E-UTRAN consists solely of the evolved Node B (eNB), which is responsible for all radio interface functionality.
eNB is the RAN node in the EPS architecture that is responsible for radio transmission to and reception from UEs in one or more cells.
The eNB is connected to EPC nodes by means of an S1 interface.The eNB is also connected to its neighbor eNBs by means of the
X2 interface. Some significant changes have been made to the eNB functional allocation compared to UTRAN. Most Rel-6 RNC
functionality has been moved to the E-UTRAN eNB. Below follows a description of the functionality provided by eNB.
1. Cell control and MME pool support
eNB owns and controls the radio resources of its own cells.
Cell resources are requested by and granted to MMEs in an ordered fashion. This arrangement supports the MME pooling concept. S-GW pooling is managed by the MMEs and is not really seen in the eNB.
2. Mobility control
The eNB is responsible for controlling the mobility for terminals in active state. This is done by ordering the UE to perform measurement and then performing handover when necessary.
3. Control and User Plane security
The ciphering of user plane data over the radio interface is terminated in the eNB. Also the ciphering and integrity protection of RRC signaling is terminated in the eNB.
4. Shared Channel handling
Since the eNB owns the cell resources, the eNB also handles the shared and random access channels used for signaling and initial access.
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