A signal transmission method for increasing the amount of data transmission is described. When a specific transmitting side transmits signals in a signal transmission mode applied to a low-speed transmitting side, the specific transmitting side reduces the number of times of pilot transmission, thereby efficiently increasing a data transmission rate. The amount of data transmitted through one subchannel is set to be the same. To this end, improved subchannel structure, and improved system parameters in which a guard interval is adjusted are provided.