The Institute of Electrical and Electronics Engineers (IEEE) introduced WiFi 6 (802.11ax) to address the WiFi challenges experienced in high-density deployments; for example, in places like auditoriums, stadiums, conference halls, and transportation centers. One of the changes introduced with WiFi 6 is updated Multi-User Multiple Input Multiple Output, or, as it’s frequently referred to, MU-MIMO.
What exactly is MU-MIMO? Why does it matter to businesses? Let’s find out.
WiFi 5: The Introduction of MU-MIMO
Before WiFi 5 (802.11ac), we had single-user routers, or SU-MIMO. As the name implies, these devices could only speak to one client device at a time. Every new device that connected to the network and wanted to send and receive data had to jump in line and wait its turn.
Then WiFi 5 introduced MU-MIMO, sometimes referred to as Next-Gen AC or AC Wave 2. It allowed a single access point (AP) to communicate with multiple client devices simultaneously. This decreased clients’ waiting time and improved the efficiency of the network. However, this version of the technology only worked for downlink connections – i.e. transmission from the AP to client devices like smartphones, laptops, and tablets. If clients needed to respond – contact the AP in an uplink connection – they still had to wait in line for a turn; only one device could communicate at a time.
The other significant drawback to the technology was that it only worked on the 5GHz spectrum. As more and more devices joined networks, businesses needed the ability to support simultaneous communication on both spectrums – especially as many IoT devices only operate on the 2.4GHz band.
WiFi 6: Expanded and Improved MU-MIMO
Then WiFi 6 (802.11ax) entered the market. As alluded to above, MU-MIMO now works with both 2.4GHz and 5GHz bands, providing more options to businesses as they design and deploy networks.
WiFi 6 supports two different types of multi-user technologies: OFDMA and MU-MIMO. These are not to be confused with each other. OFDMA subdivides a channel into smaller chunks (called as Resource Units, or RUs), and multiple users can concurrently communicate using one of the smaller chunks. MU-MIMO, on the other hand, makes use of spatial streams to allow multiple users to communicate simultaneously. The primary enhancement to MU-MIMO format of multi-user technology in WiFi 6 is that it now allows MU-MIMO in both uplink and downlink direction, whereas 802.11ac only allowed MU-MIMO in the downstream direction. Also, WiFi 6 standard allows both multi-user technologies to co-exist, it is expected though that the larger benefit will come from the use of OFDMA. All of this means that multiple devices used by end users can simultaneously send data to the AP as well as receive data simultaneously.
MU-MIMO in WiFi 6 makes use of beamforming (using explicit sounding frames), which is the ability to direct WiFi waves at certain devices vs. sending waves out over a general area. This reduces latency (the time it takes data to be transmitted) and improves signal strength for every client device.
What does TxR:N mean?
WiFi devices are often described using 3 numbers of the format: T x R :N, wherein T is # of transmit chains, R is the number of receive chains, and N is # of spatial streams. For each spatial stream, there must be at least one Tx/Rx chain. For example, Broadcom BCM43465 (802.11ac Wave 2, aka WiFi 5) is a 4×4:4 device, meaning it has 4 transmit chains, 4 receive chains, and supports up to 4 spatial streams. Another example is the Intel AX200 (WiFi-6) radio. This is a 2×2:2 device, meaning it has 2 transmit chains, 2 receive chains, and supports up to 2 spatial streams.
Each stream corresponds with an antenna. The more antennas, the more streams the AP can use to simultaneously transmit data. While 4×4 sounds the most appealing, keep in mind that most handheld devices are only 2×2 compatible (it’s hard to fit more than two antennas on a smartphone).
While there hasn’t been widespread adoption, your AP vendor also might have mentioned to you that they have 8×8 APs. While there can be throughput advantages of using 8×8 or 4×4, if you buy one of these APs but your devices are only 2×2 or 3×3, you won’t see the results you were expecting. It’s also good to be aware of the power requirements for these APs. Depending on the requirements, upgrading might require larger changes to your network than you are anticipating.
So, what does MU-MIMO mean for your business?
More simultaneous communication with less APs means that networks can improve performance in highly congested environments. Before WiFi 6, businesses could attempt to resolve the congestion problem with more APs, but there comes a point when cramming access points into an area does more harm than good. This is because APs only have so many channels available to them for communication. The best communication occurs when each channel operates in its own space and doesn’t have to share the airwaves. As soon as channels start overlapping – which is inevitable once you have enough APs on the network – they start interfering with each other.
By allowing one AP to handle more devices at the same time, WiFi 6 removes the need for more APs and the probability of channel interference decreases. In other words, MU-MIMO technology improves the capacity and efficiency of every access point.
Because client devices using MU-MIMO have to wait less time to communicate with the AP, it can make it appear that the WiFi’s speed, or data rate, has increased. However, MU-MIMO doesn’t actually increase WiFi speed. Instead, it creates a more efficient environment so that the speed that is already available isn’t lost in the congestion. (Other WiFi 6 technologies do increase speed, but that’s a topic for another post.)
Should Your Business Upgrade?
If your network is struggling to provide consistent, optimal performance in dense environments, WiFi 6 and MU-MIMO can help.
Remember that devices on the network must be WiFi 6 capable to utilize the new technology. That means that access points and all end devices have to be upgraded. It’s possible that some of the devices on your network aren’t even available yet with WiFi 6 support. That’s okay. The upgrade process can absolutely be done in phases, and even if only half of the devices connected to an AP can use MU-MIMO, the rest of the devices will still feel the ripple effects of decreased wait time.
If you want to find new products that are WiFi 6 and MU-MIMO capable, you can use this search tool from the WiFi Alliance.
If you’re wondering what capabilities your current devices have, the Wireless Intelligence Platform (WIP) can give you the answer. The AI-based WiFi Automation platform monitors the entire wireless network ecosystem. It provides automatic analysis of network health and performance in real-time, and automatically saves historical analytics for later review and budget and capacity planning. WIP can not only identify device capabilities, but also identify the most congested areas of a network, provide updates into health and performance before and after WiFi 6 upgrades, and automatically alert IT to any issues while providing actionable suggestions for resolution.
Whether you’re upgrading to WiFi 6 now or in the future, use WIP to remove the mystery from your wireless network.