Cable Forum - An introduction to DOCSIS (in 2 parts)

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Cable Forum (https://www.cableforum.uk/board/index.php)

- Virgin Media Internet Service (https://www.cableforum.uk/board/forumdisplay.php?f=12)

- - An introduction to DOCSIS (in 2 parts) (https://www.cableforum.uk/board/showthread.php?t=33677419)

Lew	05-05-2011 21:32

How cable internet works

Interesting article from Ars Technica. It's a bit geeky in places but still an interesting read.

Meet DOCSIS, Part 1: the unsung hero of high-speed cable Internet access

Meet DOCSIS, Part 2: the jump from 2.0 to 3.0

craigj2k12

05-05-2011 23:29

Re: How cable internet works

good info....no doubt ignition will find some errors in the article :D

PGPGPG

06-05-2011 01:00

Re: How cable internet works

great artical

Maggy

06-05-2011 07:55

Re: How cable internet works

Quote:

Originally Posted by Lew (Post 35229971)

Interesting article from Ars Technica. It's a bit geeky in places but still an interesting read.

Meet DOCSIS, Part 1: the unsung hero of high-speed cable Internet access

A bit geeky!! What an understatement that is..:D

Pbryanw

06-05-2011 12:47

An introduction to DOCSIS (in 2 parts)

Hi,

Just thought I'd post this article about DOCSIS I found on Ars Technica. It's not all that technical (so even I could understand it) and it may be of interest to those who want to learn a bit more about DOCSIS, and how it works (without going into great detail).

http://arstechnica.com/business/news...net-access.ars

It's aimed towards an American audience, but I assume the same system is used here on the Vigin Media Cable Network. (If any details differ, hopefully someone can point them out).

I'll post the link to part 2, when it comes out.

Chrysalis

06-05-2011 19:56

Re: An introduction to DOCSIS (in 2 parts)

thanks, I wonder if VM have this enabled on docsis2 channels.

Quote:

And there's a completely new way for multiple modems to share the upstream bandwidth: S-CDMA (Synchronous Code Division Multiple Access). S-CDMA allows multiple cable modems to transmit at the same time, and it’s also more resistant to the noise that is present on channels below 20MHz. Let's look at both the bits-per-symbol and S-CDMA issues in more detail.

pip08456

06-05-2011 20:14

Re: An introduction to DOCSIS (in 2 parts)

VM use ATDMA

"Advanced Time Division Multiplex Access (ATDMA) and Synchronous Code Division Multiple Access (SCDMA). CableLabs has mandated that, for a cable product to be fully DOCSIS 2.0 compliant, it must support both competing protocols. There have been several discussions about migration to DOCSIS 2.0 and about which protocol (ATDMA or SCDMA) is the best fit for any one particular business model. Based on recent surveys, some providers are still very unsure about the migration to DOCSIS 2.0."

Scource

craigj2k12

06-05-2011 20:17

Re: An introduction to DOCSIS (in 2 parts)

already being discussed

http://www.cableforum.co.uk/board/26...net-works.html

Chrysalis

06-05-2011 20:24

Re: An introduction to DOCSIS (in 2 parts)

wow only a day apart, I await the merge :)

Pbryanw

07-05-2011 00:05

Re: An introduction to DOCSIS (in 2 parts)

Quote:

Originally Posted by Chrysalis (Post 35230531)

wow only a day apart, I await the merge :)

Hehe, I swear I looked for a thread on this article before I posted :blush: :)

Quote:

Originally Posted by craigj2k11 (Post 35230525)

already being discussed

http://www.cableforum.co.uk/board/26...net-works.html

Sorry, didn't look in that particular forum before posting :(

pip08456

07-05-2011 00:11

Re: An introduction to DOCSIS (in 2 parts)

Quote:

Originally Posted by Pbryanw (Post 35230687)

Hehe, I swear I looked for a thread on this article before I posted :blush: :)

Don't worry, it'll gives the mods something to do.

Chrysalis

08-05-2011 19:59

Re: An introduction to DOCSIS (in 2 parts)

seems SCDMA is not used on VM according to this post.

http://www.cableforum.co.uk/board/35231921-post51.html

continuing that discussion here as this topic is relevant to it.

pip08456

08-05-2011 20:08

Re: An introduction to DOCSIS (in 2 parts)

Quote:

Originally Posted by Chrysalis (Post 35232061)

seems SCDMA is not used on VM according to this post.

http://www.cableforum.co.uk/board/35231921-post51.html

continuing that discussion here as this topic is relevant to it.

Actually Chrys it was mentioned in post 3 here, but I assumed you didn't want to discuss it.:D

DABhand

08-05-2011 22:14

Re: An introduction to DOCSIS (in 2 parts)

@Igni if he comes here

I didn't say SCDMA uses 128QAM all the time, I said it can use it. But that is not the only plus, I listed the others in the "telfordmania" thread.

pip08456

08-05-2011 22:23

Re: An introduction to DOCSIS (in 2 parts)

Quote:

Originally Posted by DABhand (Post 35232206)

@Igni if he comes here

I didn't say SCDMA uses 128QAM all the time, I said it can use it. But that is not the only plus, I listed the others in the "telfordmania" thread.

Yeh, keep going on about the plus side and forget about the negative side (as usual).

As Igni posted.

Quote:

Originally Posted by Ignitionnet (Post 35232085)

SCDMA is less efficient than ATDMA. 128QAM requires an insane upstream SNR, 64QAM is a challenge for operators to push to let alone another 3dB to cater to 128QAM and after overheads it doesn't actually provide anything more than 64QAM ATDMA.

SCDMA does indeed have a purpose, it is more resilient in the presence of burst noise that ATDMA, however horses for courses. If it were so evidently superior everyone would be doing it. They aren't.

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