Cable Forum

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

- Virgin Media News Discussion (https://www.cableforum.uk/board/forumdisplay.php?f=10)

- - LLU (https://www.cableforum.uk/board/showthread.php?t=20849)

Quote:

Originally Posted by Ignition

IGMP

You're thinking of this too much like a CATV network, rather than what it is, video over IP using ADSL as a low level transport stream. What's a webcast / multicast if it isn't accessing a broadcast on demand? Multiple streams may also be possible, depending on bandwidth and encoding requirements. Currently it's not possible to record a cable channel and watch another due to tuner restrictions, no great change here.

Thats what I was getting at, the service will be different to the one currently offered to on-net customers.

Unless the latest technology/service allows the customer to watch one TV channel and record either an off-air one, or one from a second box whilst surfing the net it will be a lower level of service. (Even if a customer doesn't have by-pass facility they can currently subscribe to a second box)

Perhaps I didn't put it over very well, but what I was getting at is it is more of a low cost VOD service for broadcast channels than an alternative to ntl CATV or SKY.

Cable & wireless are also getting into LLU big time with their purchase of Bulldog.
They claim 4 Mb speeds over DSL!!
Also the age of line equipment at the exchange is irrelevant because the line is intercepted at the MDF and connected to a DSLAM and to the exchange line card. The telephony path is transparent to DSL. As someone has already pointed out, the oldest exchanges are about 20 years old. (Ntl's oldest are about 10 years old but without the BT advantage of regular software & hardware upgrades, costs too much money you know?)
NTL are committing a lot of resources to this project. :dunce:

Quote:

Originally Posted by injuneer

The point I was trying to make is the ancient twisted pair, that was designed for audio frequencies. ADSL down an old audio cable with many repaired joints is always going to be a compromise when compared to a good quality coax cable.

Looking inside a BT cabinet around my area a while ago, when a BT engineer was working on it makes me wonder how it ever works. The twisted pair certainly needs to be made off correctly to provide correct balance and good rejection to ingress/egress, as you are probably aware (sorry if I appear to be pushing something you already know) rejection on twisted pair relies on the twist to cancel out any out of balance signal being picked up by the cable. It provides a push-push effect that is cancelled out at the twist, as both signals appear in phase and cancel one another out.

I have some past knowledge of Rediffusions old HF CATV systems using twisted pair, we also carried out some digital TV tests on one system but had big problems with group delay and balance of the twisted pair network.

The local BT box was certainly a shambles for efficiency in this area.