3dB SNR - how to achieve?

Broadband Related > FTTC and FTTP Issues

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dee.jay:
Ah, that makes sense.

So, how about for the 6 year old FTTC line that is on 6dB - can that be ever made to run at 3?

Does the effect of interleaving go away? I was hoping for two identical 57Mb lines at least.

DaveC:
Just to say I had a second FTTC line installed on a Huwaei cab a few months ago (about 150m to cabinet). Initial max attainable was about 77Mbit/s, with a line rate of about 67Mbit/s. This lasted about 44 hours, and then the line resynced itself and the line rate jumped to match the max attainable.

It's slowly improved since then, and I now get a line rate of 79999, matching my first line.

dee.jay:

--- Quote from: DaveC on September 10, 2018, 10:09:14 PM ---Just to say I had a second FTTC line installed on a Huwaei cab a few months ago (about 150m to cabinet). Initial max attainable was about 77Mbit/s, with a line rate of about 67Mbit/s. This lasted about 44 hours, and then the line resynced itself and the line rate jumped to match the max attainable.

It's slowly improved since then, and I now get a line rate of 79999, matching my first line.

--- End quote ---

Mine has done exactly the same overnight! I now have two lines at ~57000. With load balancing via pfSense, I can now download at about 112-113Mbps in real terms in Windows.

I learned on Friday when the lady from BT came and fitted the 2nd PSTN line that I am ~600M from the cabinet because the underground access point runs 100M in the wrong direction to the cabinet... I'm going to let my two modems run for now and hope that the SNR does indeed drop to 3dB. From my calculations there's no reason the 2nd line shouldn't reach 78Mb if the SNR were to drop accordingly.

In fact, stats: -

Sky, Line #1

--- Code: ---# xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 16972 Kbps, Downstream rate = 57200 Kbps
Bearer: 0, Upstream rate = 16972 Kbps, Downstream rate = 57832 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 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): 6.3 5.8
Attn(dB): 19.3 0.0
Pwr(dBm): 12.7 7.4
VDSL2 framing
Bearer 0
MSGc: -6 24
B: 227 239
M: 1 1
T: 0 64
R: 12 14
S: 0.1254 0.4499
L: 15312 4517
D: 4 1
I: 240 127
N: 240 254
Q: 4 0
V: 0 0
RxQueue: 138 0
TxQueue: 23 0
G.INP Framing: 18 0
G.INP lookback: 23 0
RRC bits: 0 24
Bearer 1
MSGc: 122 -6
B: 0 0
M: 2 0
T: 2 0
R: 16 0
S: 8.0000 0.0000
L: 32 0
D: 1 0
I: 32 0
N: 32 0
Q: 0 0
V: 0 0
RxQueue: 0 0
TxQueue: 0 0
G.INP Framing: 0 0
G.INP lookback: 0 0
RRC bits: 0 0
Counters
Bearer 0
OHF: 0 775731
OHFErr: 0 67
RS: 1776652748 3203688
RSCorr: 413079 391
RSUnCorr: 0 0
Bearer 1
OHF: 3480964 0
OHFErr: 0 0
RS: 27847221 0
RSCorr: 8 0
RSUnCorr: 0 0

Retransmit Counters
rtx_tx: 148509569 0
rtx_c: 2602 0
rtx_uc: 0 0

G.INP Counters
LEFTRS: 0 0
minEFTR: 57828 0
errFreeBits: 128985764 0

Bearer 0
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 1923376609 0
Data Cells: 16486613 0
Drop Cells: 0
Bit Errors: 0 0

Bearer 1
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 0 0
Data Cells: 0 0
Drop Cells: 0
Bit Errors: 0 0

ES: 0 118
SES: 0 0
UAS: 117 117
AS: 55914

Bearer 0
INP: 57.00 0.00
INPRein: 1.00 0.00
delay: 0 0
PER: 0.00 7.22
OR: 0.01 33.21
AgR: 57959.19 17005.69

Bearer 1
INP: 2.00 0.00
INPRein: 2.00 0.00
delay: 0 0
PER: 16.06 0.01
OR: 63.75 0.01
AgR: 63.75 0.01

