Impact-analysis for coexisting G.fast and vectored VDSL2

G.fast recently standardized by the ITU [1] aims at providing gigabit access from the Distribution Point (DP). The deployment of this new technology will be progressive as previous technological migrations, so G.fast will share the access network with existing DSL systems, particularly with vectored VDSL2. However, G.fast and vectored VDSL2 as defined by the standards are spectral-incompatible due to their overlapping spectrum, different carrier spacing implementation and conflicting multiplexing schemes. This work analyzes the coexistence issues that arise when G.fast and vectored VDSL2 services are deployed from the DP. Potential gains that could be obtained by introducing a synchronized transmission scheme, as well as the effectiveness of spectral-compatible band plans are discussed in order to help determine if those measures should be developed further and/or considered for standardization. In order to achieve this goal, we establish far-end crosstalk (FEXT) and near-end crosstalk (NEXT) models for realistic simulations and analyze the system performance for different deployment scenarios that reproduce the progressive migration from VDSL2 to G.fast. Our results show that synchronization between vectored VDSL2 and G.fast barely improves their performance, whereas the deployment of spectral-compatible band plans is an effective means to improve vectored VDSL2 performance with tolerable impact on G.fast.