Vectoring technology has emerged as a means of delivering high bandwidth over existing copper infrastructure by extracting more value from it, without investing in an extensive fiber roll-out.
What’s the idea?
Phone lines that carry VDSL2 signals are part of cables that contain from 10 to a few hundred lines positioned very closely together. This close proximity results in cross-talk (FEXT, undesired effect of a signal transmitted on one circuit to another one) and the higher the number of lines in a bundle, the more cross-talk is generated. Cross-talk is the one of the biggest impediments to deliver good VDSL2 performance. With no interference, every VDSL2 line can operate as if it were the only line in the cable, and, as consequence, deliver higher bit rates. So basically, vectoring is not a method for raising the theoretical maximum speeds, but for decreasing the gap between the theoretical upper limit of performance and the speeds that can be delivered in variable field conditions.
Opposite to Dynamic Line Management (DLM), for which there is no guarantee that the improved speed once awarded by the DLM process on a specific VDSL2 line will always remain, the vectored lines will keep their new higher rates based on a recurrent process of measurement, processing and correction.
Vectoring technology can be compared to the noise-cancelling technology used in headphones: it works by 'listening' to unwanted noise and producing a sound that is exactly like it but with an inverted phase—this way two sounds can cancel each other out.
How does it actually work?
In the Proximus network, vectoring technology has been implemented at street cabinet (ROP) level where the cross-talks of the lines of the same bundle can be properly measured and neutralized by generating appropriate anti-phase signals, which is done by DSLAM.
Surely these calculations needed for vectoring requires enormous computing power. In order to fulfill requirements mentioned above, there have been two things that have been implemented in order to bypass it: use of the new VDSL2 line cards in the ROPs and an upgrade of all installed CPE (Customer Premises Equipment) to vector-friendliness or its replacement by vector-compliant hardware.
In February 2014 Proximus started to replace VDSL2 cards, street cabinet per street cabinet. By now, almost all street cabinets do support vectoring. As for second requirement, the efficient estimation of the cross-talk between VDSL2 lines, the additional functionality at the CPE side is defined by the International Telecommunication Union (ITU vectoring standard, G.993.5 (G.vector).
On the hardware level, VDSL2 line can only be vectored if two following requirements are fulfilled: modem installed on it should be vector-compliant and, at the same time, each modem installed on every other line of the same bundle is vector-compliant or at least vector-friendly. Otherwise, a modem, which is not at least vector-friendly, is installed on any other VDSL2 line, will interfere with the calculation of the cross-talk between the lines. Thus, the cross-talk from some line will remain uncancelled, resulting in an unpredictable negative impact on all other lines of the bundle.
In order to prevent it, all modems that are not at least vector-friendly will synchronize on a fall-back profile (7 Mbps down and 512 Kbps up) that will not create more cross-talk than the one coming from ADSL2+ lines and will not disturb the continuous cross-talk estimation. On the contrary, a vector-friendly VDSL2 CPE does not disturb any other lines in the cable, but will not allow to benefit from the advantage of vectoring, being a higher speed rates.
What speeds can vectoring achieve?
No matter how far from the street cabinet VDSL line is, vectoring significantly increases its maximum speeds (by from around 30 to more than 100 per cent depending on the provisioning profile). Vectored VDSL2 lines can reach downstream speeds of 70 Mbps (and that’s not considering DLM!) at distances of up to 900 meters, with the attenuation of the cable not exceeding 0,4 dB, while 50 Mbps can be supported with loops as long as 1200 meters.
The speeds will also depend on the type of vectoring the street cabinet supports. Vectoring as it was originally launched was operating in the frequency bands above 2.2 MHz. As ADSL is currently being phased out, on ADSL-free street cabinets the vectoring can be deployed in the ADSL and ADSL2+ frequency bands (above 1,1 MHz and 552 KHz, respectively), which results in a more accurate cross-talk estimation. Learn which speed profile you are eligible for.
Back in 2009 it was the general opinion of network operators (Proximus in Belgium, KPN in the Netherlands …) that, since the VDSL2 technology was not yet mature enough, the chipset of both the modem and the DSLAM should be the same in order to prevent operational problems, performance reductions and line instabilities. Hence the idea of only allowing one VDSL2 CPE on the network.
Under influence of the alternative operators, who strongly rejected the idea of being obliged to use the specific VDSL2 CPE that Proximus told them to use, in the Decision from September 30th 2009 on WBA VDSL2 the Council of the BIPT obliged Proximus to come up with a proposal that would allow alternative operators to use their own VDSL2 CPE on the Proximus VDSL2 network. After having gathered some information, in 2011 the BIPT concluded that the VDSL2 CPE restriction was limiting competition in the market and that a review of the CPE-obligation was at order.
A VDSL2 CPE test plan was to be developed that would primarily aim to protect the Proximus network and at the same time allow alternative operators to use their VDSL2 CPE in normal competitive conditions. The original plan was written in the context of an alternative operator developing his own VDSL2 CPE. Proximus would provide the alternative operator with a series of tests that his VDSL2 CPE had to pass successfully. Then the alternative operator would be allowed to connect its own VDSL2 CPE’s to the Proximus VDSL2 network.
