Hi everyone,
I am experiencing problems with migrating from US default modulation-profile 2 to US default modulation-profile 1 on MOTOROLA CMTS BSR1000. Here are the modulation profiles:
PROFILE1:
[code]Intvl FEC FEC Burst Guard MOD Scrambl Scrambl Diff Preambl Last
usage err len len time type seed enc length code-
code cor mod
reque 0 16 2 8 qpsk scrambl 0x152 no-dif 64 fixed
initi 5 34 0 48 qpsk scrambl 0x152 no-dif 128 fixed
stati 5 34 0 48 qpsk scrambl 0x152 no-dif 128 fixed
short 5 78 8 8 16qam scrambl 0x152 no-dif 144 short
long 10 235 121 8 16qam scrambl 0x152 no-dif 160 short
[/code]
PROFILE2:
[code]Intvl FEC FEC Burst Guard MOD Scrambl Scrambl Diff Preambl Last
usage err len len time type seed enc length code-
code cor mod
reque 0 16 2 8 qpsk scrambl 0x152 no-dif 64 fixed
initi 5 34 0 48 qpsk scrambl 0x152 no-dif 128 fixed
stati 5 34 0 48 qpsk scrambl 0x152 no-dif 128 fixed
short 5 78 12 8 qpsk scrambl 0x152 no-dif 72 short
long 8 220 240 8 qpsk scrambl 0x152 no-dif 80 short
[/code]
When I used only modulation-profile 2 (qpsk) everything was ok but when the upstreams got filled up with traffic i decided to change the modulation profile to modulation-profile 1 for higher throughput. But after changing the modulation profile some modems went offline and some stayed online but experienced about 50% packet loss when ping-ed from the cmts. All these modems have nothing in common except they all are Motorola SB5101E (different firmware versions,different .cm files). The signal levels and SNR are fine on all of them and even modems with worse signal on the same upstreams are working fine(they are also SB5101E with firmwares like the bad modems).If I put back modulation-profile 2 the bad modems are ok again. I tried to upgrade the firmware to the latest "SB5101E-2.6.2.0-SCM00-NOSH-NNEMN.p7" but this doesnt help.
Here are the parameters (now when working ok on mod-prof 2) for 2 of the modems that went offline:
MODEM1-offline after modulation profile change from 2 to 1
[code]Downstream signal:68.9 dBuV (+8.9 dBmV)
Downstream SNR:40.3 dB
Upstream signal at CM:101.3 dBuV (+41.3 dBmV)
Upstream signal recieved at CMTS:59.9 dBuV (-0.1 dBmV)
Upstream SNR recieved at CMTS:28.5 dB
Model:SB5101E-2.6.2.0-SCM00-NOSH
CM file:DOCSIS 1.0
[/code]
MODEM2-offline after modulation profile change from 2 to 1
[code]Downstream signal:66.3 dBuV (+6.3 dBmV)
Downstream SNR:40.5 dB
Upstream signal at CM:104.8 dBuV (+44.8 dBmV)
Upstream signal recieved at CMTS:60 dBuV (+0 dBmV)
Upstream SNR recieved at CMTS:25.1 dB
Model:SB5101E-2.4.4.0-SCM00-NOSH
CM file:DOCSIS 1.0
[/code]
And here are the parameters of 2 of the modems (now when working ok on mod-prof 2) that stayed online but with 40-70% packet loss when pinged from the CMTS:
MODEM3-64%packet loss after modulation profile change from 2 to 1
[code]Downstream signal:66.6 dBuV (+6.6 dBmV)
Downstream SNR:39.9 dB
Upstream signal at CM:94.5 dBuV (+34.5 dBmV)
Upstream signal recieved at CMTS:60 dBuV (+0 dBmV)
Upstream SNR recieved at CMTS:26.3 dB
Model:SB5101E-2.4.1.1-SCM14-NOSH
CM file:DOCSIS 1.0
[/code]
MODEM4-71%packet loss after modulation profile change from 2 to 1
[code]Downstream signal:56.9 dBuV (-3.1 dBmV)
Downstream SNR:39.4 dB
Upstream signal at CM:98 dBuV (+38 dBmV)
Upstream signal recieved at CMTS:60.2 dBuV (+0.2 dBmV)
Upstream SNR recieved at CMTS:28.8 dB
Model:SB5101E-2.6.2.0-SCM00-NOSH
CM file:DOCSIS 1.0
[/code]
And just for an example, 2 modems that worked fine (now when also working ok on mod-prof 2):
MODEM5-OK after modulation profile change from 2 to 1
[code]Downstream signal:67.7 dBuV (+7.7 dBmV)
Downstream SNR:35.7 dB
Upstream signal at CM:99 dBuV (+39 dBmV)
Upstream signal recieved at CMTS:59.9 dBuV (-0.1 dBmV)
Upstream SNR recieved at CMTS:26.3 dB
Model:SB5100E-2.3.1.8-SCM06-NOSH
CM file:DOCSIS 1.0
[/code]
MODEM6-OK after modulation profile change from 2 to 1
[code]Downstream signal:60 dBuV (+0 dBmV)
Downstream SNR:39.6 dB
Upstream signal at CM:98 dBuV (+38 dBmV)
Upstream signal recieved at CMTS:60.2 dBuV (+0.2 dBmV)
Upstream SNR recieved at CMTS:24.7 dB
Model: SB5101E-2.4.4.0-SCM00-NOSH
CM file:DOCSIS 1.1
[/code]
DO I MISS SOMETHING? DOES ANYONE KNOWS WHAT IS THE REASON FOR THIS BEHAVIOUR?
