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Old 12-24-2007, 12:55 PM   #871
mikeyts
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lrhorer, I have to say that I too was getting the impression that you were starting to argue that SDV won't work, when it's been deployed in large systems for over a year and it is working (TWC Oceanic and TWC Austin alone are the 17th and 22nd largest cable systems in the country with 500K subs between them; your own system, TWC San Antonio is the 9th largest, with over 300K subs of its own). Are you using TiVo or a leased box? If you're using a leased box with access to the SDV groups, have you ever experience a denial when requesting an SDV channel?

Also, you claimed that your system has over 1000 channels. I took a look at the TWC San Antonio channel line-up (can you tell that I'm bored ) and found:
  • 265 apparent linear SD channels, though there's some channels duplicated, assigned multiple numbers to put them in multiple ranges (i.e., the "Family Tier")
  • 77 "On Demand" channels (why is there a set of 9 channels--100, 192-199--marked "HD Movies On Demand"?)
  • 36 distinct linear HD channels (44, but 8 have two assigned channel numbers); 4 of these channels are the "other-coast" version of 4 premiums (HBO, Cinemax, Showtime and Starz)
  • 48 "Music Choice" channels
  • 63 total channels in PPV Events, PPV Movies, Movies On Demand (movies as pay-per-viewing-period VOD) and subscription sports-league tiers (i.e., "NBA League Pass", "NHL Center Ice", "ESPN Game Plan", etc).
Altogether there seem to be 490 tunable channel numbers (on leased cable boxes subscribed to everything), with at least 20 channels with multiple assigned numbers because they appear in multiple tiers, so it's around 470 distinct channels. (That's the San Antonio line-up--I'm imagining that the Bandera, Blanco, Lake Hills and Stockdale line-ups are all smaller subsets).

So, your system's channel line-up, while impressive (particularly in the number of VOD channels and especially the number of HD VOD channels), only approaches that 500 channel model, with plenty of PPV, subscription sports and VOD stuff in there and a ton of "other-coast" premiums (all innately switched VOD or highly switchable linears).

EDIT: Sorry--you did not say that you system had more than a 1000 channels; in the post that I was thinking of (this, you said:
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Well, first of all the fact the channels here in San Antonio now exceed 1000 in numbering. Of course there are some significant gaps and 150 of those channels are audio stations with minimal picture content (more like screen savers), but still the actual number of channels is well over 500, most being pay-per-view and VOD.
Upon examination, that was bit off, but not nearly as wrong as what I thought you said .
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Old 12-24-2007, 01:19 PM   #872
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It seems like people are having difficulty understanding the state of the present argument, so here's what I understand so far.

Someone (not lrhorer) was arguing that the existence of TiVos would cause SDV to fail because (1) the headend would get swamped with requests from TiVos tuned to random channels to record suggestions and (2) local nodes might also be getting lots of suggestions requests from TiVos.

lrhorer is arguing that TiVos will *not* cause SDV to fail, because:

(1) the impact of TiVos on the headend is small: pretty much every channel is being requested from the headend at any given time anyway (that was the point he was trying to make with his "500 channels" argument--he wasn't arguing that it would fail, he was arguing that this is true regardless of TiVos or SDV), and the number of HD TiVos being served by a single headend is likely to remain an insignificant proportion for some time to come in any case.

(2) it's conceivable that there will be some issues at individual nodes, but they are likely to be infrequent, since again the proportion of TiVos among households served by a node is relatively small, and the times when TiVos are "wasting extra bandwidth" due to requesting suggestions are mostly at off-peak hours anyway (during on-peak hours, presumably a given household is likely to be watching/recording at least one show "for real", so would be considered in the calculations when deploying SDV).

I don't know who's right--it seems to me to depend on how widespread TiVos are in a given area, although lrhorer is arguing that for any plausible scenario the numbers work out--but it seems reasonably clear to me what the argument is.
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Old 12-24-2007, 01:59 PM   #873
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Originally Posted by rictus View Post
It seems like people are having difficulty understanding the state of the present argument, so here's what I understand so far.

