A base station for a frequency division duplex communications system, comprising: a processing module, configured to determine, according to downlink radio resource usage, a special timeslot in a frequency range used for downlink data transmission, wherein a downlink frequency resource in the special timeslot is used to transmit an uplink physical signal; a sending module, configured to send special-timeslot configuration information to user equipment, wherein the special-timeslot configuration information is used to instruct the user equipment to send the uplink physical signal over a downlink frequency band in the special timeslot; and a receiving module, configured to: receive, over the downlink frequency band in the special timeslot, the uplink physical signal sent by the user equipment, and, to obtain channel state information, perform channel estimation according to the uplink physical signal; characterized in that the special-timeslot configuration information further comprises first sub-frequency resource indication information, the first sub-frequency resource indication information is used to indicate a first sub-frequency resource occupied when the user equipment sends the uplink physical signal in the special timeslot, and the first sub-frequency resource is a part of frequency resources indicated by frequency resource indication information comprised in the special-timeslot configuration information wherein the first sub-frequency resource and at least one other sub-frequency resource occupied when at least one other user equipment sends an uplink physical signal are arranged in a combing structure. a frequency division duplex communications system, comprising: a processing module, configured to determine, according to downlink radio resource usage, a special timeslot in a frequency range used for downlink data transmission, wherein a downlink frequency resource in the special timeslot is used to transmit an uplink physical signal; a sending module, configured to send special-timeslot configuration information to user equipment, wherein the special-timeslot configuration information is used to instruct the user equipment to send the uplink physical signal over a downlink frequency band in the special timeslot; and a receiving module, configured to: receive, over the downlink frequency band in the special timeslot, the uplink physical signal sent by the user equipment, and, to obtain channel state information, perform channel estimation according to the uplink physical signal; a processing module, configured to determine, according to downlink radio resource usage, a special timeslot in a frequency range used for downlink data transmission, wherein a downlink frequency resource in the special timeslot is used to transmit an uplink physical signal; a sending module, configured to send special-timeslot configuration information to user equipment, wherein the special-timeslot configuration information is used to instruct the user equipment to send the uplink physical signal over a downlink frequency band in the special timeslot; and a receiving module, configured to: receive, over the downlink frequency band in the special timeslot, the uplink physical signal sent by the user equipment, and, to obtain channel state information, perform channel estimation according to the uplink physical signal; characterized in that the special-timeslot configuration information further comprises first sub-frequency resource indication information, the first sub-frequency resource indication information is used to indicate a first sub-frequency resource occupied when the user equipment sends the uplink physical signal in the special timeslot, and the first sub-frequency resource is a part of frequency resources indicated by frequency resource indication information comprised in the special-timeslot configuration information wherein the first sub-frequency resource and at least one other sub-frequency resource occupied when at least one other user equipment sends an uplink physical signal are arranged in a combing structure.