High CM Correctable Codewords

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RogersAndy
Moderator
Moderator
Posts: 556

Re: High CM Correctable Codewords

Hey @Alex4161!

 

Thank you for reaching out via PM! If you have any further questions or concerns definitely let us know.

 

@RogersAndy

Alex4161
I'm a Reliable Contributor
Posts: 402

Re: High CM Correctable Codewords

@Datalink  @RogersAndy  @RogersTony 

 

Good Morning,

 

I just notice that I keep getting these errors on the line that cause pictures to be choppy and sound to drop off on some channels time to time.  I also find some slow download speeds every so often.  How does one resolve this problem?

 
Cable Modem
HW Version:2.2
Vendor:Technicolor
BOOT Version:S1TC-3.49.18.14
Core Version:1.0
Model:CGM4140COM
Product Type:XB6
Flash Part:8192 MB
Download Version:Prod_18.1_d31 & Prod_18.1
IndexLock StatusFrequencySNRPower LevelModulation
Downstream
Channel Bonding Value
7
1
2
3
4
5
6
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
 
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
591 MHz
279 MHz
849 MHz
855 MHz
861 MHz
579 MHz
585 MHz
597 MHz
603 MHz
609 MHz
615 MHz
621 MHz
633 MHz
639 MHz
645 MHz
651 MHz
657 MHz
663 MHz
669 MHz
675 MHz
681 MHz
687 MHz
693 MHz
699 MHz
705 MHz
711 MHz
717 MHz
723 MHz
825 MHz
831 MHz
837 MHz
843 MHz
350 MHz
275600000
40.5 dB
40.6 dB
37.8 dB
37.5 dB
37.7 dB
40.6 dB
40.6 dB
40.2 dB
40.2 dB
39.5 dB
39.2 dB
39.1 dB
39.1 dB
39.4 dB
39.6 dB
40.0 dB
40.3 dB
40.6 dB
40.7 dB
40.4 dB
40.6 dB
40.5 dB
40.2 dB
39.8 dB
39.6 dB
39.1 dB
39.3 dB
39.5 dB
38.4 dB
38.6 dB
38.5 dB
38.1 dB
39.7 dB
NA
0.5 dBmV
2.9 dBmV
-4.1 dBmV
-4.5 dBmV
-4.4 dBmV
0.1 dBmV
0.5 dBmV
0.2 dBmV
-1.0 dBmV
-2.5 dBmV
-3.4 dBmV
-3.7 dBmV
-3.4 dBmV
-2.9 dBmV
-2.4 dBmV
-1.5 dBmV
0.6 dBmV
0.4 dBmV
0.9 dBmV
1.3 dBmV
0.9 dBmV
0.2 dBmV
0.7 dBmV
-1.7 dBmV
-2.2 dBmV
-2.9 dBmV
-2.6 dBmV
-1.9 dBmV
-3.2 dBmV
-3.1 dBmV
-3.3 dBmV
-3.7 dBmV
3.0 dBmV
NA
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
OFDM
OFDM
IndexLock StatusFrequencySymbol RatePower LevelModulationChannel Type
Upstream
Channel Bonding Value
1
2
3
4
Locked
Locked
Locked
Locked
22 MHz
25 MHz
30 MHz
36 MHz
2560
2560
5120
5120
32.3 dBmV
33.5 dBmV
33.8 dBmV
35.3 dBmV
QAM
QAM
QAM
QAM
TDMA_AND_ATDMA
TDMA_AND_ATDMA
ATDMA
ATDMA
IndexUnerrored CodewordsCorrectable CodewordsUncorrectable Codewords
CM Error Codewords
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
2248873409
3097935771
3097947924
3097943952
3097954757
3097959773
3097961831
3097969574
3097972148
3097971523
3097981605
3097986188
3097986568
3097984035
3097996517
3097998691
3098000601
3098014838
3098011294
3098021928
3098032349
3098031214
3098032699
3098033724
3098045222
3098048304
3098048500
3098060992
3098046395
3098030661
3097986592
3098057117
2248873409
2153082378
33
33
38
19
22
21
21
20
20
21
19
19
17
28
26
22
20
23
20
18
13
21
143
115
16
18
23
4195
22728
18758
3181
2153082378
292
77
87
85
94
84
87
85
83
87
85
86
88
90
79
82
85
84
83
86
88
93
84
89
87
88
89
81
16979
16031
40823
13392
292

 

 

RogersTony
Moderator
Moderator
Posts: 1,179

Re: High CM Correctable Codewords

Hello, @Alex4161

 

We appreciate you posting your concerns to the Community!

