What is X2 & S1 interfaces? How to Solve X2 interface Alarm?

What is X2 & S1 interfaces? How to Solve X2 interface Alarm?

X2 interface is the Signaling interface between eNodeBs and there are two types

               a) X2control-plane interfaceX2- C interfaceis between eNodeBs for transmitting signaling.

               b) X2user-plane interfaceX2- U interfaceisbetween eNodeBs for transmitting user data

S1 Interfaceisthe signaling interface between an eNodeB and the EPC,  

               a) S1control-plane interfaceS1-C interfaceisbetween an eNodeB and a mobility management entity (MME) for transmitting signaling.

               b) S1user-plane interfaceS1-U interfaceisbetween an eNodeB and a serving gateway (S-GW) for transmitting user data.       

S1 Application Partisthe main control protocol on the S1 interface between the eNodeB and theMME

S1-U interface isan interface between the eNodeB and the S-GW for transfer of user data packets

X2 Interface Fault Alarm : 

The alarm is generated because the Configuration data ofthe X2 application Protocol ( X2AP ) layer is incorrect or there is a problemat the Peer eNodeB.

Causes of Alarm :

1. The X2 interface is incorrectly configured.

2. The peer base station is not configured with an X2 interface.

3. Check that Cell of Base station of the Peer is in normal status

4. The local base station is blacklisted by the peer base station.

5. The S1 interface of the local eNodeB is blocked.

6. The S1 interface of the peer base station is blocked.

During the X2 interface setup procedure, the local base station or the peer base station does not have a cell in normal state.

Troubleshooting of the Alarm :

Step❶:Check theX2interfaceConfiguration

• Run CommandDSP X2INTERFACEto check the Value of X2 interface is Correct

• If not, Run CommandADD X2INTERFACEto add the Correct Value for X2 interface

• Run CommandLST ALMAFto check active alarms with Specified flow numbers (((((Should be repeated after each step to verify active alarm)))))

1. Start Serial No. = Equipment Alarm Serial Number

2. End Serial No. = Equipment Alarm Serial Number

Step❷:Check the S1 interface of the local base station is blocked.

• Run CommandDSP S1INTERFACEto check the S1 interface of the Local Base station is Blocked or no

Step❸: Check the peer base station is configured with the X2 interface.

• Run CommandDSP X2INTERFACEto check the Peer Station is Configured with the X2 interface value properly…

• If not, Run CommandADD X2INTERFACEto add the Correct Value for X2 interface

Step❹ :Check there is a cell in the peer base station in normal status.

• Run CommandDSP CELLto check the Cell in the Peer station is normal status

Step❺:Check the local base station is blacklisted by the peer base station.

• Run the MML commandLST X2BLACKWHITELISTto check the local base station is blacklisted by the peer base station.

• Run the MML commandRMV X2BLACKWHITELISTto removethe local base station from the blacklist of the peer base stationifthe local base stationis blacklistedby the peerbasestation..!!

Step❻:Check the S1 interface of the peer base station is blocked.

• Run CommandDSP S1INTERFACEto check the S1 interface of the Peer Base station is Blocked or no

Step❼ :To delete the faulty  X2 interface.

• Run the MML commandRMV X2INTERFACEto remove the Faulty X2 interface

1. X2Interface ID = "X2Interface ID”

Step❽ :To reconfigure the X2 interface

• Run the MML CommandADD X2INTERFACEto add an X2 interface.

Best Regards

Walid Nawar