THANKS IN ADVANCE!!!
Where to start....... the snr looks fine, 16Qam min. is about 22. what's the channel width and what does the return look like? example, have you tried a different freq.? are you configured for spec. mgnt or load balance?
would it be possible to post a sh ver and show run?
Show tech would give the whole picture, but it's too big
~Carl
Is there any checklist to make this changes in order to minimize the effects? I did the same change a long time ago and happened same too.
Thanks in advance
double check the modem's transmit levels when running on qpsk. you will find that most are running in the upper 50's, like 57, 58 and then change the modulation to 16qam. the modem will have problems registering or staying online. the error rate is something you need to watch, not just the snr. example from a BSR1k. notice the snr looks good, but then goes bad. note the numbers for the uncorrectables. those are your packets that would be bad due to snr for example.
ideal modem transmit level should be in the mid to upper 40's. 47 for example. once you go over 55 your in trouble.
cm1-ilsttn#sh int cable 0/0 up 1 sig
ifIndex 5
includesContention 0
unerroreds 4292772746
correctables 1876695
uncorrectables 317854 <<<<<<<<<<<<<<
signalToNoise 277 <<<<<<<<<<<<<<
microReflections 18
equalData 00.53.FE.F8.00.3F.01.BF.FE.EA.FA.93.3E.3E.00.00.00.A8.FC.2E
.00.C4.00.1A.00.07.FF.D9.FF.E6.00.05
cm1-ilsttn#sh int cable 0/0 up 1 sig
ifIndex 5
includesContention 0
unerroreds 4292772715
correctables 1876726
uncorrectables 317854
signalToNoise 247
microReflections 18
equalData 00.1D.FF.00.00.42.02.14.FE.7F.FA.C1.3D.B6.00.00.00.6D.FB.EC
.00.6A.00.79.00.1A.FF.C2.FF.DC.FF.E9
cm1-ilsttn#sh int cable 0/0 up 1 sig
ifIndex 5
includesContention 0
unerroreds 4292772598
correctables 1876762
uncorrectables 317935 <<<<<<<<<<<<<<<
signalToNoise 112 <<<<<<<<<<<<<<<
microReflections 19
equalData 00.20.FE.B9.FF.E2.01.2D.FE.BA.FB.99.36.6F.00.00.00.6B.FC.A7
.00.91.FF.F6.00.52.FF.93.00.47.FF.62
Thank you!!
That info is great! Sorry for the late on my answer. I'm going to try the change on this week and I will let you know how was it.
Thanks again..
Recommended some options a while back, wanted to double check if everything worked ;-)
~Carl
It's been kicked around how the snr changes and throughput goes down, as well as the modems sometimes, if the snr goes low. one option would be to configure spectrum-groups. there should be one group per reciever unless you load balance between them. here's an example of one that sets a start and end freq. what freq to use, modulation and return when it's good again.
cable spectrum-group port 0
band 23800000 39200000
hop threshold error 50
hop period 30
guard-band 500
hop action frequency 24400000 priority 10
hop action frequency 27900000 priority 20
hop action frequency 31100000 priority 30
hop action frequency 35900000 priority 40
hop action frequency 39100000 priority 50
hop action modulation-profile 2 priority 70
hop action roll-back
load-balancing static