Discussion Papers

Thomas Plückebaum

VDSL Vectoring, Bonding and Phantoming: Technical Concept and its Implications to Market and Regulation

No. 374/January 2013

(Full version only available in German)

Summary

VDSL Vectoring is a method compensating the mutual cross talks of parallel copper pairs and thus nearly reestablishing the original signal capacity of a native VDSL signal on a single copper pair, being not impacted by other pairs in the cable. The effect covers bandwidth and reach, which is naturally attenuated on a copper pair and thus is limited. A bandwidth of up to 100 Mbit/s down- and up to 40 Mbit/s upstream is achievable, depending on the length of the access line it will become lower, thus one can expect 50 Mbit/s downstream at 600 m loop length. By compensating the cross talks VDSL Vectoring allows to fully exploit a copper access cable with VDSL signals, each of the signals having a quality close to a single copper pair transmitting a VDSL signal without any disturbers from neighboring copper pairs. Signals out of the frequency spectrum of VDSL (POTS, ISDN, ADSL, HDSL/ SDSL) do not impact the VDSL transmission at all or may be excluded from impacting it with a minor downgrade.

The full exploitation of the Vectoring Effect requires all copper pairs of a bundle in a cable, which carry a VDSL signal, to be included in the cross talk compensation process. Otherwise the achievable bandwidth gain will be significantly reduced, so that one may wonder if the additional investment in the vectoring components of the DSLAM and the CPE are worth the additional income of a now lower bandwidth gain, the remaining gain in reach and the better exploitation of the cable by VDSL users.

This leads the investors in VDSL Vectoring solutions to claim for regulation of VDSL and VDSL Vectoring or to change the existing regulation of a complete unbundled access to the local loop respectively in order to allow the use of the VDSL frequency band for one operator only.

Since node-level vectoring, which allows a cross talk compensation across the DSALMs of several operators will not be available to the market in the nearer future, and since sorting the copper pairs of the access networks into per operator bundles, so that the access lines of different operators will no longer be mixed within one bundle, is not practically feasible, we do not see a natural solution in the near future term to prevent conflicts on the access lines by technical or organizational regulatory means.

In order to react on the operator’s demand of an exclusive access regulation we so far see three options for regulators:

  • Owner monopoly (Incumbent monopoly)
  • First Mover monopoly
  • Open for competition

With the owner Monopoly the incumbent receives the exclave right to use the VDSL frequency spectrum for all street cabinets (on all sub-loops). With the first Mover monopoly the first operator deploying a street cabinet with VDSL receives the exclusive right to also apply VDSL Vectoring and no other operator at this street cabinet is allowed to use the VDSL frequency spectrum on the access lines. The third approach is a laissez-faire model, which abstains from regulation of exclusive rights but trusts in the economic rationality of the operators to not invest as a second mover due to the disadvantages the parties would experience in only having a reduced bandwidth available. All three approaches assume that the competitors to the one operator deploying VDSL Vectoring will be offered an alternative to the physically unbundled access by a technically and economically equivalent nondiscriminatory bitstream access.

This study describes the technical and economic background of VDSL Vectoring, of Bonding using vectoring and of Phantoming, relying on both. It describes and discusses the regulatory options mentioned above and by this intends to contribute to the actual discussion.

Discussion Paper is available for download.

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