 

Trying to enjoy your TV service when the picture of sound is choppy can become a major source of frustration. Please provide us with the answers to the questions below.

 

  • Can you describe the way most of your devices are connected? Is it only via Wi-Fi or are some affected devices connected via Ethernet as well?
  • Do you notice the slow speeds throughout the home or do you find it improves if you are closer to the modem?

 

@-G-, has discussed the topic of correctable codewords previously and may be able to provide us with some valuable insight.

 

We look forward to your response!

 

RogersTony

Alex4161
I'm a Reliable Contributor
Posts: 402

Re: High CM Correctable Codewords

@RogersTony

Thanks for your response. My Ignite TV devices are connected by wired and wireless and they all have these issues on some channels. Both WiFi and Ethernet connected devices also experience slow speeds time to time.

I guess the errors are just how the Rogers network is with issues that they don't want to fix. Lovely.
-G-
Resident Expert
Resident Expert
Posts: 1,865

Re: High CM Correctable Codewords


@RogersTony wrote:

 

@-G-, has discussed the topic of correctable codewords previously and may be able to provide us with some valuable insight.


Hi, Tony.  I'll do my best to shed a bit more light on this topic but it's important to understand how the underlying technologies work before you can really understand what the different errors and error stats mean.  DOCSIS 3.0 and 3.1 are very different.  Uncorrectable codeword errors are bad.  They represent packet loss.  Uncorrectable codeword errors also need to be kept low on D3.1 because when they reach a certain threshold, the modem can drop down to using D3.0.  However, the correctable codewords error stats need to be interpreted differently in D3.1 than they do with D3.0.

 

With D3.0, you ideally want to assign channels that are as clean as possible.  When the bit error rate starts increasing, it's an indicator that problems on the line are getting worse, and you will start to see an increase in the number of correctable codeword errors relative to the amount of data transmitted in a given time period. You need to deal with a high correctable codeword error rate before line conditions worsen to the point that the uncorrectable codeword error rates spike and you start to get poor performance and packet loss.

 

With D3.0, you want to avoid bad line conditions; the protocol does not deal with them very well.  However, the reality is that line conditions are also never perfect.  One of the DOCSIS 3.1 design goals is to do a better job dealing with imperfect line conditions that we see in the real world, and to enable cable operators to get the most out of their cable plants.

 

For a D3.1 primer and a summary of the best practices for deploying it, I will refer you to this white paper:

https://www.viavisolutions.com/en-us/literature/docsis-31-best-practices-peak-performance-white-pape...

 

When deploying D3.1 you can encode data on the channel in different ways.  You want to use a profile that allows you to get the maximum throughput that is possible.  Let the protocol correct for errors... but you still want to keep uncorrectable codeword errors as close to zero as possible.  You can deploy D3.1 using a profile that does keep correctable errors to a minimum.  However, correctable errors do not impact performance or cause packet loss... so if you do not have any, you either have an incredibly clean line or you are not using the cable plant to its maximum capacity.

 

So... as long as the uncorrectable codeword errors are zero or close to zero, correctable codeword errors are arguably a good thing.  Don't believe me?  Then have a look at this:

 

https://www.viavisolutions.com/en-us/literature/testing-and-turn-docsis-31-services-hfc-network-fiel...

 

Even if the technical level of the paper is above you, it does echo what I have said before:

 

In reality if you aren’t pushing your higher profiles to the level that you have correctable errors and an acceptable level of uncorrectable errors, you aren’t getting the maximum effectiveness and efficiency that OFDM with LDPC can provide. You should expect to see the higher profiles continually operating with Correctable CWE’s. This is OKAY.

 

The takeaway is that as long as you are not seeing the uncorrectable codeword errors on the D3.1 channels spike, there is no cause for concern.  The downside to D3.1 is that when the correctable codeword errors spike beyond what is nominal, you will likely also see uncorrectable codeword errors spike as well, and you can no longer use correctable codeword errors as an "early warning system" of line conditions worsening.



-G-
Resident Expert
Resident Expert
Posts: 1,865

Re: High CM Correctable Codewords


@Alex4161 wrote:
Thanks for your response. My Ignite TV devices are connected by wired and wireless and they all have these issues on some channels. Both WiFi and Ethernet connected devices also experience slow speeds time to time.

Only on some channels?  That's more indicative of a problem with the source feed and how it is being processed by the IPTV encoders.

