Andre Oppermann wrote: > Thomas Kernen wrote: >> Does some have any guidance as to how much S/N margin Swisscom >> requires for their BBCS VDSL loops. I have a case where the S/N margin >> in 22dB on the downstream and it surprises me the line doesn't train >> at a higher rate (current rate is 13264kbps). > > The S/N margin is inverse proportional to the link speed. You have 22dB > at 13Mb but only 5dB at 30Mb. This is usually a symptom of some cabling > problem. You should also check the number of CRC errors you have on the > line. VDSL2 is extremely sensitive to in-house wiring. Make sure you run > the cable directly from the Swisscom UP to your VDSL modem. If necessary > put a fresh U72 cable just for VSDL. Always separate VDSL from any SDSL > on the same quad (U72 is not twisted pair but twisted quad). >
Hi Andre, This is in a brand new building with a new Swisscom intro and a new and dedicated U72 from the intro directly to the VDSL modem. Nothing else on that quad. CRC increments max by 1 or 2 every 24 hours. Swisscom recabled the trunk after an outage notice (VDSL working fine but no analogue dial tone, 50mV on the loop, not enough to get a phone to ring in any case). That is when the loop change characteristics since it was fully checked end to end and that the S/N margin jumped from approx 10/12dB to 22dB. So for me there is no question the loop is functional and am trying to figure out how to get the loop retested. It is clear to me that in the VDSL modem Swisscom sets the profile to have a min of 10db margin and optimal is considered 12dB. So I strongly suspect the line could be retrained at a higher rate but that the profile that has been uploaded to the modem by Swisscom is most likely limiting the max train speed in order to increase the line stability, which is a good thing unless all of this was performed prior to the loop being rebuilt. Thomas _______________________________________________ swinog mailing list swinog@lists.swinog.ch http://lists.swinog.ch/cgi-bin/mailman/listinfo/swinog
