A technique for boosting wireless bandwidth and range by taking advantage of multiplexing.

Multiple-input multiple-output (MIMO) wireless uses different waveforms on typically two, but sometimes three or more transmitting antennas inputting to the channel carrying radio waves from Point A to Point B. Multiple antennas and radios (typically, two or three) also are applied to the output of the radio channel at the receiver, along with a lot of signal processing, which ideally improves range and throughput compared with simpler or traditional radio designs operating under similar conditions.

MIMO is at the heart of the 802.11n draft specification for 100Mbps wireless.

MIMO is sometimes referred to as spatial multiplexing, because it users a third, spatial dimension - beyond frequency and time - as a carrier for information. The multiplicative effect of properly designed MIMO systems can be dramatic: As our tests show, the 100Mbps barrier (application-layer throughput) in wireless LANs has been broken. Indeed, the upcoming 802.11n standard will likely specify raw (physical layer) performance as high as 600Mbps via a 4-by-4 MIMO array.

Additional resources

Why buy a MIMO PC card now?

Multiple Input Multiple Output (MIMO) Systems for Wireless Communications

MIMO Research at UT-Austin
Describes different types of MIMO uses.

Network World Wireless Research Center