Reed Solomon turbo codes for high data rate transmission

We investigate the performance of different RS (Reed Solomon) turbo codes in the context of enhanced VDSL (very high bit rate digital subscriber line). We first describe the VDSL system used in our simulation link. Then we describe the block turbo decoder and, in particular, the iterative decoding algorithm that we propose. It is based on Pyndiah's SISO (soft in soft out) decoder for product block codes and can be implemented with reasonable complexity. We illustrate several BER (bit error rate) results for various RS product codes; we compare them with the ADSL (asymmetric digital subscriber line) RS(144,128) decoder results, in the case of various QAM (quadrature amplitude modulation) schemes. We show that the turbo RS decoding outperforms the classical Reed Solomon hard decoding used in the ADSL system; it allows a better bitloading and thus, a better bit rate. Finally, we display the obtainable bit rates for various RS codes as a function of the local loop length for different numbers of interfering lines.