Thursday, 3 September 2015

LTE- X2 Signaling


 https://www.youtube.com/watch?v=nhnMLAPm46A





The purpose of this procedure is to exchange configuration data at the application layer required for two eNodeBs to interoperate correctly over the X2 interface. All configuration data at the application layer is removed from the two nodes and replaced by the one received in this procedure. In addition, the X2 interface resets in the way the Reset procedure resets in this procedure.
Non-UE-related signaling is required in this procedure.




Successful Operation
 
The eNodeB1 and eNodeB2 function as an initiating eNodeB and a candidate eNodeB, respectively. The eNodeB sends the eNodeB2 an X2 SETUP REQUEST message to initiate the procedure. The eNodeB2 responds with an X2 SETUP RESPONSE message. The eNodeB1 sends the complete list of its served cells to the eNodeB2. Then, the eNodeB2 responds to the eNodeB1 with a complete list of its served cells.
If a cell is switched off for energy saving, it must be activated before initiating or responding to the X2 Setup procedure and must be included in the list of served cells.
The eNodeB1 can include the Neighbour Information IE in an X2 SETUP REQUEST message. The eNodeB2 can include the Neighbour Information IE in an X2 SETUP RESPONSE message. The Neighbour Information IE must include only evolved universal terrestrial radio access network (E-UTRAN) cells that are neighboring to the cells in the eNodeB2. A neighboring cell of eNodeB2 may be any cell that is neighboring to an eNodeB2 cell even if the cell has not been reported by a UE.
The eNodeB1 can include the Number of Antenna Ports IE in an X2 SETUP REQUEST message. The eNodeB2 can include the Number of Antenna Ports IE in an X2 SETUP RESPONSE message. The eNodeB receiving the IE uses the information according to TS 36.331 [9].
The eNodeB1 can include the PRACH Configuration IE in an X2 SETUP REQUEST message. The eNodeB2 can include the PRACH Configuration IE in an X2 SETUP RESPONSE message. The eNodeB receiving the IE uses the information for random access channel (RACH) optimization.
The eNodeB1 can include the MBSFN Subframe Info IE in an X2 SETUP REQUEST message. The eNodeB2 can also include the MBSFN Subframe Info IE in an X2 SETUP RESPONSE message. The eNodeB receiving the IE uses the information according to TS 36.331 [9].

Unsuccessful Operation



If the eNodeB2 cannot accept the setup, it responds to the eNodeB1 with an X2 SETUP FAILURE message.
If the X2 SETUP FAILURE message contains the Time To Wait IE, the eNodeB1 waits at least for the indicated time before reinitiating the X2 Setup procedure towards the eNodeB2. 


 




1.         The UE sends measurement reports to the eNodeB to instruct the eNodeB to initiate a handover.
2.         The source eNodeB sends a HandoverRequest message to the target eNodeB. 
3.    Upon receiving the HandoverRequest message, the target eNodeB makes an admission decision. If the target eNodeB allows the UE to enter the network, the target eNodeB sends the HandoverRequestAck message to the source eNodeB, indicating the handover is successful
 4.    The source eNodeB sends the RRCConnectionReconfiguration message to the UE
5.    The source eNodeB initiates the forwarding procedure by sending the SNStatusTransfer message if E-RABs need to be forwarded
6.         Based on the RRCConnectionReconfiguration message containing the MobilityControlInfo IE, the UE changes radio parameter values and hands over to the target eNodeB.  
7. After accessing the target eNodeB, the UE sends the RRCConnectionReconfigurationComplete message to the target eNodeB 
8.Upon receiving the RRCConnectionReconfigurationComplete message, the target eNodeB sends the PathSwitchRequest message requesting the EPC to change the user-plane path 
9.    The EPC sends a PathSwitchRequestAck message to the target eNodeB if the EPC allows the user-plane handover.
10.Upon receiving the PathSwitchRequestAck message, the target eNodeB sends the UEContextRelease message to the UE, requesting the source eNodeB to release the UE. This indicates the handover is successful. After receiving the UEContextRelease message, the source eNodeB waits until local data transmission is complete and then releases the UE.  

Budi Prasetyo

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