Hello Mike:
Two of the main reasons why CDMA is not attractive
for broadband wireless data are:
a) Like all fixed assignment schemes (which include
also TDMA), it does not allocate bandwidth dynamically
to users as a function of their needs. In contrast,
contention based protocols allocate bandwidth to users
as a function of their needs at a given time.
b) Another reason is that the robustness to noise
and interference of CDMA, as well as the number of users
that can be supported, are proportional to the spreading gain.
If you want to offer about 50Mb/sec to users with a spreading
gain of 100, and assuming about 2bits/Hz/sec, you would need
a bandwidth of 2.5GHz. Even LMDS operators in the 28GHz
band do not have that much BW (only 1.3GHz, which is already
huge)-- TGNT has ''only'' 400MHz, and WCII has about 750MHz.
So, I do not believe that you will see QCOM's patents
used for wireless ATM systems rolled out by LU, NT, Bosch
Telecom, etc... Wireless ATM protocols tend to be relatives
of the Ethernet protocol, or of MAC protocols used by cable
modems.
Best regards,
Bernard Levy |
