Community Forum

Gigabit Speeds (CM1000)

Frequent Visitor

Gigabit Speeds (CM1000)

I have a CM1000, just upgraded to gigabit tier.  I typically get somewhere in the 200-300 mbps range.  Every once in a while I'll briefly spike up to about 500, but also often get sub 100 mbps speeds.

There's one channel that's really noisy and generating a ton of uncorrectables.  I actually had this issue when I only had the 60 megabit service and an 8 channel modem.  But back then I could sometimes reboot the modem a few times and get a new channel allocation, and I'd be back up to full speed.  No such luck with the gigabit service.

I will attempt to attach the stats.

Advice?

 

Dowstream

Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked QAM256 17 531000000 Hz -10.5 dBmV 39.3 dB 49674908 0 0
2 Locked QAM256 9 483000000 Hz -8.2 dBmV 40.9 dB 47688728 0 0
3 Locked QAM256 10 489000000 Hz -9.7 dBmV 39.9 dB 47692600 0 0
4 Locked QAM256 11 495000000 Hz -10.7 dBmV 39.3 dB 47696052 0 0
5 Locked QAM256 12 501000000 Hz -9.7 dBmV 39.9 dB 47699954 0 0
6 Locked QAM256 13 507000000 Hz -8.5 dBmV 40.7 dB 47703302 0 0
7 Locked QAM256 14 513000000 Hz -11.2 dBmV 38.7 dB 47707687 0 0
8 Locked QAM256 15 519000000 Hz -11.9 dBmV 26.0 dB 5319138 30620911 11758124
9 Locked QAM256 16 525000000 Hz -10.0 dBmV 32.0 dB 47714578 0 0
10 Locked QAM256 18 537000000 Hz -12.7 dBmV 37.6 dB 47718531 0 0
11 Locked QAM256 19 543000000 Hz -13.8 dBmV 37.0 dB 47722284 0 0
12 Locked QAM256 20 549000000 Hz -12.1 dBmV 38.3 dB 47726138 0 0
13 Locked QAM256 21 555000000 Hz -13.8 dBmV 35.0 dB 47729778 0 0
14 Locked QAM256 22 561000000 Hz -13.1 dBmV 36.2 dB 47733215 0 0
15 Locked QAM256 23 567000000 Hz -10.7 dBmV 32.8 dB 47737221 0 0
16 Locked QAM256 24 573000000 Hz -10.8 dBmV 37.9 dB 47740654 0 0
17 Locked QAM256 25 579000000 Hz -13.8 dBmV 34.6 dB 47744690 0 0
18 Locked QAM256 26 585000000 Hz -12.6 dBmV 37.1 dB 47748034 0 0
19 Locked QAM256 27 591000000 Hz -9.5 dBmV 40.1 dB 47751856 0 0
20 Locked QAM256 28 597000000 Hz -9.7 dBmV 39.9 dB 47755712 0 0
21 Locked QAM256 29 603000000 Hz -11.6 dBmV 38.5 dB 47759259 0 0
22 Locked QAM256 30 609000000 Hz -10.8 dBmV 38.7 dB 47763089 0 0
23 Locked QAM256 31 615000000 Hz -10.4 dBmV 39.3 dB 47766643 0 0
24 Locked QAM256 32 621000000 Hz -11.4 dBmV 38.6 dB 47770406 0 0
25 Locked QAM256 33 627000000 Hz -11.6 dBmV 38.4 dB 47774333 0 0
26 Locked QAM256 34 633000000 Hz -10.3 dBmV 39.4 dB 47777895 0 0
27 Locked QAM256 35 639000000 Hz -11.3 dBmV 38.5 dB 47781386 0 0
28 Locked QAM256 36 645000000 Hz -13.0 dBmV 37.3 dB 47785753 0 0
29 Locked QAM256 37 651000000 Hz -12.8 dBmV 37.4 dB 47788958 0 0
30 Locked QAM256 38 657000000 Hz -11.6 dBmV 38.3 dB 47792981 0 0
31 Locked QAM256 39 663000000 Hz -12.5 dBmV 37.7 dB 47793609 0 0
32 Locked QAM256 40 669000000 Hz -13.2 dBmV 36.9 dB 47794774 0 0