Bitswap: 30121/30121 1301/1302

Total time = 1 days 5 min 13 sec
FEC: 697487 602
CRC: 0 129
ES: 0 118
SES: 0 0
UAS: 117 117
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 15 minutes time = 5 min 13 sec
FEC: 36 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 64 17
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 5 min 13 sec
FEC: 36 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 1 day time = 24 hours 0 sec
FEC: 697451 602
CRC: 0 129
ES: 0 118
SES: 0 0
UAS: 117 117
LOS: 0 0
LOF: 0 0
LOM: 0 0
Since Link time = 15 hours 31 min 53 sec
FEC: 413079 391
CRC: 0 67
ES: 0 63
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0

--- End code ---

AAISP, Line #2

--- Code: ---# xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 1
Last initialization procedure status: 0
Max: Upstream rate = 16544 Kbps, Downstream rate = 56504 Kbps
Bearer: 0, Upstream rate = 16679 Kbps, Downstream rate = 57731 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 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): 6.1 5.9
Attn(dB): 18.7 0.0
Pwr(dBm): 12.7 7.5
VDSL2 framing
Bearer 0
MSGc: -6 24
B: 235 239
M: 1 1
T: 0 64
R: 12 14
S: 0.1301 0.4578
L: 15250 4439
D: 8 1
I: 248 127
N: 248 254
Q: 8 0
V: 1 0
RxQueue: 48 0
TxQueue: 12 0
G.INP Framing: 18 0
G.INP lookback: 12 0
RRC bits: 0 24
Bearer 1
MSGc: 122 -6
B: 0 0
M: 2 0
T: 2 0
R: 16 0
S: 8.0000 0.0000
L: 32 0
D: 1 0
I: 32 0
N: 32 0
Q: 0 0
V: 0 0
RxQueue: 0 0
TxQueue: 0 0
G.INP Framing: 0 0
G.INP lookback: 0 0
RRC bits: 0 0
Counters
Bearer 0
OHF: 0 1605382
OHFErr: 0 27
RS: 873708048 179303
RSCorr: 7297 159
RSUnCorr: 0 0
Bearer 1
OHF: 1776124 0
OHFErr: 0 0
RS: 14208498 0
RSCorr: 2 0
RSUnCorr: 0 0

Retransmit Counters
rtx_tx: 192 0
rtx_c: 178 0
rtx_uc: 0 0

G.INP Counters
LEFTRS: 2 0
minEFTR: 57722 0
errFreeBits: 25115869 0

Bearer 0
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 3167267419 0
Data Cells: 14559980 0
Drop Cells: 0
Bit Errors: 0 0

Bearer 1
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 0 0
Data Cells: 0 0
Drop Cells: 0
Bit Errors: 0 0

ES: 12 59
SES: 10 0
UAS: 152 142
AS: 28530

Bearer 0
INP: 48.00 0.00
INPRein: 0.00 0.00
delay: 0 0
PER: 0.00 7.35
OR: 0.01 32.64
AgR: 57822.51 16712.04

Bearer 1
INP: 2.00 0.00
INPRein: 2.00 0.00
delay: 0 0
PER: 16.06 0.01
OR: 63.75 0.01
AgR: 63.75 0.01

Bitswap: 18113/18113 306/306

Total time = 1 days 4 min 7 sec
FEC: 93839 427
CRC: 4454 63
ES: 12 59
SES: 10 0
UAS: 152 142
LOS: 1 0
LOF: 8 0
LOM: 0 0
Latest 15 minutes time = 4 min 7 sec
FEC: 26 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 70 2
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 4 min 7 sec
FEC: 26 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 1 day time = 24 hours 0 sec
FEC: 93813 427
CRC: 4454 63
ES: 12 59
SES: 10 0
UAS: 152 142
LOS: 1 0
LOF: 8 0
LOM: 0 0
Since Link time = 7 hours 55 min 29 sec
FEC: 7297 159
CRC: 0 27
ES: 0 25
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0

--- End code ---

j0hn:

--- Quote ---From my calculations there's no reason the 2nd line shouldn't reach 78Mb if the SNR were to drop accordingly
--- End quote ---

3dB is worth roughly 11Mb if your line makes good use of the D3 band. Probably less if not

Never in a million years will you see 21Mb improvement with a reduction to 3dB.

dee.jay:
My maths were fag packet on the basis of seeing 1dB when reducing rate from 57000 to 50000 - so yeah - would be nice.

BT checker claims line should be 70.7Mb, maybe that more realistic?

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