35 Comments to Simple questions: What is MU-MIMO in WiFi? Do I need it?

  1. Art says:

    This is the best article on MU-MIMO that I found in several hours of searching and no other came close. It’s clear and complete and makes the technology understandable to a MU-MIMO newbie …. thank you!

    • Ciprian Adrian Rusen says:

      It was a lot of work to make it. I’m happy that you found it well written and useful. Appreciate the compliment.

  2. Srinivas says:

    I have 2 SU-MIMO devices(clients). So, can I enjoy uninterrupted gaming on both devices if I purchase a 2×2 MIMO router ?

    • Ciprian Adrian Rusen says:

      Performance should be better.

      • Srinivas says:

        Thank you for answering my question. Also, this article(tutorial) is very clear and I found answers to several of my questions, for which I could not find any proper answers even after searching for several days. Thank you.

  3. JS says:

    This technology still doesn’t make sense to me and I’ve followed wifi specs in detail for 15 years and read six websites so far on MU-MIMO. What is missing is an explanation of how the internet speed you pay for from your ISP relates to the speed/bandwidth provided by the Wifi access point, MU-MIMO or not. I would like to see an example with realistic numbers.

    For example, if my ISP is giving me 155Mbps between the internet and my Wifi access point(router), and my 802.11ac wifi gives me 1300Mbps of bandwidth over the air, then how does MU-MIMO benefit me? Isn’t it true that with or without MU-MIMO, my devices have an aggregate of 155Mbps to share, and it doesn’t matter what happens on the air interface, i.e. MU-MIMO or not? If not, why not? This is the kind of detailed analysis I need in order to understand this technology. Ultimately, aren’t all devices’ datastreams de-multiplexed from the pipe coming from the internet, over the wifi to the devices? If so, why would it matter if the air interface downloads “simultaneous” streams to the devices, if the bottleneck is in the pipe from the ISP, which is the case with almost all users? I mean, I don’t think too many ISP customers have 1300Mbps internet access…

    • Ciprian Adrian Rusen says:

      Once principle to remember is that you CANNOT have faster internet on WiFi than the source you have available. In your case, 155 Mbps is the maximum you can achieve on the internet. End of story. But, if your WiFi has 1300 Mbps of bandwidth, it can achieve that speed when transferring stuff in your network (like copying a large file from one PC to another), but not when downloading stuff from the internet.

      • JS says:

        Thanks – so are you saying that, in my example, which I think represents a realistic ratio of internet access speed to wifi bandwidth for the vast majority of users (please correct me if i’m wrong), MU-MIMO provides a benefit only *within the LAN*, i.e. between machines on the local network?? This seems to contradict the marketing for MU-MIMO, which I think is advertising things like, multiple users streaming movies and playing games “from over the internet”. I’m thinking that intra-LAN traffic for the typical home user is only a tiny fraction of internet download transfers. Am I still missing something about MU-MIMO?

        Or, can you devise a better example than mine, using realistic throughputs for internet access and wifi air interface, that show how MU-MIMO benefits a user?

        Oh – since my post, I’ve found out that regular (non MU-MIMO) wifi is single-user and half-duplex, so only one user gets to send/receive, and in one direction, at a time.

        thanks for the discussion….
        js.

        • Ciprian Adrian Rusen says:

          MU-MIMO refers to the connection and data exchanged between the router and the network device. That data can come from the internet. Therefore, you see real speed benefits both when transferring data through the local network, and from the internet.

          • JS says:

            Hi,
            Can you provide an example with real numbers, showing the benefit that MU-MIMO provides with data downloaded from the internet, i.e. the difference between SU-MIMO and MU-MIMO given the same wifi network speed, i.e. the difference that changing just this one parameter makes, for example, all parameters and speeds the same in both cases, for example … say… 600Mbps actual(or theoretical) wifi speed, and then just switch between SU-MIMO and MU-MIMO? In other words, instead of saying “real speed benefits”, can you just make an example with real numbers? Because I am unable to make these numbers work to show how MU-MIMO makes a difference.

            Very frustrating that I have not seen this proven with a simple numerical example.

            Just an example of the kinds of numbers that I think are necessary to demonstrate that something like MU-MIMO really works, here are numbers from my own 802.11n MCS index=15 network:

            1000Mbps = cabled Ethernet theoretical max (local LAN traffic)
            _933Mbps = cabled Ethernet actual LAN traffic
            _686Mbps = cable modem 16-bonded channels download max (Arris SB6183)
            _300Mbps = theoretical 2-antenna 802.11n MCS index=15
            _150Mbps = practical 2-antenna 802.11n MCS index=15
            _155Mbps = internet access speed you’re paying for
            __94Mbps = 10/100 Mbps cabled Ethernet speed

            thanks,
            js.

          • Leo Liang says:

            Do you mean you want to get an example of the real benefits of MU-MIMO comparing with SU-MIMO at a same wifi internet speed?

            For MU-MIMO benefits, you need more than one station in your wifi networks. If your wifi internet max speed is 600Mbps, assume that you have two clients which both support MU-MIMO and each of 1 antenna. If only a single station, the max speed is 300Mbps, therefore:
            1. router in SU-MIMO mode, the two clients max speed is 300Mbps at the same time;
            2. router in MU-MIMO mode, the two clients max speed can be able to get 600Mbps at the same time.

