A base station, characterized by comprising: an uplink receiving module (512, 613, 714), configured to receive uplink data that is sent by user equipment in a specified multiple-access manner on a time-frequency resource corresponding to the specified multiple-access manner, wherein the specified multiple-access manner is selected by the user equipment from at least two multiple-access manners according to a predetermined condition; and a downlink sending module (514, 615, 716), configured to send downlink data to the user equipment in a corresponding multiple-access manner on a time-frequency resource corresponding to the corresponding multiple-access manner, wherein the corresponding multiple-access manner is obtained by searching the at least two multiple-access manners according to a prestored correspondence and is associated with the specified multiple-access manner received by the uplink receiving module (512, 613, 716), wherein the at least two multiple-access manners comprise at least two of a first multiple-access manner, a second multiple-access manner, and a third multiple-access manner, the first multiple-access manner is an Orthogonal Frequency Division Multiple Access, OFDMA, multiple-access manner or a Single-carrier Frequency-Division Multiple Access, SC-FDMA, multiple-access manner, the second multiple-access manner is an OFDMA+Code Division Multiple Access, CDMA, multiple-access manner or an SC-FDMA+CDMA multiple-access manner, and the third multiple-access manner is an OFDMA+Interleaver-Division Multiple Access, IDMA, multiple-access manner or an SC-FDMA+IDMA multiple-access manner. an uplink receiving module (512, 613, 714), configured to receive uplink data that is sent by user equipment in a specified multiple-access manner on a time-frequency resource corresponding to the specified multiple-access manner, wherein the specified multiple-access manner is selected by the user equipment from at least two multiple-access manners according to a predetermined condition; and a downlink sending module (514, 615, 716), configured to send downlink data to the user equipment in a corresponding multiple-access manner on a time-frequency resource corresponding to the corresponding multiple-access manner, wherein the corresponding multiple-access manner is obtained by searching the at least two multiple-access manners according to a prestored correspondence and is associated with the specified multiple-access manner received by the uplink receiving module (512, 613, 716), wherein the at least two multiple-access manners comprise at least two of a first multiple-access manner, a second multiple-access manner, and a third multiple-access manner, the first multiple-access manner is an Orthogonal Frequency Division Multiple Access, OFDMA, multiple-access manner or a Single-carrier Frequency-Division Multiple Access, SC-FDMA, multiple-access manner, the second multiple-access manner is an OFDMA+Code Division Multiple Access, CDMA, multiple-access manner or an SC-FDMA+CDMA multiple-access manner, and the third multiple-access manner is an OFDMA+Interleaver-Division Multiple Access, IDMA, multiple-access manner or an SC-FDMA+IDMA multiple-access manner.