A signal transmission method, comprising: determining, by a first device according to a first subcarrier-frequency mapping manner, a first frequency corresponding to a first subcarrier that is used for mapping a first signal in a first period, and sending the first signal at the first frequency, wherein the first subcarrier-frequency mapping manner is an uplink subcarrier-frequency mapping manner; and determining, by the first device according to a second subcarrier-frequency mapping manner, a second frequency corresponding to a second subcarrier that is used for mapping a second signal in a second period, and sending the second signal at the second frequency, wherein the second subcarrier-frequency mapping manner is a downlink subcarrier-frequency mapping manner, wherein: the first subcarrier-frequency mapping manner is different from the second subcarrier-frequency mapping manner, the first frequency and the second frequency belong to a same frequency band, and the second period comprises one or more transmission time intervals except a transmission time interval used for transmitting a physical broadcast signal and a transmission time interval used for switching a downlink transmission to an uplink transmission, wherein subcarriers in the first subcarrier-frequency mapping manner and in the second subcarrier-frequency mapping manner are of a subcarrier frequency width Δf, and the subcarriers in the first subcarrier-frequency mapping relationship are offset from the subcarriers in the second subcarrier-frequency mapping relationship by (N+1/2) Δf, N being an integer. determining, by a first device according to a first subcarrier-frequency mapping manner, a first frequency corresponding to a first subcarrier that is used for mapping a first signal in a first period, and sending the first signal at the first frequency, wherein the first subcarrier-frequency mapping manner is an uplink subcarrier-frequency mapping manner; and determining, by the first device according to a second subcarrier-frequency mapping manner, a second frequency corresponding to a second subcarrier that is used for mapping a second signal in a second period, and sending the second signal at the second frequency, wherein the second subcarrier-frequency mapping manner is a downlink subcarrier-frequency mapping manner, wherein: the first subcarrier-frequency mapping manner is different from the second subcarrier-frequency mapping manner, the first frequency and the second frequency belong to a same frequency band, and the second period comprises one or more transmission time intervals except a transmission time interval used for transmitting a physical broadcast signal and a transmission time interval used for switching a downlink transmission to an uplink transmission, wherein subcarriers in the first subcarrier-frequency mapping manner and in the second subcarrier-frequency mapping manner are of a subcarrier frequency width Δf, and the subcarriers in the first subcarrier-frequency mapping relationship are offset from the subcarriers in the second subcarrier-frequency mapping relationship by (N+1/2) Δf, N being an integer. the first subcarrier-frequency mapping manner is different from the second subcarrier-frequency mapping manner, the first frequency and the second frequency belong to a same frequency band, and the second period comprises one or more transmission time intervals except a transmission time interval used for transmitting a physical broadcast signal and a transmission time interval used for switching a downlink transmission to an uplink transmission, wherein subcarriers in the first subcarrier-frequency mapping manner and in the second subcarrier-frequency mapping manner are of a subcarrier frequency width Δf, and the subcarriers in the first subcarrier-frequency mapping relationship are offset from the subcarriers in the second subcarrier-frequency mapping relationship by (N+1/2) Δf, N being an integer.