the present invention relates to a method for processing digital signals and to a transmission / reception system implementing said method ; the present invention is based on the use of ldpc codes , in particular the ldpc code of the dvb - s2 standard , in combination with a qam modulation , in particular the 1024qam and 4096qam modulations ; in transmission , a bit permutation is carried out prior to the qam constellation mapping function ; in reception , the bit permutation is carried out after the qam constellation demapping function .