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Author Topic: G.fast Line Length  (Read 567 times)

adslmax

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G.fast Line Length
« on: January 31, 2020, 12:52:56 AM »

Are these figure correct between VDSL2 and G.fast?

Mine is according to google map (dsl cable route to the pcp cabinet from back garden to the cabinet - not straight line)

831 ft - 253.1 metres line length - VDSL2 (this the same reported as GEA Test Estimated Line Length In Metres: 253.1

929 ft - 283.1 metres line length - G.fast
                      or
732 ft - 223.1 metres line length - G.fast


How does signal attenuation relate to wire gauge and distance ?
Attenuation relates to wire gauge and distance (approximately) as follows:

wire gauge  thickness   @300kHz    @68kHz
22 AWG      .64 mm       8.62      4.62    db/km
24 AWG      .51 mm      11.90      6.65    dB/km
26 AWG      .40 mm      13.81      9.37    dB/km

A sensible formula, in common use, assuming 26AWG wire, is:
DS_Atn = 13.81 dB/km * distance

It is important to note that long loop wire thickness is not consistent, it tends to increase with distance from the CO. Thinner twisted pairs are often used underground near the CO while thicker wires are used on long loops in the regions closer to the subscriber location in order to minimize the total loop resistance.

Because most loops are made up of different gauges of wire the Atn/km ratio can decrease (stepwise) with distance and is not a linear function of the loop length.

https://www.speedguide.net/dsl_speed_calc.php
« Last Edit: January 31, 2020, 01:52:26 AM by adslmax »
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CarlT

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Re: G.fast Line Length
« Reply #1 on: January 31, 2020, 10:57:19 AM »

I have no idea what you're actually asking?

It doesn't matter. The numbers from the modem in terms of maximum achievable rate matter, not a theoretical calculator that takes no account of actual conditions or indeed the attenuation it reports as how this is arrived at varies.
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kitz

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Re: G.fast Line Length
« Reply #2 on: January 31, 2020, 12:56:41 PM »

^This
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burakkucat

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Re: G.fast Line Length
« Reply #3 on: January 31, 2020, 05:47:00 PM »

Are these figure correct between VDSL2 and G.fast?

Mine is according to google map (dsl cable route to the pcp cabinet from back garden to the cabinet - not straight line)

831 ft - 253.1 metres line length - VDSL2 (this the same reported as GEA Test Estimated Line Length In Metres: 253.1

929 ft - 283.1 metres line length - G.fast
                      or
732 ft - 223.1 metres line length - G.fast

I'm stopping at this point and will offer a comment on the above. We know the infrastructure layout for both a VDSL2 and a G.Fast circuit.

For the former, it is a metallic pathway of length X metres (the NTE5 to the PCP) and tie-cable length of Y metres (linking the PCP to the DSLAM in a separate cabinet). If I were to attach a time domain spectrometer to the pair at the NTE5 I could easily see the low-pass filter in the "fibre cabinet", which would be a distance (essentially) equal to X + Y metres. (The 253.1 metres you mention, above.)

For the latter, it is the same metallic pathway of length X metres (the NTE5 to the PCP) and an additional length of Z metres (linking the PCP to the DSLAM in the PCP's side-pod). The length of Z metres will be less than Y metres (from the VDSL2 case). Again, if I were to attach a time domain spectrometer to the pair at the NTE5 I could easily see the low-pass filter in the PCP's side-pod, which would be a distance (essentially) equal to X + Z metres.

As (Y > Z), then (X + Y) > (X + Z). Hence looking at the distances you mention, above, I suggest that out of the two the 223.1 metres would be correct.

Finally I am going to drop the decimal point ones from both values and say, from what you have shown, your VDSL2 circuit length was 253 metres and your G.Fast circuit length is 223 metres.
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adslmax

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Re: G.fast Line Length
« Reply #4 on: January 31, 2020, 05:51:24 PM »

Thanks burakkucat

VDSL2 80/20 about right for 253.1m (max rate 90/26)
G.fast 229/50 about right for 223.1m (max rate 249/52)
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burakkucat

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Re: G.fast Line Length
« Reply #5 on: January 31, 2020, 05:55:19 PM »

You are welcome. But please do not obsess over those values.
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adslmax

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Re: G.fast Line Length
« Reply #6 on: January 31, 2020, 05:57:14 PM »

Look like ISPreview are spot on

Distance to cabinet (metres)    Estimated downstream speed    Estimated upstream speed    Cumulative %’age of premises at this distance
100m    500 Mbps    50 Mbps    11%
150m    300 Mbps    45 Mbps    20%
200m    250 Mbps    40 Mbps    31%
300m    150 Mbps    20 Mbps    52%
370m    100 Mbps    20 Mbps    64%
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Iam_TJ

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Re: G.fast Line Length
« Reply #7 on: January 31, 2020, 09:05:35 PM »

300m    150 Mbps    20 Mbps    52%
370m    100 Mbps    20 Mbps    64%
I think I'd cry if I knew what the stats are for 2,000m !
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re0

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Re: G.fast Line Length
« Reply #8 on: January 31, 2020, 09:19:53 PM »

I think I'd cry if I knew what the stats are for 2,000m !
0 Mbps. Now you know.
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biohead

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Re: G.fast Line Length
« Reply #9 on: February 02, 2020, 03:46:06 PM »

I think I'd cry if I knew what the stats are for 2,000m !
My 450m line wouldn't even sync.... so technically no stats to even be had!
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