Additional VDSL2 Vectoring Benefits
n our previous post, we introduced VDSL2 vectoring as a viable solution for eliminating crosstalk, improving wireline performance and allowing carriers to support attractive service offerings of 50 Mbps or higher over their existing copper networks. The main benefit of VDSL2 vectoring is improved reach and subscriber coverage, as it increases the 50 Mbps service radius from 400 meters to 800 meters, allowing carriers to increase the potential premium-service subscriber base by 300% using the existing copper plant.
Now let’s take a look at some of additional benefits of VDSL2 vectoring.
VDSL2 vectoring minimizes the effects of ADSL2+ local loop unbundling
A common concern among incumbent wireline operators (ILECs) is that ADSL2+ local loop unbundling prevents vectored VDSL2 transmissions from achieving their anticipated capacity. In this scenario, the competitive carrier (CLEC) could lease copper pairs at a central office (CO), provide ADSL2+ service and hamper the performance of the incumbent’s vectored VDSL2 service running on the same feeder cable, as illustrated below.
According to tests performed by ECI with European Tier 1 operators, it was shown that the performance of the vectored VDSL lines was not significantly impaired. Only minor performance degradation occurred in the above-described scenario.
Four VDSL2 lines running profile 17a were tested – with and without vectoring – in the same 300-meter feeder cable with four ADSL2+ links. Whereas the performance of non-vectored VDSL2 lines degraded on average by 34%, the vectored VDSL2 links performed well, with a bit rate loss of only 11%. These results are shown in the following table.
Upstream power back-off (UPBO) is a technique developed for VDSL2 systems in which signals from nearby subscribers disrupt communications with more remote subscribers. In UPBO, the power level of upstream transmission for nearby subscribers is reduced in order to minimize the disruption of other lines. Of course, as power levels are reduced, so are link performance levels.
A common result of FEXT crosstalk is that some VDSL2 lines perform well, while traffic on other lines may be disturbed, yielding far lower bandwidth rates. This “unfairness” can alienate affected subscribers and prevent operators from fulfilling service level agreements (SLAs).
VDSL2 vectoring, which allows operators to offer higher bandwidth rates, also promotes fairness between subscribers. To demonstrate this, ECI and European Tier 1 operators tested the bandwidth capacity of eight 150-meter VDSL2 lines running profile 17a, both with and without vectoring. As shown in the following table, the non-vectored lines showed a wide level of performance deviation, while the deviation of the vectored lines was well under 2%.
In our next post, we’ll look at the economic justification for vectored VDSL2 deployments.
xDSL Product Line Manager