Overview of SHDSL system performance

SHDSL is the first standardized multi-bit-rate symmetric DSL for data rates between 192 kbit/s and 2312 kbit/s. A 16-level trellis-coded PAM line code is used. The main challenges of SHDSL system design are optimization with respect to reach, spectral compatibility, power consumption and implementation cost. The loop reach of PAM-based DSL systems can be estimated by a method independent of specific implementation details. In this paper, techniques to increase loop reach using shaped and asymmetric PSD are discussed. With asymmetric PSD, some increase in loop reach can be obtained if ideal assumptions are made on the system. but in application this theoretical increase is limited by practical implementation issues, and is counter-balanced by higher power consumption.