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Technology Stocks : Broadband Wireless Access [WCII, NXLK, WCOM, satellite..]
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To: zbyslaw owczarczyk who wrote (999)1/6/2000 12:12:00 PM
From: Bernard Levy  Read Replies (1) of 1860
 
CDMA is not practical for truly broadband wireless
because the bandwidth required for a basic channel
of say 100MHz and a spreading factor of 100
would be 10GHz. The most appropriate multiple access
tehniques for broadband wireless for data fall in
the category of random access protocols. The most
basic among those ic CSMA, which is in essence
the old Bob Metcalfe Ethernet protocol.

The current CDMA hoopla, initiated to a large extent
by the likes of George Gilder or Walter Piecyk,
masks the fact there are lots of contention based
statistical multiplexing protocols which are better
suited for data than CDMA. The bandwidth efficiency of
current CDMA systems is also very poor since they use
BPSK or QPSK instead of more efficient QAM or OFDM
systems.

Note however that old FDMA-based LMDS systems are very
inefficient. Dynamically allocated time-slot based systems
are more appropriate.
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