In our final post in the VDSL vectoring blog series, we’ll discuss the major issues involved in access network maintenance, and introduce ECI’s unique approach that virtually eliminates high-opex in-the-field cable management.
VDSL2 vectoring - per card or per shelf?
Most VDSL2 vendors who have developed vectoring solutions have implemented them on a per-card basis. The vectoring engine resides on the VDSL2 line card and controls the vectoring activity on the ports of the line card. This approach has two drawbacks:
- Vectoring requires significant processing power and memory resources. These resources are allocated from the ports and may force the operator to reduce the number of ports deployed or accept a traffic performance hit.
- The card-based vectoring approach requires that all the pairs in a feeder cable be connected to the same card; if not, the vectoring engine misses out on crucial measurements and the subsequent pre-coding that ensures the efficiency of the vectoring operation is compromised. With typical feeder cables containing 100 pairs or more, this approach is highly impractical. In addition, as customers churn, card-based vectoring requires significant cable management activity, with all the relevant opex implications.
Let’s take a look at some specific scenarios.
Scenario 1: high take-up rate
One hundred subscribers want the premium service enabled by vectoring. Assuming the use of a 48-port VDSL2 line card, card-based vectoring would be enabled only if 48 pairs were utilized in each 100-pair feeder – a waste of 52 copper pairs.
Scenario 2: low take-up rate
The take-up rate is low, say, 40 subscribers – 20 from one neighborhood (and feeder cable) and 20 from another. It’s no problem managing both cables from a single card, as shown in the following figure.
However, if 10 new subscribers join the following year, there won’t be enough free ports on the card to satisfy the demand. We can install a new line card and connect the additional customers, but the vectoring won’t work.
It becomes necessary to send technicians to the street cabinet to perform some cable management.
The cables are now re-aligned with the line cards. The result? Unused line card ports! In other words, we have made unnecessary capital expenditures.
Would it not be far preferable to add the capacity and flexibility of shelf-based vectoring, with better scalability, capex minimization and less cable management? That’s ECI’s approach. Let’s examine such a solution.
Shelf-based vectoring solution
A shelf-based vectoring platform is the preferred solution for the deployment of dynamic high-speed access networks. In such a vectored VDSL2 platform, the vectoring engine resides on a dedicated service card that controls the vectoring activity of all the VDSL2 line cards. Connect any card to any pair in any feeder!
In this case, the vectoring engine card controls ECI’s four 64-port VDSL2 line cards, without compromising performance or capacity. A schematic diagram follows:
The following table summarizes the advantages of shelf-based VDSL2 vectoring.
This concludes our series on VDSL2 vectoring. Please feel free to contribute your ideas and suggestions in the comments.
Product Marketing Manager
Network Solutions Division