A signal transmission apparatus of a wireless cellular system, the signal transmission apparatus being constituted by a base station on the network-side thereof, comprising: a determining module , configured to determine a modulation type of service data that needs to be transmitted, wherein the modulation type comprises hierarchical modulation and non-hierarchical modulation; a first sending module , configured to modulate, by means of the hierarchical modulation when the determining module determines that the modulation type is the hierarchical modulation, the service data that needs to be transmitted, and send a modulated hierarchical modulation signal to user equipment, UE; and characterized by a second sending module , configured to send modulation configuration information to the UE, wherein the modulation configuration information comprises information used to indicate the modulation type, wherein the service data comprises base-layer data and additional-layer data, and a priority of the base-layer data is higher than a priority of the additional-layer data; and the hierarchical modulation comprises base-layer modulation and additional-layer modulation, wherein the base-layer modulation is modulation performed on the base-layer data in the service data, and the additional-layer modulation is modulation performed on the additional-layer data in the service data; wherein the second sending module is further adapted to notify the UE, in order to correctly demodulate the received hierarchical modulation signal, of other modulation parameter values except the modulation type, wherein the other modulation parameter values comprise a modulation order at either layer, a transport block size, TBS, index value, a power of a modulation signal at either layer, and an encoding rate. a determining module , configured to determine a modulation type of service data that needs to be transmitted, wherein the modulation type comprises hierarchical modulation and non-hierarchical modulation; a first sending module , configured to modulate, by means of the hierarchical modulation when the determining module determines that the modulation type is the hierarchical modulation, the service data that needs to be transmitted, and send a modulated hierarchical modulation signal to user equipment, UE; and characterized by a second sending module , configured to send modulation configuration information to the UE, wherein the modulation configuration information comprises information used to indicate the modulation type, wherein the service data comprises base-layer data and additional-layer data, and a priority of the base-layer data is higher than a priority of the additional-layer data; and the hierarchical modulation comprises base-layer modulation and additional-layer modulation, wherein the base-layer modulation is modulation performed on the base-layer data in the service data, and the additional-layer modulation is modulation performed on the additional-layer data in the service data; wherein the second sending module is further adapted to notify the UE, in order to correctly demodulate the received hierarchical modulation signal, of other modulation parameter values except the modulation type, wherein the other modulation parameter values comprise a modulation order at either layer, a transport block size, TBS, index value, a power of a modulation signal at either layer, and an encoding rate. <EOS>