Question: For a UE transmitting NR Sidelink Communication/Discovery on a secondary frequency, what is the basis for selecting a transmission reference cell when in coverage of that frequency?
Option 1: Always use the PCell (Primary Cell) as the reference.
Option 2: Use the concerned SCell (Secondary Cell) associated with that frequency as the reference.
Option 3: Select the cell with the strongest downlink signal as the reference, regardless of its type.
Option 4: Use a neighboring cell's configuration as a reference for synchronization.
Explanation: According to the specified protocol for NR Sidelink Communication/Discovery, when transmitting on a secondary frequency and the UE is in coverage of that frequency, the correct approach is to use the concerned Secondary Cell (SCell) associated with that specific frequency as the reference for synchronization. This ensures alignment with the network's configuration for dual-frequency operations, maintaining optimal communication performance.