Apparatus and method for controlling handover to prevent femtocell interference

Abstract

Provided are apparatus and method for controlling handover to prevent femtocell interference. The apparatus may include an event receiving module, a handover determining module, and an inter-frequency processing module. The event receiving module may be configured to receive a control message from user equipment. The handover determining module may be 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. The inter-frequency processing module may be 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.

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.