50MB deteriorating SNR

GMCinema · 24-02-2010, 19:06

Cable Modem Downstream
DS-1 DS-2 DS-3 DS-4
Frequency 299000000 307000000 315000000 323000000
Lock Status
(QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y Y/Y/Y
Channel Id 5 6 7 8
Modulation 256QAM 256QAM 256QAM 256QAM
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 6.952
Interleave Depth I=12
J=17 I=12
J=17 I=12
J=17 I=12
J=17
Power Level
(dBmV) 1.56 1.75 1.64 1.77
RxMER
(dB) 30.65 30.88 31.01 31.07
Correctable
Codewords 427166789 294589043 225646075 212412201
Uncorrectable
Codewords 486 520 446 480

SNR values have dropped by about 5dB over the last few days and correctable codewords count has shot up ..... Madness .....

Ignitionnet · 24-02-2010, 20:36

I trust you have reported this issue and checked that all connections to the modem are nice and tightly done up, would be madness not to.

GMCinema · 24-02-2010, 20:48

Quote:

Originally Posted by Ignitionnet

I trust you have reported this issue and checked that all connections to the modem are nice and tightly done up, would be madness not to.

Report to who in India? I seriously dread another waste of my time with a 4 hour wait slot for an engineer where the fault is way outside my domicile. And yes, connections are as tight as before and we have had no eartquake.

III · 24-02-2010, 20:56

Call at 8am sir/madam, you'll have a greater chance of getting a UK agent.

Ignitionnet · 24-02-2010, 20:57

Quote:

Originally Posted by GMCinema

Report to who in India? I seriously dread another waste of my time with a 4 hour wait slot for an engineer where the fault is way outside my domicile. And yes, connections are as tight as before and we have had no eartquake.

Engineers come in 4 hour time slots and regrettably you have to have a service technician in before they can escalate the issue to a network engineer.

The 50M support line seems to improve the odds of getting a UK agent.

calmpitbull · 25-02-2010, 19:42

If you can't wait in for 4 hours it obviously isn't that bad.

As the fault could be anywhere, it is impossible to speculate

Sephiroth · 25-02-2010, 22:18

Quote:

Originally Posted by GMCinema

Cable Modem Downstream
DS-1 DS-2 DS-3 DS-4
Frequency 299000000 307000000 315000000 323000000
Lock Status
(QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y Y/Y/Y
Channel Id 5 6 7 8
Modulation 256QAM 256QAM 256QAM 256QAM
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 6.952
Interleave Depth I=12
J=17 I=12
J=17 I=12
J=17 I=12
J=17
Power Level
(dBmV) 1.56 1.75 1.64 1.77
RxMER
(dB) 30.65 30.88 31.01 31.07
Correctable
Codewords 427166789 294589043 225646075 212412201
Uncorrectable
Codewords 486 520 446 480

SNR values have dropped by about 5dB over the last few days and correctable codewords count has shot up ..... Madness .....

Igni's advice is sound. Your SNR is at the lower threshold for 256QAM and if all your home connexions are sound, including in the wall box, an engineer is required.

GMCinema · 26-02-2010, 10:11

I am up by 2dB today as the weather is a little less humid...

---------- Post added at 11:11 ---------- Previous post was at 11:08 ----------

Quote:

Originally Posted by calmpitbull

If you can't wait in for 4 hours it obviously isn't that bad.

As the fault could be anywhere, it is impossible to speculate

I have waited a multitude of 4 hours on 4 occasions so far and eveytime the engineer did absolutely nothing of importance. It was always NETWORK. I have no more 4 hours slots to give away for an appaling setup like this as my hours are counted in decapounds.

GMCinema · 26-02-2010, 23:05

My incloming levels were "too high" and during the first engineer visit I had installed two Forward Path Equalizers: one -4dB and another -8dB in line summing up to -12dB peak.

Now the levels indicated by the modem are down to around +2dB from around +10dB. This leads me to the question weather the Equalizers are the right choice as they are highly frequency dependent in their attenuation characteristics and normally tune/equalize signalling in long cable runs at set frequencies. Should it not be Forward Path Attenuators to be utilised as they have a linear attenuation over the utilised frequency range?

Ignitionnet · 27-02-2010, 09:24

Given how relatively flat the sloping is across your 4 downstream channels:

Power Level (dBmV) 1.56 1.75 1.64 1.77

They would appear to be just fine.

GMCinema · 27-02-2010, 17:43

Cable Modem Downstream
DS-1 DS-2 DS-3 DS-4
Frequency 299000000 307000000 315000000 323000000
Lock Status
(QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y Y/Y/Y
Channel Id 5 6 7 8
Modulation 256QAM 256QAM 256QAM 256QAM
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 6.952
Interleave Depth I=12
J=17 I=12
J=17 I=12
J=17 I=12
J=17
Power Level
(dBmV) 1.93 2.15 1.98 2.19
RxMER
(dB) 29.44 29.67 29.81 29.85
Correctable
Codewords 298517077 216838359 172841268 163876881
Uncorrectable
Codewords 297 258 270 251

calmpitbull · 27-02-2010, 17:56

Quote:

Originally Posted by GMCinema

I am up by 2dB today as the weather is a little less humid...

---------- Post added at 11:11 ---------- Previous post was at 11:08 ----------

I have waited a multitude of 4 hours on 4 occasions so far and eveytime the engineer did absolutely nothing of importance. It was always NETWORK. I have no more 4 hours slots to give away for an appaling setup like this as my hours are counted in decapounds.

Fair point, can't argue with that really. By the way love decapounds!

sollp · 27-02-2010, 18:14

Quote:

Originally Posted by GMCinema

Cable Modem Downstream
DS-1 DS-2 DS-3 DS-4
Frequency 299000000 307000000 315000000 323000000
Lock Status
(QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y Y/Y/Y
Channel Id 5 6 7 8
Modulation 256QAM 256QAM 256QAM 256QAM
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 6.952
Interleave Depth I=12
J=17 I=12
J=17 I=12
J=17 I=12
J=17
Power Level
(dBmV) 1.56 1.75 1.64 1.77
RxMER
(dB) 30.65 30.88 31.01 31.07
Correctable
Codewords 427166789 294589043 225646075 212412201
Uncorrectable
Codewords 486 520 446 480

SNR values have dropped by about 5dB over the last few days and correctable codewords count has shot up ..... Madness .....

It's the Downstream that is giving you a low MER value, this is either being caused by the local network, Headend issues or your installation. So initially the service tech SHOULD eliminate any issues with your premise, then if the problem still exists SHOULD be passed to the Network team to eliminate issues in the network.

Now obviously the initial 4 visits have only identified the slope to be of an issue, as usual instead of checking the levels at the cabinet and adjusting as necessary or reporting issues with the levels, they have taken the quick and easy route of adjusting the levels within the property and as a result not reporting any potential problems in the network you still have problems!