let me remind you guys,
in this very forum i asked one
question

whos technologys is mimo and today i found answer to that

Bell Labs researcher Jack Winters first filed a patent on multiple
antenna arrays in the mid-1980s, and research continued through the
1990s until Gerard Foschini and M.J. Gans of Bell Labs wrote a paper in
1996 that refined the concept a bit and clearly stated how
"multi-element arrays" could be used to deliver increased capacity
in wireless local area network (LAN) deployments. Though the days of
commercial Wi-Fi hot spots in coffee houses were years away, the paper
caused a sensation in the wireless technology research community, and
many other researchers contributed important findings and theories.
Greg Raleigh, eventual co-founder of Airgo Networks, popularized the
concept of MIMO in an orthogonal frequency division multiplexing (OFDM)
architecture, which fueled a road map for the 802.11n wireless LAN
standard. That standard was just ratified in January and will propel
Wi-Fi past the 100 Mb/s bandwidth mark in the next year or two.

Meanwhile, MIMO has made its way from the LAN into the wide area
network (WAN). The technology was specified in the 802.16e standard
approved last December, and the WiMAX Forum has made it part of the
certification profile for Mobile WiMAX.

"MIMO was specified in the 802.16e standard, but it's even more
important what the WiMAX Forum has done - any Mobile WiMAX equipment
will invariably include MIMO," said Lars Johnsson, vice president of
business development for Beceem Communications.

However, MIMO actually is classified as "implementation-optional"
for Mobile WiMAX, according to Frank Van Heeswyk, chief scientist for
software systems at SOMA Networks.

Byron Young, vice president of marketing and product management for
Adaptix, added, "When vendors really will be expected to support MIMO
isn't that clear. The second wave of Mobile WiMAX certification in the
second half of next year will probably be the first that has testing
and certification of MIMO-based systems."

MIMO may have taken a while to go mainstream because it was viewed as
complex and expensive to integrate into user devices such as handsets,
vendor sources said. "You have to have two antennas on each side to
take advantage of it," said Johnsson, meaning that antennas on a
mobile handset would be inches or less apart.

"One of the downsides is the effect of the cost of CPE," said
SOMA's Flak. "MIMO takes more space, and it takes more power."
While theoretically doubling capacity, actual increases may be less,
and also may vary depending on how much bandwidth service providers are
willing to allocate.

Still, Johnsson said that MIMO has benefited from its long journey into
the WAN and the tremendous amount of research that has gone into the
technology, and the result is a much-improved and more cost-effective
technology.

"The algorithms have gotten better," he said. "People can do more
elegant number-crunching now, and that improves the signal-processing
capability, which ultimately means cheaper devices."

In addition to increasing the data rate, the ability to craft two
usable channels in the same spectrum allows service providers to get
more value out of the frequencies they own, which is particularly
important as the WiMAX market's spectrum future remains in flux in many
countries. Also, as WiMAX service providers increasingly look to offer
voice-over-IP service and video service in addition to Internet access
and other data applications, they can consider keeping the more
sensitive applications like voice and video on a separate channel from
data.

Initially, WiMAX systems using MIMO will be of the 2×2 (two antennas
at the base station, two in the user device) variety, and that is the
only approach mentioned in the Mobile WiMAX profile, but the bandwidth
can be increased by continuing to add more antennas. Some companies
have discussed the deployment of 4×4 MIMO solutions, but the cost and
complexity challenges resurface as you up the antenna ante.

"The first wave of Mobile WiMAX gear that gets certified will be 2×2
MIMO," Intel's Knudsen said. "There is no specific plan to do more
than that, but as other silicon gets developed, more sophisticated
multi-antenna systems will continue to come to market and get
certified."

While the WiMAX community awaits its MIMO experience, the technology
also is being positioned as part of other mobile broadband genres. Not
long after publishing his influential MIMO paper, Bell Labs' Foschini
developed a MIMO-based technology for Lucent Technologies called Bell
Labs Layered Space-Time (BLAST). The "space-time" referred to the
fact that MIMO-based BLAST brought a spatial enhancement to the time,
or frequency, domain wireless transmission. The technology was highly
touted during 1998 as Lucent claimed demonstrated bandwidth increases
of at least 10 to 20 times and more with experimental systems that used
far more than just the two antennas being talked about in current
systems. Lucent eventually announced plans to incorporate BLAST into
its Flexent base station architecture.

However, a Lucent spokesman said last week that the company still has
not commercialized BLAST because it hasn't yet seen the demand for
vastly higher mobile bandwidth among its customers. The spokesman said
Lucent is continuing to study the technology and monitor market demand.

Meanwhile, MIMO certainly looks to have some kind of future in the
mobile broadband road map. Looking beyond today's 3G system, MIMO and
OFDM were incorporated into the 3GPP/3GPP2 Long-Term Evolution (LTE)
standards document in December 2005. Nortel Networks also recently
demonstrated its high-speed OFDM packet access (HSOPA) technology,
which employs MIMO, and has been an aggressive proponent of MIMO.

Doug Wolff, vice president and general manager of Nortel's CDMA group,
recently said, "We're very keen on MIMO and OFDM being in the LTE and
part of [CDMA 1X] EV-DO Rev. C. We think you'll see this as a
commercial technology in 2008 or maybe 2009."

In improving overall capacity, MIMO delivers on one part of the
broadband wireless promise. The technology is sometimes misconstrued as
providing network coverage enhancements, but it actually requires
signal strength as a foundation for being able to provide its capacity
enhancements. "MIMO has nothing to do with coverage, and it requires
a strong signal, so you can't really do it at the cell's edge," said
Beceem's Johnsson.

But, Mobile WiMAX won't be lacking in the coverage department either
because another long-heralded smart antenna technology called
beam-forming (or adaptive antenna system, or smart beam-forming, by
some) can be used to strengthen weak antenna signals. Beam-forming, as
the name implies, enables antenna transmissions to be dynamically
shaped to avoid the interference that weakens them.

"Beam-forming makes a weak signal stronger, but with MIMO, it's the
rich getting richer," Johnsson said.

However, some companies - including SOMA Networks, according to Flak
- favor beam-forming over MIMO.

For that reason, the technologies might be used in different situations
depending on the pre-existing coverage conditions, but also could be
used in the same market. For instance, if there's a lack of coverage in
a particular area, beam-forming might be used to rectify that
situation, while in another zone, MIMO will enhance capacity for users
because the signal already is strong enough. Beam-forming also could be
used in advance of MIMO to create the right signal conditions for the
latter technology to be employed.

"Beam-forming is something you might see first in an early network
rollout, when network operators are always more fixated on coverage,"
Johnsson said. "In the second stage of network life, it's all about
capacity, and that means MIMO."