Question: In UTRAN Iub interface NBAP signalling, when a Node B receives a REQUEST message for a Class 1 Elementary Procedure it supports, but cannot perform the requested functionality, how shall the Node B respond?
Option 1: Ignore the request and continue with ongoing procedures.
Option 2: Respond with a success message, omitting the unsupported functionality.
Option 3: Respond with the message used to report an unsuccessful outcome, containing an appropriate cause value.
Option 4: Request additional information from the CRNC before responding.
Explanation: According to procedure specification principles for NBAP signalling, if a receiving Node B supports a procedure but cannot perform the requested functionality in a Class 1 EP's REQUEST message, it shall respond with the message indicating an unsuccessful outcome, including an appropriate cause value to inform the requesting node about the failure.