LTE: What may be the reason for S1 setup failure ?

Question

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.
1. All supported TAIs match at MME
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.

Answer 1

The S1-Setup failure will happen with some cause. it can have many reasons and to specify that reason Failure message has one information element named as CAUSE. So this CAUSE IE is specified in

TS 36.416 Section 9.2.1.3

For instance i can explain with one example:
Suppose eNodeB has initiated a connection by sending a S1 setup Request message,including the TAC and the configured PLMN Identity included into the Broadcast.PLMNs IE,

• MME responds with the S1 setup failure including the reason of the unsuccessful establishment (e.g unknown TAC, unknown PLMN Id, etc)
• No resource is hold by any network element after the unsuccessful S1 establishment