Someone (not lrhorer) was arguing that the existence of TiVos would cause SDV to fail because (1) the headend would get swamped with requests from TiVos tuned to random channels to record suggestions and (2) local nodes might also be getting lots of suggestions requests from TiVos.

lrhorer is arguing that TiVos will *not* cause SDV to fail, because:
Your interpretation agrees with mine. lhorer has been arguing (successfully from my view) that SDV will not be negatively effected at the headend due to TiVo suggestions.
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Old 12-24-2007, 02:11 PM   #874
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I don't know who's right--it seems to me to depend on how widespread TiVos are in a given area, although lrhorer is arguing that for any plausible scenario the numbers work out--but it seems reasonably clear to me what the argument is.
One thing that's perfectly clear is that the worst case load of a Tivo - recording two switched channels in prime time - is exactly the same as for a cableco DVR. One Tivo user can't bring a switched video system to its knees. It's impossible.
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Old 12-24-2007, 03:32 PM   #875
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Having looked over lrhorer's posts, I can see what he's been arguing, though I'm not sure what the assertion that a system with 100K subs, 270K receivers and 500 linear channels would get 100% of the channels requested during peak hours has to do with SDV, or the post by bicker he quoted in that response. It only takes one "5000 channel super-DVR recording every available channel 24 hours a day" to break SDV, since the premise is that the channels in SDV groups are assigned to over-provisioned pools of bandwidth (typically less than 50% as much as necessary to transmit all of them concurrently). A "super-DVR" sitting on one segment will break the system if it attempts to simultaneously request more of the channels in an SDV group than will fit in the bandwidth assigned to that group; any attempt to simultaneously tune all of them will definitely break it.

Whether any bunch of TiVos on a given network segment recording suggestions would, by themselves, simultaneously request too many SDV channels is another topic. It seems highly unlikely, but creating recordings of suggestions, all of which have a very low probability of actually being viewed, is just not an important enough activity to allocate any portion of a precious shared network resource to. No properly planned SDV group should contain any really popular services, so any 500 channel system should contain a couple of hundred non-SDV services to record suggestions from, if you simply must .
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Old 12-26-2007, 12:39 AM   #876
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lrhorer, I have to say that I too was getting the impression that you were starting to argue that SDV won't work
'Not even. I'm flabbergasted anyone would get that impression. I was rebutting the notion that TiVo Suggestions breaks the SDV model and would cause a severe problem for CATV providers and so TiVo should limit the scope of its Suggestions feature. The notion is nonsense. Ignoring the legal and logistical mess we're in with a lack of unified standards and the inability of any TV / DVR manufacturer to hedge their bets against losing money by picking one of the flavors of SDV, SDV already provides a vastly expanded set of features with far, far more to come. Exactly what statement in any of my posts would have led you to believe I was arguing SDV would not work? It works very well , indeed. It works substantially just as well with myriads of TiVos with Suggestions turned on as without.

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Are you using TiVo or a leased box? If you're using a leased box with access to the SDV groups, have you ever experience a denial when requesting an SDV channel?
TiVos, but that's beside the point. I worked on early trials of SDV and other technologies when I was an Engineer for the company which was bought by TWC, and I still have several friends in the Engineering department there. Denial requests are uncommon, and TiVos won't change that appreciably, suggestions or not. Denials are far more likely to be produced by and experienced by non-scheduled event requests which leaves the TiVo mostly out of the equation.

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Also, you claimed that your system has over 1000 channels.
No, I said the channel numbers exceed 1000. In fact, the highest channel number is 1310. I also pointed out there were substantial gaps.

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(can you tell that I'm bored )
Uh, yeah. No way was I going to do a count of the channels.

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(why is there a set of 9 channels--100, 192-199--marked "HD Movies On Demand"?)
Each channel has a different set of movies available. The VOD interface is clumsy, so to help they divide it up into different channel numbers. The VOD interface needs lots of work, if you ask me.

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So, your system's channel line-up, while impressive (particularly in the number of VOD channels and especially the number of HD VOD channels), only approaches that 500 channel model, with plenty of PPV, subscription sports and VOD stuff in there and a ton of "other-coast" premiums (all innately switched VOD or highly switchable linears).
The point being? Note classical Pay-Per-View venues are still scheduled. They require authorization, but they starta sn stop at a specific time. IF one person in the city requests the PPV event, then every node in the city can request it without additional impact at the headend, and if one subscriber on the node has requested it then every subscriber on the node can request it without additional impact at the node level.

