[c-nsp] Max bandwith in cable modem (uBR7200)

[Ong Beng Hui]

Hi,

The cable modulation-profile specific the modulation to be used for
upstream. ie... 16qam or qpsk.

Demon wrote:

> Hello to everyone!
> 
> I have a Cisco uBR 7223, and i want to put the maximal bandwith in one cable modem. Here´s my config :
> 
> cable modulation-profile 2 request 0 16 1 8 16qam scrambler 152 no-diff 128 fixed uw16
...cut off...
>  no cable upstream 0 shutdown
> 
> 
>     With this  configuration, i don´t have problem with the bandwith in downstream, but in upstream my modem can´t pass the 2Mbs of bandwith!!! 
>     I need simetrical bandwith 10Mbs in both directions ( upstream/downstream)

Depending on the modem that you are using, it might not be able
to handle 2Mbps downstream. Test shown that better cable modem can
do between 5Mbps to 10Mbps. but some barely cope with 3Mbps, assuming
no fancy things running.

Also, the upstream is shared 2.5Mbps to 10Mbps, depending on the
modulation type and channel width. I see that you are trying to
use a channel-width of 3.2Mhz, and 16qam. Which in theory, you
will get 10Mbps shared. Depending on if there is noise in your
cable plant, actual thru-put might be lesser.

Cable modem works on a grant and offer type of bandwidth allocation
mechanism. If your cable modem support concatenation, your upstream
will be higher.

My personal experience is that 10Mbps on the upstream is very
difficult to achieve. Either, reduce your expectation, or see
if you have means to use two cable modems to split/recombine the
traffic.