Achievable rates vs. operating characteristics of local loop transmission: HDSL, HDSL2, ADSL and VDSL

Prior work has focused on achievable rates for digital subscriber lines, only to have future technology surpass the "achievable" bounds. This paper focuses on how achievable rates vary under different operating characteristics. We show how the achievable rates change as transmission moves from echo-cancelled symmetric transport (HDSL), to frequency-division transport (original ADSL), partially overlapped transport without bandwidth coordination (echo-cancelled ADSL), to partially-overlapped, frequency-coordinated transmission (HDSL2). The limitations of spectral compatibility and crosstalk from existing services are discussed as they effect the fundamental limits and deployable services. The lessons learned are related to higher rate services in a next-generation network employing VDSL.