Method and apparatus for conditional handover in network

1 . A user equipment (UE) for wireless communication, comprising:

at least one memory; and

at least one processor coupled with the at least one memory and configured to cause the UE to:

receive, from a serving cell, a conditional handover (CHO) configuration and at least an associated CHO execution condition for a candidate cell, the associated CHO execution condition including one or more time-based conditions and one or more measurement-based conditions;

evaluate the associated CHO execution condition, wherein evaluating the associated CHO execution condition comprises evaluating a measurement-based condition of the one or more measurement-based conditions based on a time-based condition of the one or more time-based conditions, and wherein the time-based condition is fulfilled based on a threshold for a beginning of a time range being met; and

determine whether to execute a CHO based on the evaluation.

2 . The UE of claim 1 , wherein a time-based condition of the one or more time-based conditions includes a first timer, and the one or more measurement-based conditions includes a first measurement-based condition, wherein the time-based condition is fulfilled in response to expiry of the first timer and the at least one processor is configured to cause the UE to:

one or more of declare a radio link failure (RLF) or receive a handover command;

access a target cell; and

transmit at least one of:

an indication to indicate whether the first timer expires when the RLF occurs;

an indication to indicate whether the first timer expires when receiving the handover command;

an indication to indicate whether the first measurement-based condition is met;

an indication to indicate whether the first measurement-based condition is met before the first timer runs in response to the first measurement-based condition being met;

an indication to indicate whether the first measurement-based condition is met while the first timer runs in response to the first measurement-based condition being met;

an indication to indicate whether the first measurement-based condition is met after the first timer expiry in response to the first measurement-based condition being met; or

an indication to indicate time information associated with that the first measurement-based condition is met.

3 . The UE of claim 1 , wherein the one or more measurement-based conditions includes a second measurement-based condition, and a time-based condition of the one or more time-based conditions includes at least a first second threshold of a starting time, a third threshold of an end time, and wherein the time-based condition is fulfilled in response to that a current time is between the starting time and the end time, and the at least one processor is configured to cause the UE to:

one or more of declare a radio link failure (RLF) or receive a handover command;

access a target cell; and

transmit at least one of:

an indication to indicate whether the RLF occurs before, within, or after a time range determined by the starting time and the end time;

an indication to indicate whether reception of the handover command occurs before, within, or after the time range;

an indication to indicate whether the second measurement-based condition is met;

an indication to indicate whether the second measurement-based condition is met before the time range in response to the second measurement-based condition being met; or

an indication to indicate time information associated with that the second measurement-based condition is met.

4 . The UE of claim 1 , wherein the time-based condition comprises:

the threshold for the beginning of the time range; and

a value of the time range, wherein the time-based condition is fulfilled in response to that a current time is within the time range.

5 . The UE of claim 4 , wherein the at least one processor is configured to cause the UE to one or more of:

start to evaluate the measurement-based condition in response to the threshold for the beginning of the time range being met; or

start to evaluate the measurement-based condition at an offset value ahead of the beginning of the time range.

6 . The UE of claim 5 , wherein the at least one processor is configured to cause the UE to:

determine, in response to the time-based condition being fulfilled, whether the measurement-based condition is fulfilled within the time range; and

initiate the CHO in response to the measurement-based condition being fulfilled within the time range.

7 . The UE of claim 5 , wherein the at least one processor is configured to cause the UE to, in response to the measurement-based condition being unfulfilled within the time range:

stop evaluation of the measurement-based condition; or

release the associated CHO execution condition.

8 . The UE of claim 1 , wherein the one or more measurement-based conditions includes a third measurement-based condition, and a time-based condition of the one or more time-based conditions comprises:

a second timer; and

a third timer, wherein the time-based condition is fulfilled in response to expiry of the second timer and the third timer running.

9 . The UE of claim 8 , wherein the at least one processor is configured to cause the UE to start the second timer in response to receiving the CHO configuration and the associated CHO execution condition.

10 . The UE of claim 9 , wherein the at least one processor is configured to cause the UE to:

start, in response to the second timer expiry, the third timer; and

in response to the second timer expiry or in response to starting the third timer, one or more of start to evaluate the third measurement-based condition or start to evaluate the third measurement-based condition at an offset value ahead of the second timer expiry.

11 . The UE of claim 10 , wherein the at least one processor is configured to cause the UE to:

determine, in response to the time-based condition being fulfilled, whether the third measurement-based condition is fulfilled before the third timer expires; and

initiate the CHO in response to the third measurement-based condition being fulfilled before the third timer expires.

12 . The UE of claim 4 , wherein the at least one processor is configured to cause the UE to:

one or more of declare a radio link failure (RLF) or receive a handover command;

access a target cell; and

transmit at least one of:

an indication to indicate whether the RLF occurs before, within, or after the time range;

an indication to indicate whether reception of the handover command occurs before, within, or after the time range;

an indication to indicate whether the measurement-based condition is met;

an indication to indicate whether the measurement-based condition is met before the time range in response to the measurement-based condition being met; or

an indication to indicate time information associated with that the measurement-based condition is met.