  4. Hussain says:

    I had never heard of MIMO before. I had assumed that WiFi routers used TDMA to support multiple clients.
    In a recent test, I had 2 laptops streaming YouTube and downloading large files. The third couldn’t open simple web pages.
    This was a shock to me.
    How can I have a few dozen users in an office environment? Install a separate router for each user? Switch to wired?

  5. Eagl3Eyes says:

    I have 8 wifi devices, one TV, two laptops, 5 smart phones. Sometimes me and two of my family member play online game. What will happen if I buy 4X4 MU-MIMO router?
    I what to buy ASUS RT-AC1300UHP.
    https://www.asus.com/Networking/RT-AC1300UHP/specifications/

    • Anonymous says:

      You will get better speeds and coverage, as well as built-in security (if you choose an ASUS or Netgear router).

      • Missy Ryan says:

        Hi-I’m somewhat in the same boat as Eagl3Eyes but my ISP only offers 30mbps,their highest?? Anyway,we have so many devices fighting for WiFi. I’m wondering what WiFi Netgear or ? router you would recommend. I’m so new to all of this & I’m sooo overwhelmed!!!! Thank you.
        Missy

    • Lee CL says:

      You can consider goggle wifi.

  6. Missy Ryan says:

    @Eagl3Eyes Do you have any suggestions my crappy situation? TIA

  7. Arrow says:

    Do i-phones support MUMIMO?

  8. DAVE says:

    Does the modem itself have to be compatible for mu-mimo to work. I have had issues with a linksys ea 9500 mu-mimo router just dropping out and not auto reconnecting…..i took it back to the store.

  9. Keith says:

    In the “Here’s what MU-MIMO does when it come to WiFI” section, you say that for each antenna configuration (2×2, 3×3 etc.) you can have a “maximum of clients”. But I would think this isn’t what you actually mean to say… Do you mean that the spatial stream count is the maximum number of clients you can have IF you want each client to have a dedicated spatial stream? It’s not really the “maximum” number of clients the AP can support, is it? Surely you can have more than one client per spatial stream, using CDMA or something similar? Or am I missing something?

  10. HANS KUMAR says:

    I AM GOING TO PURCHASE A ROUTER & RECEIVED VERY USEFUL INFORMATION & HELP ME TO BUY BETTER CHOICE OF PRODUCT

  11. Gerard says:

    Best article I’ve seen that explains the technology! Started looking into MU-MI when adding Wifi cameras. Switched to an Archer AX-6000 and with close to 18 devices, should have made the switch long ago. It made a drastic difference. Cost is another thing altogether but our lives depend on good quality access to the internet

  12. Angela says:

    Great article. Finally someone who can explain it in a way that I can understand. Thank you.

    • Anonymous says:

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  13. Alex G says:

    There is no such thing as 1×1 MIMO

    MIMO stands for multiple input mul;tiple output. It uses path diversity to send more data towards a client using the same channel at the same time. It needs more antennas to do that and the most common implementation is 2×2 with some of the more expensive APs using 3×3. A 1 antenna device cannot do MIMO. Standard MIMO, the one in n and ac Wave 1 can only speak to a single client. They only improve throughput.
    MU-MIMO, present in ac wave 2 devices allows you to send the different streams to multiple clients. It only works for downstream clients though, clients cannot use the same technology to upload data
    The MU-MIMO is 802.11ax allows multiple clients to upload data at the same time to the AP using this technology.

  14. mthqwork says:

    1×1 MIMO does not exists. MIMO stands for multiple-input and multiple-output.
    1×1 is single-in single-out, so it’s SISO.

  15. Az says:

    Even though this article is now over 1.5 years old, I found it very useful and well written. I was struggling to find clear info about the differences between 2×2, 3×3, 4×4 and this was perfect.
    I really appreciate the effort you put in to make it easy to understand. As someone who has dabbled in writing tutorials for others, I know it’s not so straight forward to distill information to a point that is this clear.

  16. Venky says:

    Thanks for this article. Really a good one and detailed.

  17. Steve says:

    Hey! This article is great. But I’ve been wondering, if a device is MU-MIMO 4×4 and the router is 3×3 how does the device behave?

    Does the MU-MIMO just not work and behaves as a 1×1 MIMO? Does it send the signal as 1×1 but the receiver uses the best of the four? Or does it drop an antenna and work as 3×3? Or does it attempt to use 4×4 but because router is only 3×3 it just sort of slows down to 3×3 and it sort of “load balances” the 4 antennas amongst the 3 available?

    There are a lot of diagrams about how devices with less antennas behave on a network with more, but I can’t seem to find any answers to a devices with more? If the device is being treated as a 1×1 MIMO, maybe it’s worth an upgrade to get 4×4 matching router, but if it’s simply handling the 4×4 device as 3×3, I’m more inclined to leave it as is.

  18. Christopher Enriquez says:

    I have been having issues with MU-MIMO. The 5GHZ frequency connection has been inconsistent when its on. I disabled it on my Nighthawk and connections have been much improved. The signal was still present when i had MU-MIMO on, but I’d lose connection with every piece of tech connected to the signal. I’m not sure why that was.

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