Revisiting Bridged Tap and Spectrum Issue for VDSL Performance (99-560)

This paper addresses the issue of robust VDSL transmission in the presence of bridged taps in the local loop. The impact of bridged taps on transmission performance is described and evaluated for various frequency-division duplexing plans. It is shown that using only 4 bands will under several realistic circumstances result in very poor performance. The conclusion is that a robust duplexing plan will need at least 7 bands (4 upstream and 3 downstream). An action for T1E1.4 is that should this group try to reach consensus on a spectrum plan that such a plan must include 7 bands, 4 up and 3 down, in order to ensure that VDSL system performance requirements are met in the presence of bridged-taps. __________________________________________________________________________________ NOTICE This contribution has been prepared to assist Standards Committee T1 Telecommunications. This document is offered to the Committee as a basis for discussion and is not a binding on Stanford University. The requirements are subject to change after further study. The authors specifically reserve the right to add to, amend, or withdraw the statements contained herein. 12/04/99 2 T1E1.4/99-560 Revisiting Bridged Tap and Spectrum Issue for VDSL Performance (99-560) J. Cioffi, W. Yu, and G. Ginis Department of Electrical Engineering Stanford University, Stanford, CA 94305 Phone: 650-723-2525 ; Fax: 650-724-3652 ABSTRACT This paper addresses the issue of robust VDSL transmission in the presence of bridged taps in the local loop. The impact of bridged taps on transmission performance is described and evaluated for various frequency-division duplexing plans. It is shown that using only 4 bands will under several realistic circumstances result in very poor performance. The conclusion is that a robust duplexing plan will need at least 7 bands (4 upstream and 3 downstream). An action for T1E1.4 is that should this group try to reach consensus on a spectrum plan that such a plan must include 7 bands, 4 up and 3 down, in order to ensure that VDSL system performance requirements are met in the presence of bridged-taps.