Methods for Supporting Vectoring when Multiple Service Providers Share the Cabinet Area

Vectoring cancels crosstalk between multiple VDSL2 lines and can greatly improve rate reach performance of VDSL2, particularly on short loops. Vectoring is only performed on lines within a vector group so that vectored lines may experience un-cancelled crosstalk from nearby lines that are either non-vectored or in a separate vector group (mixed scenario). If nothing is done to mitigate the effects of un-cancelled crosstalk in mixed scenarios, then vectored lines may suffer performance degradation which in some cases may be substantial. This argument has been used to advocate for market competition restrictions that would only allow the incumbent service provider (SP) to manage all vectored lines in a single DSLAM in order to save the full benefits of vectoring. In this paper, we address the issue of compatibility between lines within a vectored group and outside of it, pointing out that there are various solutions that allow reaping the full benefits of vectoring even when multiple SPs are allowed to share the lines in a cabinet, which is the typical case where Sub-Loop Unbundling (SLU) is permitted by the regulator. We conclude that there are no technical reasons for arguing in favor of imposing restrictions on SLU, a very harsh limitation to competition that would severely damage competitive SPs and penalize subscribers.