E-UTRAN and e-NB

The key difference between UTRAN and E-UTRAN architectures is the non-existence of a Radio Network Controller (RNC). The utility of the RNC has now been shifted into e-NB.

Responsibilities of e-NB are:

·       Mobility control in the active state.

·       Selection of Mobility Management Entity (MME) during a call.

·       Transfer of Broadcast Control  Channel (BCCH) information over the air.

·       Transfer of radio messages over the air.

·       Uplink / downlink radio resource allocation.

·       IP header compression and encryption of the user data stream.

·       Radio Resource Management (RRM) functionalities – radio admission control and radio bearer control.

E-UTRAN

·       No centralized controller (RNC).

·       e-NBs linked via X2 interface to coordinate handovers and data transfers.

The e-NBs are connected to the MME and Serving Gateways (MME / S-GW) via the S1 interface. An e-NB communicate with multiple gateways to enable load sharing and redundancy.