High CM Correctable Codewords

Need Help?

That's what we're here for! The goal of the Rogers Community is to help you find answers on everything Rogers. Can't find what you're looking for? Just ask!
cancel
Showing results for 
Search instead for 
Did you mean: 
Reply
Highlighted
I'm Here A Lot
Posts: 6

High CM Correctable Codewords

What is considered too high for CM error codewords -Correctable Codewords?

 

 

 Index
1
2
3
4
5
 
Unerrored Codewords
2,074,189,647
3821514707
3821400635
3821402275
3821407401
 
Correctable Codewords
1,025,937,593
124
164
186
158
 
Uncorrectable Codewords
273
530
793
792
791
 

 

H/W

Model:                        CGM4140COM
Vendor:                      Technicolor
Hardware Revision:  2.2
 
S/W
eMTA & DOCSIS Software Version:     Prod_18.1_d31 & Prod_18.1
Software Image Name:                          CGM4140COM_3.12p10s2_PROD_sey
Advanced Services:                                CGM4140COM
Packet Cable:                                           2.0
 
Highlighted
Resident Expert
Resident Expert
Posts: 847

Re: High CM Correctable Codewords


@Robert85 wrote:

What is considered too high for CM error codewords -Correctable Codewords?


That would depend on the channel/frequency.  I think that Rogers assigns a single downstream channel closer to the split point so that they can get another measurement of worst-case link performance on your line.  @Datalink  can probably elaborate more on this.

 

Generally, I'm more concerned about the number of Uncorrectable Codewords because that indicates actual packet loss on the network due to link errors.



Highlighted
Resident Expert
Resident Expert
Posts: 6,751

Re: High CM Correctable Codewords

@Robert85 can you post the whole table?  To copy the whole table, top to bottom, left to right, select the left side initially, then scroll right and use "shift" + "mouse click" on the right hand corner, that should select the whole table.  At that point you should be able to right click .... copy.  Then start a new post,right click .... paste.  The whole table should paste in and we should be able to scroll right to see all of the data.  That has been done recently, so I know that it can work. 

 

I'd like to see the frequency associated with that higher uncorrected number.  Looks like channel 1, but, whats the frequency where channel 1 starts.  

 

At the moment I don't have any info on the limit of the uncorrected words, at which point Rogers should dispatch a tech to determine what the problem is for your external cable and connectors.  There's also the possibility of signal ingress into the cable system from an external transmitter, which is where one would have to know the frequency of the affected channel(s).



Highlighted
I'm Here A Lot
Posts: 6

Re: High CM Correctable Codewords

Thanks @Datalink    I have just rebooted the modem prior to reading this.  I will wait a day or two then past the table.   Here is the current info.

 

Rogers Network
Internet:Active
System Uptime: 0 days 1h: 0m: 52s
 
 
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
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
42.3 dB
42.1 dB
39.8 dB
40.1 dB
40.0 dB
40.5 dB
39.7 dB
39.7 dB
40.4 dB
41.9 dB
43.4 dB
43.2 dB
41.6 dB
39.3 dB
39.3 dB
40.0 dB
41.6 dB
41.8 dB
40.5 dB
39.2 dB
39.0 dB
38.8 dB
40.3 dB
41.2 dB
42.0 dB
41.6 dB
40.9 dB
40.0 dB
39.9 dB
39.3 dB
39.0 dB
39.2 dB
41.2 dB
NA
6.7 dBmV
6.7 dBmV
6.4 dBmV
6.0 dBmV
5.4 dBmV
8.3 dBmV
8.0 dBmV
8.4 dBmV
8.7 dBmV
8.5 dBmV
8.4 dBmV
7.8 dBmV
7.9 dBmV
7.7 dBmV
7.4 dBmV
7.3 dBmV
7.2 dBmV
6.9 dBmV
6.9 dBmV
7.2 dBmV
7.1 dBmV
7.2 dBmV
7.3 dBmV
7.0 dBmV
7.1 dBmV
6.7 dBmV
6.8 dBmV
6.6 dBmV
7.3 dBmV
7.3 dBmV
7.1 dBmV
6.9 dBmV
7.7 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
34.8 dBmV
34.8 dBmV
35.8 dBmV
35.8 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
47607940
163359527
163364536
163368557
163372970
163377699
163382499
163388010
163392967
163398030
163403639
163408465
163412796
163417812
163422754
163428691
163432797
163438309
163443301
163447568
163452345
163457741
163461722
163466949
163471519
163476755
163481664
163486641
163490916
163495566
163496722
163499243
47607940
2325104
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2325104
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

 

 
 
Highlighted
I'm Here A Lot
Posts: 6

Re: High CM Correctable Codewords

Thanks @Datalink       Here is the current info.

