A method and apparatus for inserting dummy sequences during data modulation in a communication system, according to channel status, link status, and the like, is disclosed. In one embodiment, a method for data modulation by a wireless communication node of a wireless communication system, includes: inserting at least one first dummy sequence to a first data sequence in a first data block; and inserting at least one second dummy sequence to a second data sequence in a second data block; wherein a first length of a first dummy sequence is different from a second length of a second dummy sequence, and wherein the second dummy sequence includes the first dummy sequence or is included in the first dummy sequence.