✅ – MME, SGW, PGW, HSS, PCRF ✅ Interfaces – S1, S5, S8, S11, SGi, and more ✅ Essential procedures – Initial attach, dedicated bearer setup, tracking area update, X2 handover ✅ Step-by-step call flows – Message-level signaling with explanation ✅ Practical tips – Troubleshooting attach failures and bearer issues
Here is the classic combined with PDN Connectivity Establishment (Default Bearer setup).
MME updates the user plane path from the old eNodeB to the new eNodeB via the S-GW. 4. Summary Table of Key Interfaces Connecting Nodes Description S1-MME eNodeB - MME Control Plane traffic S1-U eNodeB - S-GW User Plane traffic S5/S8 S-GW - P-GW User plane and mobility management S6a Authentication and Subscription data Gx P-GW - PCRF Policy and Charging rules Conclusion ✅ – MME, SGW, PGW, HSS, PCRF ✅
MME instructs SGW to establish a user plane radio bearer. Active Session: Data transmission starts. C. S1 Handover (Mobility Procedure) When a user moves between eNodeBs served by the same MME.
The EPC is a flat, all-IP architecture designed to reduce latency. It consists of four primary network elements: Summary Table of Key Interfaces Connecting Nodes Description
+-------------------------------------------------------------+ | HSS (Database) | +------------------------------+------------------------------+ | | S6a | +------------------------------+------------------------------+ | MME (Control Plane) | +--------------+------------------------------+---------------+ | | | S1-MME | S11 | | +--------------+---------------+ +---------------+ | eNodeB | | S-GW | +--------------+---------------+ +-------+-------+ | | | S1-U | S5/S8 +--------------------------------------+ | +-------+-------+ | P-GW | +-------+-------+ | SGi +-------+-------+ | PDN / IP | +---------------+
: Interacts with the HSS to authenticate the user during attach procedures. S1 Handover (Mobility Procedure) When a user moves
The MME queries the HSS to authenticate the subscriber identity (IMSI) and establishes NAS (Non-Access Stratum) security keys to encrypt further control signaling.
The is the all-IP, flat architecture core network for 4G LTE, designed to provide high-speed data, low latency, and efficient mobility management . It simplifies network operations by separating the control plane (signaling) from the user plane (data traffic). Core Concepts & Key Entities