Method and apparatus for handling timing advance for uplink transmission in a wireless communication system

A User Equipment (UE), comprising:

• a control circuit;
• a processor installed in the control circuit;
• and
• a memory installed in the control circuit and operatively coupled to the processor;
• wherein the processor is configured to execute a program code stored in the memory to:
• maintain a first timing advance value for uplink transmissions;
• receive a signaling, via a downlink control channel, to schedule a first uplink transmission in a cell, wherein the signaling includes a first information to assist the UE to determine a specific timing advance value for the first uplink transmission, and the first information indicates an index value used to control an offset value to be applied to the first timing advance value;
• determine, by the UE, the specific timing advance value based on the first information and the first timing advance value;
• and
• perform the first uplink transmission in the cell at transmission timing determined at least based on the specific timing advance value.