Method and apparatus for identifying uplink timing advance in a wireless communication system
A method and apparatus are disclosed from the perspective of a UE. In one embodiment, the method includes maintaining a first timing advance for a cell, wherein the first timing advance is associated with a first identifier. The method further includes performing a random access procedure in the cell. The method also includes receiving an initial value of a second timing advance for the cell via a random access response of the random access procedure. In addition, the method includes receiving a second identifier to associate with the second timing advance. Furthermore, the method includes maintaining the first timing advance and the second timing advance for the cell.
1. A method for a UE (User Equipment) to maintain timing advances for multiple network nodes in a cell of a wireless communication system, comprising:
maintaining a first timing advance for the cell, wherein the first timing advance is associated with a first identifier;
performing a random access procedure in the cell;
receiving an initial value of a second timing advance for the cell via a random access response of the random access procedure;
receiving a second identifier to associate with the second timing advance; and
adjusting the first timing advance if a first timing advance command with the first identifier is received and adjusting the second timing advance if a second timing advance command with the second identifier is received.
2. The method of claim 1 , wherein the second identifier is received together with the initial value for the second timing advance.
3. The method of claim 1 , wherein the second identifier is received via a contention resolution of the random access procedure.
4. The method of claim 1 , wherein the second identifier is received via a signaling used to trigger the random access procedure.
5. The method of claim 4 , wherein the signaling indicates a dedicated preamble.
6. The method of claim 1 , wherein the second identifier is received via a signaling used to add at least one serving beam.
7. The method of claim 1 , wherein the first timing advance is used for at least a first network node of the multiple network nodes in the cell, and the second timing advance is used for at least a second network node of the multiple network nodes in the cell.
8. The method of claim 1 , wherein the UE applies the first timing advance to adjust timing of a first UL transmission associated with the first timing advance.
9. The method of claim 1 , wherein the UE applies the second timing advance to adjust timing of a second UL transmission associated with the second timing advance.
10. A User Equipment (UE) to maintain timing advances for multiple network nodes in a cell of a wireless communication system, 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 for the cell, wherein the first timing advance is associated with a first identifier;
perform a random access procedure in the cell;
receive an initial value of a second timing advance for the cell via a random access response of the random access procedure;
receive a second identifier to associate with the second timing advance; and
adjust the first timing advance if a first timing advance command with the first identifier is received and adjust the second timing advance if a second timing advance command with the second identifier is received.
11. The UE of claim 10 , wherein the second identifier is received together with the initial value for the second timing advance.
12. The UE of claim 10 , wherein the second identifier is received via a contention resolution of the random access procedure.
13. The UE of claim 10 , wherein the second identifier is received via a signaling used to trigger the random access procedure.
14. The UE of claim 13 , wherein the signaling indicates a dedicated preamble.
15. The UE of claim 10 , wherein the second identifier is received via a signaling used to add at least one serving beam.
16. The UE of claim 10 , wherein the first timing advance is used for at least a first network node of the multiple network nodes in the cell, and the second timing advance is used for at least a second network node of the multiple network nodes in the cell.
17. The UE of claim 10 , wherein the processor is further configured to execute the program code stored in the memory to:
apply the first timing advance to adjust timing of a first UL transmission associated with the first timing advance.
18. The UE of claim 10 , wherein the processor is further configured to execute the program code stored in the memory to:
apply the second timing advance to adjust timing of a second UL transmission associated with the second timing advance.