In any case, the fact is any VOD "channel" is not a single channel, but rather an interactive stream, and two different individuals requesting the same program 5 minutes apart are NOT using the same data stream, but an entirely different one - effectively a separate channel. Thus, as I already pointed out, the load on the CATV headend from those two lone subscribers is as high as that of several thousand TiVos with suggestions turned on. Out of 300,000 subscribers, the number of data streams from people ordering VOD offerings and / or requesting Video Rewind will far exceed the number of scheduled programs being requested, which includes all TiVos running Suggestions. At the node, it's unlikely the two subscribers in question will both be on the same node, so the impact from VOD and Video Rewind on an individual node is much less than at the headend. Conversely, the impact from a TiVo running suggestions is much higher at the node level than at the headend (where it is virtually zero), but still quite manageable and quite small. Even if every single household had Series III TiVos with suggestions turned on, the CATV provider would not have to increase the number of nodes by even 5% or 6% - if that - and it's going to be a very long time indeed before TiVo penetration in the CATV subscriber population even reaches 10%, let alone 100%.

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EDIT: Sorry--you did not say that you system had more than a 1000 channels;
That's right, I didn't. I also didn't say SDV would not work.

To sum up what I DID say, the maximum possible load both at the headend and at any node produced by TiVos running suggestions is equal to the total number of scheduled channels. which in my local system is less than 200, and in my hypothetical system is 500. The number of "channels" the headend must produce for VOD, Video Rewind, and other interactive services is in the 10s of thousands. If the headend can handle that, handing all the TiVo suggestions on Earth is trivial. At the node, Suggestions do increase the load very slightly, but only to speak of amnd mostly in off-peak hours when increasing the load is not a problem. Is it possible one or two of the 300,000 subscribers a day might experience a denial they otherwise would not have experienced if there weren't a bunch of TiVos on his node? Yeah, maybe, but that averages out to maybe once a year per subscriber, and that only once the number of TiVos running Suggestions exceeds 20% - 50% of the customer base. At the rate Series III TiVos are selling, that's going to be a couple of decades, at least.

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Old 12-26-2007, 01:04 AM   #877
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The math, the math

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I'm not sure what the assertion that a system with 100K subs, 270K receivers and 500 linear channels would get 100% of the channels requested during peak hours has to do with SDV, or the post by bicker he quoted in that response. It only takes one "5000 channel super-DVR recording every available channel 24 hours a day" to break SDV,
No, it doesn't (at least at the headend) and that's the point I'm trying to make. It doesn't matter if there are millions of 2 channel DVRs or thousands of 5000 channel DVRs, All put togethr they can only request 500 channels, because that's all there are. Now yes, that single 5000 channel DVR could swamp the node its on, if it actually tried to request all 500 channels, because the node can't handle the entire linear bandwidth, let alone adding in the interactive requests on the node.

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Whether any bunch of TiVos on a given network segment recording suggestions would, by themselves, simultaneously request too many SDV channels is another topic. It seems highly unlikely, but creating recordings of suggestions, all of which have a very low probability of actually being viewed
How low is "low"? Again, when we are talking about DVRs in general and TiVo Suggestions specifically, we are talking about a scheduled event. It could be PPV, but it isn't VOD and it isn't Video Rewind or any other interactive service. A total of 500 scheduled channels is very large, indeed, but lets say they wind up with 1000 scheduled channels and 5000 interactive events. In order not to be wiewed by at least 1 subscriber, the event is going to have to have a less than 1 in 300 share. Given 1000 channels broadcasting during primetime, every idle stream must have a less that 1 in 300 market share during primetime. Does anyone really believe any significant number of broadcasters are going to schedule a show during primetime which has a less than .34% rating? The notion is just silly, but even if a bunch of broadcasters did schedule a bunch of lost causes during primetime, it still would not even come within several orders of magnitude of the number of streams whihc could be requested by interactive services like VOD and ezpecially Video Rewind.

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No properly planned SDV group should contain any really popular services
Well, eventually it will be essentially 100% SDV, except for basic service. After all, it doesn't cost the CATV provider anything more to deliver a channel as SDV than not. It's the same equipment producing the same streams. The differentiation is not between SDV and linear, but between scheduled and interactive. The DVR - Suggestions or not - has a limited impact on the number of scheduled programs being viewed at the node level and zero at the headend. It has zero impact period on interactive services.
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Old 12-26-2007, 01:27 AM   #878
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Number of Channels

