MIMO or ‘multiple-input, multiple-output’ is a wireless technology that, when deployed, uses multiple antennas at both the source (transmitter) and the destination (receiver). This allows for more data to be sent and received at the same time, unlike in conventional wireless communications where only a single antenna is used.
MIMO utilises a natural radio-wave phenomenon known as ‘multipath’ or ‘multipath wave propagation’.
Multipath effects are when an electromagnetic field is met with obstructions such as buildings, walls, hills or other objects and they scatter, taking various different paths and reaching the destination at different times. Without MIMO this can result in fade-out, intermittent reception or total cut-off.
In the past, multipath caused interference and significantly slowed down wireless networks. However now, by using multiple smart transmitters and receivers, MIMO technology adds another dimension and increases performance and range.
By enabling antennas to combine their data streams that are arriving from different paths at different times, receiver signal-capturing is greatly increased using MIMO.
This methods ability to multiply the capacity of the antenna links has made it an essential element of current wireless standards including Wi-Fi, HSPA+, WiMAX and LTE.
MIMO is one of several forms of smart antenna technology, the others are MISO (multiple input, single output) and SIMO (single input, multiple output). Legacy wireless devices use SIMO and so can only receive one spatial stream at a time.
Due to its nature, MIMO is being adopted more and more with the development of IoT and 5G. BT recently announced a successful collaboration with Bristol and Lund Universities in their quest for highly efficient 5G wireless connectivity.