Hi Dennis, re:<<How much of an impediment is the use of CDMA to the use of spectrally efficient (ie trellis coded) modulation? >>
I'm not completely sure I understand what you're looking for, but TERN's modem uses rate 3/4 trellis coded modulation which then feeds a fixed depth of 2 interleaver (pretty shallow, eh?) which then feeds the constellation mapper followed by the spread modulation with a 144 chip spreading sequence. The fall back QPSK mode uses an effective rate 3/8 trellis and has half the throughput.
Here's my re-do on Gilder's latest Terayon "piece"
<<All in good fun of course, but Gilderites with a weak stomach may not want to read below here...that includes you Dan B.>>
Terayon....Ain't no pot 'o gold at the end of THAT rainbow!
All my readers are probably aware of this but TERN's system is symmetric upstream and downstream, and is far less flexible than DOCSIS in too many ways to begin to mention. Not just symmetric, mind you, but only 64kbps for each user channel and accommodating a mere 128 simultaneous users MAXIMUM per CMTS (that's cable jargon for the "server" on the cable network), under perfect noise conditions. DOCSIS has no such inflexible capacity limits.
All those naysayers that claimed it doesn't measure up because of its complexity vs. cost vs. performance....well....they were right! Their technology hasn't kept up with capacity increases in such industry standards as DOCSIS and DVB, and now they must scramble to reinvent themselves as a company since their core competancy has lost its legs.
If they reinvent fast enough that wont even be a materially significant event, will it? [Ed: (be sure to remove this before you publish)....how can I spin this CherryPicker multiplexer to make it sound like the greatest product ever to hit the planet....how about "amazing flexibility"...think they'll fall for that? I know it's just a multiplexer but I need a metaphor. help me].
The moral of the story is this: when comparing TERN's system to cable modem technology from 3-5 years ago, it was a very good system. Not superb, and not a hands down winner even then, but it was a much closer call.
Today, no dice. The infrastructure and the equipment technology has passed TERN by. The DOCSIS Hi-PHY spec, which vendors will begin building to soon, just blows the doors off TERN's upstream (it already does blow the doors off the downstream (the most important part for an internet connection), I just forgot to mention that before). There won't even be any HYPOTHETICAL questions about which one gives superior all-around performance. Game, Set, Match DOCSIS.
And TERN is left high and dry. No one to adopt their "ascendant technology" except third-world countries and cable execs "hot for the equity take," or so they say.
My astute readers have also no doubt heard of Zenith. Zenith proposed an SCDMA system for cable (IEEE802.14) back several years. There have been a number of independent standards committees worldwide that have looked at various spread spectrum and CDMA systems by various vendors for use in cable systems. None has ever made it as a standard, for good reason.
It's been put through the wringer by completely independent groups around the world and CDMA just doesn't measure up in the cable world. It is NOT analogous to the wireless world unless you're writing Dick-and-Jane Techno-psychology letters. Truth be told, they're just not even in the same universe as Qualcomm--I just went a bit metaphor-crazy in my last installment.
My astute readers are also no doubt aware that I've been very hot on fiber optics and all-optical networks for some time. The whole world will be strung with fiber optic cables soon, so you might be wondering why I ever even considered TERAYON--which is a Coaxial Cable play--as an "ascendant technology" anyway.
Can you say "incongruent?" Would you believe "brain Fart?" I just don't know what came over me. Nevermind. Buy some JDSU instead. I'm just running out of companies to hype I suppose--hey, it's hard to keep up with that Steve Harmon guy and come up with a new one each month you guys! Oh gosh, I almost forgot, I know this great little company based in the West Indies that was in the hotel business until a few months ago, but now they're B2B Baby!!!!!! You know what to do.
-----------------
SHIELDS UP, FIRE HOSE READY!!!!!! |
