A data transmission method, comprising: sending, by a sender device, to-be-transmitted data to a receiver device according to a transmission policy, wherein the to-be-transmitted data is data carried by a subframe that is after a guard interval of a last radio frame in a first scheduling window; and receiving, by the sender device, feedback information sent by the receiver device; wherein: the transmission policy is setting a feedback time length of feedback information of the to-be-transmitted data to be greater than a time length of a contention window between the first scheduling window and a third scheduling window, wherein the third scheduling window is the first scheduling window after the first scheduling window; the sending, by a sender device, to-be-transmitted data to a receiver device according to a transmission policy comprises: sending, by the sender device, the to-be-transmitted data in the last radio frame in the first scheduling window according to the transmission policy; and the receiving, by the sender device, feedback information sent by the receiver device comprises: receiving, by the sender device, the feedback information sent by the receiver device in a radio frame in the third scheduling window. sending, by a sender device, to-be-transmitted data to a receiver device according to a transmission policy, wherein the to-be-transmitted data is data carried by a subframe that is after a guard interval of a last radio frame in a first scheduling window; and receiving, by the sender device, feedback information sent by the receiver device; wherein: the transmission policy is setting a feedback time length of feedback information of the to-be-transmitted data to be greater than a time length of a contention window between the first scheduling window and a third scheduling window, wherein the third scheduling window is the first scheduling window after the first scheduling window; the sending, by a sender device, to-be-transmitted data to a receiver device according to a transmission policy comprises: sending, by the sender device, the to-be-transmitted data in the last radio frame in the first scheduling window according to the transmission policy; and the receiving, by the sender device, feedback information sent by the receiver device comprises: receiving, by the sender device, the feedback information sent by the receiver device in a radio frame in the third scheduling window. the transmission policy is setting a feedback time length of feedback information of the to-be-transmitted data to be greater than a time length of a contention window between the first scheduling window and a third scheduling window, wherein the third scheduling window is the first scheduling window after the first scheduling window; the sending, by a sender device, to-be-transmitted data to a receiver device according to a transmission policy comprises: sending, by the sender device, the to-be-transmitted data in the last radio frame in the first scheduling window according to the transmission policy; and the receiving, by the sender device, feedback information sent by the receiver device comprises: receiving, by the sender device, the feedback information sent by the receiver device in a radio frame in the third scheduling window. sending, by the sender device, the to-be-transmitted data in the last radio frame in the first scheduling window according to the transmission policy; and the receiving, by the sender device, feedback information sent by the receiver device comprises: receiving, by the sender device, the feedback information sent by the receiver device in a radio frame in the third scheduling window.