Kitz Forum

Broadband Related => FTTC and FTTP Issues => Topic started by: Windows10User on August 22, 2019, 02:31:33 PM

Title: What's my expected SNR Margin for BT
Post by: Windows10User on August 22, 2019, 02:31:33 PM: Hi,

I was wondering since if my SNR Margins are correct. Currently I've to 6.4db Up and 7.5Db down. If they're incorrect, how do I fix it?
Title: Re: What's my expected SNR Margin for BT
Post by: tubaman on August 22, 2019, 02:50:09 PM: Without seeing your other modem stats (sync speed, attainable speed, line attenuation) you can't say if those figures are reasonable or not.
:)
Title: Re: What's my expected SNR Margin for BT
Post by: j0hn on August 22, 2019, 04:34:06 PM: For FTTC/VDSL2 the default target SNRM is 6dB.
It's always 6dB on ECI cabinets.

Some lines on Huawei cabinets can have a 5, 4 or even 3dB SNRM target.

The actual SNRM can be higher than the target if a line is capped or at the product cap.
Title: Re: What's my expected SNR Margin for BT
Post by: kitz on August 22, 2019, 09:48:52 PM: Sounds about right. The default Target SNRm for ECI's is 6.3dB.

As others have said would also need to see more stats, but I'd guess with you being 6.4dB that your line conditions have slightly improved since you last sync'd.
Most lines SNRM will vary over the course of the day. 0.1 dB is going to make very little difference to your attainable speed.

As regards to the upstream, usually that indicates a line that has full 20Mbps/10Mbps upstream sync (depending upon which product they are on).

For example these are mine
Code: [Select]
Max: Upstream rate = 25642 Kbps, Downstream rate = 67508 Kbps Bearer: 0, Upstream rate = 20000 Kbps, Downstream rate = 67469 Kbps SNR margin (dB): 6.3 9.1
The 9.1dB shows that I have surplus SNRm whereby if the upstream rate wasn't capped at 20Mbps, then my line would be capable of attaining 25.6 Mbps upstream.
Title: Re: What's my expected SNR Margin for BT
Post by: Windows10User on August 28, 2019, 07:23:56 PM: Hi,

Here are the full stats from DSLStats:
Stats recorded 28 Aug 2019 19:23:29

DSLAM type / SW version:   IFTN:0xb206 (178.6) / v0xb206
Modem/router firmware:    AnnexA version - A2pv6C038m.d24j
DSL mode:     VDSL2 Profile 17a
Status:     Showtime
Uptime:      8 hours 26 min 12 sec
Resyncs:    0 (since 28 Aug 2019 19:23:27)

            Downstream   Upstream
Line attenuation (dB):    23.4      0.0
Signal attenuation (dB):   Not monitored
Connection speed (kbps):   29997      5017
SNR margin (dB):    6.9      6.1
Power (dBm):    3.2      3.1
Interleave depth:     1      1
INP:    52.00      0
G.INP:    Enabled      Not enabled
Vectoring status:     5 (VECT_UNCONFIGURED)

RSCorr/RS (%):    0.0028      0.0029
RSUnCorr/RS (%):    0.0000      0.0000
ES/hour:    0      0
Title: Re: What's my expected SNR Margin for BT
Post by: kitz on August 29, 2019, 02:29:45 AM: Ahh yes.. the ECI line with G.INP and capped at 30Mbps.

It looks like your SNRm wavers slightly over the course of the day.
From figures we have seen 6.4 > 7.3 which will probably be reflected in DSLstats graphs. May be worth observing those to see if there is any pattern although your range is within acceptable parameters.
Title: Re: What's my expected SNR Margin for BT
Post by: Windows10User on August 29, 2019, 08:03:52 PM: These are some graphs from DSLStats from around 12 to just before 8pm and it does fluctuate a bit throughout the day.
Title: Re: What's my expected SNR Margin for BT
Post by: pxr5 on August 30, 2019, 11:40:21 AM: I'm on an ECI cab too with BT. SNR down has been on 4.8/4.9 for a long while now:

xdslctl info --stats
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 26376 Kbps, Downstream rate = 73207 Kbps
Bearer: 0, Upstream rate = 20000 Kbps, Downstream rate = 77345 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 4.8 8.3
Attn(dB): 15.1 0.0
Pwr(dBm): 4.1 4.1