 

If you are seeing audio/video dropouts on all channels, then that is indicative of a network problem somewhere.  It could be a problem within your home or it could be a problem on Rogers' side, or both.  It could also be caused by problems on the HDMI link between the set-top box and the TV.

 

Ignite TV is streamed/buffered and consumes roughly 10 Mb/s for HD channels.  The traffic is sent in bursts.  You will get a dropout when the decoder in the set-top box needs to process the next segment in the video stream but either did not receive it or did not receive it in time.

 

If your WiFi network is performing exceptionally poorly, the data rate on the link may drop down to only 6 Mb/s and that will cause problems for Ignite TV on wireless set-top boxes.

 

I won't go into troubleshooting WiFi here.  However, keep in mind that even wired set-top boxes maintain WiFi connections, and I've seen even wired set-top boxes do weird things when their WiFi connection is unstable.

 

It's possible that you can also see problems even on a wired Ethernet connection.  (It could be caused by a bad Ethernet cable or a problem with the LAN switch hardware.)  Unfortunately, these can be hard to diagnose because neither the Ignite modem nor most consumer LAN switches report MAC-level errors or provide you with any helpful diagnostic tools.

 

If your local Rogers node is overloaded and network latency is exceptionally high, or you are getting packet loss (due to uncorrectable codeword errors or packet buffers in network gear overflowing), that will also cause problems for Ignite TV.

 

If you suspect a perform with the Rogers network, you need to perform the following sustained ping tests:

  • From your computer to the Ignite modem, to test for high latency/packet loss in your home network.
  • From your computer to the local CMTS router: to test for high latency/packet loss in your connection to the Rogers network.
  • From your computer to a well-connected Internet host: to test for high latency/packet loss upstream.

 

To resolve any Ignite TV issues, I would recommend simplifying your network as much as possible and connecting all of your set-top boxes over WiFi.  At that point, you will be running Ignite TV on infrastructure that Rogers can test and troubleshoot end-to-end.



TheBings
I'm Here A Lot
Posts: 5

Re: High CM Correctable Codewords

Just wanting to know if this is normal to have error codewords so high seems like my channel 1 and 33 are crazy high
IndexLock StatusFrequencySNRPower LevelModulation
Downstream
Channel Bonding Value
17
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
 
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
657 MHz
279 MHz
849 MHz
855 MHz
861 MHz
579 MHz
585 MHz
591 MHz
597 MHz
603 MHz
609 MHz
615 MHz
621 MHz
633 MHz
639 MHz
645 MHz
651 MHz
663 MHz
669 MHz
675 MHz
681 MHz
687 MHz
693 MHz
699 MHz
705 MHz
711 MHz
717 MHz
723 MHz
825 MHz
831 MHz
837 MHz
843 MHz
350 MHz
275600000
37.6 dB
41.3 dB
34.2 dB
33.6 dB
33.4 dB
39.8 dB
39.3 dB
38.9 dB
38.8 dB
38.6 dB
38.6 dB
38.8 dB
38.8 dB
38.6 dB
38.4 dB
38.3 dB
37.8 dB
37.5 dB
37.7 dB
36.6 dB
37.9 dB
37.6 dB
37.0 dB
36.6 dB
36.2 dB
36.0 dB
36.3 dB
36.6 dB
35.2 dB
35.2 dB
35.3 dB
34.8 dB
41.1 dB
NA
0.6 dBmV
8.0 dBmV
-4.7 dBmV
-5.1 dBmV
-5.5 dBmV
1.6 dBmV
1.1 dBmV
0.6 dBmV
0.4 dBmV
0.1 dBmV
0.2 dBmV
0.3 dBmV
0.5 dBmV
0.2 dBmV
0.3 dBmV
0.1 dBmV
0.4 dBmV
0.5 dBmV
0.4 dBmV
0.1 dBmV
0.2 dBmV
0.5 dBmV
-1.2 dBmV
-1.9 dBmV
-2.1 dBmV
-2.5 dBmV
-2.3 dBmV
-2.0 dBmV
-3.7 dBmV
-3.6 dBmV
-3.6 dBmV
-3.9 dBmV
7.6 dBmV
NA
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
OFDM
OFDM
IndexLock StatusFrequencySymbol RatePower LevelModulationChannel Type
Upstream
Channel Bonding Value
1
2
3
4
Locked
Locked
Locked
Locked
21 MHz
25 MHz
32 MHz
38 MHz
2560
5120
5120
5120
37.0 dBmV
37.5 dBmV
38.0 dBmV
39.0 dBmV
QAM
QAM
QAM
QAM
TDMA_AND_ATDMA
ATDMA
ATDMA
ATDMA
Index Unerrored Codewords Correctable Codewords Uncorrectable Codewords
CM Error Codewords
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
1827732444
3051610829
3051600898
3051575327
3051569711
3051629764
3051638575
3051649019
3051648244
3051673032
3051661410
3051699894
3051693000
3051690363
3051716991
3051709578
3051717512
3051737652
3051726928
3051493900
3051757640
3051778581
3051783976
3051792088
3051809460
3051804009
3051816052
3051834303
3051825321
3051849931
3051846322
3051874022
1827732444
457879418
6411
12254
34031
63878
6413
6605
6641
6571
6649
6598
7071
7616
7274
7240
7738
7906
7730
7354
87233
7547
7475
7195
7497
7231
7101
6988
6834
6575
6623
6483
7101
457879418
63629016
33318
34218
42106
52385
33595
33641
33848
33907
33747
33862
34414
37004
34653
35689
36617
37092
36981
36514
135646
37323
36896
35517
34786
34487
34613
34461
34185
33449
33430
33584
33544
63629016
-G-
Resident Expert
Resident Expert
Posts: 1,865

