The present invention provides a base station, UE and method for implementing LBT by using a mobile communications system. Contention time periods are classified according to uplink and downlink transmission segments, and it is specified that a UE only contends for unlicensed spectra in an uplink time period and a base station only contends for unlicensed spectra in a downlink time period, so that a LBT mechanism can be more effectively used in a mobile communications system in which uplink time periods and downlink time periods are independent. In addition, embodiments of the present invention also provide a base station, UE and method for implementing LBT by using a mobile communications system. After a base or a UE occupies a channel, whether a carrier signal sent by another base station exists in the channel is detected in a conflict detection timeslot by determining the conflict detection timeslot, and whether signals continue to be sent subsequently according to the monitoring result, thereby reducing the probability that channel occupation conflicts occur among multiple base stations and multiple UEs.