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The key thing in how you phrase the question. It is NOT "Does anyone ever want to watch this channel?". The question is "Given the number of homes in this node, is someone watching this channel at this given instant?".
Right. The other piece of the puzzle is that the number of subscribers on the node is quite small, comparatively speaking. A program only watched by 1 person in 1000 is still going to be watched by 300 households in a 300,000 subscriber system, but those 300 households are only going to impact roughly 300 nodes, and the other 300 nodes in the system can use that same bandwidth to transmit something else - or a bunch of something elses.
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Old 12-26-2007, 05:53 AM   #879
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Well, eventually it will be essentially 100% SDV, except for basic service. After all, it doesn't cost the CATV provider anything more to deliver a channel as SDV than not. It's the same equipment producing the same streams.
It certainly does cost more. The switching function isn't free, nor are QAM modulators free.
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Old 12-26-2007, 06:55 AM   #880
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It certainly does cost more. The switching function isn't free, nor are QAM modulators free.
The signal has to be encoded and modulated no matter what. So while there might be a slightly higher cost for a frequency agile configuration or to be able to divert the signal to any of many different encoder/modulators, the cost is still there.

Once you've invested in the technology, there's little reason not to fully utilize it. Nodes will be small enough that even popular channels won't be viewed by anyone at some time. And the bandwidth that would otherwise be wasted to carry a channel 100% of the time when it is needed perhaps only 90% of the time does have value.

Though it's still the use of any channels to carry analog signals that's starving cable systems of bandwidth needed to handle more SD and HD channels. SDV wouldn't be necessary anywhere yet if analog could go away completely... or even be reduced to just 15 or so channels.
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Old 12-26-2007, 07:03 AM   #881
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The signal has to be encoded and modulated no matter what. So while there might be a slightly higher cost for a frequency agile configuration or to be able to divert the signal to any of many different encoder/modulators, the cost is still there.
But for broadcast, this cost can be shared across many nodes.
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Old 12-26-2007, 07:12 AM   #882
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But for broadcast, this cost can be shared across many nodes.
I don't necessarily know how SDV systems in use today are implemented, but if I were creating one, I'd be encoding the signal once and distributing it to all my nodes; each node would then only need to combine that digital signal with whatever other digital signals are going out in a single QAM channel. The node always has to have the ability to modulate every QAM channel it can use for outgoing channels. This cost is per QAM channel, not per broadcast channel. One of the test systems that put most everything on SDV only needed 8 QAM channels for each node, for instance.
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Old 12-26-2007, 09:56 AM   #883
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I don't necessarily know how SDV systems in use today are implemented, but if I were creating one, I'd be encoding the signal once and distributing it to all my nodes; each node would then only need to combine that digital signal with whatever other digital signals are going out in a single QAM channel. The node always has to have the ability to modulate every QAM channel it can use for outgoing channels.
The node itself does not have any modulators. It just converts from optical to electrical.
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Old 12-26-2007, 10:52 AM   #884
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lrhorer, let's try to get down to the salient points, so that we can tell whether we're actually arguing. The original assertion was:
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Theoretically, a rich guy could set up a monster DVR (or multiple DVRs) to record every single channel. In that case, switched video doesn't save any bandwidth regardless of service area size.
As I read this, he's stating that one subscriber running a sufficient number of simultaneous tuners to request all offered channels will break SDV, no matter how small the total number of subscribers on his local node. This is intuitively true: in a system using SDV, if all of the channels offered are requested by one or any combination of tuners in a single node then many requests will have to be denied. If they only request services offered as SDV, the total number of tuners necessary to break SDV should be only a fraction of the total number of channels offered. I pointed out a article in a post above (this) wherein TWC Austin was claiming to offer 175 SD channels and 8 HD ones by dynamically switching them onto a total of 8 shared QAMs. On that system, concurrently requesting any combination of 81 or fewer of those 183 channels (presumably a subset of the system total) from any one optical node will "break" SDV.

