Why do I keep losing OFDM Downstream channels on my modem?

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I'm a Reliable Contributor
Posts: 332

Why do I keep losing OFDM Downstream channels on my modem?

I had a look at the signal levels on my CODA-4582 and noticed that after several days, I lose the OFDM Downstream channels.

 

Is it normal for the OFDM Downstream channel to disappear every few days?  I would restart the modem and I get the channel lock.  After a few days, the channel disappears.  My internet connection speed seems fine and I am getting the 500/20 speed I am on.  I am just wondering what could be the problem.  

 

In terms of connectivity, the main line goes into a 2 way splitter and then into an Antronix amp that sends the signal equally across all devices on this run (CODA modem, 4K PVR, and 8300HD box).  My signal levels and modem logs without the MAC info are listed below.  Should I remove the amp and just replace it with a 3-way Antronix splitter?  Any help you can provide would be appreciated.  Thank you.

 

CODA-4582 Router - Hitron Technologies

Downstream Overview
Port IDFrequency (MHz)ModulationSignal strength (dBmV)Channel IDSignal noise ratio (dB)
1603000000256QAM2.800938.605
2849000000256QAM0.000237.636
3855000000256QAM0.000338.605
4861000000256QAM-0.100437.356
5579000000256QAM2.000538.605
6585000000256QAM2.900638.983
7591000000256QAM3.600738.605
8597000000256QAM3.500838.983
9303000000256QAM0.600137.636
10609000000256QAM2.1001038.605
11615000000256QAM1.1001138.605
12621000000256QAM0.1001237.356
13633000000256QAM-0.4001337.636
14639000000256QAM-0.3001437.636
15645000000256QAM0.2001538.605
16651000000256QAM1.2001638.605
17657000000256QAM2.2001738.983
18663000000256QAM3.1001838.983
19669000000256QAM3.9001938.983
20675000000256QAM4.2002038.605
21681000000256QAM3.7002138.605
22687000000256QAM3.0002238.983
23693000000256QAM1.9002338.605
24699000000256QAM1.0002438.605
25705000000256QAM0.1002538.605
26711000000256QAM-0.4002638.983
27717000000256QAM-0.6002737.636
28723000000256QAM-0.8002837.636
29825000000256QAM-0.2002937.636
30831000000256QAM0.2003037.636
31837000000256QAM0.4003137.636
32843000000256QAM0.2003237.636
OFDM Downstream Overview
ReceiverFFT typeSubcarr 0 Frequency(MHz)PLC lockedNCP lockedMDC1 lockedPLC power(dBmv)
0NANANONONONA
1NANANONONONA
Upstream Overview
Port IDFrequency (MHz)ModulationSignal strength (dBmV)Channel IDBandwidth
138596000ATDMA - 64QAM36.75033200000
230596000ATDMA - 64QAM33.25016400000
323700000ATDMA - 64QAM32.75026400000
OFDM/OFDMA Overview
Channel IndexStatelin Digital AttDigital AttBW (sc's*fft)Report PowerReport Power1_6FFT Size

 

Modem logs:

 

No. Time Type Priority Event

1 11/14/2018 04:01:39 82000200 critical No Ranging Response received - T3 time-out;CM-MAC=X:b0;CMTS-MAC=X;CM-QOS=1.1;CM-VER=3.1;
2 11/14/2018 06:11:03 68010300 error DHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=X:b0;CMTS-MAC=X;CM-QOS=1.1;CM-VER=3.1;
3 11/15/2018 00:55:17 82000200 critical No Ranging Response received - T3 time-out;CM-MAC=X;CMTS-MAC=X;CM-QOS=1.1;CM-VER=3.1;
4 11/15/2018 06:11:03 68010300 error DHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=X;CMTS-MAC=X;CM-QOS=1.1;CM-VER=3.1;
5 11/15/2018 09:07:32 84020200 warning Lost MDD Timeout;CM-MAC=X;CMTS-MAC=X;CM-QOS=1.1;CM-VER=3.1;
6 11/15/2018 23:43:20 82000200 critical No Ranging Response received - T3 time-out;CM-MAC=X;CMTS-MAC=X;CM-QOS=1.1;CM-VER=3.1;
7 11/16/2018 06:11:04 68010300 error DHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=X;CMTS-MAC=X;CM-QOS=1.1;CM-VER=3.1;
8 11/16/2018 11:44:15 84020200 warning Lost MDD Timeout;CM-MAC=X;CMTS-MAC=X;CM-QOS=1.1;CM-VER=3.1;
9 11/17/2018 06:11:04 68010300 error DHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=X;CMTS-MAC=X;CM-QOS=1.1;CM-VER=3.1;

