Question: In E-UTRAN, which network element sends the UE Radio Capability ID Mapping Response message, and what is its primary purpose?
Option 1: Sent by the MME to the eNB, primarily to provide UE Radio Capability information matching a specific UE Radio Capability ID requested earlier.
Option 2: Sent by the eNB to the MME, mainly to acknowledge receipt of UE Radio Capability IDs.
Option 3: Sent by the MME to the eNB, primarily to request additional UE Radio Capability details.
Option 4: Sent by the eNB to the MME, mainly to update the UE's radio bearer configuration.
Explanation: This is correct because, according to the E-UTRAN protocol (S1AP), the MME (Mobility Management Entity) is responsible for sending the UE Radio Capability ID Mapping Response. The primary purpose of this message is to provide the eNB (evolved Node B) with the UE's (User Equipment) radio capability details that correspond to a specific UE Radio Capability ID, which was previously requested by the eNB through a UE RADIO CAPABILITY ID MAPPING REQUEST message. This exchange ensures efficient communication and resource allocation based on the UE's capabilities.