Question: In a UE Radio Capability Match procedure initiated by the MME, what triggers the establishment of a UE-associated logical S1-connection if it's not already established?
Option 1: Receipt of the UE RADIO CAPABILITY MATCH RESPONSE message at the MME
Option 2: Inclusion and receipt of the MME UE S1AP ID IE in the UE RADIO CAPABILITY MATCH REQUEST message at the eNB
Option 3: Successful processing of the UE Radio Capability ID IE by the eNB
Option 4: Automatic timer expiration for S1-connection setup
Explanation: The correct answer is Option 2 because, according to the procedure, if the UE-associated logical S1-connection is not established when the MME initiates the UE Radio Capability Match procedure, the MME allocates a unique MME UE S1AP ID. This ID is included in the UE RADIO CAPABILITY MATCH REQUEST message. Upon receiving this message with the MME UE S1AP ID IE, the eNB establishes the UE-associated logical S1-connection.