Various embodiments of the present disclosure adjusts the size (nm) of a message input to a corresponding check node in case the unsatisfied check equation increases as the iteration count increases.Another embodiment of the present disclosure relates to a method for selecting a message and grasps the data distribution characteristics of the message vector values converted using the signal to noise ratio (SNR) and modulation and coding scheme (MCS) parameters of the receiver to select the message value with a value smaller than the threshold value in each message vector.