An interleaving method performed by a transmitter for a communication system with spatial multiplexing over T transmit antennas employing quasi-cyclic low-density parity-check codes, T being an integer greater than 1, the interleaving method being used for applying bit permutation to bits of a codeword of a quasi-cyclic low-density parity-check code in order to generate a plurality of constellation words of one or more spatial-multiplexing blocks from the codeword, the codeword consisting of N cyclic blocks, and each cyclic block consisting of Q bits, each of the one or more spatial-multiplexing blocks consisting of B bits and consisting of T constellation words, wherein the T constellation words are simultaneously transmitted over the T transmit antennas, each constellation word indicating one of a plurality of constellation points of a predefined constellation used for constellation mapping of the constellation word, the bits of each constellation word being divisible into pairs of bits having the same robustness, characterized in that the interleaving method comprises the step of applying the bit permutation to the bits of the codeword such that: when N is a multiple of B/2: the N cyclic blocks are divided into a plurality of sections each including B/2 cyclic blocks; each of the one or more spatial-multiplexing blocks is made up of only bits from B/2 different cyclic blocks included in a respective same one of the sections; each constellation word of the one or more spatial-multiplexing blocks is made up of bits from Bt/2 different cyclic blocks, Bt being the number of bits of the constellation word; and each of said pairs of bits having the same robustness of said each the constellation word is made up of bits from a common one of the Bt/2 different cyclic blocks, and when N is not a multiple of B/2: N-X cyclic blocks are divided into a plurality of sections each including B/2 cyclic blocks, where X is the remainder when N is divided by B/2; each of spatial-multiplexing blocks generated from the N-X cyclic blocks, among the one or more spatial-multiplexing blocks, is made up of only bits from B/2 different cyclic blocks included in a respective same one of the sections; each constellation word of each of the spatial-multiplexing blocks generated from the N-X cyclic blocks is made up of bits from Bt/2 different cyclic blocks, Bt being the number of bits of the constellation word; and each of said pairs of bits having the same robustness of said each constellation word of each of the spatial-multiplexing blocks generated from the N-X cyclic blocks is made up of bits from a common one of the Bt/2 different cyclic blocks. when N is a multiple of B/2: the N cyclic blocks are divided into a plurality of sections each including B/2 cyclic blocks; each of the one or more spatial-multiplexing blocks is made up of only bits from B/2 different cyclic blocks included in a respective same one of the sections; each constellation word of the one or more spatial-multiplexing blocks is made up of bits from Bt/2 different cyclic blocks, Bt being the number of bits of the constellation word; and each of said pairs of bits having the same robustness of said each the constellation word is made up of bits from a common one of the Bt/2 different cyclic blocks, and when N is not a multiple of B/2: N-X cyclic blocks are divided into a plurality of sections each including B/2 cyclic blocks, where X is the remainder when N is divided by B/2; each of spatial-multiplexing blocks generated from the N-X cyclic blocks, among the one or more spatial-multiplexing blocks, is made up of only bits from B/2 different cyclic blocks included in a respective same one of the sections; each constellation word of each of the spatial-multiplexing blocks generated from the N-X cyclic blocks is made up of bits from Bt/2 different cyclic blocks, Bt being the number of bits of the constellation word; and each of said pairs of bits having the same robustness of said each constellation word of each of the spatial-multiplexing blocks generated from the N-X cyclic blocks is made up of bits from a common one of the Bt/2 different cyclic blocks. N-X cyclic blocks are divided into a plurality of sections each including B/2 cyclic blocks, where X is the remainder when N is divided by B/2; each of spatial-multiplexing blocks generated from the N-X cyclic blocks, among the one or more spatial-multiplexing blocks, is made up of only bits from B/2 different cyclic blocks included in a respective same one of the sections; each constellation word of each of the spatial-multiplexing blocks generated from the N-X cyclic blocks is made up of bits from Bt/2 different cyclic blocks, Bt being the number of bits of the constellation word; and each of said pairs of bits having the same robustness of said each constellation word of each of the spatial-multiplexing blocks generated from the N-X cyclic blocks is made up of bits from a common one of the Bt/2 different cyclic blocks.