You eventually state in apparent response to the posing of this scenario (though not in direct response to Luke M's post):
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Changing out every single one of the 235,000 receivers to a 5000 channel super-DVR recording every available channel 24 hours a day on 10 times over won't increase the load on the server farm by any amount whatsoever, except to increease the number of broadcast addresses in the headers.
This may also be true, but I'm having a hard time understanding why it's relevant. At a glance, it sounds as though you're disputing that placing such a "super-DVR" on the system will break SDV, but on closer reading you're sayng that it doesn't matter, because all offered channels will be concurrently requested from the headend across the entire system during peak periods. What does the number of channels concurrently requested by all of the subs on the system have to do with the price of peas? SDV uses the fact that no single optical node will face a demand for anything approaching that number. The main bottleneck in these systems is the coax running from those optical nodes into people's homes. No matter how much capacity of that medium might be expanded in the future (and apparently at least one source is offering tech to get 3GHz capacity out of coax), technology currently deployed in the home can only utilitize about 800 MHz of its downstream capacity; I assume that the fiber backbone of the network can carry much more. It's like a bunch of people sipping from a large stream through soda straws.
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Old 12-26-2007, 11:15 AM   #885
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lrhorer, let's try to get down to the salient points, so that we can tell whether we're actually arguing.
I have to acknowledge and praise the patience you've shown with the guy (i.e., not plonking him a long time ago . . . ) You are a far better man than I.
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Old 12-26-2007, 11:59 AM   #886
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The node itself does not have any modulators. It just converts from optical to electrical.
Even if that conversion from optical to electrical is a straightforward one (i.e., the individual signals can be captured in one form and re-expressed as the other without demodulating and remodulating), an optical node capable of carrying SDV not only has to be able to demodulate and modulate a signal, it has to be able to compose MPEG Transport Streams. A channel in an SDV group might be present on the fiber in a transport stream in a QAM carrier at 525 MHz (or whatever); the optical node has to strip the packets for the particular requested program from that transport stream, find space in the SDV bandwidth pool for it (which might be in a stream in another carrier at say, 615 MHz), reencode those packets to appear in that stream as a program with a different number and add stuff to tables in the security and information loops on that new stream. (It might not have to re-encode the packets in the stream to have a different program number; it seems to be becoming popular to use very sparse program numbering in transport streams, with direct correspondence ot the tuned channel number). The node further has to be able to modulate all the streams in the SDV bandwidth pool, since its creating those streams dynamically according to demand for channels in the SDV group.

I don't know how these things work precisely, but intuitively it's gotta be something like that. I'm sure that anyone who does know will feel free to correct me .
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Old 12-26-2007, 12:28 PM   #887
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Even if that conversion from optical to electrical is a straightforward one (i.e., the individual signals can be captured in one form and re-expressed as the other without demodulating and remodulating), an optical node capable of carrying SDV not only has to be able to demodulate and modulate a signal, it has to be able to compose MPEG Transport Streams.
The node itself, like I said, just converts optical to electrical. It's a dumb device. It doesn't care whether it receives analog, QAM, or whatever.

The point is, there does not necessarily need to be a bank of QAM modulators for each node. They can very easily be combined at the location where the nodes are fed. Since broadcast channels are the same for every node, there's no reason why each node would need a private QAM modulator for broadcast. Hence, switched video does mean more QAM modulators are needed.
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Old 12-26-2007, 12:46 PM   #888
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Lets put to rest this rich guy with 1000 tuner system that breaks SDV by tuning every channel. First off, they would all need to be digital tuners that utilize the Tuning Resolver. I would think that the cable companies would recognize this quite quickly.

Lets try to stay in the real world.
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Old 12-26-2007, 12:50 PM   #889
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The node itself does not have any modulators. It just converts from optical to electrical.
and what form of electrical does it get converted to?

A: It gets modulated onto QAM channels therefore there must be modulators at the node.
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Old 12-26-2007, 01:08 PM   #890
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and what form of electrical does it get converted to?

A: It gets modulated onto QAM channels therefore there must be modulators at the node.
As I explained, this is not the case. Some people just can't understand that optical is not always baseband digital, I guess.
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Old 12-26-2007, 01:46 PM   #891
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As I explained, this is not the case. Some people just can't understand that optical is not always baseband digital, I guess.
Very simple question for you... How does the optical get to electrical that STBs and TiVos can decode? I say the MPEG streams embedded in multicast streams get modulated onto RF QAM channels but you may have another answer.
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Old 12-26-2007, 02:06 PM   #892
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Very simple question for you... How does the optical get to electrical that STBs and TiVos can decode? I say the MPEG streams embedded in multicast streams get modulated onto RF QAM channels but you may have another answer.
The conversion from optical to electrical is signal format independent. If you send QAM channels into a node, you get QAM channels out. If you send analog in, you get analog out.

The Hybrid Fiber-Coax architecture was conceived and implemented before digital cable even existed. It was all analog originally. So naturally, the optical input needed to be an analog (broadband) signal. This is in contrast to the "normal" use of optical signals in telecommunications, which is baseband digital.

Does that clear it up?
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Old 12-26-2007, 02:18 PM   #893
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The conversion from optical to electrical is signal format independent. If you send QAM channels into a node, you get QAM channels out. If you send analog in, you get analog out.

The Hybrid Fiber-Coax architecture was conceived and implemented before digital cable even existed. It was all analog originally. So naturally, the optical input needed to be an analog (broadband) signal. This is in contrast to the "normal" use of optical signals in telecommunications, which is baseband digital.

