A data transmission method includes obtaining a data stream. The data stream includes a plurality of bit groups. The method also includes modulating the data stream into a modulated symbol stream according to a modulation rule, and generating a modulated signal based on the modulated symbol stream. The modulated symbol stream includes a plurality of modulated symbol. The modulation rule includes determining, in a symbol period of one modulated symbol based on a value of a first bit group, a zero time point corresponding to the first bit group. The zero time point is a zero crossing point of the modulated signal in the symbol period. The first bit group includes at least one bit. The first bit group is one of the plurality of bit groups. The method further includes sending the modulated signal.