How does NTL "send" a broadband signal down your tv cable?

podgeandrodge

prob a silly question but how does ntl send a broadband signal down your tv cable? or more to the point, how does it say, if you upgrade, send a signal to your modem that you have paid for a higher speed?

is it all down to the modem i.e. could i connect my modem to ANY ntl signal and it would know it was me?


Or does NTL know which specific cable to "send" authorised speeds/broadband signal down to each person i.e. the actual cable going into each house?

Just curious!

mwrf

The cable is two way,
your modem is identified on the network via it's mac address

http://en.wikipedia.org/wiki/MAC_address

podgeandrodge

so it wouldnt matter which ntl cable u attached modem to? It would know your modem and supply the broadband? E.g i go to a friends house with my modem and connect my modem and it would recognise my subscription?

It is already there, if its available in your area.

One Downstream Frequency and one Upstream Frequency.

Cable company's send everything down the pipes, Which leaves it a bit open.

podgeandrodge

podgeandrodge wrote: »

so it wouldnt matter which ntl cable u attached modem to? It would know your modem and supply the broadband? E.g i go to a friends house with my modem and connect my modem and it would recognise my subscription?

It would work yes.

DingDong

cisk wrote: »

It is already there, if its available in your area.

One Downstream Frequency and one Upstream Frequency.

Cable company's send everything down the pipes, Which leaves it a bit open.

Some areas have more than one downstream channel and usually four upstreams(this depends if the cable network still have band I).

One Frequency , and 4 US channels is correct(area Dependent).

watty

Up to 9 upstream fullsize channels are possible. Upstream Channels can be 0.8MHz to 6.4MHz. Downstream is usually 8MHz spacing channels Europe, 6MHz spacing channels North America. 7MHz is also possible. "Cable" on Wireless is usually 2MHz for lower frequency systems and 6MHz or 8MHz for MMDS or Microwave FWA type systems.

They could eventually have maybe 12 or more downstream channels. Each downstream is a multiplexed 45Mbps approx. DOCSIS3.0 allows a user to have more than one downstream channel allowing upto 200Mbps. (Virgin Media are testing).

The data both ways is encrypted.

15 to 45MHz or 5MHz to 65MHz for upstream

Downstream is 110MHz to 862MHz. Each "channel" can be modem data, Many Digital TV channels or one Analogue channel. Some areas the cable may only be good up to 560MHz.

Downstream data is modulated and multiplexed exactly like Digital TV, using MPEG2-TS and 256QAM. Wireless or MMDS systems use 16QAM or 64QAM

Obviously Analogue on Cable is doomed.

Nice one watty.

Yep Docsis 3.0 Uses Channel bonding to archive those sort of speeds, i think UPC may even start testing soon, when then get there upgrades done.

Ranicand

watty wrote: »

Up to 9 upstream fullsize channels are possible. Upstream Channels can be 0.8MHz to 6.4MHz. Downstream is usually 8MHz spacing channels Europe, 6MHz spacing channels North America. 7MHz is also possible. "Cable" on Wireless is usually 2MHz for lower frequency systems and 6MHz or 8MHz for MMDS or Microwave FWA type systems.

They could eventually have maybe 12 or more downstream channels. Each downstream is a multiplexed 45Mbps approx. DOCSIS3.0 allows a user to have more than one downstream channel allowing upto 200Mbps. (Virgin Media are testing).

The data both ways is encrypted.

15 to 45MHz or 5MHz to 65MHz for upstream

Downstream is 110MHz to 862MHz. Each "channel" can be modem data, Many Digital TV channels or one Analogue channel. Some areas the cable may only be good up to 560MHz.

Downstream data is modulated and multiplexed exactly like Digital TV, using MPEG2-TS and 256QAM. Wireless or MMDS systems use 16QAM or 64QAM

Obviously Analogue on Cable is doomed.

Can broadband down a regular phone line ever come close to this?

I am talking copper not fibre.:)

DingDong

They have no plans to switch Analogue off any time soon its still a big selling point to a lot of people. Plus some of the upcoming areas are to go all the way up to a 1GHz so they shouldn't be too short on space.
Currently the only reason they add a second downstream at the moment is too relieve congestion on a node. But like watty says channel bonding is the way to go for massive speeds.

Amalgam

podgeandrodge, thank you for asking a question I secretly wanted to ask.. :pac:

Ranicand

Ranicand wrote: »

Can broadband down a regular phone line ever come close to this?

I am talking copper not fibre.:)

Only Fiber could compete with it. You standard telephone line is prone to all sorts of interference and limitations.

Ranicand

cisk wrote: »

Only Fiber could compete with it. You standard telephone line is prone to all sorts of interference.

Yes DSL was a disaster for me.

Got the 2meg pack but was dropped to 1meg as my line could not support.

1meg still kept cutting out I was let out of my contract and I went for UPC.

Broadband on cable has been great for me.

I think you can be lucky or unlucky depending on where you live in terms of broadband.

A provider might be great in one area but be bad in another.

watty

Phone lines drop sharply in speed with distance. A high proportion of Irish phone lines are too long for ANY DSL. At 1km you are often limited to less than 10Mbps with ADSL2+ / VDSL. At 5km you are typically limited to 1Mbps. As more users get DSL in a multipair cable the crosstalk means interleaving must go up (higher latenency) and speed drop.

With FTTC you can have similar speeds on VDSL or Cable, upto 200Mbps, but the cabinet to house distance much more limited on copper pair than on coax.

Coax can in theory do 1024 QAM and 1500MHz of spectrum = 160Mbps x 180 channels, so at 10:1 contention for 180 people on FTTC /Coax hybrid a max theoretical 1,600Mbps per user using Bonding. Not supported on DOCSIS 3 though. Phone cable pretty much reached the limit over 5 years ago.

godskitchen

watty wrote: »

Phone lines drop sharply in speed with distance. A high proportion of Irish phone lines are too long for ANY DSL. At 1km you are often limited to less than 10Mbps with ADSL2+ / VDSL. At 5km you are typically limited to 1Mbps. As more users get DSL in a multipair cable the crosstalk means interleaving must go up (higher latenency) and speed drop.

With FTTC you can have similar speeds on VDSL or Cable, upto 200Mbps, but the cabinet to house distance much more limited on copper pair than on coax.

FTTC = Fibre to the curb (Kurb)

http://en.wikipedia.org/wiki/Fiber_to_the_x

Just in case anyone was wondering.

Just reading the Wiki, should cable not be refered to as FTTCab?

watty

FTTC + VDSL in most of ireland would be Fibre to the Cabinet.

HFC = Hybrid Fibre Cable aka Fibre to Cabinet + DOCSIS coax to home.

Really you do Fibre To Cabinet (1/2 street, 1 street, 2 streets depending on Geography) or FTTH (fibre to home).

Unless you want more than 100Mbps and there is no coax OR FTTC to home distance is more than 200m (VDSL), there is not much extra value but a lot of extra cost to fibre to home (FTTH) unless the fibre can be pulled in cheaply. You still need a cabinet at kerb to to "split" backhaul fibre to individual fibres to home, unless you are going to have mega cost of individual fibres to homes from exchange.

An individual backhaul fibre can do more than 10Gbps and a cable usually has a number of fibres. So FTTC is a good split of resource.