Greg, re: max number of video channels on a cable system
I don't think any universally applicable number exists. The lower end of the spectrum is currently being supported by 6 MHz ~ FDM technology and is capable of handling upwards of ~90 to ~120 channels. The higher end, above 550 MHz, generally regarded as the new digital spectrum, is designated for additional program services, interactive services, HDTV and voice. This region will employ digital compression techniques of varying rates, in contrast to the FDM used in the previous (lower spectrum).
The digital (upper) region of the cable spectrum is capable of another several hundred services, depending on what compression rates are used (which could be dictated by the type of program content), and the ultimate mix and types of those services. Since the mix and type are arbitrary, depending on the individual providers requirements, and because each of these could be using anywhere from 1.5 Mb/s to 12 Mb/s, with each demanding of a different amount of spectrum, the total number of channels will vary with each operator.
Arriving at a total number of channels (a la Mallone's one time mantra of 500) may not be as straightforward as it appears, however. Up until now, most systems employed a dedicated channel for every cable program service. In the future, some services will be dynamically assigned to downstream spectrum using wild card channels, so that the total number of potential services could be far greater (from a program standpoint) than 400 or 500, if market demand dictates, and these might be selected on the basis of some form of video on demand feature, or a lookup, point and click. Certain channels in the downstream might be designated as common pipes, under the control of user preference, in other words. This has been an evasive capability, but some vendor-service provider initiatives are pointed in this direction already.
"Is it practical to let other ISP on cable with out diminishing the usefulness of it in broadband sense?"
From the foregoing you might conclude that if these services are available for video, then they surely could be transformed for data services as well, except that the upstream would still require a lot of work. So as not to trivialize the matter, the head end would also require considerable re-engineering, as well. But the fact remains that the upper region of the spectrum has been designed around a specific set of parameters, fashioned after a very deliberate frame work by CableLabs and the MSOs, with specific features in mind. I'm rather certain that the work they've already put into this was not done with outside ISPs in mind, although some aspects of their interactive capabilities could most likely be leveraged in that direction, if they so chose. Nor would they fancy the government's commandeering those capabilities, either.
"If my thinking is correct the headend could be considered the CO (center office of the cable world) so the AOL's or the world would have to be given space to attach there or at the bone."
That would be the preference of all the independent ISPs, and a bunch of regular TV program providers, as well. Such would be the case if the MSOs were relegated to the role of common carrier, or physical facilities custodian for all players, as I've suggested in some previous posts. But that, apparently, is not the preference of the MSOs. They do not wish to be considered as such, rather, preferring to have their own proprietary services supported, or they prefer to consort as in the case of ATHM.
[[Side note: I believe that this stems from matters which are largely cultural, deriving from anthropological tendencies, in the cable operators' historic tribal battles with the ILECs. But that is only my opinion, and I welcome contrasting comments from those who are familiar with the folk lores of both cultures.]]
I mention the regular TV program providers as a reminder that this "new" controversy over open access for the ISPs is not really new at all. For years preceding this point in time, independent program providers have wanted in, as well, and certain initiatives were put in motion in the past to allow what was called Open Video Services, or OVS.
Perhaps Dave H. or some other such qualified citizen of these boards can bring us up to speed on how far that initiative has gone, and where it stands today. The major point being, however, that these battles have all been fought before, under a different heading, namely that of independent program video services... as opposed to today's Internet access.
"..with T going to a 50 home topology, making the ISP connect there way too costly so at the bone would be the way to go."
They first have to pass through the head end before they can reach the bone, and the way that this is achieved has not been worked out yet for large numbers of providers.
"But why should T be forced to sell space on it's bone when the Qwest of the world are free to use the free market system to sell there bandwidth?
A plausible argument can be made that QWST, LVLT, WMB are competing in a wide open market, whereas in the local distribution par of T's purview, as well as those of Comcast, TWX, etc., they are operating under monopoly franchise arrangements. Big difference there.
Hope this helped. Comments and corrections are always welcome.
Regards, Frank Coluccio |