 

System Uptime: 1 days 9h: 28m: 15s
 

 

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
42.4 dB
42.1 dB
39.8 dB
40.0 dB
40.0 dB
40.5 dB
39.5 dB
39.5 dB
40.2 dB
41.8 dB
43.2 dB
43.0 dB
41.7 dB
39.4 dB
39.4 dB
40.0 dB
41.5 dB
41.8 dB
40.5 dB
38.9 dB
39.0 dB
38.9 dB
40.1 dB
41.1 dB
42.0 dB
41.7 dB
40.9 dB
40.0 dB
40.1 dB
39.5 dB
39.1 dB
39.3 dB
41.4 dB
NA
6.6 dBmV
6.9 dBmV
6.4 dBmV
5.8 dBmV
5.2 dBmV
7.4 dBmV
7.1 dBmV
7.6 dBmV
8.0 dBmV
7.9 dBmV
7.9 dBmV
7.4 dBmV
7.6 dBmV
7.6 dBmV
7.3 dBmV
7.2 dBmV
7.1 dBmV
6.7 dBmV
6.8 dBmV
7.0 dBmV
6.9 dBmV
7.0 dBmV
7.1 dBmV
6.9 dBmV
7.0 dBmV
6.6 dBmV
6.7 dBmV
6.6 dBmV
8.3 dBmV
8.4 dBmV
7.9 dBmV
7.2 dBmV
7.8 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
 
 
Upstream
Channel Bonding Value
1
2
3
4
Locked
Locked
Locked
Locked
22 MHz
25 MHz
30 MHz
36 MHz
2560
2560
5120
5120
35.3 dBmV
35.0 dBmV
35.8 dBmV
36.5 dBmV
QAM
QAM
QAM
QAM
TDMA_AND_ATDMA
TDMA_AND_ATDMA
ATDMA
ATDMA

 

This time channel 33 and 1 are high.

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
3828246062
1178264247
1178260196
1178210438
1178141486
1178284793
1178290221
1178292903
1178298788
1178305206
1178309869
1178315001
1178319593
1178323404
1178329235
1178334161
1178339947
1178342822
1178347888
1178353113
1178357744
1178363123
1178367753
1178373284
1178377973
1178382708
1178387526
1178393017
1178396423
1178400429
1178400486
1178399967
3828246062
275589359
0
5179
42203
71806
44
340
371
336
336
62
0
0
7
54
32
14
14
12
47
70
62
20
88
110
150
894
1218
617
2147
3013
3373
275589359
22
0
4824
21136
65579
28
162
1113
903
150
4
0
0
0
11
0
18
45
58
96
175
112
109
305
479
459
358
559
1362
1744
3221
4339
22

 

 

Highlighted
Resident Expert
Resident Expert
Posts: 847

Re: High CM Correctable Codewords

@Robert85  A high number of correctable codewords aren't necessarily anything to freak out about but when you see them, you need to look at the other stats, especially when the error counters are very high.

 

I don't have any practical experience troubleshooting DOCSIS 3.1 (so take anything that I say with a HUGE grain of salt) but I didn't think that you were supposed to see ANY uncorrectable codeword errors on the downstream OFDM stats as that might be indicative of the modem dropping to DOSSIS 3.0.

 

Do you see anything alarming/out of the ordinary when you look at the modem's error logs?

 



Highlighted
I'm a Reliable Contributor
Posts: 372

Re: High CM Correctable Codewords

I was looking at my cable modem stats and noticed the following:

 

CM Error Codewords

Index 1
Correctable Codewords
1358115282
Uncorrectable Codewords
42

 

I had a ticket open for noise on the line and they said the issue was resolved.  After rebooting my modem, I still get this coming up.

 

Is this normal or do I still have some unresolved signal issues?  

 

Thanks

Highlighted
Resident Expert
Resident Expert
Posts: 847

Re: High CM Correctable Codewords


@Alex4161 wrote:

I was looking at my cable modem stats and noticed the following:

 

CM Error Codewords

Index 1
Correctable Codewords
1358115282
Uncorrectable Codewords
42

 

I had a ticket open for noise on the line and they said the issue was resolved.  After rebooting my modem, I still get this coming up.

 

Is this normal or do I still have some unresolved signal issues?  


I see the same as you with DOCSIS 3.1: a scary-looking number of correctable codewords but a fairly low number of uncorrectable codewords.  After doing some more thinking and research into this, I believe that this is not only normal but actually a good thing.

