What is MIMO?

1. What is "multiple input multiple output"?

Multiple input multiple output (MIMO) is a wireless technology that uses multiple transmitters and receivers to transmit more data at the same time. All 802.11n wireless products support multiple input multiple output. This technology helps 802.11n achieve higher speeds than products without 802.11n. To implement multiple input multiple output, the workstation (mobile device) or access point (AP) must support multiple input multiple output. To obtain the best performance and range, both the station and the AP must support multiple input multiple outputs.

2. About the multiple input multiple output technology

Multiple input multiple output technology uses a natural radio-wave phenomenon called multipath. With multipath, the transmitted information will bounce off walls, ceilings, and other objects and reach the receiving antenna multiple times at different angles and slightly different times. In the past, multipath caused interference and slowed the speed of wireless signals. With multi-path, multiple input multiple output technology uses multiple smart transmitters and receivers and increases the space size, thereby improving performance and range.

Multiple input multiple output technology enables the antenna to combine data streams arriving from different paths and at different times, thereby enhancing the receiver's signal capture power. Smart antennas use spatial diversity technology to make good use of the remaining antennas. When the number of antennas exceeds the spatial flow, the antennas can increase the diversity of the receiver and increase the range.

There are more and more antennas, and usually, the speed will be higher. A wireless adapter has three antennas and its speed is 600 Mbps. The speed of the adapter with two antennas is 300 Mbps. The router requires multiple antennas and must fully support all the features of 802.11n to achieve the highest possible speed. Different from the application of MIMO, traditional wireless devices use single-input single-output (SISO) technology. They can only send or receive one spatial stream at a time.