: The MME contacts the HSS via the S6a interface to verify credentials and generate ciphering keys.
Midway through the finale, you leave the train and walk into a café. As your signal shifts from one cell tower to another, the MME orchestrates a silent X2 Handover . The S-GW acts as an anchor, buffering a split-second of data and forwarding it to the new tower. You never notice the switch. The villain’s monologue continues without a single glitch.
Performs Deep Packet Inspection (DPI) and policy enforcement (QoS).
The EPC consists of four main functional components that handle authentication, session management, and data routing: : The MME contacts the HSS via the
Uses S1AP (S1 Application Protocol) over SCTP (Stream Control Transmission Protocol) to provide reliable signaling transport.
Routes and forwards user data packets while acting as the mobility anchor during handovers between eNodeBs.
While 5G introduces the new Service-Based Architecture (SBA) and its own 5G Core (5GC), the EPC remains foundational for several reasons: The S-GW acts as an anchor, buffering a
Determines policy rules, such as QoS and charging, for a subscriber and instructs the PGW to enforce them. 3. Essential 4G LTE EPC Call Flows
Manages Quality of Service (QoS) and charging rules. Standard LTE Call Flow
Unlike the legacy 2G/3G architectures that maintained separate domains for voice (Circuit Switched) and data (Packet Switched), the 4G LTE EPC is an . This means that everything—voice, video, and internet data—is transported as packets. For telecom engineers and enthusiasts, understanding the EPC is the gateway to mastering modern mobile networking. Performs Deep Packet Inspection (DPI) and policy enforcement
LTE call flow explained - sessions rooted across the network
Transports control signaling between the eNodeB and the MME using the S1-AP protocol.