Cable networks RE: best effort has economic problems, maybe OT

Petri Helenius pete at
Sun May 30 18:19:33 UTC 2004

Christopher J. Wolff wrote:

>This is a great discussion.  I'm interested in understanding these types of
>limitations in the context of HFC cable networks.  In my opinion, HDTV
>channel bandwidth (30mhz?) , increased demand for voip, and growing demand
>for IP connectivity is going to stress the cable network model as well,
>forcing cable operators to convert everything to IP before going out across
>the wire.  Any input is appreciated.
The bandwidth you quote refers to the unencoded signal bandwidth. The 
actual transmission has the same channel spacing than traditional 
television, be that NTSC or PAL or SECAM. Terrestial applications 
typically carry 20-25 megabits and cable & satellite applications 
typically 40-50 megabits per channel/transponder. HDTV channel usually 
consumes 19.8Mbps for video plus some extra for audio + multiplexing 
information. So a channel that used to carry one NTSC analog channel 
over the air can be used to carry one HDTV channel or in the case of 
cable/satellite networks, two.

I´m all for encapsulating all transmission to IP packets, because it 
would make a lot of things easier, but I would suspect some places need 
to freeze first :-)


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