Vectoring--Board or system-level?
A typical system-level architecture consists of a DSLAM shelf for street cabinet deployment, four 64-port VDSL2 line cards, a network interface card and a vectoring engine card (See Figure 6). This type of any-to-any configuration is well suited to the deployment of dynamic, high-speed broadband access services.
It all comes down to performance
As previously established, vectoring at the board level potentially presents both opex and capex challenges. An even more critical issue, however, is that the VDSL2 lines in the cable going from the street cabinet to the subscribers cannot be controlled through board-level vectoring. This limitation means that only marginal performance gains are possible, normally a fraction of what can be achieved with system-level vectoring.
To illustrate the performance gap between system- and board-based vectoring, Figure 7 compares the operation of the two approaches using a 0.5 mm cable with 50 lines and 2 line cards.
The graph shows that while system-level vectoring is capable of achieving near single line performance, board-level vectoring is able to provide only a trivial improvement over no vectoring at all.
Throwdown, vectoring style!
The following table provides a head-to-head comparison of the key attributes related to system-level and board-level vectoring:
And the winner is…
Today, wireline operators face considerable challenges from cable companies and alternative providers alike, and they need every competitive advantage they can get. That’s why they are welcoming with open arms new technologies like vectoring which can help them keep pace with the competition by extending the range and speed of their existing copper plant.
But telcos must tread carefully when deploying vectoring solutions, as not all implementations are created equal. Huge performance disparities can exist between system- and board-based systems, and these can have a dramatic impact on bottom-line capex and opex.
When considering a vectoring solution, operators must look at key attributes including: crosstalk noise cancellation, cable management requirements, port density and usage, and pay-as-you-grow investment.
A system-level vectoring architecture can meet the needs of most next-generation networks. This approach suits perfectly the FTTC/N deployments of street cabinets with active VDSL2 DSLAMs, as it enables operators to fully control all copper terminated at the DSLAM. The FTTC/N deployment is taking off rapidly because it enables wireline operators to convert their passive street cabinets into a perfect springboard towards a next-generation network.
While communication service providers continue to extend their fiber reach, they continue to face major issues when it comes to providing fiber-based services in the very last part of the access network. This is where board-level vectoring is well suited, as FTTB (fiber to the building) enables these providers to primarily target apartment buildings and offer the residents real broadband services.
About the Author
Ariel Caner is Product Marketing Manager at ECI Telecom.