Question: For a UE transmitting sidelink discovery announcements on a secondary frequency, which cell is used as a reference for synchronization and DL measurements if no dedicated configuration or common configuration is provided for that frequency?
Option 1: Neighboring Cell with the strongest signal
Option 2: The PCell (Primary Cell)
Option 3: A randomly selected cell from the UE's serving cells
Option 4: The concerned SCell (Secondary Cell) associated with the secondary frequency
Explanation: According to sidelink discovery announcement reference carrier selection rules, if the frequency concerns a secondary frequency and there are no specific dedicated or common configurations provided for that frequency, the UE should use the concerned Secondary Cell (SCell) as a reference for synchronization and downlink measurements. This ensures coordinated operation across frequencies in a multi-frequency deployment scenario, leveraging the existing cell structure for efficient resource management and reduced interference.