Coexistence in fourth generation digital subscriber lines: Experiment, modeling, and simulation results

The deployment of fourth generation digital subscriber line (DSL) technology (“G.fast”) will be gradual and it may therefore share the cable infrastructure with legacy DSL technologies such as Very high speed DSL transceivers 2 (VDSL2). We perform experiments on coexistence of G.fast with legacy VDSL2, highlighting the practical relevance of out-of-band leakage and aliasing. Furthermore, the differences in transmission parameters (e.g., carrier width and sampling rate) and asynchronous transmission results in inter-carrier and inter-symbol interference (ICSI). Previous work on modeling ICSI in the communication field focused on modeling only a subset of these effects. Hence, we analytically derive a simplified ICSI model, which notably includes the effects of aliasing, leakage, and worst-case symbol misalignment. Our results partially based on simulations show that a) neglecting ICSI potentially leads to significant bit-rate overestimation (e.g., 18% in G.fast rates); and b) a G.fast start frequency of approximately 23MHz may provide sufficient spectral separation with VDSL2 profile 17a transceivers.