Definition: 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 MU-MIMO, Massive MIMO, 802.11n, antenna diversity, beamforming and HSPA.

 ARCHITECTURE AND ADVANTAGES OF
 MULTIPLE ANTENNA TECHNOLOGIES

                       Compared to Single
                           Antenna (SISO)
                           Technologies
                           --------------
       Transmit  Receive   Data
 Type  Antennas  Antennas  Rate  Distance

 MIMO  Multiple  Multiple    >     >

 MISO  Multiple  Single      =     =

 SIMO  Single    Multiple    =     >

 M = Multiple   S = Single
 I = Input      O = Output

MIMO Wireless Router