You are here

16QAM Modualtion-profile

3 posts / 0 new
Last post
flavio.mali
16QAM Modualtion-profile

Dear,

I have the following situation.

- CMTS uBR10K with PRE-4 with two channels of upstream 6.4Mhz in QPSK modulation. on average 150-200 only cables modens docsis 2.0 on each channel beyond 3.0

              I intend to pass the upstream channels to 16QAM modulation with minimal impact due to the SNR. If SNR increase I want the modulation to pass to QPSK. I will use the following modulation-profine:

cable modulation-profile 223 request 0 16 0 22 qpsk scrambler 152 no-diff 36 fixed qpsk0 1 2048
cable modulation-profile 223 initial 5 34 0 48 qpsk scrambler 152 no-diff 98 fixed qpsk0 1 2048
cable modulation-profile 223 station 5 34 0 48 qpsk scrambler 152 no-diff 98 fixed qpsk0 1 2048
cable modulation-profile 223 a-short 4 76 7 22 16qam scrambler 152 no-diff 64 shortened qpsk1 1 2048
cable modulation-profile 223 a-long 9 232 0 22 16qam scrambler 152 no-diff 64 shortened qpsk1 1 2048
cable modulation-profile 223 a-ugs 9 232 0 22 16qam scrambler 152 no-diff 64 shortened qpsk1 1 2048

cable modulation-profile 222 request 0 16 0 22 qpsk scrambler 152 no-diff 36 fixed qpsk0 1 2048
cable modulation-profile 222 initial 5 34 0 48 qpsk scrambler 152 no-diff 98 fixed qpsk0 1 2048
cable modulation-profile 222 station 5 34 0 48 qpsk scrambler 152 no-diff 98 fixed qpsk0 1 2048
cable modulation-profile 222 a-short 3 76 12 22 qpsk scrambler 152 no-diff 64 shortened qpsk0 1 2048
cable modulation-profile 222 a-long 9 232 0 22 qpsk scrambler 152 no-diff 64 shortened qpsk0 1 2048
cable modulation-profile 222 a-ugs 9 232 0 22 qpsk scrambler 152 no-diff 64 shortened qpsk0 1 2048

For this situation the best configuration for these two commands.

cable upstream 0 threshold snr-profiles 24 19
cable upstream 0 modulation-profile 223 222

Thanks. Flavio.

flavio.mali
qpsk x 16qam

Dear, I put into production on a node this configuration and even the snr is great it passed to qpsk and not back to 16qam. I tried the command below but without success. I figured that below the snr of 25 db it went to qpsk and above to 16qam. Does anyone have any suggestions?

cable upstream 2 threshold snr-profiles 25 0
cable upstream 3 threshold snr-profiles 25 0

thank you

File attachments: 
uscallesen
I believe there is a 'Show

I believe there is a 'Show cable hop history' command that lets you follow the dynamic modulation profile changes - remember there are some default values set for the dynamic modulation profile function - you should probably look into those as not only SNR is used to decide if the modulation profile should be higher/lower.

Check out: https://www.cisco.com/c/en/us/td/docs/cable/cmts/config_guide/b_cmts_ds_...

docsis