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Smart Antennas
Facilitate 4G |
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Vendors already are dabbling in 4G
smart antennas. Bell Labs' technology — called Bell Labs Layered
Space-Time (BLAST) — is being studied as part of one EU-sponsored
pre-competitive advanced antenna-technology project. A BLAST
prototype uses an array of eight transmit and 12 receive antennas.
During its first weeks of operation, it achieved at least 10
times the wireless capacities of today's fixed-wireless-loop
systems. |
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| “The idea here is if you try to increase
capacity of a wireless system, you run up against a brick wall
because capacity is limited by the interference of other users,
so increasing bit rate by increasing power does not work at
all,” Valenzuela said. |
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| Although the classic approach is
to throw more bandwidth at the problem, high prices and low
spectrum availability have made this option unattractive. However,
several years ago, the idea was introduced that adding transmit
and receive antennas can create parallel channels that don't
interfere with one other. This process does not require increased
power or additional frequency. |
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| “MIMO antennas are a very practical
system, and if you combine it with adaptive coding and modulation,
interference cancellation and beam-forming technologies, you
can realize gains that are 30 times better, in terms of bit
rates and capacity, than 3G,” Nortel's Javed agreed. |
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| Nortel has operational MIMO systems
in its lab. Tests show a 10X capacity increase at speeds of
20Mb/s. Next year, the company expects to hit 40Mb/s, as well
as conduct field trials of its technologies. |
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| Source: www.about.com |
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| www.cingular.com
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| www.sprintpcs.com
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| www.verizonwireless.com |
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| www.attws.com |
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| www.research.att.com
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