A method of a master base station, BS (300;700;800), in a wireless communication system in which BSs having different size cells coexist, the method comprising: receiving, from at least one other BS (310,312;710,712;810), load information of the at least one other BS (310,312;710,712;810); determining a secondary BS (310;710,712), from which a terminal (320, 321, 322; 720, 721, 722, 723) can receive a signal, among the at least one other BS (310,312;710,712;810) based on load information of the at least one other BS (310,312;710,712;810); transmitting, to the terminal (320, 321, 322; 720, 721, 722, 723), information requesting for an access of the terminal (320, 321, 322; 720, 721, 722, 723) to the secondary BS (310;710,712); receiving, from the terminal (320, 321, 322; 720, 721, 722, 723), first channel state information of a channel between the master BS (300;700;800) and the terminal (320, 321, 322; 720, 721, 722, 723), and second channel state information of a channel between the secondary BS (310;710,712) and the terminal (320, 321, 322; 720, 721, 722, 723) after accessing the terminal (320, 321, 322; 720, 721, 722, 723) to the secondary BS (310;710,712); determining a resource distribution ratio of resources of the master BS (300;700;800) and resources of the secondary BS (310;710,712) based on the first channel state information and the second channel state information); determining a first amount of data and a second amount of data based on the resource distribution ratio; transmitting, to the terminal (320, 321, 322; 720, 721, 722, 723), the first amount of data by using the resources of the master BS (300;700;800); and controlling the secondary BS (310;710,712) to transmit the second amount of data by using the resources of the secondary BS (310;710,712). receiving, from at least one other BS (310,312;710,712;810), load information of the at least one other BS (310,312;710,712;810); determining a secondary BS (310;710,712), from which a terminal (320, 321, 322; 720, 721, 722, 723) can receive a signal, among the at least one other BS (310,312;710,712;810) based on load information of the at least one other BS (310,312;710,712;810); transmitting, to the terminal (320, 321, 322; 720, 721, 722, 723), information requesting for an access of the terminal (320, 321, 322; 720, 721, 722, 723) to the secondary BS (310;710,712); receiving, from the terminal (320, 321, 322; 720, 721, 722, 723), first channel state information of a channel between the master BS (300;700;800) and the terminal (320, 321, 322; 720, 721, 722, 723), and second channel state information of a channel between the secondary BS (310;710,712) and the terminal (320, 321, 322; 720, 721, 722, 723) after accessing the terminal (320, 321, 322; 720, 721, 722, 723) to the secondary BS (310;710,712); determining a resource distribution ratio of resources of the master BS (300;700;800) and resources of the secondary BS (310;710,712) based on the first channel state information and the second channel state information); determining a first amount of data and a second amount of data based on the resource distribution ratio; transmitting, to the terminal (320, 321, 322; 720, 721, 722, 723), the first amount of data by using the resources of the master BS (300;700;800); and controlling the secondary BS (310;710,712) to transmit the second amount of data by using the resources of the secondary BS (310;710,712). <EOS>