Does digital cable consume bandwidth?

[jnowl]

Not really sure where to ask this and search turned up nothing but I'm wondering if someone can give an answer as to how digital cable and the internet interoperate?

I.e. we have rogers digital cable and rogers hi-speed internet. If I was downloading a large file could this interfere with a tv program? Can't remember/don't know all the tech involved but am familiar with some of it. I.e. is it ethernet? Doesn't my computer and cable stb each get their own ip address but congestion could still be an issue.

And if all this is true and with the recent talk of bandwidth limits, how does it apply if I leave my t.v. on on some hd channel?

Am I making sense?

[hugh]

Yes Digital Cable consumes bandwidth but its segmented from HSI and Digital telephony so its not an issue.

[jnowl]

Thnx. Can you elaborate a bit on what you mean by segmented?

[magnet]

Think of each analog tv station you watch on tv as a single pipe.
Your regular analog tv has channels 2 to 125.
Each channel uses a different frequency. see frequency table here
Channel 2 is at 55.25 MHz, Channel 125 is at 799.25 Mhz. The total bandwidth is about 800 MHz.
So your High Speed Internet or Digital phone will be carried on a frequency that is not occupied by another service or tv station (SEGMENTED)


Analog TV uses 1 whole pipe worth of frequency to carry the signal (highly inefficient and why the switch to digital)
Cable companies can squeeze 2 or 3 HD channels per pipe or "QAM".
They also can squeeze 10 SD channels or 30 audio only channels per QAM.

On a side note, in Ottawa if you tune your radio to 87.7 MHz FM, you can hear Global (TV 6). This is because the audio portion of TV 6 is at about the same frequency.

[technut]

Simple answer is that each digital service uses its own channel assignments on the cable. You just don't see the channel assignments for your Internet and Voice services, they are hidden from the end user.

So they use those channels no matter what you might be watching on your TV. The bandwidth is statically allocated to each service.

It's a different story if you are getting TV from your telephone company, but you asked about cable so I'll skip that explanation.

Edit: Magnet beat me to it.

[57]

See the link in post one of the following thread to see how cable typically consumes bandwidth.

http://www.digitalhome.ca/forum/showthread.php?t=51559

[jnowl]

Thanks for the answers.

So, it sounds like a certain 'frequency range' is reserved for internet and a certain range for t.v. and I should just leave it at that.

I suppose I need to look at a networking book and/or review current technologies to understand better since now I'm thinking 'what about wireless & ota?' could that be a 'last mile' solution? Not an original thought but hey, just wonderin'

On a side note, along the read a book lines, is there a glossary somewhere? I read you guys talking about QAM, 'head end', etc. and I'm lost but curious. Any pointers?

[57]

Cable Stuff: http://www.digitalhome.ca/forum/showthread.php?t=79742

http://www.digitalhome.ca/forum/show...416#post725416

Acronyms & Definitions: http://www.digitalhome.ca/forum/showthread.php?t=17715

Hope that helps.