Broadband Related > FTTC and FTTP Issues
3dB SNR - how to achieve?
dee.jay:
Hi all,
I've had FTTC with Sky for the past 6 years. I've enjoyed, mostly decent speeds of ~60Mbit, but I notice lately that SNR targets should be 3dB.
I've now got a second FTTC line in, this time with AAISP. It went live yesterday. Strangely that line claims an attainable of 57000, but only runs at 50000. But, that is a new line, so I am going to have to let it do it's thing for a while anyway.
But, both lines are definitely 6dB. Is there some secret sauce to getting it down to 3dB? I have HG612's on both lines. Thanks!
dee.jay:
I think 7Mb roughly is 1dB on my lines - I can add 1dB to SNR by dropping rate from 57000 to 50000 with the xdslcmd configure command that is elsewhere.
If that is the case, then surely I could be missing out on 21Mb per line?
Ixel:
New VDSL2/FTTC lines will have interleaving (low error correction) by default instead of fastpath, whether ECI or Huawei. If the DSLAM is ECI then DLM should switch your new connection to fastpath if it seems stable. If the DSLAM is Huawei then DLM should switch your new connection to G.INP and possibly reduce the downstream SNRM target after an unknown time (a week? I have no experience of Huawei sadly). While interleaving is active the attainable rate will be incorrect/inaccurate.
If you're on an ECI DSLAM then you won't get 3dB or G.INP either, however you can SNRM tweak this (if your line is stable enough) with a modem that has an Infineon/Lantiq chipset such as the DrayTek Vigor.
dee.jay:
Probably should have stated that I am on a Huawei cabinet.
j0hn:
The discrepancy you see between sync (50Mb) and attainable (57Mb) is due to the interleaving+INP that comes with all new FTTC lines.
The attainable is always over estimated under these circumstances (by roughly 10%).
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