Hi all,
During testing, i've discovered that my US is in QPSK, although my CMTS modulation profile is:
cable modulation-profile 222 request 0 16 0 22 16qam scrambler 152 no-diff 32 fixed qpsk1 1 2048
cable modulation-profile 222 initial 5 34 0 48 16qam scrambler 152 no-diff 64 fixed qpsk1 1 2048
cable modulation-profile 222 station 5 34 0 48 16qam scrambler 152 no-diff 64 fixed qpsk1 1 2048
cable modulation-profile 222 a-short 4 76 7 22 16qam scrambler 152 no-diff 64 shortened qpsk1 1 2048
cable modulation-profile 222 a-long 7 231 0 22 16qam scrambler 152 no-diff 64 shortened qpsk1 1 2048
cable modulation-profile 222 a-ugs 7 231 0 22 16qam scrambler 152 no-diff 64 shortened qpsk1 1 2048
the CM config file is docsis 2.0 and the upstreamport of the CMTS is atdma, minislot =2 and channel width = 3.2MHz.
Test results are: DS = 36Mbit/s --> ok i'm satisfied (qam256) ....
US = 2.4Mbit/s --> = bitrate for QPSK on channelwidth 3.2MHz.
CNR 19dB
SNR 22.3dB
I've been told that there mightbe an issue with my CMTS (chipset problem ?)
It's a Cisco ubr10012 with a MC5x20U card.
Is there anyone with suggestions or even better... THE solution for a US in qam16 or qam64 ?
THANKS in advance,
W.
Things to check for.. rate limit on the upstream port. max burst on your modem config file and keep in mind there's docsis overhead to consider when you make a modem file. 3.2Mhz wide @ qpsk should be about 5 Mbps. but you'll never get it because of the overhead. more like 3 or 3.7.
same goes for 16Qam. 10 Mbps but more like 7 or so. try and set your max burst to zero. how many modems on the upstream port? polling interval may also come into play