A wireless communications system (100) configured to use a predetermined bandwidth of unlicensed bandwidth, the wireless communications system (100) comprising: a base station (110) configured to transmit a control signal including information that indicates an offset value from a reference timing (301) to a transmission start timing (305) or a carrier sensor start timing (303); and a terminal (120, 130) configured to: receive the control signal; determining, according to the offset value, the transmission start timing (305) at which the terminal (120, 130) should start transmitting a signal, or the carrier sensor start timing (303); performing a process of detecting a wireless signal of the predetermined bandwidth in a predetermined period (304) from the carrier sensor start timing (303) to the transmission start timing (305); and transmitting the signal at the transmission start timing (305), when no wireless signal of the predetermined bandwidth is detected in the predetermined period (304).