Handover control method

1. A handover control method for performing conditional handover of user equipment from a source cell to which the user equipment is connected to a target cell, the handover control method comprising:

receiving, by the user equipment, from the source cell, a handover command including identifiers of a plurality of candidate cells being candidates for the target cell; and

transmitting, by the user equipment, a report message including information related to a connection failure detected when connecting to the source cell, to a cell to which the user equipment connects after the connection failure, wherein

the report message includes the identifiers of all the candidate cells included in the handover command.

2. The handover control method according to claim 1 , wherein:

the handover command includes at least one of trigger condition from among a plurality of trigger conditions for triggering the handover,

each of the trigger conditions includes an event identifier indicating a predetermined event for triggering the handover and a duration for which a state with the predetermined event satisfied is to be maintained to trigger the handover, and

the method further comprises, in a case where the trigger conditions for two or more candidate cells of the plurality of candidate cells are satisfied, selecting, by the user equipment, from among the two or more candidate cells, a candidate cell to be accessed by the user equipment.

3. A user equipment comprising:

circuitry including a processor and a memory, wherein the circuitry is configured to:

receive, from a source cell, a handover command including identifiers of a plurality of candidate cells being candidates for a target cell; and

transmit a report message including information related to a connection failure detected when connecting to the source cell, to a cell to which the user equipment connects after the connection failure, wherein

the report message includes the identifiers of all the candidate cells included in the handover command.

4. A chipset for controlling a user equipment configured to conditional handover from a source cell to which the user equipment is connected to a target cell, the chipset comprising:

a processor and a memory coupled to the processor, the processor configured to execute processes of:

receiving, by the user equipment, from the source cell, a handover command including identifiers of a plurality of candidate cells being candidates for the target cell; and

transmitting, by the user equipment, a report message including information related to a connection failure detected when connecting to the source cell, to a cell to which the user equipment connects after the connection failure, wherein

the report message includes the identifiers of all the candidate cells included in the handover command.

5. The handover control method according to claim 1 , wherein the report message includes time information related to a time of detection of the connection failure.

6. The user equipment according to claim 3 , wherein the report message includes time information related to a time of detection of the connection failure.

7. The chipset according to claim 4 , wherein the report message includes time information related to a time of detection of the connection failure.

8. The user equipment according to claim 3 , wherein:

the handover command includes at least one of trigger condition from among a plurality of trigger conditions for triggering the handover,

each of the trigger conditions includes an event identifier indicating a predetermined event for triggering the handover and a duration for which a state with the predetermined event satisfied is to be maintained to trigger the handover, and

the circuitry is further configured to, in a case where the trigger conditions for two or more candidate cells of the plurality of candidate cells are satisfied, select, by the user equipment, from among the two or more candidate cells, a candidate cell to be accessed by the user equipment.

9. The chipset according to claim 4 , wherein:

the handover command includes at least one of trigger condition from among a plurality of trigger conditions for triggering the handover,

each of the trigger conditions includes an event identifier indicating a predetermined event for triggering the handover and a duration for which a state with the predetermined event satisfied is to be maintained to trigger the handover, and

the processor is further configured to execute the processes of, in a case where the trigger conditions for two or more candidate cells of the plurality of candidate cells are satisfied, selecting, by the user equipment, from among the two or more candidate cells, a candidate cell to be accessed by the user equipment.

10. A non-transitory computer-readable medium comprising, stored thereupon, computer program instructions for execution by a user equipment, the program instructions being configured to cause the user equipment to execute processing of:

receiving, from a source cell, a handover command including identifiers of a plurality of candidate cells being candidates for a target cell; and

transmitting a report message including information related to a connection failure detected when connecting to the source cell, to a cell to which the user equipment connects after the connection failure, wherein

the report message includes the identifiers of all the candidate cells included in the handover command.

11. A system comprising:

a user equipment configured to:

receive, from a source cell, a handover command including identifiers of a plurality of candidate cells being candidates for a target cell; and

transmit a report message including information related to a connection failure detected when connecting to the source cell, to a cell to which the user equipment connects after the connection failure, wherein

the report message includes the identifiers of all the candidate cells included in the handover command.