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

To: Dan B. who wrote (1793)	2/21/2000 7:35:00 PM
From: Mark Laubach	Read Replies (1) \| Respond to of 2347

The use of high pass filters in cable plant is specific to each plant and the operator. Sometimes they use them, sometimes they don't. Again, much depends on the types of ingress noise products that are appearing on the cable. Sometimes filters are used to keep broad-band interferors at bay as well as narrow band. Broadband distrupts everything. Com21 has been operating for several years on the Palo Alto cable co-op plant in Palo Alto Ca. It's a 50K HHP system, all coax, that wasn't using high pass filters. The Com21 equipment worked ok. I haven't checked back in a long time if they're use of filter has changed. Com21 also has the ingress noise blocker (INB) product which offers signficant advantage also. I don't have examples of other all coaxial plants at this time. S-CDMA does have advantage of working in certain types of narrow band interference. However, not to the mutual exclusion of other solutions working just fine on the same upstream cable plant. If the plant is really that bad that QPSK with good FEC cannot run anywhere on the upstream, then S-CDMA might run if the noise if mostly narrow band however, the data carry capacity may be drastically reduced as less spreading codes are used to overcome the noise. This has the effect of reducing the number of modems that can be supported. Yes, you do get service, technically. From a business standpoint, there may not be enough revenue flow and the operator has to clean up the upstream anyway. Also, if the system is changing spreading too often, the delays and dropped packets may cause noticeable performance problems at higher layers. The claim is that S-CDMA buys you insurance. However, S-CDMA is very complicated and that complexity may not be worth it. Which is part of the CableLabs arguments. 1) show it works, and 2) show it remains economical. Mark