 

Upstream

Channel Lock Status Modulation Channel ID Frequency Power
1 Locked ATDMA 1 35800000 Hz 48.0 dBmV
2 Locked ATDMA 2 29400000 Hz 47.0 dBmV
3 Locked ATDMA 3 23000000 Hz 47.0 dBmV
4 Locked ATDMA 4 16600000 Hz 46.5 dBmV
5 Not Locked Unknown 0 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Hz 0.0 dBmV
Diamond Problem Solver

Re: Gigabit Speeds (CM1000)

Every downstream channel is too low and out of spec. The SNR is low on multiple channels. How many splitters do you go through? Try to hook up your modem before any splitters to have a comparison to inside and outside levels

I am a Retired Official Comcast Employee
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark a post as the Best Answer!
Frequent Visitor

Re: Gigabit Speeds (CM1000)

One splitter, I believe this was an issue before I installed the splitter, but of course I'll remove it and retest at the next opportunity.

Diamond Problem Solver

Re: Gigabit Speeds (CM1000)

If that’s the case you should have a tech out to check outside.

I am a Retired Official Comcast Employee
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark a post as the Best Answer!
Contributor

Re: Gigabit Speeds (CM1000)

If you are actually on gigabit then the only downstream channel that matters is the docsis3.1 and you did not post the information for it .  Some docsis 3.1 modems have a firmware problem and report incorrect snr numbers for the plc. I have the mb8600 and it has that issue, not sure about the cm1000. Your docsis 3.1 downstream is most likely also out of spec. 

Frequent Visitor

Re: Gigabit Speeds (CM1000)

Is this the correct info?  This is without the splitter.  The numbers did improve somewhat.  

 

Downstream OFDM

Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked 0, 1 159 690000000 Hz -8.6 dBmV 36.3 dB 1246 ~ 2849 17641400 3831302 0
2 Not Locked 0 0 0 Hz -0.7 dBmV 0.0 dB 0 ~ 4095 0 0 0
Expert

Re: Gigabit Speeds (CM1000)


@jw32097 wrote:

If you are actually on gigabit then the only downstream channel that matters is the docsis3.1   


Not quite. Any channel can inject noise into the mix and poison / impair the entire connection.



I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!
Highlighted
Frequent Visitor

Re: Gigabit Speeds (CM1000)

There's some relevant information that I carelessly omitted, I do have an internal MoCA network, so there's also a MoCA filter at the POE, 1 passive splitter, then the MoCA device which I guess could be thought of as a powered splitter in this context.

 

Anyway, after checking all connections and buttoning everything up, I was able to get it to where that dirty channel has no uncorrectables and fewer correcables, but power levels are still really low and SNR not great on some channels:

 

Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked QAM256 17 531000000 Hz -11.1 dBmV 39.0 dB 96025743 0 0
2 Locked QAM256 9 483000000 Hz -8.4 dBmV 40.9 dB 94825115 0 0
3 Locked QAM256 10 489000000 Hz -9.9 dBmV 40.0 dB 94828534 0 0
4 Locked QAM256 11 495000000 Hz -10.9 dBmV 39.2 dB 94832554 0 0
5 Locked QAM256 12 501000000 Hz -9.9 dBmV 40.0 dB 94836291 0 0
6 Locked QAM256 13 507000000 Hz -8.6 dBmV 40.8 dB 94839608 0 0
7 Locked QAM256 14 513000000 Hz -11.3 dBmV 39.0 dB 94843758 0 0
8 Locked QAM256 15 519000000 Hz -12.1 dBmV 28.4 dB 94818860 28294 0
9 Locked QAM256 16 525000000 Hz -10.4 dBmV 34.9 dB 94850585 0 0
10 Locked QAM256 18 537000000 Hz -14.3 dBmV 36.3 dB 94854734 0 0
11 Locked QAM256 19 543000000 Hz -13.1 dBmV 37.6 dB 94858518 0 0
12 Locked QAM256 20 549000000 Hz -11.5 dBmV 38.9 dB 94862321 0 0
13 Locked QAM256 21 555000000 Hz -13.7 dBmV 36.1 dB 94866666 0 0
14 Locked QAM256 22 561000000 Hz -13.2 dBmV 37.3 dB 94869262 0 0
15 Locked QAM256 23 567000000 Hz -10.8 dBmV 37.2 dB 94873825 0 0
16 Locked QAM256 24 573000000 Hz -11.0 dBmV 38.9 dB 94877500 0 0
17 Locked QAM256 25 579000000 Hz -14.1 dBmV 35.4 dB 94880453 0 0
18 Locked QAM256 26 585000000 Hz -12.9 dBmV 37.0 dB 94884557 0 0
19 Locked QAM256 27 591000000 Hz -9.8 dBmV 40.0 dB 94888204 0 0
20 Locked QAM256 28 597000000 Hz -10.0 dBmV 39.9 dB 94892155 0 0
21 Locked QAM256 29 603000000 Hz -11.8 dBmV 38.4 dB 94895587 0 0
22 Locked QAM256 30 609000000 Hz -11.0 dBmV 38.8 dB 94899552 0 0
23 Locked QAM256 31 615000000 Hz -10.6 dBmV 39.3 dB 94903306 0 0
24 Locked QAM256 32 621000000 Hz -11.7 dBmV 38.5 dB 94907025 0 0
25 Locked QAM256 33 627000000 Hz -11.9 dBmV 38.4 dB 94910710 0 0
26 Locked QAM256 34 633000000 Hz -10.6 dBmV 39.2 dB 94914167 0 0
27 Locked QAM256 35 639000000 Hz -11.5 dBmV 38.5 dB 94917721 0 0
28 Locked QAM256 36 645000000 Hz -13.3 dBmV 37.2 dB 94922044 0 0
29 Locked QAM256 37 651000000 Hz -13.1 dBmV 37.3 dB 94925570 0 0
30 Locked QAM256 38 657000000 Hz -11.8 dBmV 38.4 dB 94929422 0 0
31 Locked QAM256 39 663000000 Hz -12.7 dBmV 37.6 dB 94929794 0 0
32 Locked QAM256 40 669000000 Hz -13.5 dBmV 36.8 dB 94931356 0 0
 

 

OFDM still has what?  Low Power, Marginal SNR, and a high proportion of correctables?  Is that okay?

 

Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked 0, 1 159 690000000 Hz -13.8 dBmV 33.0 dB 1246 ~ 2849 57834639 16031615 0
2 Not Locked 0 0 0 Hz -4.9 dBmV 0.0 dB 0 ~ 4095 0 0 0
Expert

Re: Gigabit Speeds (CM1000)

ALL the downstream channel power levels are still on the weak side. Needs more work. If you can't improve it any further, then book a tech visit as @CCAndrew has advised. Good luck with it !



I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!
Diamond Problem Solver

Re: Gigabit Speeds (CM1000)

@SBG6580dude
Whatever you did, you actually made it worse. If you can, hook up your modem at the ground block, take your readings again. This will at least tell you if your troubles are inside or outside.

I am a Retired Official Comcast Employee
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark a post as the Best Answer!
Frequent Visitor

Re: Gigabit Speeds (CM1000)

Yes, I reinstalled the splitter and other paraphernalia, that's why it got worse compared to the first OFDM reading, which was taken with a homerun to the cable modem.  But it's better now than it was when I made the OP.  

Expert

Re: Gigabit Speeds (CM1000)

All channels matter.



I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!
Frequent Visitor

Re: Gigabit Speeds (CM1000)

Just following up to say that at this point the 519 mhz channel won't lock on at all and I'm running at a blazing 30 mbps.  Will try to get a tech out.

Expert

Re: Gigabit Speeds (CM1000)

Please post back with how things turn out.



I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!
Frequent Visitor

Re: Gigabit Speeds (CM1000)

Tech was here for a couple of hours this morning.  Checked all the house wiring and ran a new cable to the PoE.  He didn't say specifically what was wrong, but the noise on the line seems to be gone and I'm consistently getting 900+ mbps.

Expert

Re: Gigabit Speeds (CM1000)

Good to hear this ! Hope that this holds up for you ! Good luck !


I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!