eNB
eNodeB: the LTE base station that manages radio resources, handles scheduling, and connects UEs to the Evolved Packet Core (EPC) via the S1 interface.
The eNodeB is the box at the bottom of the tower (or in the cabinet beside it) that does almost everything radio-related in LTE. Unlike 3G, where a separate controller (the RNC) sat above the base stations, LTE folded that intelligence into the eNB itself — scheduling, radio resource management, handover decisions, ciphering, the lot. That flattening is a big part of why LTE latency dropped versus 3G.
A few interfaces are worth keeping straight. The eNB talks to the EPC over S1: S1-MME to the MME for control signalling, S1-U to the Serving Gateway for user data. And crucially, eNBs talk to each other directly over the X2 interface, which is what lets them coordinate handovers and exchange interference information without routing everything back through the core. The 5G equivalent is the gNB. Two cousins cause confusion: an ng-eNB is an LTE node connected to the 5G Core, while an en-gNB is an NR node connected to the 4G EPC for NSA dual connectivity.
Frequently asked questions
- What's the difference between an eNB and a gNB?
- An eNB is the LTE (4G) base station; a gNB is the 5G NR one. Functionally they play the same role, but a gNB speaks NR on the air interface and connects to the 5G core over the NG interface, where the eNB speaks LTE and connects to the EPC over S1. In non-standalone 5G the two work together: an LTE eNB acts as the anchor and a gNB is added for the 5G data leg.
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