Does that clear it up?
So I believe you are saying that the dark fiber is basically carrying multiple frequency shifted chunks of spectra which are already modulated QAM channels. The node 'hetrodynes/frequency translates' them to the appropriate RF frequencies. Right?

If so... this would suggest that the 'node' in SDV terms isnt all in one place... the frequency translation points would be distributed wherever they need to be to serve their assigned 'neighborhood' while the heavy lifting of building the transport streams and QAM modulation is somewhere else (like the headend?).
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Old 12-26-2007, 02:39 PM   #894
Luke M
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So I believe you are saying that the dark fiber is basically carrying multiple frequency shifted chunks of spectra which are already modulated QAM channels. The node 'hetrodynes/frequency translates' them to the appropriate RF frequencies. Right?
No, I'm saying that the node is passing the signal unmodified. All the intelligence is upstream of the node.
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Old 12-26-2007, 02:50 PM   #895
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The node itself, like I said, just converts optical to electrical. It's a dumb device. It doesn't care whether it receives analog, QAM, or whatever.

The point is, there does not necessarily need to be a bank of QAM modulators for each node. They can very easily be combined at the location where the nodes are fed. Since broadcast channels are the same for every node, there's no reason why each node would need a private QAM modulator for broadcast. Hence, switched video does mean more QAM modulators are needed.
Hmmm. I'd thought that switching was being done on the level of the optical node at the optical node, but examination of the literature online about specific switched digital video technologies (in particular, BigBand Network's stuff, apparently the most widely deployed at the moment, the switching equipment lives at the distribution hub level (see this popular Wikipedia diagram); each distribution hub sits on an optical transport ring with the headend and has continuous access to all of the offered content, fanning that out over private sets of fibers to each of the optical nodes. Those customized sets of SDV streams (possibly mixed with VOD traffic) are composed in that equipment. Makes sense, and simplifies network maintenance greatly.

From what I just read, every channel starts out in the headend as an RF signal, converted to optical and then converted back by the optical nodes for transmission over "last mile" coax. Some of them are 6 MHz NTSC analog signals, some of them broadband digital streams.
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Old 12-26-2007, 02:58 PM   #896
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The conversion from optical to electrical is signal format independent. If you send QAM channels into a node, you get QAM channels out. If you send analog in, you get analog out.

The Hybrid Fiber-Coax architecture was conceived and implemented before digital cable even existed. It was all analog originally. So naturally, the optical input needed to be an analog (broadband) signal. This is in contrast to the "normal" use of optical signals in telecommunications, which is baseband digital.

Does that clear it up?
The frequency range and capacity of the fiber is much higher than the freq range of the coax so there must be some conversion going on. The channels need to get mapped into the RF frequencies that the cable STB can understand. Once again, I say that the edge QAMs in the node select the proper multicast stream based on current usage patterns and modulate the selected MPEG stream onto the RF QAM channel. You and I may never see eye to eye on this. Simply saying that fiber is the same as electrical does not make sense to me.
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Old 12-26-2007, 03:18 PM   #897
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Simply saying that fiber is the same as electrical does not make sense to me.
Please don't invent nonsense and attribute it to me. Thanks.
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Old 12-26-2007, 03:20 PM   #898
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From what I just read, every channel starts out in the headend as an RF signal, converted to optical and then converted back by the optical nodes for transmission over "last mile" coax. Some of them are 6 MHz NTSC analog signals, some of them broadband digital streams.
Correct.
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Old 12-26-2007, 03:26 PM   #899
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Please don't invent nonsense and attribute it to me. Thanks.
This is what you said...
Quote:
The conversion from optical to electrical is signal format independent. If you send QAM channels into a node, you get QAM channels out. If you send analog in, you get analog out.
which implies you can take RF QAM at a central location and jam it into a fiber then suck it back out on the other end and push it back into a coax with no additional modulation at the node.

Anyway, if you have any hope of convincing people that there are no modulators at the node you should be able to answer my question about how you map the fiber optic signals/frequencies to the 800mhz RF spectrum. You keep skirting this issue because you can't answer it and know that you are about as wrong as can be.
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Old 12-26-2007, 03:46 PM   #900
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This is what you said...
which implies you can take RF QAM at a central location and jam it into a fiber then suck it back out on the other end and push it back into a coax with no additional modulation at the node.
Yes, that's how HFC works.

Instead of tossing around insults, why don't you spend a couple minutes reading up on HFC?
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