 

Moderator
Moderator
Posts: 24

Re: Why do I keep losing OFDM Downstream channels on my modem?

Hey @mahomed!

 

The good news is, if there's no visible service impact there's nothing to worry about Smiley Happy. OFDM channels not appearing in the GUI, can occur for a number of reasons, most of which aren't service impacting, the channel is still locked, it just isn't visible in the GUI. If there are any service issues at any point though you can reach out to us for assistance. To do so, send us a private message @CommunityHelps and we'll have the ability to confirm for you what the issue is. For more information on our Private Messaging system, click here.

 

RogersAndy

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I Plan to Stick Around
Posts: 71

Re: Why do I keep losing OFDM Downstream channels on my modem?

@mahomed

I would not change the configuration, your signal levels and SNR look fine. I would keep an eye on the 2 blue lights on the Modem. If the DOWN arrow turns DARK blue, I believe you are losing DOCSIS 3.1 

Looking at the event log I suspect it will happen. Just judging by experience.

Resident Expert
Resident Expert
Posts: 5,813

Re: Why do I keep losing OFDM Downstream channels on my modem?

I would agree with that.  Don't do anything beyond rebooting the modem is you so choose.  Unless your neighborhood node is highly congested, you should see that the modem runs very well when its running DOCSIS 3.0 on the downstream side.

 

@mahomed, what exactly to you mean when you indicate that the modem loses DOCSIS 3.1?  That the user interface OFDM and OFDMA sections are not displayed at all, or that they are present within the display, but that the OFDM section indicates that neither channel is running.  Your posted data shows that neither OFDM channel is running.  

 

If the OFDM and/or OFDMA sections aren't displayed, that might indicate some type of memory leak which prevents the modem from running normal housekeeping tasks.  

 

If the singular OFDM channel goes inactive, that could indicate a problem in the lower 100 to 500 Mhz band within your cable system (both internal and/or external), or, that the uncorrected symbol or word count has exceeded its maximum allowable value and as a result the modem bails out of DOCSIS 3.1 operation.  While the signal levels look ok, there isn't anywhere near enough data for the OFDM channel available to the user or first line tech support to really indicate the true health of that channel.  

 

When you have time, can you clarify your original post please, that the user interface OFDM and OFDMA sections are not displayed at all, or that they are present within the display, but that the OFDM section indicates that neither channel is running, as is shown in your post. 



I'm a Reliable Contributor
Posts: 564

Re: Why do I keep losing OFDM Downstream channels on my modem?

@mahomed

 

I'm having the same problem too.  I would have to reboot the modem to get the modem interface to show the OFDM channel stats again.

 

I rebooted the modem last night, and here we are today with the modem displaying no OFDM stats. On the OFDM downstream overview, everything appears as NA, and under OFDMA overview, it shows nothing (it shows the same thing as what you pasted). In my case, I'm pretty sure my modem actually loses D3.1 lock, because in DOCSIS Event, it shows "Lost MDD timeout" log every time it occurs, so I would watch for that.

 

The current OFDM overview doesn't show the proper information for the OFDM carrier... weren't we supposed to receive an update showing the correct OFDM stats?

I wonder when that "big" update for the CODA-4582 is supposed to arrive.......RDK-B Smiley Happy

 

 

I'm a Reliable Contributor
Posts: 332

Re: Why do I keep losing OFDM Downstream channels on my modem?

