APPARATUS AND METHOD FOR CONTROLLING HANDOVER TO PREVENT FEMTOCELL INTERFERENCE

1 . A method for controlling handover in a communication network where a first cell is overlapped with a plurality of second cells, the method comprising:

receiving a request of inter-cell handover from a first cell base station of the first cell to a second cell base station of one of the second cells; and

performing an inter-frequency handover in response to the request of the inter-cell handover.

2 . The method of claim 1 , wherein user equipment makes the request of inter-cell handover when the user equipment in a traffic state enters into the one of the second cells.

3 . The method of claim 1 , wherein the receiving a request of inter-cell handover includes:

determining whether the second cells are femtocells,

wherein, if the second cells are femtocells, performing the inter-frequency handover.

4 . The method of claim 3 , further comprising:

performing the inter-cell handover from the first cell base station to the second cell base station when the second cells are macrocells.

5 . The method of claim 1 , wherein the receiving a request of inter-cell handover includes:

determining whether a first frequency used by the first cell base station is equivalent to a second frequency assigned to the second cell base station, and, if so,

performing the inter-frequency handover.

6 . The method of claim 5 , further comprising:

performing the inter-cell handover from the first cell base station to the second cell base station when the first frequency is different from the second frequency.

7 . The method of claim I, wherein the performing the inter-frequency handover in response to the request of the inter-cell handover includes:

selecting an unshared frequency; and

performing the inter-frequency handover to the selected unshared frequency,

wherein the unshared frequency is a frequency unassigned to the one of the second cells.

8 . The method of claim 7 , wherein, in the selecting an unshared frequency:

a frequency having load less than a given load level and quality higher than a given quality level is selected from frequencies assigned to the first cell and unassigned to the second cells.

9 . The method of claim 1 , wherein, after performing the inter-frequency handover, coupling user equipment to the first cell base station using the selected unshared frequency.

10 . A method for controlling handover in a communication network where a macrocell is overlapped with a plurality of femtocells, the method comprising:

transmitting a measurement control message to user equipment when the user equipment in a traffic state enters from the macrocell to one of the femtocells;

receiving a measurement report message from the user equipment;

determining whether the measurement report message includes a request of inter-cell handover from a macrocell base station of the macrocell to a femtocell base station of the one of the femtocells;

selecting an unshared frequency from unshared frequencies assigned to a macrocell base station of the macrocell and unassigned to a femtocell base station of the one of the femtocells when the measurement report message includes the request of inter-cell handover from the macrocell to the one of the femtocells; and

performing inter-frequency handover based on the selected unshared frequency in response to the request of the inter-cell handover.

11 . The method of claim 10 , further comprising:

performing the inter-cell handover from the macrocell to another macrocell when the measurement report message includes a request of inter-cell handover from the macrocell to another macrocell.

12 . The method of claim 11 , further comprising:

determining whether a first frequency used by the macrocell base station is equivalent to a second frequency assigned to the femtocell base station;

performing an inter-cell handover from the macrocell base station to the femtocell base station when the first frequency is different from the second frequency; and

performing the inter-frequency handover using the unshared frequency when the first frequency is equivalent to the second frequency.

13 . An apparatus for controlling handover in a communication network where a first cell is overlapped with a plurality of second cells, the apparatus comprising:

an event receiving module configured to receive a control message from user equipment;

a handover determining module configured to analyze the received control message and determine whether the control message includes a request of inter-cell handover from a first cell base station of the first cell to a second cell base station of one of the second cells; and

an inter-frequency processing module configured to perform inter-frequency handover using an unshared frequency when the handover determining module determines that the control message includes the request of inter-cell handover.

14 . The apparatus of claim 13 , wherein the event receiving module receives the control message when the user equipment in a traffic state enters the one of the second cells.

15 . The apparatus of claim 13 , wherein:

the handover determining module determines whether or not the second cell base station is a femtocell base station; and

the inter-frequency processing module performs the inter-frequency handover when the second cell base station is the femtocell base station.

16 . The apparatus of claim 15 , further comprising:

an inter-cell handover processing module configured to perform an inter-cell handover when the handover determining module determines that the second base station is a macrocell base station.

17 . The apparatus of claim 13 , wherein:

the handover determining module determines whether or not a first frequency used by the first cell base station is equivalent to a second frequency assigned to the second cell base station; and

the inter-frequency processing module performs the inter-frequency handover when the first frequency is equivalent to the second frequency,

18 . The apparatus of claim 17 , further comprising:

an inter-cell handover processing module configured to perform an inter-cell handover when the first frequency is different from the second frequency.

19 . The apparatus of claim 13 , wherein the handover determining module includes:

a frequency selector configured to select the unshared frequency from frequencies assigned to the first cell base station and un assigned to the second cell base station,

wherein a frequency having load less than a given load level and quality higher than a given quality level is selected from the frequencies, as the unshared frequency.

20 . The apparatus of claim 13 , wherein, after performing the inter-frequency handover, the user equipment is coupled to the first cell base station using the unshared frequency.