How mme will react when it didn't receive WRITE-REPLACE WARNING RESPONSE after sending WRITE-REPLACE WARNING REQUEST.

Question

How mme have to react when it didn't receive WRITE-REPLACE WARNING RESPONSE from a eNB after sending WRITE-REPLACE WARNING REQUEST to it.

Because of some S1-AP failure.

1) what if eNB didn't receive the WRWRequest.

2) what if eNB received the WRWRequest and cannot send WRWResponse.

Answer 1

I could not find exact behavior of the scenarios in specifications. I think, If eNodeB does not receive Write-Replace Warning Request message then it will not broadcast the warning message. And if eNodeB does not respond to MME or not able to send response message, MME should re-transmit. Since some of the places mentioned that eNodeB may receive re-transmitted Write-Replace Warning Request message.

Answer 2

As u mentioned MME should re-transmit the WRWRequest to eNB if it didn't receive any WRWResponse from eNB. So, when MME should re-transmit the WRWRequest. Is there any timer or anything at MME side.

Answer 3

This should be implementation specific. If there is no response, then MME should retry the request for 'n' number of times for 't' time period which should be configurable. After this, MME may abort the procedure or retry again after a time period