Method and apparatus of selecting bandwidth part for random access (RA) procedure in a wireless communication system
A method and apparatus are disclosed from the perspective of a UE (User Equipment). In one embodiment, the method includes the UE initiating a Random Access (RA) procedure on a Serving Cell, wherein the UE has multiple active uplink bandwidth parts (UL BWP) for the Serving Cell. The method further includes the UE selecting a UL BWP from the multiple active UL BWPs for an Msg1 transmission, based on a first rule. The method also includes the UE transmitting the Msg1 on the selected UL BWP.
1. A method of a UE (User Equipment), comprising:
initiating a Random Access (RA) procedure on a Serving Cell, wherein the UE has multiple active uplink bandwidth parts (UL BWP) for the Serving Cell;
selecting, from the multiple active UL BWPs, a UL BWP corresponding to an active downlink bandwidth part (DL BWP) with the best DL channel quality for an Msg1 transmission; and
transmitting the Msg1 on the selected UL BWP.
2. The method of claim 1 , wherein the UE determines the best DL channel quality according to measurements on downlink reference signals (DL-RS) from active DL BWPs.
3. The method of claim 1 , further comprising:
selecting a downlink (DL) BWP from multiple active DL BWPs for an Msg2 reception, based on a second rule, and monitoring PDCCH (Physical Downlink Control Channel) for the Msg2 on the selected DL BWP after transmitting the Msg1, wherein the UE has multiple active DL BWPs for the Serving Cell.
4. The method of claim 3 , wherein the second rule is selecting the DL BWP corresponding to the UL BWP transmitting the Msg1.
5. The method of claim 1 , wherein the first rule is selecting the active UL BWP corresponding to an active DL BWP on which a PDCCH (Physical Downlink Control Channel) order is received, wherein the UE initiates the RA procedure in response to reception of the PDCCH order.
6. The method of claim 1 , wherein the first rule is selecting the active UL BWP based on a logical channel (LCH) which triggers the RA procedure due to UL data arrival on the LCH.
7. The method of claim 1 , wherein each of the multiple active UL BWPs is allocated with PRACH resources for Msg1 transmission before the RA procedure is initiated.
8. The method of claim 1 , wherein the Msg1 is a Random Access Preamble of the RA procedure.
9. The method of claim 1 , wherein the Msg2 is a Random Access Response of the RA procedure.
10. 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:
initiate a Random Access (RA) procedure on a Serving Cell, wherein the UE has multiple active uplink bandwidth parts (UL BWP) for the Serving Cell;
select, from the multiple active UL BWPs, a UL BWP corresponding to an active downlink bandwidth part (DL BWP) with the best DL channel quality for an Msg1 transmission; and
transmit the Msg1 on the selected UL BWP.
11. The UE of claim 10 , wherein the UE determines the best DL channel quality according to measurements on downlink reference signals (DL-RS) from active DL BWPs.
12. The UE of claim 10 , wherein the processor is further configured to execute a program code stored in the memory to:
select a downlink (DL) BWP from multiple active DL BWPs for an Msg2 reception, based on a second rule, and monitors PDCCH (Physical Downlink Control Channel) for the Msg2 on the selected DL BWP after transmitting the Msg1, wherein the UE has multiple active DL BWPs for the Serving Cell.
13. The UE of claim 12 , wherein the second rule is selecting the DL BWP corresponding to the UL BWP transmitting the Msg1.
14. The UE of claim 10 , wherein the first rule is selecting the active UL BWP corresponding to an active DL BWP on which a PDCCH (Physical Downlink Control Channel) order is received, wherein the UE initiates the RA procedure in response to reception of the PDCCH order.
15. The UE of claim 10 , wherein the first rule is selecting the active UL BWP based on a logical channel (LCH) which triggers the RA procedure due to UL data arrival on the LCH.
16. The UE of claim 10 , wherein each of the multiple active UL BWPs is allocated with PRACH resources for Msg1 transmission before the RA procedure is initiated.
17. The UE of claim 10 , wherein the Msg1 is a Random Access Preamble of the RA procedure.
18. The UE of claim 10 , wherein the Msg2 is a Random Access Response of the RA procedure.