What is MU-MIMO? Everything You Need to Know

what is mu-mimo
Confusing acronyms are not uncommon in the world of tech. MU-MIMO is simply one of these. The MIMO stands for Multiple Input, Multiple Output. The MU means Multiple User. MU-MIMO is the more evolved form of SU-MIMO (Single User MIMO). MU-MIMO is the latest Wi-Fi standard that promises to revolutionize the wireless networking world. This article will help you understand how it works.

How MU-MIMO Works

Traditional Wi-Fi routers are good at sending and receiving data in a single direction. You can obviously use this Wi-Fi for multiple devices (which everyone does), but that happens in an inefficient and slower way. This is why your internet seems to be slower when many people are using it at the same time.

So what is MU-MIMO then? MU-MIMO allows advanced wireless routers to communicate with several devices at once, making the whole process much more efficient. MU-MIMO allocates a separate stream to each device connected to a Wi-Fi. The results are as if each device has a router of its own.

MU-MIMO solves some of the problems that its predecessor, SU-MIMO. For instance, MU-MIMO doesn’t have the antenna requirements of SU-MIMO, and it doesn’t have the same problems with data interference.

The Defining Features of MU-MIMO

Now that you know what MU-MIMO is, let’s look at some important aspects of how it functions practically.

One-way vs Two-way Communication

The Wi-Fi standard or the kind of router you have will determine whether MU-MIMO enables one-way or two-way data acknowledgments. Wireless routers and APs can simultaneously send data to multiple users, and this can be more than one stream to each user.

Wireless devices, like smartphones or laptops, can only send one stream back as a whole, that is, they must take turns sending data to the router. This is one-way communication.

Wireless devices will be able to send back multiple data streams using Wave 2 of 802.11ax (also called Wi-Fi 6) when it comes. For now, using SU-MIMO for each device can allow them to send multiple streams of data when it’s their turn. This is (theoretical) two-way communication.

Other Possibilities with Wi-Fi 6

Wave 1 of Wi-Fi 6 is referred to as 802.11ac. This is what we currently use. The 11ac standard only allows four clients at a time in an MU-MIMO group. This limits the AP or wireless router to sending data to four devices at a time. 11ax allows up to eight clients at a time and in a certain group, which means even speedier connections.

For 11ac, SU-MIMO works with 2.4GHz and 5GHz bands, but MU-MIMO works only with 5GHz. With 11ax, MU-MIMO can be used with both of these as well. This improvement also holds the potential to make the (usually congested) 2.4GHz band more usable in dense environments.

Another noteworthy feature that MU-MIMO uses, with both 11ac and 11ax, is beamforming. This means that MU-MIMO can direct signals to the intended devices more accurately, rather than sending signals out in random directions. This means the signal is more efficiently used and helps increase both Wi-Fi range and speed.

Antennas for User Devices

SU-MIMO requires multiple antennas on wireless routers and MU-MIMO does not. However, the wireless user devices will need a minimum of one or two antennas. One is enough to receive a single MU-MIMO stream from an AP. Two are enough to transmit an MU-MIMO stream back to an AP or router, even for single-stream connections.

More antennas can be used if you want more data streams and better Wi-Fi performance. Having around eight antennas will allow you to take full advantage of MU-MIMO features with 11ax.

Channel Width

Channel bonding is a technique used to increase Wi-Fi performance, and it entails combining two adjacent channels to create a single channel that’s twice as wide, hence effectively doubling the Wi-Fi speed.

While 11ac supports up to 80MHz wide channels and 11ax supports up to 160MHz wide channels, you can use channel bonding with MU-MIMO if you don’t have these specific channels available. If your network uses narrower channels like 20MHz or 40MHz wide channels, MU-MIMO can help double the overall performance even without channel bonding.

Network Capacity and Signal Security

By increasing Wi-Fi speeds, MU-MIMO effectively increases network capacity itself. Since each connected device is being served more quickly, there is more airtime left to serve even more devices. MU-MIMO, in this way, solves congestion present in dense networks like Wi-Fi hotspots.

MU-MIMO also increases signal security because of the way that it processes signals. This is an interesting side effect of the process which results in a larger relative benefit. MU-MIMO scrambles data before transmitting it, and the data can only be unscrambled by the intended receiving device. This is especially good news for open networks such as hotspots, and for Wi-Fi security in general.

OFDMA

ODFMA or Orthogonal Frequency-Division Multiple Access technology is sometimes thought to be a substitute for MU-MIMO (in certain situations) but it works better as a complement. OFDMA is a part of 11ax and divides channels into smaller segments. It allows devices to coordinate better and faster when communicating; which means more efficient use of said channels.

OFDMA and MU-MIMO both allow simultaneous transmissions between multiple devices, but they function differently. They complement each other because MU-MIMO is better for environments with high throughput applications, whereas OFDMA works well in dense environments with lower throughput.

Drawbacks of MU-MIMO

Sure, MU-MIMO sounds great so far, but there has to be a catch, right? Yes. Certain drawbacks to MU-MIMO are listed here.

  • MU-MIMO will obviously only work if both the router or AP and the receiving device (or devices) are fully MU-MIMO compatible.
  • Current MU-MIMO routers are only able to broadcast at 11ac (and obviously and theoretically, 11ax) which is still quite new and many devices aren’t equipped to decode it yet. This is changing rather fast though, so maybe not as much of a drawback.
  • You will have to drop some extra coin for routers with MU-MIMO capability.
  • Multiple antennas (more than the minimum needed), while beneficial, also take up more space and cost more overall.
  • Even with MU-MIMO enabled, the issue of maxing out all available streams still remains. Since there are only four streams actually available in MU-MIMO for now, adding a fifth device would mean stream-sharing in a way similar to SU-MIMO, which defeats the purpose of having MU-MIMO in the first place.
  • Since MU-MIMO streams are directional, stream-sharing can again happen (and again defeat the purpose) depending on where the user devices are situated.

How You Can Get MU-MIMO

The first thing you need to do is make sure that your computer (and other devices) and router have MU-MIMO enabled. MU-MIMO compatibility is becoming more and more of a common feature in devices now. The specs for either device will say ‘MU-MIMO,’ or you will know anyway because the brand will most likely put a lot of marketing into it.

Should You Get MU-MIMO?

Remember that MU-MIMO is more or less just an advanced bandwidth management tool, so the amount of speed/efficiency it gives you will depend on the amount of bandwidth you have available in the first place.

If you are still on DSL, MU-MIMO is not going to give you any dramatic results. But if you are living in a house with gamers and hardcore Netflix streamers, MU-MIMO will make things easier for you in the long run. The same goes for if you already have devices that are compatible with MU-MIMO because you should take advantage of this fact.

With everything being said, if you wait, MU-MIMO will probably come to you. Waiting is a smart move because MU-MIMO is still a relatively new technology, and so there is still probably more to come in regards to it.

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