How does cable internet work?

[RyuKokoro]

Hi,

It may be a strange request but I wanted to know if there are any online resources which explain how cable internet works.

Here's an ADSL-based example of what I'm looking for: http://www.kitz.co.uk - that site has pretty much all the info you can get on ADSL.

I did search the forum but didn't turn up anything relevant.

Thanks in advance.

[Welshchris]

Well basically, u get a group of idiots that call themselves technicians or engineers that come along and wreck ur garden and paintwork first doing the install.

From there ur handed over to a bigger group of idiots that deal with the billing and tech support side of things when it all goes wrong.

Hope that helped.

[RyuKokoro]

Not really, but thanks for the input.

The speed test result in your signature suggests they're doing an okay job.

[Welshchris]

apart from the continued drop outs of connection which they know theres a problem but dont know how to fix which has been going on since August.

What u have to imagine is the set of a Carry on film and then u kind of get a picture of how Virgin Media operate except the Carry on Films are funny.

[RyuKokoro]

Ahh, fair enough. I do agree that, for the most part, their CS is pretty shocking.

[Sephiroth]

Start here:

http://en.wikipedia.org/wiki/Hybrid_fibre-coaxial

Then read Broadbandings' posts in this forum (and my interpretation of his acronyms)!

[RyuKokoro]

I just found this link (from one of your posts I think, Sephiroth): http://homepage.ntlworld.com/draig.goch/Draig/cablemodem_files/frame.htm - fairly good explanation!

[Ignitionnet]

That's pretty good but be aware a lot of it is out of date as it's several years old now.

[Sephiroth]

Yeah - that'll do as its VM NTL specific. I forgot about that one.

It's so old that 512Kbps is considered fast. The bottleneck now is usually from the street box to the hub when the theoretical proportions of browsers to downloaders doesn't hold good. When this presentation was put together, Iplayer, Youtube and torrents hadn't been invented.

So we're gonna be up sh*t creek for bandwidth whatever happens to the infrastructure.

[RyuKokoro]

Yeah, I noticed they referred to NTL and not Virgin Media. Plus the reference to 512k. Is there any more up-to-date info available or does that link show how it works in a nutshell?

[Sephiroth]

Yeah, I noticed they referred to NTL and not Virgin Media. Plus the reference to 512k. Is there any more up-to-date info available or does that link show how it works in a nutshell?

I gave you the up to date link. You can transpose the diagram onto the NTL diagram. The princuiple is the same. They key to cable internet is the DOCSIS modulation rules, which screws the most out of the transmission medium.

Good luck.

[RyuKokoro]

Ahh, I didn't see that diagram on the right of that Wiki page. Thanks for the info, Seph!

[ezzzy]

apart from the continued drop outs of connection which they know theres a problem but dont know how to fix which has been going on since August.

What u have to imagine is the set of a Carry on film and then u kind of get a picture of how Virgin Media operate except the Carry on Films are funny.

lol thats very true

[Boabyboy]

I found this site to be a very helpful source of information on cable internet but keep in mind that some of the content of the site is out of date:

http://homepage.ntlworld.com/robin.d.h.walker/

[Jon T]

I found this site to be a very helpful source of information on cable internet but keep in mind that some of the content of the site is out of date:

http://homepage.ntlworld.com/robin.d.h.walker/

If i remember correctly, Robin Walkers pages used to be quoted very often indeed in the earlier days of the forum(ntlhellworld days). I also seem to recall that he used to post on the forums as well. Wander what every happened to him, as has been pointed out, his webpages are getting a bit dated.

[xocemp]

Further reading from this forum, instigation by Sephiroth.

http://www.cableforum.co.uk/board/12/33656200-is-vm-cable-broadband-half-duplex.html
http://www.cableforum.co.uk/board/12/33656582-virgin-media-how-does-work-splinter.html

I'll add to the latter thread Sephiroth, since Broadbandings touched on MPEG/MPEG 2. My additions will be looking to the D3 network and MPEG/MPEG 2 framing.
I look forward to the coming questions :)

[Sephiroth]

Further reading from this forum, instigation by Sephiroth.

http://www.cableforum.co.uk/board/12/33656200-is-vm-cable-broadband-half-duplex.html
http://www.cableforum.co.uk/board/12/33656582-virgin-media-how-does-work-splinter.html

I'll add to the latter thread Sephiroth, since Broadbandings touched on MPEG/MPEG 2. My additions will be looking to the D3 network and MPEG/MPEG 2 framing.
I look forward to the coming questions :)

Nice one, XO. I'll add something here that many people mustbe wondering about. It is taken from http://en.wikipedia.org/wiki/Symbol_(data).

Broadbandings has provided a lot of information on bits/symbol linked to the QAM size (e.g. 16, 64, 256). In the old days, we spoke about the baud rate. Today, it's symbols.

Here's the rather elegant explanation which ties in beautifully with the QAM concept:

The difference between baud (or signalling rate) and the data rate (or bit rate) is like a man using a single semaphore flag who can move his arm to a new position once each second, so his signalling rate (baud) is one symbol per second. The flag can be held in one of eight distinct positions: Straight up, 45° left, 90° left, 135° left, straight down (which is the rest state, where he is sending no signal), 135° right, 90° right, and 45° right. Each signal carries three bits of information. It takes three binary digits to encode eight states. The data rate is three bits per second. In the Navy, more than one flag pattern and arm can be used at once, so the combinations of these produce many symbols, each conveying several bits, a higher data rate.

Nice, eh?