Terminal for performing measurement operation for handover, communication system including the same, and operation methods thereof

1. A method of operating a terminal, the method comprising:

receiving, from a source cell, a radio resource control (RRC) reconfiguration message including a list of a plurality of first objects in a measurement order;

reordering the list of the plurality of first objects based on handover information to obtain a reordered list, the handover information corresponding to a connection history of the terminal;

sequentially measuring the plurality of first objects based on the reordered list to obtain a measurement result; and

transmitting a measurement report to the source cell based on the measurement result, wherein

the handover information includes first priorities of a plurality of second objects corresponding to a plurality of cells to which the terminal was previously connected within a period of time,

the first priorities of the plurality of second objects are determined such that a second object corresponding to a cell among the plurality of cells to which the terminal connected more recently is assigned a higher priority, and

the handover information includes second priorities of the plurality of second objects, the second priorities of the plurality of second objects are determined such that a second object corresponding to a cell among the plurality of cells of which a higher electric field strength has been measured by the terminal is assigned a higher priority.

2. The method of claim 1 , wherein the reordering the list of the plurality of first objects comprises reordering the list of the plurality of first objects based on the first priorities of one or more of the plurality of second objects corresponding to one or more of the plurality of first objects.

3. The method of claim 1 , wherein the handover information includes network coverage-specific priorities of the plurality of second objects.

4. The method of claim 1 , wherein the sequentially measuring the plurality of first objects comprises:

measuring a plurality of electric field strengths of a plurality of frequency bands respectively corresponding to the plurality of first objects in an order based on the reordered list;

comparing the electric field strengths to obtain a comparison result; and

controlling a time to trigger (TTT) timer based on the comparison result.

5. The method of claim 4 , wherein

the plurality of electric field strengths includes a first electric field strength and a second electric field strength, and the plurality of first objects includes a currently measured object and a previously measured object; and

the controlling the TTT timer comprises resetting the TTT timer in response to determining the first electric field strength corresponding to the currently measured object is greater than the second electric field strength corresponding to the previously measured object, the TTT timer corresponding to the previously measured object.

6. The method of claim 1 , wherein the measurement result corresponds to one of the plurality of first objects, the one of the plurality of first objects corresponding to an expired TTT timer.

7. The method of claim 1 , further comprising:

collecting the connection history of the terminal; and

updating the handover information based on the collected connection history.

8. The method of claim 1 , wherein the sequentially measuring comprises:

measuring a first electric field strength of a first measured object among the plurality of first objects;

measuring at least one second electric field strength of at least one second measured object among the plurality of first objects, the at least one second measured object being ordered after the first measured object on the reordered list, and the at least one second electric field strength being measured within a time period after the measuring the first electric field strength; and

determining the measurement result to correspond to the first electric field strength based on,

the first electric field strength being greater than a first threshold, and

the first electric field strength being greater than the at least one second electric field strength.

9. The method of claim 1 , wherein the sequentially measuring comprises:

measuring a first electric field strength of a first measured object among the plurality of first objects;

measuring at least one second electric field strength of at least one second measured object among the plurality of first objects, the at least one second measured object being ordered after the first measured object on the reordered list, and the at least one second electric field strength being greater than the first electric field strength; and

determining the measurement result to correspond to the first electric field strength based on the first electric field strength exceeding a reference value.

10. The method of claim 1 , wherein each of the plurality of first objects corresponds to:

a respective cell; and

a respective frequency of the respective cell.

11. A terminal comprising:

a memory storing handover information indicating a connection history; and

processing circuitry configured to,

reorder a list of a plurality of first objects based on the connection history to obtain a reordered list in response to a radio resource control (RRC) reconfiguration message from a source cell, the RRC reconfiguration message including the list of the plurality of first objects in a measurement order,

measure a plurality of electric field strengths corresponding to the plurality of first objects in order of the first objects in the reordered list to obtain a measurement result, and

transmit a measurement report to the source cell based on the measurement result,

wherein

the plurality of electric field strengths include a currently measured electric field strength and a previously measured electric field strength, and

the processing circuitry is configured to control resetting of a time to trigger (TTT) timer before the TTT timer expires in response to determining that the currently measure electric field strength is higher that the previously measure electric field strength, the TTT timer corresponding to the previously measure electric field strength.

12. The terminal of claim 11 , wherein the handover information includes priorities of a plurality of second objects corresponding to a plurality of cells to which the terminal was previously connected within a period of time.

13. The terminal of claim 12 , wherein the processing circuitry is configured to reorder the list of the plurality of first objects based on the priorities of one or more of the plurality of second objects corresponding to one or more of the plurality of first objects.

14. The terminal of claim 11 , wherein the processing circuitry is configured to control resetting of the TTT timer to suspend the resetting of the TTT timer in response to determining the previously measured electric field strength is greater than a reference value.

15. The terminal of claim 11 , wherein the processing circuitry is configured to measure the plurality of electric field strengths including:

measuring a first electric field strength of a first measured object among the plurality of first objects;

measuring at least one second electric field strength of at least one second measured object among the plurality of first objects, the at least one second measured object being ordered after the first measured object on the reordered list, and the at least one second electric field strength being measured within a time period after the measuring the first electric field strength; and

determining the measurement result to correspond to the first electric field strength based on,

the first electric field strength being greater than a first threshold, and

the first electric field strength being greater than the at least one second electric field strength.

16. A communication system comprising:

a source cell configured to transmit, to a first terminal, a radio resource control (RRC) reconfiguration message including a list of a plurality of first objects in a measurement order; and

the first terminal configured to,

reorder the list of the plurality of first objects based on first handover information to obtain a first reordered list, the first handover information indicating a connection history of the first terminal, and

measure a plurality of electric field strengths of a plurality of second objects among the plurality of first objects based on the first reordered list, and wherein the first terminal is configured to:

start a plurality of time to trigger (TTT) timers corresponding to a plurality of third objects among the plurality of first objects, the plurality of third objects corresponding to respective electric field strengths among the plurality of electric field strengths greater than a threshold, the plurality of TTT timers being started in an order in which the respective electric field strengths are measured,

compare the respective electric field strengths of the plurality of third objects to obtain a comparison result, and

reset one or more of the plurality of TTT timers based on the comparison result.

17. The communication system of claim 16 , further comprising

a second terminal connected to the source cell, the second terminal being configured to,

reorder the list of the plurality of first objects based on second handover information to obtain a second reordered list, the second handover information indicating a connection history of the second terminal, and

measure a plurality of electric field strengths of a plurality of fourth objects among the plurality of first objects based on the second reordered list.

18. The communication system of claim 17 , wherein at least one of the plurality of second objects is different from at least one of the plurality of fourth objects.