06-05-2011, 21:57
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#1
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Inactive
Join Date: Sep 2009
Location: Preston, Lancashire
Posts: 260
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Qam16/qpsk
Hi all, am normally on QAM16, noticed today though am on QPSK done several reboots and still on QPSK anyone kno why this could be? am not facing any problems.
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06-05-2011, 21:59
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#2
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Sad Doig Fan!
Join Date: Aug 2007
Location: Barry South Wales
Age: 69
Services: With VM for BB 250Mb service.(Deal)
Posts: 11,845
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Re: Qam16/qpsk
Noise on your upstream. QPSK is more noise tolerant. They should be aware of it.
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06-05-2011, 22:01
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#3
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Inactive
Join Date: Sep 2009
Location: Preston, Lancashire
Posts: 260
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Re: Qam16/qpsk
So would they have turned off QAM16 until fixed and put everyone on QPSK?
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06-05-2011, 22:07
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#4
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Inactive
Join Date: Jun 2008
Location: Leeds, West Yorkshire
Age: 47
Posts: 13,995
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Re: Qam16/qpsk
It's automatic.
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06-05-2011, 22:15
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#5
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cf.mega poster
Join Date: Nov 2008
Location: Lincoln
Services: phone + 1gbit BB + SkyQ
Posts: 11,021
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Re: Qam16/qpsk
I noticed by accident that I was on qpsk for over a week back in February and truth be told, I didnt notice any performance degradation. I still got full upload speed and I think my download speed maxed out at 4.5mbit instead of 6 but it wasnt anything to moan about.
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06-05-2011, 23:31
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#6
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cf.mega poster
Join Date: Nov 2010
Location: Stafford
Posts: 4,225
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Re: Qam16/qpsk
it happened to me the other bank holiday, upload speeds slowed to about 2 to 3 meg and pings were all over the place
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07-05-2011, 10:53
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#7
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Sad Doig Fan!
Join Date: Aug 2007
Location: Barry South Wales
Age: 69
Services: With VM for BB 250Mb service.(Deal)
Posts: 11,845
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Re: Qam16/qpsk
You need a tech out to adjust your power level. That is the whole reason it is happening in your case.
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07-05-2011, 17:13
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#8
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Inactive
Join Date: Sep 2010
Posts: 260
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Re: Qam16/qpsk
And if you're on the Dud I'm guessing:
ATDMA = QAM16
TDMA = QPSK?
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07-05-2011, 17:27
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#9
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Inactive
Join Date: Jun 2008
Location: Leeds, West Yorkshire
Age: 47
Posts: 13,995
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Re: Qam16/qpsk
Nah. ATDMA = 6.4MHz channel width, TDMA = 3.2MHz channel width.
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07-05-2011, 18:02
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#10
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Inactive
Join Date: Sep 2010
Posts: 260
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Re: Qam16/qpsk
So if you're switched to TDMA there's noise issues, or is this a completely different thing altogether?
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07-05-2011, 19:18
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#11
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cf.mega poster
Join Date: Sep 2003
Posts: 12,048
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Re: Qam16/qpsk
What I say is subject to been wrong.
But generally interpret ATDMA as been docsis2, if there is a noise issue it will drop back to QPSK, on the superhub that will appear as ATDMA 10240kbit/sec. Still be the equivelent to QAM16 on docsis1 in terms of capacity. If no noise issue you should be seeing ATDMA 20480kbit/sec.
Docsis1 would show as TDMA 10240kb/src if no noise issue or TDMA 5120kbit/sec if a noise issue, the latter been QPSK on docsis1.
I have never heard of someone been rolled back to docsis1 due to noise it would just go to QPSK but stay on docsis2.
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07-05-2011, 19:33
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#12
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cf.mega poster
Join Date: Nov 2010
Location: Stafford
Posts: 4,225
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Re: Qam16/qpsk
Quote:
Originally Posted by Chrysalis
What I say is subject to been wrong.
But generally interpret ATDMA as been docsis2, if there is a noise issue it will drop back to QPSK, on the superhub that will appear as ATDMA 10240kbit/sec. Still be the equivelent to QAM16 on docsis1 in terms of capacity. If no noise issue you should be seeing ATDMA 20480kbit/sec.
Docsis1 would show as TDMA 10240kb/src if no noise issue or TDMA 5120kbit/sec if a noise issue, the latter been QPSK on docsis1.
I have never heard of someone been rolled back to docsis1 due to noise it would just go to QPSK but stay on docsis2.
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he wont be put back to docsis 1, his area wont have the upload increase, and will be on docsis 1 in the first place
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07-05-2011, 21:44
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#13
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Inactive
Join Date: Jun 2008
Location: Leeds, West Yorkshire
Age: 47
Posts: 13,995
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Re: Qam16/qpsk
Quote:
Originally Posted by Chrysalis
What I say is subject to been wrong.
But generally interpret ATDMA as been docsis2, if there is a noise issue it will drop back to QPSK, on the superhub that will appear as ATDMA 10240kbit/sec. Still be the equivelent to QAM16 on docsis1 in terms of capacity. If no noise issue you should be seeing ATDMA 20480kbit/sec.
Docsis1 would show as TDMA 10240kb/src if no noise issue or TDMA 5120kbit/sec if a noise issue, the latter been QPSK on docsis1.
I have never heard of someone been rolled back to docsis1 due to noise it would just go to QPSK but stay on docsis2.
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Correct. The secondary / fallback profile is still a 6.4MHz wide DOCSIS 2 channel, just the modulation changes.
They could actually have 3 profiles, 64QAM, 16QAM and QPSK for example, perhaps one to think about once plant upgrades are done.
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07-05-2011, 22:31
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#14
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Inactive
Join Date: Sep 2009
Location: Preston, Lancashire
Posts: 260
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Re: Qam16/qpsk
I am still on QPSK.
Cable Modem Downstream
Downstream Lock : Locked
Downstream Channel Id : 166
Downstream Frequency : 307000000 Hz
Downstream Modulation : QAM256
Downstream Symbol Rate : 6952 Ksym/sec
Downstream Interleave Depth : taps12Increment17
Downstream Receive Power Level : 7.5 dBmV
Downstream SNR : 37.4 dB
Cable Modem Upstream
Upstream Lock : Locked
Upstream Channel ID : 1
Upstream Frequency : 35800000 Hz
Upstream Modulation : QPSK
Upstream Symbol Rate : 5120 Ksym/sec
Upstream transmit Power Level : 49.7 dBmV
Upstream Mini-Slot Size : 4
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09-05-2011, 17:58
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#15
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Inactive
Join Date: May 2006
Posts: 317
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Re: Qam16/qpsk
Would this explain why my PL is shocking for the past 3 days
im also on the QPSK crap now
20 mbit at POPLAR ubr London..
Its unplayable peak hours
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