A method of processing a transmission signal may comprise grouping a coded bit sequence including a plurality of coded bits into a plurality of groups; comparing indices of code bits belonging to a first group among the plurality of groups and indices of code bits belonging to a second group among the plurality of groups; configuring the coded bits belonging to the first group as higher bits among bits constituting each modulation symbol based on a result of comparing the indices of the coded bits; configuring the coded bits belonging to the second group as lower bits among the bits constituting each modulation symbol based on the result of comparing the indices of the code bits; and generating the each modulation symbol by using the higher bits and the lower bits.