Improving BICM performance of QAM constellations for broadcasting applications

A technique intended to improve the performance of bit-interleaved coded modulations over non Gaussian channels is presented. It introduces signal space diversity by the means of modifications to the constellation mapper and to the corresponding demapper. A rotation of the constellation is followed by a signal space component interleaving. Iterative processing at the receiver side is shown to provide additional error correction. This method outperforms state-of-the-art systems over flat fading channels and substantial gains with respect to bit-interleaved coded modulation are obtained for severe channel conditions. It has been adopted by the Digital Video Broadcasting European consortium in the upcoming next generation of digital terrestrial television, DVB-T2, for the 4-, 16-, 64- and 256-QAM constellations. The resulting improvement in performance can vary from 0.2 dB to several dBs depending on the order of the constellation, the coding rate and the channel model.