 

With DOCSIS 3.0, a high number of correctable codeword errors is not good; it's either a reflection of deteriorating line conditions or could also be a precursor to some other failure.  However, DOCSIS 3.1 deals with and adapts to line conditions differently so we need to interpret the error stats differently.

 

Forgive me for oversimplifying but with DOCSIS 3.1, you gain efficiency by being able to deal with errors better, and better error correction is what allows you to use higher modulations and achieve transmission speeds that are close to the theoretical limit.  In a way, having a low number of correctable errors is actually an indicator that you could be using higher order modulations and are not maximizing the efficiency that DOCSIS 3.1 offers.  In the end, what you ideally want to see are correctable codeword errors and little or no uncorrectable codeword errors.



Highlighted
Resident Expert
Resident Expert
Posts: 6,751

Re: High CM Correctable Codewords

I'll offer a different interpretation.  At the end of the day, you should see zero Corrected and Uncorrectable Codewords.  Have a look at the following post which is from an SB8200 Docsis 3.1 modem.  Take note of the two columns on the right hand side, which are, second from the right, corrected codewords, and the right hand column, uncorrectable codewords.  

 

https://www.dslreports.com/forum/r32626244-

 

The corrected codeword count increases with frequency and there is a huge leap with the OFDM channel 159.  At the end of the day however, the uncorrected codeword count is nearly zero, as it should be.  If you look closely at the data, the signal levels drop slightly with increasing frequency and the signal to noise ratio drop slightly as well.  Not large changes, but you can see the increase in the corrected codeword count as the frequency increases.  

 

I'd have to see your signal level data and the whole codeword table to arrive at any conclusion, but, if the remainder of the table resembles what you posted, I'd say that you still have a noise problem.  Have a look at the OFDM channel on the right hand side codeword data which should be on the far right hand side.   For the one active OFDM channel, if you have uncorrected codewords you definitely have a problem as the OFDM waveform, encoding and error correction is vastly improved from the DOCSIS 3.0 generation.  

 

Now, given that you only presented a small snippet of the whole table after a reboot, consider posting more data now that the modem has been up and running for a while.  

 

Are you using a power bar of any type?  If so, disconnect the power bar completely from the wall socket and equipment.  Run everything off of extension cords if necessary for test purposes.  Reboot the modem and keep an occasional eye on the codewords to see if there is any difference in the amount of corrected and uncorrected codewords and the time it takes for the numbers to build up.  Pay particular attention to the codeword data for the OFDM channel.  You might see a high number of corrected codewords, which might be normal with the OFDM channel, but the uncorrected codewords should at zero or very close to it.  If the modem is running in 4k mode with an OFDM channel width of 192 Mhz, you have 4096 sub-carriers used for the OFDM channel, give or take, depending on how many of the edge sub-carriers are used, versus 32 SC-QAM channels used for DOCSIS 3.0.  So, the use of 4096 sub-carriers simply multiplies the number of codewords, both corrected and uncorrected that you might see in the OFDM channel data.  Ideally they should be close to zero. 



Highlighted
Resident Expert
Resident Expert
Posts: 847

Re: High CM Correctable Codewords

When I said that I did some research, that meant going through deployment guides from D3.1 equipment vendors as well as white papers from test and measurement companies such as Viavi.

 

I didn't want to get too down-in-the-weeds technical but what cable operators are aiming for is to use a modulation that provides the highest possible throughput while keeping the uncorrectable codeword errors at an acceptable level.  If you can achieve that AND negligible correctable codeword errors, then that's perfect.  However, that isn't always realistic and one of the goals of DOCSIS 3.1 (with OFDM and LDPC) is to allow you to get the most out of available line conditions.  I'm not saying that any errors are good in and of themselves, just that the presence of correctable codeword errors is not necessarily a bad thing.  Furthermore, since OFDM spreads data across multiple subcarriers, we can't look at and interpret BER stats like we did with D3.0.

 

So... if you are getting zero correctable errors but using a lower modulation, then you may not be (and most likely are not) maximizing efficiency.  If you are using a lower modulation and getting high error rates, then that is really bad.  Neither of these conditions are apparent just from looking at the error stats alone.

 

Given that I can't do a deep dive into my D3.1 stats, if my signal levels (Power and SNR) are okay, my uncorrectable codeword error counts remain low, and I'm getting the speeds that I am paying for, then I'm not going to get too concerned about a seemingly high number of correctable errors on the D3.1 channels.