HDSL design issues-optimization and achievable gains

The principle design goal for high rate digital subscriber lines (HDSL) is to achieve the maximum field length for a given bit error probability. A transmission system can be decomposed in the functions channel equalization, line coding and channel coding. The largest distance gain compared to an existing, non-optimized system is achieved by channel coding. However, line coding and the optimization of the symbol rate and the number of levels remain important issues. In the paper, optimization criteria for all three areas are discussed and numerical results are given. If a new line coding scheme using trellis shaping is employed, the overall distance gain achieves 20% compared to the systems in use today