Crosstalk between physically co-located lines is apressing issue in VDSL2 access networks. In order to enhance the crosstalk mitigation capabilities of the latest extension to VDSL2, vectoring G.993.5, full control over all lines within the same cable binder is required. However, this is not always possible in practical deployments due to regulatory, structural, or late technology adoption constraints. In these cases a technique tominimize interference from non-controlled lines, known as binder management, aims at rearranging the line configuration within each binder. In this work, we quantify the advantages of binder management in a partially controlled setup. We initially establish a model of a commonly used 50-pair cable binder and provide its far-end crosstalk (FEXT) characterization. We then carry out an extensive simulation study for various degrees of control over the lines and realistic line length distributions to yield tangible metrics on vectoring performance fordownstream transmission. Our results show that binder management is of limited use in partially controlled systems. Consequently, we provide an additional comparison study to help DSL providers to evaluate the remaining gains of upgrading to VDSL2-vectoring in such scenarios for different levels of dominance in the cable binder

Vehicle-To-Everything (V2X) communication is a fundamental pillar of autonomous driving. It enables the exchange of safety-critical data between vehicles, infrastructure and pedestrians to enhance the awareness of the surrounding environment and coordinate the execution of collective functionalities vital to achieve full automation. Due to the safety-critical nature of the interchanged information, V2X communication must be resilient, so that it provides reliable connectivity despite of the very dynamic characteristics of both its environment and network topology. In this position paper, we propose a novel concept that aims at achieving resilient V2X communication. We introduce the Quality of Service Manager (QoSM), a collaborative and distributed implementation concept for the Heterogeneous Link Layer (HLL) that operates on the top of the Medium Access Control (MAC). QoSMs first monitor and predict QoS indicators of Radio Access Technologies (RAT) in Heterogeneous Vehicular Networks (HetVNET). Then, under the Always Resiliently Connected (ARC) principle, they determine and set timely the configuration settings of RAT that meet performance and reliability requirements of autonomous driving applications. Should it not be possible to fulfill applications demands, the QoSM can instruct applications in advance to lower the requirements or run in a safe mode. Like in many autonomous driving applications, the concept of our proposed QoSM is distributed and collaborative to enhance accuracy, self-awareness and safety. QoSMs shall be grouped hierarchically according to correlation of applications demands, conditions of communication links and mobility information. Group's members share monitored and predicted indicators, as well as configuration settings. This information is used to determine collectively the configuration of the HetVNET. On the one hand, sharing information among QoSMs increases the amount of correlated data used by prediction algorithms, which improves prediction accuracy. On the other hand, hierarchical groups allow to extend the proposed methodology to other hierarchical elements of the access and core network. With this position paper, we intend to open the discussion on the importance of implementing protocols for sharing parameters that allow distributed and collaborative QoS management for resilient V2X communication.

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G.fast recently standardized by the ITU 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