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Technology Stocks : COM21 (CMTO)

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To: Dennis O'Bell who wrote (1829)	2/22/2000 6:29:00 PM
From: Mark Laubach	of 2347

First, I've been talking about upstream mostly. The worldwide standard for downstream digital video is in the ITU J.83 specification. The Forward Error Correction methods are different between Europe and the North America. Common to both are the use of 64QAM and 256QAM. My mind is blanking right now as to the noise floor requirements in the downstream. I think somewhere between 35dB and 45dB for digital video. The downstream is always cleaner because there is no noise funneling. Terayon's spreading codes are proprietary and have been selected for maintaining orthogonality between the codes as is needed to support synchronous transmission behavior. DMT/OFDM type modulation is still alive, I think. Ultracomm is still working on their approach, I heard a little while ago. The inventor of DMT (at Telebit), Paul Baran, is also the founder of CMTO. Personally, in my own opinion only, I feel that DMT/OFDM is a much better advanced modulation for captive signal (ie vs wireless) for cable television upstream environments. The world with use ITU J.83 based standards for digital video and digital high speed data. Everything is pretty well covered there. Mark

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