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What MME does when it receives "S1-setup request" from eNodeB with an unknown TAC ?

+2 votes

I have a use case in which
ENodeB sends "S1-Setup Request" message to MME. TAC within the request is unknown for MME but at least one PLMN from the list of broadcasted PLMN is known by MME. How MME shall react ?

posted May 20, 2015 by Vimal Kumar Mishra

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1 Answer

0 votes

As per the 3GPP specs 36.413, S1 setup request message is as below.

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As per this message, LIST of plmn AND TAC are in Supported TAs IE. So if any of TAC/PLMN is unknow to MME then MME will send the S1 setup failure to eNodeB with cause "Unknown PLMN". The failure cause will be same for both if TAC is unknown or PLMN is unknow because in the s1 setup request message rejection is on the basis of Supported TAs(Criticality - Global).

answer May 20, 2015 by Veer Pal Singh Yadav
Which MME you have used to test s1-setup failure ?
What behaviour are you getting in this scenario?
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Generally MME serves a group of tracking areas and belongs to at least one PLMN.
Lets assume, MME receives S1-setup request from eNodeB with the list of supported TAs.
Now, there are three possibilities as captured below.
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2. Not even a single TAI match at MME
3. Few TAIs match at MME

I want to know, what MME will do for case 2 and case 3 ? How it will respond to eNodeB ?
If MME responds with S1-setup failure then what would be the cause value ? I did not find any reference in 36.413 for these scenarios.

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