Re: High CM Correctable Codewords


@TheBings wrote:
Just wanting to know if this is normal to have error codewords so high seems like my channel 1 and 33 are crazy high

The CM Error Codewords stats in index 1 and 33 are identical, and those are the counts are for the DOCSIS 3.1 OFDM channel.  It's totally normal to have a high number of correctable codewords errors on the OFDM channel but the number of uncorrectable codewords errors should be 0, or as close to 0 as possible.  Yours error counts are VERY high.

 

Actually, all your error counts are high across the board... and your SNR values on the downstream channels are low.  How long has your modem been up for and are all the error counts still climbing at a high rate or have they levelled off?

 

I would call into Rogers and have them check the signal levels to your modem, check the error counts on the CMTS, noise levels, and whether there are any issues affecting your neighbourhood.  All of this could potentially also be caused by something as simple as a bad coax patch cable, or perhaps noise leakage onto a common ground.  Hard to say for sure what this could be but things definitely do not look right to me.



TheBings
I'm Here A Lot
Posts: 5

Re: High CM Correctable Codewords

My modem has been up for 7 days now and yes my numbers are still climbing and thanks for the info the last time I called in I was told that everything looked fine. Which I knew was not the case is there anyway that I can be sure to talk to someone that knows this kind of stuff when I call in? Below is the new numbers 

 

Index Unerrored Codewords Correctable Codewords Uncorrectable Codewords

CM Error Codewords
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
933306219
2682726826
2682698311
2682675957
2682661716
2682732417
2682735339
2682747272
2682744983
2682772396
2682764022
2682804206
2682796636
2682792684
2682819312
2682810221
2682820720
2682840947
2682827324
2682520065
2682859271
2682889677
2682891781
2682896467
2682917852
2682908101
2682926422
2682942436
2682932165
2682957943
2682952430
2682981875
933306219
3678142388
8128
15018
39379
72784
8170
8378
8413
8431
8535
8572
9148
9776
9641
9630
10045
10238
9904
9360
113936
9516
9387
9078
9342
9079
8981
8888
8577
8365
8462
8328
8994
3678142388
63634744
42510
43496
51866
63026
42758
42808
43016
43092
43080
43443
44370
47571
45647
46969
48134
48451
47418
46597
175428
46814
46308
44916
44137
43900
43961
43738
43594
42636
42589
42748
42763
63634744
-G-
Resident Expert
Resident Expert
Posts: 1,865

Re: High CM Correctable Codewords

@TheBings  I would call into tech support, tell them that you are seeing a ton of packet loss and that your modem is logging a huge number of uncorrectable codeword errors.

 

Before calling, log into your modem, go to "Troubleshooting > Logs" and view the "Events log" for the Last week.  Normally, that error log should be clean.  If you are seeing a bunch of Critical errors, let them know as well.

 

If they still tell you that everything looks good then, as nicely as possible, ask why the modem would logging all of those errors, on all downstream channels, if there is nothing wrong.  Request that they open a ticket and transfer you to a level-2 agent that can troubleshoot further.

 

There's definitely a problem somewhere.  Hopefully they will see something amiss that can be corrected.