The BIPT approved the test plan, which resulted in 2 types of VDSL2 CPE’s being possible from then onwards: the Proximus CPE (Sagem) and an OLO CPE.
Upon approval by the BIPT, edpnet immediately started with the preparations of having its own VDSL2 CPE certified for use on the Proximus VDSL2 network. It did not take long to find out that both financially and technically the approved certification procedure was nearly impossible to pass. It took edpnet many months and many convincing to get the BIPT and Proximus to soften the requirements a little.
edpnet was the first alternative operator to officially inform both Proximus and the BIPT of its intention to have the AVM FRITZ!Box 7360 certified as VDSL2 CPE, the first official step into the certification process. During the months that followed it became quite clear that Proximus had been allowed to make the requirements way more extensive than the requirements in other countries. It took edpnet almost another year before an agreement could be made with Proximus and the BIPT on a test plan that was do-able and acceptable for all parties.
edpnet submitted the necessary test samples to Proximus as a final step in the certification process.
|FRITZ!Box 7360 and the newer FRITZ!Box 7490 both got certified.|
|FRITZ!Box 7430 became the third alternative certified modem.|
There are mainly two reasons for that.
On one hand, it is the result of the vectoring technology itself. Different copper lines are bundled in a cable that arrives in a street cabinet. These lines disturb each other because they create cross-talk, noise, which results in a loss of quality and a loss of performance (read: speed). Vectoring technology eliminates this cross-talk, noise, resulting in better performance (read: speed). All VDSL2 modems connected to the copper lines in the same cable must support ITU G993.5 (a.k.a. G.Vector), otherwise the performance of all modems falls back to "normal" VDSL2. Nobody wants that to happen. Following the above, it’s crucial to prevent one VDSL2 CPE causing problems for 383 others connected to the same cable.This leads to reason number 2. Each national VDSL network operator has introduced some kind of a whitelist procedure (read: a certification procedure) based on chipset + firmware combinations (CFC). If a specific CFC has been tested and approved for vectoring and interoperability with DSLAM upgrades, it appears on the whitelist. If it is on the whitelist, it will be recognized as such by the DSLAM and will pass the security test. If not, the line at which the non-compliant CPE is attached will automatically be put on a VDSL2 fall-back profile (equal to an ADSL2+ type of speed).
Proximus was allowed by the BIPT to take it one step further and work with a CPE-model + chipset + firmware combination. The certification / whitelisting procedure from Proximus (as approved by the BIPT) is far more extensive and strict than what national xDSL network operators in other countries use. In Belgium, only an alternative operator can initiate a certification procedure, while in other countries also CPE vendors can do this. This results in a very short whitelist in Belgium, containing only the Proximus CPE’s, since June 2014 — the FRITZ!Box 7360 and 7490 and, since March 2017, the FRITZ!Box 7430.
A vectoring-compliant VDSL2 CPE will allow the VDSL2 end-user to benefit from higher downstream speeds resulting from the application of vectoring.
A vectoring-friendly VDSL2 CPE does not disturb any other lines in the cable, nor the network, but won’t allow to benefit from the advantage of vectoring, being a higher downstream speed.
The third kind, a so-called legacy CPE is a CPE that’s neither vectoring-compliant nor vectoring-friendly and will result in the line being limited to a VDSL2 fall-back profile (equal to an ADSL2+ type of speed).
The FRITZ!Box 7360, 7490 and 7430 are vectoring-compliant, provided that the modem is equipped with the appropriate version of the modem firmware (06.31, 06.52, 06.53).
Most other AVM modems are not vector-friendly or vector-compliant. The reason is simple enough: the restrictions that Proximus applied to the certification procedure, making it almost impossible to whitelist more non-Proximus CPE. For every extra CPE + chipset + firmware combination—even if part of them are the same as of FRITZ!Box 7360—the whole certification process has to be passed and price has to be paid, but despite that obstacle edpnet has worked hard and got FRITZ!Box 7490 and 7430 certified, as well.
These are not—and will not be—vector-compliant. Nevertheless, they are and will be vector-friendly, provided that they are equipped with the latest vector-friendly version of the modem firmware.
These are vectoring-compliant and allow to benefit from vectoring technology.
In case your CPE is not one of the above, you have two options: you either obtain one of the above mentioned VDSL2 CPE’s or you do not and will be put on the fallback profile as soon as vectoring is being activated on the ROP you are connected to. Note that FRITZ!Box 7360, 7490 and 7430 can be put in bridge mode, which means that you can install the modem between your current CPE and the xDSL network. This way you can keep your current modem configuration / settings, and avoid the risk of automatically being put on the fallback profile once vectoring is being activated. Sagem can be also put in bridge mode, but you should keep in mind that since it is not vector-compliant hardware, it will permit to keep actual VDSL2 profile, but not to obtain any higher speeds.
Basically it will have effect on all VDSL2 lines, no matter the distance from the street cabinet. This means that every VDSL customer needs at least a Proximus whitelisted vectoring-friendly CPE.
The edpnet availability tool will allow you to verify the feasibility of the vectoring profile on a specific address after vectoring will be rolled out: just enter your address or your fixed telephone number
We will gladly answer any questions you might have, just drop us a line at info[at]edpnet[dot]com