Quote:
Originally Posted by Sephiroth
You made me re-read Broadbandings' helpful update to the NTLWorld diagram and I came up with the above quote.
What's this about "analogue" in the broadband transport chain? Where is it analogue? Which equipments are analogue devices?
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The cable side of the CMTS / uBR outputs analogue signals, these are combined with the analogue outputs from the TV multiplexers and used to modulate the downstream laser.
Digital information is encoded in analogue signals using
QAM these outputs are then used to modulate the downstream laser's output.
Lasers don't just have to be on or off
---------- Post added at 13:31 ---------- Previous post was at 13:24 ----------
Quote:
Originally Posted by digitalspace
Take this for example, if the green cab is a simple RF amplifier and nothing intelligent, and all the fancy stuff lies in the UBR in some building somewhere, then why is it seemingly so difficult to upgrade an analogue cabled area to a digital service? Surely all it takes is to pull the fibre cable from analogue UBR and plug it in to a digital one?  |
The RF amplifiers have certain specifications.
For example,
this kind of thing may well be what's used in analogue areas. If all that 550MHz is used up there's no space to put the digital signals.
Yes a straight switching over, unplug one input and plug in the other would be ideal but the people who receive analogue cable in the area might get a tad upset at their TV just going off like that
The upgrades in areas with restrictions on amplifiers usually consist of replacing the amplifiers with higher rated ones that go to 750 or 860MHz, and depending on the quality of the coax in the network this may necessitate replacing that as well as higher frequency signals don't travel as well as lower frequency ones.