APPARATUS AND METHOD FOR HANDOVER IN A WIRELESS COMMUNICATION SYSTEM

1 . A method performed by a User Equipment (UE) for handover, the method comprising:

receiving a Radio Resource Control (RRC) message from a source base station; and

performing a handover procedure to handover from the source base station to a target base station in response to the RRC message, wherein:

the RRC message comprises one of a first dedicated random access configuration associated with a Channel State Information-Reference Signal (CSI-RS) of the target base station and a second dedicated random access configuration associated with a first Synchronization Signal Block (SSB) of the target base station,

the CSI-RS is configured with a first dedicated random access resource by the first dedicated random access configuration, and

the first SSB is configured with a second dedicated random access resource by the second dedicated random access configuration.

2 . The method of claim 1 , further comprising:

receiving a measurement configuration from the source base station;

performing a measurement according to the measurement configuration; and

transmitting a measurement report for the measurement to the source base station according to the measurement configuration,

wherein the measurement report comprises beam information.

3 . The method of claim 2 , wherein the measurement configuration comprises an information element indicating to the UE to transmit the measurement report when a condition of beam information change is satisfied.

4 . The method of claim 3 , wherein the condition of beam information change is satisfied when a beam identifier (ID) included in the measurement report is different from another beam ID included in a previous measurement report transmitted by the UE.

5 . The method of claim 3 , wherein the condition of beam information change is satisfied when the beam information included in the measurement report is different from beam information included in a previous measurement report transmitted by the UE.

6 . The method of claim 3 , wherein the condition of beam information change is satisfied when a beam set included in the measurement report is different from another beam set included in a previous measurement report transmitted by the UE.

7 . The method of claim 1 , wherein the RRC message further comprises a configuration of a common random access resource.

8 . The method of claim 7 , wherein the RRC message further comprises a parameter indicating a maximum number of random access attempts before the UE is allowed to use the common random access resource.

9 . The method of claim 1 , further comprising:

receiving the first dedicated random access resource from the source base station, the first dedicated random access resource being a contention-free random access resource associated with the CSI-RS;

determining whether a Channel State Information-Reference Signal Received Power (CSI-RSRP) of the CSI-RS is greater than a CSI-RS threshold; and

transmitting a random access preamble to the target base station by using the contention-free random access resource after determining that the CSI-RSRP is greater than the CSI-RS threshold.

10 . The method of claim 9 , further comprising:

determining that the CSI-RSRP is not greater than the CSI-RS threshold;

determining whether a Synchronization Signal (SS)-RSRP of a second SSB associated with a contention-based random access resource is greater than an SS-RSRP threshold; and

transmitting a random access preamble by using any SSB with a common random access resource after determining that the SS-RSRP is not greater than the SS-RSRP threshold.

11 . A User Equipment (UE) for handover, the UE comprising:

a memory storing instructions; and

a processing circuitry coupled to the memory and configured to execute the stored instructions to:

receive a Radio Resource Control (RRC) message from a source base station; and

perform a handover procedure to handover from the source base station to a target base station in response to the RRC message, wherein:

the RRC message comprises one of a first dedicated random access configuration associated with a Channel State Information-Reference Signal (CSI-RS) of the target base station and a second dedicated random access configuration associated with a first Synchronization Signal Block (SSB) of the target base station,

the CSI-RS is configured with a first dedicated random access resource by the first dedicated random access configuration, and

the first SSB is configured with a second dedicated random access resource by the second dedicated random access configuration.

12 . The UE of claim 11 , wherein the processing circuitry is further configured to execute the stored instructions to:

receive a measurement configuration from the source base station;

perform a measurement according to the measurement configuration; and

transmit a measurement report for the measurement to the source base station according to the measurement configuration,

wherein the measurement report comprises beam information.

13 . The UE of claim 12 , wherein the measurement configuration comprises an information element indicating to the UE to transmit the measurement report when a condition of beam information change is satisfied.

14 . The UE of claim 13 , wherein the condition of beam information change is satisfied when a beam identifier (ID) included in the measurement report is different from another beam ID included in a previous measurement report transmitted by the UE.

15 . The UE of claim 13 , wherein the condition of beam information change is satisfied when the beam information included in the measurement report is different from beam information included in a previous measurement report transmitted by the UE.

16 . The UE of claim 13 , wherein the condition of beam information change is satisfied when a beam set included in the measurement report is different from another beam set included in a previous measurement report transmitted by the UE.

17 . The UE of claim 11 , wherein the RRC message further comprises a configuration of a common random access resource.

18 . The UE of claim 17 , wherein the RRC message further comprises a parameter indicating a maximum number of random access attempts before the UE is allowed to use the common random access resource.

19 . The UE of claim 11 , wherein the processing circuitry is further configured to:

receive the first dedicated random access resource from the source base station, the first dedicated random access resource being a contention-free random access resource associated with the CSI-RS;

determine whether a Channel State Information-Reference Signal Received Power (CSI-RSRP) of the CSI-RS is greater than a CSI-RS threshold; and

transmit a random access preamble to the target base station by using the contention-free random access resource after determining that the CSI-RSRP is greater than the CSI-RS threshold.

20 . The UE of claim 19 , wherein the processing circuitry is further configured to:

determining that the CSI-RSRP is not greater than the CSI-RS threshold;

determine whether a Synchronization Signal (SS)-RSRP of a second SSB associated with a contention-based random access resource is greater than an SS-RSRP threshold; and

transmit a random access preamble by using any SSB with a common random access resource after determining that the SS-RSRP is not greater than the SS-RSRP threshold.