MU-MIMO

What is MU-MIMO？

MU-MIMO, short for Multi-User Multiple-Input Multiple-Output, is a significant feature of the latest Wi-Fi technology standard known as 802.11ac Wave 2 (or 802.11ac 2.0). It has the potential to revolutionize the operations of Wi-Fi networks by significantly increasing network throughput, capacity, and tripling internet access speeds. Multi-user MIMO algorithms have been developed to enhance MIMO systems when there are multiple users or connections. MU-MIMO represents the next evolution from single-user MIMO (SU-MIMO). In MU-MIMO, the router divides the available bandwidth into individual streams that are shared equally among connected devices. MU-MIMO routers are available in variations such as 2x2, 3x3, or 4x4, which indicate the number of streams (two, three, or four) created by the router. Each access point (AP) or router supports a specific fixed number of streams.

MU-MIMO vs. MIMO

To comprehend MU-MIMO, it's essential to understand MIMO's function. MIMO divides network resources spatially, transmitting them concurrently through multiple antennas. This technology significantly improves data transmission efficiency without requiring additional spectrum resources. However, in a MIMO system, an access point (AP) can communicate with only one terminal at a time, known as single-user MIMO (SU-MIMO). Mismatched antenna numbers between APs and terminals restrict the optimal utilization of channel resources. For instance, a 4x4 MIMO Wi-Fi 5 AP can reach a theoretical speed of 1.732 Gbit/s. When communicating with a 1x1 MIMO mobile phone, the maximum speed is limited to 433 Mbit/s, leaving three antennas unused. To address this limitation, MU-MIMO enables APs to communicate simultaneously with multiple terminals, fully utilizing AP capacity and enhancing throughput. MU-MIMO is denoted as MxN:U, with M representing the number of transmit antennas, N representing the number of receive antennas, and U indicating the number of terminals that can communicate concurrently. For instance, in an 8x8:8 MU-MIMO specification, up to eight terminals can communicate simultaneously with the AP, optimizing space resources and improving network performance.

MIMO divides network resources spatially, transmitting them concurrently through multiple antennas. This technology significantly improves data transmission efficiency without requiring additional spectrum resources. However, in a MIMO system, an access point (AP) can communicate with only one terminal at a time, known as single-user MIMO (SU-MIMO). Mismatched antenna numbers between APs and terminals restrict the optimal utilization of channel resources. For instance, a 4x4 MIMO Wi-Fi 5 AP can reach a theoretical speed of 1.732 Gbit/s. When communicating with a 1x1 MIMO mobile phone, the maximum speed is limited to 433 Mbit/s, leaving three antennas unused.

To address this limitation, MU-MIMO enables APs to communicate simultaneously with multiple terminals, fully utilizing AP capacity and enhancing throughput. MU-MIMO is denoted as MxN:U, with M representing the number of transmit antennas, N representing the number of receive antennas, and U indicating the number of terminals that can communicate concurrently. For instance, in an 8x8:8 MU-MIMO specification, up to eight terminals can communicate simultaneously with the AP, optimizing space resources and improving network performance.

MU-MIMO Benefits

The introduction of MU-MIMO brings several benefits. It leverages the multiplexing gain of multiple antennas to expand system throughput, improves system performance through the diversity gain of multiple antennas, and maximizes the value of Wi-Fi devices. MU-MIMO enables concurrent data transmission from multiple terminals, making wireless network communication more efficient, reducing latency, and meeting the demands of high-traffic applications like video and audio. To enable simultaneous communication across multiple terminals, MU-MIMO is often combined with beamforming techniques. Unlike traditional MIMO, which sends different spatial streams through each antenna, transmit beamforming sends the same stream through multiple antennas with deliberate timing offsets to increase the range and optimize communication with multiple clients simultaneously.

Wi-Fi 6 Applying MU-MIMO Technologies With Diversities

MU-MIMO is a significant advancement in wireless communication technology, particularly in the context of Wi-Fi networks. It builds upon the foundation of MIMO systems and enables efficient multi-user communication. By dividing available bandwidth into individual streams shared among devices, MU-MIMO enhances network performance, capacity, and overall user experience. The demand for diverse STA types necessitates enterprises to opt for APs equipped with a greater number of spatial streams in Wi-Fi 6 networks. Currently, the market offers two commonly found types of Wi-Fi 6 APs: those with a 2x2 MIMO configuration and those with a 4x4 MIMO configuration.