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Technology Stocks : The New Qualcomm - a S&P500 company

QCOM 170.90

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Nov 7 9:30 AM EST

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To: Dooker who wrote (7080)	2/29/2000 1:22:00 AM
From: engineer	Read Replies (1) of 13582

FIXED Optical wireless is something which has been in research for a few years. the big problem is light polution and the dispersion of hte optical beams. very tough to make things work fast. In the case of handheld or portable systems, the amount of ambient light increases the bias current on the optical device to a much higher level than can be sustained by regular batteries. An IR system for instance has about 2 mW power in very low ambient light, but increase to more than 1000 mW in sunlight. (Or in relative terms...2mW is the average transmit power of the HDR transmit power amp, 1000 mW is 5 times more than the max power ever used by any CDMA device) The background light also affects the noise density increases in which you must detect a very fast signal. It is the same as would be experienced by CDMa in a high jammer state. the problem with optics also is it in generally not possible to have a difuse wideangle beam with any kind of transmit power. thus you are limited to many single beams or rotating type transmit beams. there are many associated problems wiht this. In the Wireless RF domain, it is quite easy to make an isotropic antenna which radiates in a full 360 degrees. Also in the return link, it is not possible to get enough power in hte IR device to transmit far enough without pointing the device. the user is limited to making up a pointing algorithm of some sort which allows the beam to become more focused. Otherwise, you have to radiate even that much more power. Infra-red also has a mean path length in outside daylight of FEET, not KM, so it would not be a wide area network type threat to HDR. As for a closed-in fixed wireless office running IR, it may be possible to provide a very fast system, but research done at Berkeley in the early 1990's shows that this is really not all that practical or feasable (See Marsh Et. All...PhD thesis circa 1995). (for those not technonerds....I think they are FUDging it also...)

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