Mark, Re:
"This includes Motorola, Com21, and
also Terayon. Every intelligent head-end controller with forward
error correction (FEC) has the ability to offer[s] a shared medium
system with more flexible handling of bursty data, greater capacity,
and far superior immunity to noise.
..that statement(Gilders, as above applied specifically to Terayon) is inaccurate due to not mentioning the
other alternatives which are equally/more effective which were found
in Com21 and Motorola."
Thanks for the history review- it's good stuff. I'm sure Motorola and Com21 and Terayon can all do better than they used to do, just as you say. However, I don't see that you've proven that S-CDMA doesn't have "far superior" immunity to noise relative to the others. In fact, Terayon operates on all coax systems while the others you mention cannot. Immunity to noise is the reason they can. Gilder is quite accurate and makes no error of omission there so far as I know- the others just aren't equals in this regard.
Dave Horne(best, funniest personal page on SI, last I looked- ggg) first led me to the fact that S-CDMA would not offer more bandwidth on upgraded plant than it can on all coax- and he referenced that reply in an earlier post to you(I think) on this thread. But the extra immunity to noise for TERN is real. Hence, a value to operators who want to pass homes in noisy areas without the expense of upgrades is created- Hence deployments by Cable operators around the world. Also, where noise is loud, even on upgraded plant, Tern's immunity makes for reliability, as I understand it. Also, since even in upgraded plant it's true that each home on a node adds to the noise in the line, I gather that S-CDMA in upgraded plant can reliably operate while passing many times the homes per node than competitors can. I therefore believe that your idea that TERN's noise immunity is exaggerated...or that it is matched by competing systems, is widely known to be otherwise:
terayon.com
...and click on the case study for Shaw.
" Shaw found that it could certify its plants to the upstream signal-to-noise ratio of 25 dB for deployment of Terayon modems ? a full 10 dB below the certification standard for the TDMA modems (Figure 2). This meant that, rather than waiting for a system to be fully upgraded, Shaw could introduce high-speed data service over systems where fiber linked the primary distribution hubs but did not extend out to the secondary node level. As a result, Shaw is now offering high-speed data services using S-CDMA-based systems over two-way, upgraded HFC with node sizes of up to 12,000 homes passed without installing return-path filters. Thus, the company has been able to meet its goal of rolling out data services aggressively without having to accelerate its capital-spending plan."
Also, S/N can fall to 15db before S-CDMA begins to suffer from self/auto-lowered bandwidth(but stays up and running with less- all the way down to -13db)- a 10db quality cushion for bursts of noise entering. It might be helpful to read the several "case studies" of Terayon S-CDMA installations on the link above{if you have not already) and decide for yourself if you think another offering can accomplish what S-CDMA does for these operators.
Dan B |
