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Technology Stocks : METRICOM - Wireless Data Communications

MCOM 0.0144

+2.9%

Dec 24 12:09 PM EST

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To: Dragonfly who wrote (658)	3/26/1998 10:34:00 AM
From: WTC	Read Replies (1) of 3376

Dragonfly, re: <Spread spectrum radio communications is not affected by visually opauque or non-metallic walls.> Not quite so. The issue of LOS is frequency dependent, not modulation dependent. If you spread above ~10GHz (not the case with Metricom's topology), you will definitely introduce LOS issues regardless of the modulation. A case can be made that coverage through foliage, in urban canyons, etc. might be a bit superior in actual implementation with spread spectrum vs. say, QAM or QPSK at the same data throughput levels, but that comparison gets very complicated because you are basing the comparison on noise margins as well as native data rates. In theory, it is the same. The key point is one that Mr. Waitt put it quite correctly: at 902-928 MHz (ISM) or at ~850 MHz (celluar), LOS does not depend on spread spectrum vs. any other transmission modulation scheme. The system just needs adequate power for the link budget to overcome any obstacles and absorbers encountered to stay above its noise floor at the receiver.

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