One of the embodiments of the present invention relates to a method for modulation. The method comprises: providing a first bit sequence of continuous bits “1” or continuous bits “0” generating a second bit sequence by replacing, in each of a plurality of modulation intervals with a predetermined bit number, at least one bit of the first bit sequence at at least one fixed position of the respective modulation interval with one information bit from an information bit sequence; and modulating the second bit sequence so as to generate a positioning packet with a modulated continuous wave signal for transmission. The embodiments further relate to a method for demodulation. Embodiments of the present invention also provide corresponding apparatuses and computer program products.