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

Alex4161
I'm a Reliable Contributor

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;

 

20 REPLIES 20

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

RogersAndy
Retired Moderator
Retired Moderator

Hey @Alex4161!

 

The good news is, if there's no visible service impact there's nothing to worry about :). 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

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

Hucklebury
I Plan to Stick Around

@Alex4161

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.

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.

 

@Alex4161, 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. 



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

RyzenFX
I'm a Reliable Contributor

@Alex4161

 

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

 

 

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

Alex4161
I'm a Reliable Contributor
@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.

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

Alex4161
I'm a Reliable Contributor
@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?

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

RyzenFX
I'm a Reliable Contributor

@Alex4161

 

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

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

Alex4161
I'm a Reliable Contributor

@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

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

eyeeifmx
I Plan to Stick Around

 

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. 

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

toolcubed
I'm a Senior Contributor
@Alex4161,

You said the main line goes into a 2-way splitter, and then from there into an amp, and the CODA is on the amp. Just curious as to what’s on the other port of the splitter? Why isn’t the CODA on the splitter instead of the amp? Not that it would make a difference with the problem you’re having...just curious. Also, I’ve had packet loss issues when I had my CODA on an Antronix amp. After I reconfigured my setup by putting the main line on a 2-way splitter, connecting the CODA on that splitter, and then the amp running off of the 2nd splitter port where then everything else is connected (home phone and TVs), the internet performance was better. Not saying you should reconfigure anything. I was just wondering why your CODA is on the amp if the amp is running off the splitter.

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

Alex4161
I'm a Reliable Contributor

@toolcubed

 

Good question and here is the answer 🙂

 

The main line comes to the side of the house into a 2 way splitter. 

 

One run from that splitter goes into the basement into a unity gain amp that connects into an 8300HD and a Netbox3.  This run has some old RG59 cable buried in the walls and higher frequencies tend to get weaker without the unity amp to keep things level.

 

 

The other run is all new RG6 cable that goes into my bedroom and into the Antonix Amp.  From there, it connects 3 devices:  CODA modem, 4K PVR, 8300 HD.

 

If I wanted to feed the CODA unamped, I would have to add another splitter and connect one leg into the CODA modem and the other into the AMP that would then feed the 2 TV boxes.

 

In the current setup, the biggest drop is only 3.5 dB from the splitter on the side of the house.  Adding more splitters would further weaken the signal on the forward/return lines.  I understand your idea of packet losses but I have not had this issue on the Antronix amp so far.  

 

Hope this helps to clear things up.

 

  

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

@Alex4161 is that splitter located inside or outside of the house?  If it was inside the house, I'd replace that with a three port splitter.  That splitter would have one port with a -3.5 dB drop and two with a -7 dB drop.  I'd use the -3.5 dB port for the modem and run the other ports to the amplifiers.  

 

Just to point out, there are a couple of amps that are in use.  The older version amplifies everything and is known to cause packet loss.  The newer versions have one port that is marked as a VOIP port.  That amp has a built in splitter, with one leg going to the VOIP port and the other leg going to the amplifier and then out to the ports.  That VOIP port is used for VOIP or modem purposes.  From what I've been told, techs will remove the older amps and replace them with a newer version whenever they run into any that are still in use. 

 

So, depending on where that splitter is, and what amp you have in use for the modem, there might be a way to improve the signal levels and get rid of any packet loss that might currently be caused by the amp. 



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

Alex4161
I'm a Reliable Contributor

@Datalink

 

The 2 way splitter is located outside of the house in the green rogers box.  The only way to run another leg unamplified would be to drill a larger hole in the brick and then run wires for another run as well as the cable to power the amp.  This is something I am not wanting to do.

 

As for the Antronix amp, the one I have is the one with the VOIP port (MVRA501B) but that port does not seem to work.  I tried disconnecting the modem run and connect it to the VOIP port and it didn't seem to lock on to any signal.  I then disconnected it and plugged it to one of the other ports and it locked on just fine.  Either I plugged it in wrong or the amp is defective.  It was a brand new sealed amp that was installed.

 

Thanks 

 

 

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

Hucklebury
I Plan to Stick Around

@Alex4161

Short of having a Tech visit the home again, You could try disconnecting everything and couple the coax going to Coda with the main coax coming in, taking all else out of the picture and giving yourself a direct line to Coda for troubleshooting purposes. See what the signal levels are.

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

RyzenFX
I'm a Reliable Contributor

I rebooted the modem twice within the last 2 days to regain OFDM stats and within 24 hours since the reboots, the modem interface shows OFDM stats as NA. 

 

This issue is starting to become more replicable. Over the past 4 days there has been 3 reboots, and 3 cases were the modem OFDM stats appear as NA. Not sure what to do next.

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

Alex4161
I'm a Reliable Contributor

@Hucklebury

 

I think the signal levels would be about the same given that the Amp is a unity design and not adding any boost on the line.

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

Alex4161
I'm a Reliable Contributor

@RyzenFX

 

Where abouts are you located (City, Major intersection) as perhaps others may be in the same area or feeding off the same node?  I am in Toronto (Meadowvale Road and Hwy 401) area.  

 

The issue we have here is that we need someone from the Maintenance/Network team to see why the drop occurs.  Calling a Rogers tech visit from a first line tech would be pointless in my case as I have good signal.  In my experience, they will tend to screw something up than fix something.  as @Datalink mentioned, the tools they would need are something they don't carry and won't be able to identify this type of issue.  They have enough tools to identify bad signal and fix it but not when things get more complex.

 

Perhaps if @Datalink or someone more technical can look into things at the main distribution port that might be handy.  The Linex of mine is at Muirbank Blvd just 200 ft. east of Lavery Trail.  The number on the box is 10059431.

 

 

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

RyzenFX
I'm a Reliable Contributor

@Alex4161

 

I'm located in Vaughan, and I have good signal as well (that's what my 32 SC-QAM channels are saying), and my area is really clean in terms of noise. I remember having encountering this issue in 2017 when Dave was around and we diagnosed that everyone connected to my node were affected by the same issue (we found that their OFDM stats were appearing as NA). This led to a firmware fix shortly afterwards (b/c we were able to probe logs out of my modem Smiley Very Happy), but this issue we're experiencing now could possibly be something related with the firmware or could be an area issue. Note: before we diagnosed the problem, a senior tech was sent to confirm good signal strength and that my area was unaffected by noise. This basically localizes the problem down to the firmware.

 

I think the best way to check if this is a widespread issue is checking if the neighbors with the CODA-4582 display the same symptoms as our modems have experienced. When we diagnosed the problem, we found the support tool that front line agents use will falsely show the modem connected to an OFDM carrier, but when logging into the modem user interface, we found that the OFDM stats appeared as NA. 

 

Just some food for thought... but it's worth considering doing the above in order to find the source of the problem.

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

Alex4161
I'm a Reliable Contributor

@RyzenFX

 

Thanks for the info.  At this point, I am reluctant about getting a tech visit as my TV and Internet seems to work just fine.  In my experience, I find the first line tech do more harm troubleshooting complex situations than just fixing a bad signal.

 

 

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

toolcubed
I'm a Senior Contributor
+1
Couldn’t agree more. Those non-senior techs are terrible. They always seem to leave things in a worse state and always make a mess of the wiring at my electrical panel. I had to watch the last tech that came here very closely. It’s something a homeowner should not have to worry about. Rogers should really reconsider their contractors. Bell isn’t perfect, but you know what? I’ve witnessed their normal techs several times (family and friends who use Bell service) and wow...what a difference. They’re so much more professional and courteous than the techs Rogers uses.
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