13 . The UE of claim 8 , wherein the at least one processor is configured to cause the UE to:

one or more of declare a radio link failure (RLF) or receive a handover command;

access a target cell; and

transmit at least one of:

a state of the second timer and the third timer when the RLF or reception of the handover command occurs;

an indication to indicate whether the third measurement-based condition is met;

a state of the second timer and the third timer when the third measurement-based condition is met in response to the third measurement-based condition being met; or

an indication to indicate time information associated with that the third measurement-based condition is met.

14 . The UE of claim 11 , wherein the at least one processor is configured to cause the UE to:

in response to the third measurement-based condition being unfulfilled before the third timer expires, one or more of stop evaluation of the third measurement-based condition or release the CHO execution condition.

15 . A method performed by a user equipment (UE), the method comprising:

receiving, from a serving cell, a conditional handover (CHO) configuration and at least an associated CHO execution condition for a candidate cell, the associated CHO execution condition including one or more time-based conditions and one or more measurement-based conditions;

evaluating the associated CHO execution condition, wherein evaluating the associated CHO execution condition comprises evaluating a measurement-based condition of the one or more measurement-based conditions based on a time-based condition of the one or more time-based conditions, and wherein the time-based condition is fulfilled based on a threshold for a beginning of a time range being met; and

determining whether to execute a CHO based on the evaluation.

16 . A user equipment (UE) for wireless communication, comprising:

at least one memory; and

at least one processor coupled with the at least one memory and configured to cause the UE to:

receive, from a serving cell, a conditional handover (CHO) configuration and associated CHO execution condition for a candidate cell, the associated CHO execution condition including at least a time-based condition, the time-based condition including a first timer and a first measurement-based condition, and the time-based condition being fulfilled in response to expiry of the first timer;

start the first timer in response to reception of the CHO configuration and the associated CHO execution condition;

evaluate the first measurement-based condition in response to the time-based condition being fulfilled, wherein the time-based condition is fulfilled based on a threshold for a beginning of a time range being met; and

determine whether to execute a CHO at least according to a state of the associated CHO execution condition.

17 . A method performed by a user equipment (UE), the method comprising:

receiving, from a serving cell, a conditional handover (CHO) configuration and associated CHO execution condition for a candidate cell, the associated CHO execution condition including at least a time-based condition, the time-based condition including a first timer and a first measurement-based condition, and the time-based condition being fulfilled in response to expiry of the first timer;

starting the first timer in response to reception of the CHO configuration and the associated CHO execution condition;

evaluating the first measurement-based condition in response to the time-based condition being fulfilled, wherein the time-based condition is fulfilled based on a threshold for a beginning of a time range being met; and

determining whether to execute a CHO at least according to a state of the associated CHO execution condition.

18 . The method of claim 15 , wherein a time-based condition of the one or more time-based conditions includes a first timer, and the one or more measurement-based conditions includes a first measurement-based condition, wherein the time-based condition is fulfilled in response to expiry of the first timer, and further comprising:

one or more of declaring a radio link failure (RLF) or receiving a handover command;

accessing a target cell; and

transmitting at least one of:

an indication to indicate whether the first timer expires when the RLF occurs;

an indication to indicate whether the first timer expires when receiving the handover command;

an indication to indicate whether the first measurement-based condition is met;

an indication to indicate whether the first measurement-based condition is met before the first timer runs in response to the first measurement-based condition being met;

an indication to indicate whether the first measurement-based condition is met while the first timer runs in response to the first measurement-based condition being met;

an indication to indicate whether the first measurement-based condition is met after the first timer expiry in response to the first measurement-based condition being met; or

an indication to indicate time information associated with that the first measurement-based condition is met.

19 . The method of claim 15 , wherein the one or more measurement-based conditions includes a second measurement-based condition, and a time-based condition of the one or more time-based conditions includes at least a second threshold of a starting time, a third threshold of an end time, and wherein the time-based condition is fulfilled in response to that a current time is between the starting time and the end time, and further comprising:

one or more of declaring a radio link failure (RLF) or receiving a handover command;

accessing a target cell; and

transmitting at least one of:

an indication to indicate whether the RLF occurs before, within, or after a time range determined by the starting time and the end time;

an indication to indicate whether reception of the handover command occurs before, within, or after the time range;

an indication to indicate whether the second measurement-based condition is met;

an indication to indicate whether the second measurement-based condition is met before the time range in response to the second measurement-based condition being met; or

an indication to indicate time information associated with that the second measurement-based condition is met.

20 . The method of claim 15 , wherein the time-based condition comprises:

the threshold for the beginning of the time range; and

a value of the time range, wherein the time-based condition is fulfilled in response to that a current time is within the time range.