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Technology Stocks : COM21 (CMTO) -- Ignore unavailable to you. Want to Upgrade?

To: JoeWhoa who wrote (1122)	9/29/1999 11:29:00 AM
From: Mark Laubach	Read Replies (1) \| Respond to of 2347

Hi Joe, Any CDMA scheme needs to have power management. From what I know of the S-CDMA that was discussed in IEEE 802.14 HiPHY, it varies power with the number of spreading codes that are in use and some factors including the number of transmitting cable modems. So for any given time period, the power in a cable modem is being constantly adjusted by the head-end based on how codes have been distributed for access. Pretty complicated. Note also that the IEEE 802.14a HiPHY effort using 128 spreading codes versus TERN's current 144 code system. TERN selected the 128 codes to maintain the symbol orthogonality for the synchronous operation. What that means is that what TERN is shipping now is not "the standard" as touted. What I don't know is how easy it is for TERN's modems to just use the same 128 codes so it is almost "the standard". Note that a wired cable upstream plant is very different than an open air wireless system. In a wired upstream plant, all signals, including noise, get funneled towards the head-end, so power control is critical. Especially for other services that may be running on the upstream. The community has found that HFC fiber nodes are very sensitive to being over driven by too much power in the upstream pass band (e.g. 5 to 42 MHz). Wireless open air systems get the benefit of having propagation dropoff due to normal radiation issues. What this means is the S-CDMA control of constantly changing power is more complex, and critical, than simple single carrier modulations. Mind you, power is controllable in S-CDMA, it's just that it is more complicated in the more complicated modulation system. Personally (Mark's opinion), I like single carrier modulation systems, such as what is in DOCSIS 1.0 (and CMTO...<g>) over CDMA systems, including TERN's due to power management for captive signal (i.e., wired) cable plants. I'd like to see more work in the industry on CDMA and the other alternatives with realistic public disclosure of performance, etc. I suspect that there'll be one or more advanced techniques that will come to market in the next several years. Mark