MIMO - One of the specifications of wireless data transmission, when several antennas are used simultaneously for receiving and transmitting. It is used to increase the bandwidth of the network. It works if both the access point and the receiving device are compatible with this technology. It is most often used in WiFi networks and 4G (LTE, WiMAX), but in theory it can be used in any radio equipment.
What is the purpose of the technology
WiFi access point 802.11n with one antenna provides a theoretical bandwidth of 150 Mbps in both directions. In practice, it is rarely possible to get download speeds over 70 Mbps. And if 5-6 devices are simultaneously connected to the router, and each of them is actively accessing the access point, not only the bandwidth drops dramatically, but the ping indicator - the delay in getting the signal back - also increases. This is due to the fact that 802.11n WiFi by default works as a single-user system. It means that data is sent one by one: first to one client, then to the second one, then to the third one, and so on.
Key Features of MIMO:
- Multiple increase in wireless network capacity. If a WiFi 802.11n router with one antenna can provide speeds up to 150 Mbps, then with four antennas - up to 600 Mbps. And if it's WiFi 802.11ac at 5 GHz, you'll get up to 3-4 Gbps.
- Send data to multiple devices at once.
- Lower ping for each client if more than one is connected to the router.
- Smaller load on each wireless datapoint.
Principle of operation
How does MIMO work? Multiple antennas send or receive data simultaneously. They operate on the same frequency but are spaced apart (to minimize channel crossover). Their total bandwidth is summarized.
There are 2 variations of the technology:
- SU-MIMO. Connection with only one client.
SU-MIMO. Used in WiFi 802.11n.
- MU-MIMO. Multiuser communication. Sends data to multiple devices at the same time. Used in WiFi 802.11ac and 802.11ax.
And if a router has multiple antennas, it does not mean that it will have more signal strength or coverage. It indicates exactly the support for MIMO technology. With WiFi 802.11ac, it can theoretically provide access speeds of up to 2.53 Gbps. In WiFi 802.11ax it is over 7 Gbps.
There is a nuance: MIMO only works if the receiving device is also equipped with multiple antennas. The technology is actively used by manufacturers of smartphones, tablets, laptops since 2015 - 2016. That is, equipment released earlier is not compatible with MIMO (data reception is possible only from one antenna).
How to check the support for MIMO in devices
Learn about support for MIMO in smartphones, laptops, tablets (those devices where the antennas are hidden in the case) can only be the declared technical specifications. Most likely it is present in the devices that support the 802.11ac or 802.11ax data transfer standard.
As for the router with the MIMO support it is possible to distinguish the one with the bigger number of the external antennas. And it is present by default in 802.11ax access points (this WiFi standard is exactly the same one with the MU-MIMO optimization).
In summary, what is MIMO? It is a technology by which multiple antennas are deployed simultaneously to transmit or send data. It is a simple way to increase the bandwidth for WiFi and 4G networks.