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Technology Stocks : Qualcomm Incorporated (QCOM)

QCOM 165.99

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3:45 PM EST

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To: John Stichnoth who wrote (24624)	3/22/1999 10:38:00 AM
From: Clarksterh	Read Replies (3) of 152472

John - The central issues for Cinecomm and CDMA are the same This is actually my point - the central issues are not the same. In a cell mobile system one of the primary concerns is interference from neighboring cells (their calls are your interference). The primary purpose of CDMAOne is to minimize the effects of this interference (and in the bargain also getting some additional benefits like multipath resistance). But, in point-to-point communications these are much less of an issue and hence CDMA buys much less. (For instance, CDMA is not normally used for satellite communications outside of the military (e.g. GPS) who need spread spectrum for its anti-jam capabilities). None of this is to say that CDMA can't be used for Cinecomm, but just that CDMA is not the be-all-and-end-all and there are many situations in which CDMA is not particularly beneficial. Just for interest, the items you listed as the primary concerns are done almost equally well by TDMA and CDMA: Encryption/Privacy - Lots of ways to do this in a TDMA system, including PGP type systems. Compression/Capacity - TDMA can do compression as well as CDMA, although it is true that CDMA does allow the uncoordinated handsets to 'give back' spectrum when they have no-data periods. In a point-to-point system this giving back is not an issue for TDMA since all the 'senders' are colocated and hence coordinated. This 'giving back' is what Cisco stat-muxes do without CDMA. Quality/Noise - Spread spectrum is better in a completely unpredictable environment (what engineers refer to as non-gaussian noise spikes), but in point to point this type of environment is rare. Cost - TDMA is simpler and hence cheaper unless one of the other issues (self-noise) limits TDMA. Hope this helps. Clark

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