Hi Eric, please pardon the late reply. Let me begin by stating that very few VDSL users experience a full 52 Mb/s due to the distance gradients involved, and no cable modem users receive data at 58 Mb/s. The best that I've seen reported in recent times for a cable modem user (bear me out Graciella) was something on the order of 6 to 8 Mb/s downstream under ideal conditions.
I'm not saying that it's impossible for the MSOs to do some tweaking and change their settings to get the results that you mentioned, but I doubt that they will, due to a number of other system constraints that they are forced to live with under the current DOCSIS regime. I therefore think that it would be more prudent not to mention those rates (for DOCSIS modems), at all, and for VDSL I would instead use the 12 and 25 Mb/s benchmarks for the majority of user experiences, with only the upper edge of the curve (those who almost live on central office property, or who have field nodes in their immediate reach... and of course, those tenants in MDUs who have a VDSL DSLAM in the basement) receiving a full 52. But even here I think that we are about to see some interesting tradeoffs, as the costs for Gb (and future 10Gb/s) Ethernet backbones, and user links, begin to nose down over time.
Your view of the modes that users have as options seem to be skewed to two distinct sets of applications. You have enumerated and compared the data-centric PC use to that of the TV and made different assumptions for each.
My view, in contrast, is that Internet-based (or IP protocol-based) video will, over time, supplant a goodly part of what we now know as video in the form of NTSC over RF, i.e., as it is currently being delivered over cable, and in those rare instances where it is being delivered over VDSL in the form of NTSC over MPEG. In the interim, I see NTSC over MPEG over Ethernet as just as viable a choice now as I do NTSC over MPEG over VDSL. If not immediately, then very soon.
And for these types of combined multimegabit data applications (combined multi-megabit data and video), the cable modem approach using the DOCSIS modem is no match, due to the windowing that takes place in the downstream. Let me clarify that somewhat:
Unless the MSOs with the assistance of Cable Labs bring their home-cluster size per node down to between 30 to 50 homes (AND increase their allotted spectrum for data purposes, at least in the downstream), there is little guarantee that users on those systems will ever be able to receive the IP based video and data services that I am suggesting, even at the line rates that you are suggesting.
And when we look at VDSL, what is it actually but a variant of (or, in actuality) Fiber to the Curb or Neighborhood? Most of the homes that were reachable by the central office have already been served or will be served by the less-expensive and lower-speed ADSL. It's ironic, isn't it?
VDSL platforms which use fiber in the backbone are the closest things that you can have to FTTH without actually being FTTH. Were it not for the last couple hundred or thousand feet of copper emanating from the field node to the home, terminating into a "modem," it would be very similar to some forms of FTTH. Imagine simply moving the side of the garage out into the brush by some distance.
Here, too, I should use some more caution than I have up until now, because the term "FTTH" can be parsed to mean a number of things: PON ala ITU, or GbE to the residence, or a form that simply mimics RF cable systems by modulating fiber with FM until it gets to the garage, where it is demod'ed into black coax, same as usual.
In the last of these cases of FTTH just mentioned above, FTTH is different than MSO black cable delivery only due to the following two exceptions: (i) it uses FM modulation over fiber instead of other forms of (mostly AM and vestigial sideband) modulation over coax; and, (ii) the amount of bandwidth allotted to data in the RF mimicker is usually higher, starting at 10 Mb/s Ethernet now - both ways - scalable up to 100 Mb/s (Fast Ethernet) and beyond, in the future. Some already offer 100 Mb/s now.
One point that I'd like to repeat here is that there is more than one type of FTTH scheme being deployed today. In time, most of them will be more economical and bountiful, on a cost per bit basis, than what we have in place now. Comments, corrections, always welcome.
FAC |
