A wireless device determines a reference duration for contention window adjustment. The reference duration is from a beginning of a channel occupancy and until an end of a first slot where at least one physical uplink shared channel (PUSCH) is transmitted. The wireless device determines a contention window value based on one or more new data indicators (NDIs) of one or more first transport blocks transmitted during the reference duration. The wireless device performs a listen before talk (LBT) procedure based on the contention window value. The wireless device transmits one or more second transport blocks based on the LBT procedure indicating a clear channel.