Cisco ASR 5x00 Home eNodeB Administration Manual page 19

HeNB Gateway in Wireless LTE Network
1. e-UTRAN Uu Interface Logical Representation
The physical layer in LTE is based upon the Orthogonal Frequency Division Multiplexing (OFDM) using
Orthogonal Frequency Division Multiple Access (OFDMA) in the downlink and variant of this Single Carrier
Frequency Division Multiple Access (SC-FDMA) in the uplink.
 S1 Interface: The communication between the E-UTRAN and the EPC has been designated to the S1 interface.
The S1 interface has been separated by the Control plane signalling and User plane traffic:
 S1-MME: The S1 variant used for Control plane signalling is referred to as S1-MME interface.
 S1-U: The S1 variant used for User plane traffic is referred to as S1-U interface.
The S1-MME interface is governed by the S1-AP protocol, whose functions include:
 E-RAB Management Function: This functionality is responsible for setting up, modifying and
 Initial Context Transfer Function: This functionality is used to establish an S1-UE context in the
 UE Capability Information Indication Function: This functionality is used to provide the UE
 Paging: This functionality provides the EPC with the capability to page the UE.
 S1 Interface Management Functions: These functions comprise the following:
releasing evolved Radio Access Bearers (E-RABs), which are triggered by the MME. The release of
E-RABs may be triggered by the eNodeB as well.
eNodeB. It is also used to setup the default IP connectivity, to setup one or more E-RAB(s) if
requested by the MME, and to transfer NAS signalling related information to the eNodeB if needed.
Capability Information when received from the UE to the MME.
 Reset functionality for ensuring a well defined initialization on the S1 interface.
 Error Indication functionality for allowing a proper error reporting/handling in cases where no
failure messages are defined.
 Overload function for indicating the load situation in the control plane of the S1 interface.
 Load balancing function for ensuring equally loaded MMEs within an MME pool area.
 S1 Setup functionality for initial S1 interface setup for providing configuration information.
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