure
• Lawful intercept
• Packet routing/forwarding
• Transport level packet marking (uplinking and downlinking)
• Accounting on user and Quality of Service (QoS) class identifier granularity
for inter-operator charging
• Uplink and downlink charging per user equipment, packet data node (PDN), and
QoS class identifier (for roaming with home routed traffic)
PDN Gateway (P-GW)
• PDN gateway
• Per-user packet filtering
• Lawful intercept
• User equipment (UE) IP address allocation
• Transport level packet marking for downlinking
• Uplink/downlink service level charging, gating, and rate enforcement
• Downlink rate enforcement based on aggregate maximum bit rate (AMBR)
Policy and charging rules function (PCRF)
• Interfaces with application functions such as the proxy-call session control function
(P-CSCF) or other policy enabled applications
• Interfaces with the PDN gateway to convey policy decisions to it
• Decides how services shall be treated in the PDN gateway in accordance with
a user subscriber policy
Home Subscriber Server (HSS)
• Storage of subscriber data
• Enhanced Presence Service (EPS) QoS subscriber profile
• Roaming restrictions list
• Accessible Access Point Names (APNs)
• Address of current serving mobility management entity (MME)
• Current Tracking Area (TA) of user equipment (UE)
• Authentication vectors and security keys per UE