@Datalink

Just to clarify, when the OFDM Downstream section appears, it would show me 1 channel connected with a PLC power level. After some time, that section would appear as it is now showing nothing connected. on either channel. Looking at the modem lights, the down arrow is purple and the up arrow is blue. I still don't see any OFDM Downstream channel with a value unless I reboot the modem.

I hope that helps to clarify things.
I'm a Reliable Contributor
Posts: 332

Re: Why do I keep losing OFDM Downstream channels on my modem?

@RyzenFX

I see that there is a new firmware available to Beta testers a few days ago which I didn't get. Does it fix this problem?
I'm a Reliable Contributor
Posts: 564

Re: Why do I keep losing OFDM Downstream channels on my modem?

@mahomed

 

Nope, I'm on the firmware right now and I'm still having these issues. 

I'm a Reliable Contributor
Posts: 332

Re: Why do I keep losing OFDM Downstream channels on my modem?

@Datalink

 

I just rebooted my modem and these are the signal levels and channel info now.  Let's see how long it lasts.

 

Software Version2.0.10.36T6

 

Downstream Overview
Port IDFrequency (MHz)ModulationSignal strength (dBmV)Channel IDSignal noise ratio (dB)
1603000000256QAM3.100938.605
2849000000256QAM0.400237.636
3855000000256QAM0.500338.605
4861000000256QAM0.300437.356
5579000000256QAM2.200538.605
6585000000256QAM3.100638.605
7591000000256QAM3.900738.605
8597000000256QAM3.700838.605
9303000000256QAM0.500137.636
10609000000256QAM2.3001038.605
11615000000256QAM1.4001138.605
12621000000256QAM0.4001237.356
13633000000256QAM-0.2001337.356
14639000000256QAM0.1001437.356
15645000000256QAM0.4001538.605
16651000000256QAM1.5001637.636
17657000000256QAM2.5001738.605
18663000000256QAM3.4001838.983
19669000000256QAM4.2001938.983
20675000000256QAM4.5002038.605
21681000000256QAM3.9002138.605
22687000000256QAM3.3002238.983
23693000000256QAM2.1002338.605
24699000000256QAM1.3002437.636
25705000000256QAM0.3002538.605
26711000000256QAM-0.2002638.605
27717000000256QAM-0.3002737.636
28723000000256QAM-0.4002837.356
29825000000256QAM0.1002937.356
30831000000256QAM0.5003037.636
31837000000256QAM0.9003137.636
32843000000256QAM0.5003237.636
OFDM Downstream Overview
ReceiverFFT typeSubcarr 0 Frequency(MHz)PLC lockedNCP lockedMDC1 lockedPLC power(dBmv)
0NANANONONONA
14K275600000YESYESYES0.099998
Upstream Overview
Port IDFrequency (MHz)ModulationSignal strength (dBmV)Channel IDBandwidth
138596000ATDMA - 64QAM36.75033200000
230596000ATDMA - 64QAM33.00016400000
323700000ATDMA - 64QAM32.75026400000
OFDM/OFDMA Overview
Channel IndexStatelin Digital AttDigital AttBW (sc's*fft)Report PowerReport Power1_6FFT Size
0DISABLED0.50000.00000.0000-inf-1.00004K
1DISABLED0.50000.00000.0000-inf-1.00004K
I Plan to Stick Around
Posts: 10

Re: Why do I keep losing OFDM Downstream channels on my modem?

 

I'm on 2.0.10.36T6 and I noticed that I lose the OFDM downstream, came to the forums and see that I'm not the only one with this issue. My downstream light modem is light blue.  When I go onto the DOCSIS WAN page on the modem, the OFDM Downstream and OFDM/OFDMA Overview sections would be blank initially but after 30 seconds or so then information would appear with both rows showing NA under Downstream overview.  Performance does not seem to be impacted.  A reboot of the modem returns things to normal. 

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