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North American Network Operators Group

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

  • From: Petri Helenius
  • Date: Sun May 30 14:21:46 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.

Im 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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