The disclosure relates to a communication method and system for converging a 5G communication system for supporting higher data rates beyond a 4G system with a technology for IoT. The disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method of operating a BS includes monitoring a channel for a plurality of subbands, based on a first contention window configured in each of the plurality of subbands; transmitting a downlink signal to a terminal, based on a result of the monitoring; obtaining, from the terminal, a transmission result of the downlink signal for a reference duration; and determining a second contention window for monitoring a next channel for the plurality of subbands, based on the obtained transmission result.