MIMO

(Multiple Input/Multiple Output) Pronounced "my-mo," it is the use of multiple transmitters and receivers (multiple antennas) on wireless devices for improved performance. When two transmitters and two or more receivers are used, two simultaneous data streams can be sent, which double the data rate. Multiple receivers alone allow greater distances between devices. For example, the IEEE 802.11n (Wi-Fi) wireless standard uses MIMO to increase speed to 100 Mbps and beyond, doubling at minimum the 802.11a and 11g rates. MIMO antennas are also used in WiMAX and LTE.

MIMO, MISO and SIMO
The M, S, I and O relate to the air, not the device. For example, multiple inputs (MI) means multiple transmitters send multiple data streams "into" the air. Multiple outputs (MO) means multiple receivers acquire multiple data streams "out of" the air (see illustration below). See 802.11n, antenna diversity, beamforming and HSPA.

ARCHITECTURE AND ADVANTAGES OFMULTIPLE ANTENNA TECHNOLOGIES Compared to Single Antenna (SISO) Technologies -------------- Transmit Receive DataType Antennas Antennas Rate Distance MIMO Multiple Multiple > > MISO Multiple Single = = SIMO Single Multiple = > M = Multiple S = Single I = Input O = Output

MIMO Wireless Router

In 2004, Belkin introduced the first 802.11n wireless router with multiple transmit/receive antennas (see 802.11n). (Image courtesy of Belkin Corporation, www.belkin.com)

MIMO Wireless Router

In 2004, Belkin introduced the first 802.11n wireless router with multiple transmit/receive antennas (see 802.11n). (Image courtesy of Belkin Corporation, www.belkin.com)