A method of determining and configuring a maximal clear channel assessment (CCA) duration based on channel loading information for frame-based equipment (FBE) listen before talk (LBT) channel access mechanism is proposed. The CCA period is a random CCA duration generated out of the maximal CCA duration, which is configurable and is carried in the radio resource control (RRC) signaling or the beacon signal of LAA. To solve the collision problem in synchronous network and the unfairness problem in asynchronous network, the maximal duration of CCA should be adaptive based on the experienced channel occupancy status and/or the experienced synchronization difference within the network. First, the maximal duration of CCA should be adjusted according to the channel loading. Second, the maximal duration of CCA should be larger than the timing difference between eNBs or between UEs.