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Author Topic: Summer - Winter  (Read 6590 times)

burakkucat

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Re: Summer - Winter
« Reply #15 on: January 09, 2022, 12:34:42 AM »

I can confirm that arithmetically --

20 x log10 1.0786 = 0.657 (to three decimal places)

However I am uncertain if one can say that the above is equivalent to a +0.657 dB power gain in an xDSL link.
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Weaver

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Re: Summer - Winter
« Reply #16 on: January 09, 2022, 01:28:26 AM »

The idea is that that’s the difference (ratio) between winter and summer of received power as seen at the far end. I’m not at all sure that’s correct; I agree with you. The thinking is that there’s a voltage drop across each resistance element and these drops are proportional to the resistance of the element by V=IR, and the current is fixed, by the continuity equation. I don’t know whether the input current is fixed regardless of other parameters.
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Weaver

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Re: Summer - Winter
« Reply #17 on: January 22, 2022, 05:39:22 AM »

I’m seeing some amazing downstream and upstream sync rates, even though there has been almost no snow since xmas and it’s not down to 0 C. But it has been cold at times. See line 1 upstream, 673 kbps as opposed to 500-550 k, and line 4 downstream with 3.184 Mbps as opposed to around 2.5-2.9 Mbps. That could be the highest downstream sync rate ever seen, I forget. And it’s 100% reliable at the moment.

Code: [Select]
Modems’ sync rates:
  #1: downstream 2.902 Mbps, upstream 673 kbps
  #2: downstream 3.019 Mbps, upstream 528 kbps
  #4: downstream 3.184 Mbps, upstream 402 kbps

--------
* Estimated combined IP PDU rate totals (*):   
     downstream:  7.650 Mbps ( at an assumed 95% MLF ),
       upstream:  1.346 Mbps ( at an assumed 95% MLF ),

(*) calculated from:
IP PDU rate upstream   = sync rate upstream   × protocol efficiency × MLF upstream,
IP PDU rate downstream = sync rate downstream × protocol efficiency × MLF downstream
   where :
   * if MLF, the so-called 'modem loading factor' = 100% = no rate-limiting, driving at maximum rate,
   * MLF downstream = 95% (assumed);
   * MLF upstream   = 95% (assumed);
   * 'protocol efficiency' is concerned with a protocol's bytestream bloat,
   * protocol efficiency = 0.884434 ⇐ (
ADSL and ATM,
assumed PDU size = 1500 bytes,
DSL header overhead = 32 bytes
)
« Last Edit: January 22, 2022, 05:45:06 AM by Weaver »
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Alex Atkin UK

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Re: Summer - Winter
« Reply #18 on: January 22, 2022, 06:52:25 AM »

I’m seeing some amazing downstream and upstream sync rates, even though there has been almost no snow since xmas and it’s not down to 0 C. But it has been cold at times. See line 1 upstream, 673 kbps as opposed to 500-550 k, and line 4 downstream with 3.184 Mbps as opposed to around 2.5-2.9 Mbps. That could be the highest downstream sync rate ever seen, I forget. And it’s 100% reliable at the moment.

Code: [Select]
Modems’ sync rates:
  #1: downstream 2.902 Mbps, upstream 673 kbps
  #2: downstream 3.019 Mbps, upstream 528 kbps
  #4: downstream 3.184 Mbps, upstream 402 kbps

--------
* Estimated combined IP PDU rate totals (*):   
     downstream:  7.650 Mbps ( at an assumed 95% MLF ),
       upstream:  1.346 Mbps ( at an assumed 95% MLF ),

(*) calculated from:
IP PDU rate upstream   = sync rate upstream   × protocol efficiency × MLF upstream,
IP PDU rate downstream = sync rate downstream × protocol efficiency × MLF downstream
   where :
   * if MLF, the so-called 'modem loading factor' = 100% = no rate-limiting, driving at maximum rate,
   * MLF downstream = 95% (assumed);
   * MLF upstream   = 95% (assumed);
   * 'protocol efficiency' is concerned with a protocol's bytestream bloat,
   * protocol efficiency = 0.884434 ⇐ (
ADSL and ATM,
assumed PDU size = 1500 bytes,
DSL header overhead = 32 bytes
)

Didn't you say there IS FTTC somewhere far the other end of your looooong wire?  Could some customers be moving off ADSL onto that thus causing some minor improvements to your own lines?
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Weaver

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Re: Summer - Winter
« Reply #19 on: January 22, 2022, 12:10:38 PM »

Alex that’s quite correct, good point.

Doesn’t VDSL2/FTTC use any of the same frequencies?

FTTC was introduced near NSBFD some few years ago, can’t remember when, but I’m thinking that now is a bit late for people to be switching. You would think that if people were going to upgrade at all, then they would have upgraded fairly soon the moment the technology was advertised in the area. Perhaps some don’t care or don’t understand then I’m assuming they would never upgrade at all unless they were kicked off ADSL2+. ( Like Burakkucat? ) Could the latter be happening in the area.

I hear what you say, and that would explain things if the frequencies do compete but it’s just the timing that seems odd to me.
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Alex Atkin UK

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Re: Summer - Winter
« Reply #20 on: January 25, 2022, 04:29:43 AM »

Moving to VDSL at least takes the crosstalk off the E side and we know there is something done at the cabinet to determine the power levels to avoid swamping out ADSL lines.

When the lines are as long as yours I doubt it takes much to make a dramatic difference.  I'm actually surprised more wasn't done to get people on super long times some solution from the nearest cabinet, at least shrinking the distance a little. Presumably LLU scuppers that as you'd need NO lines on legacy products.
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Weaver

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Re: Summer - Winter
« Reply #21 on: January 25, 2022, 09:26:34 AM »

The nearest cab would only be about 0.75 mi nearer, so still 3.75 mi to go.
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Re: Summer - Winter
« Reply #22 on: January 25, 2022, 10:37:14 AM »

Doesn’t VDSL2/FTTC use any of the same frequencies?

Openreach did conduct trials running LR-VDSL from cabinets, however to work well these required the shutdown of ADSL which in turn caused complaints from a couple of LLU operators. Those trials were removed from the network in 2018.

Diminishing returns on investment the real killer - AIO cabinets nearly always needed public subsidy as they tended to serve fewer premises and were expensive in turns of copper 'splicing', power and backhaul.

Weaver

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Re: Summer - Winter
« Reply #23 on: January 25, 2022, 11:14:39 AM »

> which in turn caused complaints from a couple of LLU operators. Those trials were removed from the network in 2018.

I don’t understand why the LLU moaners should be a problem. Could just give them a free upgrade to FTTC, like Burakkucat. Shouldn’t let the primitives stall progress.
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Re: Summer - Winter
« Reply #24 on: January 25, 2022, 06:24:57 PM »

Perhaps but OLOs are entitled to MPF. This would have prevented it. They had every right to complain free upgrade or not.

They are still not overjoyed with being forced to take bitstream FTTP.

Alex Atkin UK

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Re: Summer - Winter
« Reply #25 on: January 26, 2022, 09:07:40 PM »

They are still not overjoyed with being forced to take bitstream FTTP.

They are welcome to run their own fibres to every property they want to serve. ;)

I get the reasoning why MPF was a good thing and got us the healthy competition we have today, but sooner or later it had to go.  I'd argue that should have happened with FTTC but now it HAS to happen with FTTP.
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