An operation method of a terminal for initial access in a communication system may comprise: receiving a plurality of SSBs having different indexes through a plurality of antennas included in a base station; calculating a channel capacity using the plurality of SSBs; feeding back, to the base station, index(es) of one or more SSBs for having a maximum channel capacity among the plurality of SSBs; and performing communication with the base station through a combination of two or more antennas that have transmitted the one or more SSBs for having the maximum channel capacity among the plurality of antennas.