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Is it possible to use multiple WiFi cards to create a 8x8 MU-MIMO access point with example HostAPD. The reason for why I'm asking, is because I can only find PCI-E WiFi card that support up-to 4x4, so I was thinking of a AP setup with two 4x4 MIMO cards and running these two beside each other to create a 8x8 MU-MIMO network.

And just of curiosity, if it is possible. Is it possible to extend it to like 12x12, 16x16 or 20x20 MU-MIMO?

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MIMO works by using the signal from all antennas at the same to do some "magic" signal processing that allows you to differentiate between stations from different directions (to phrase the underlying physics very simply). So you need to be able to see and process all antennas directly, at the hardware level.

That means, no, you can't make an 8x8 MIMO out of two 4x4 MIMO cards. Or 12x12, 16x16, or 20x20 MIMO. But if you place the antennas of the 4x4 MIMO cards sufficently wide apart, each card will have it much easier to ignore the signals from the other card, or from stations communicating with the other card.

May I ask what kind of setup you intend that will actually use 8x8 MIMO (not to speak of 20x20 MIMO)? A hotel with 100 guests in a single big lounge, who all want to use the internet at the same time?

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  • Not only does one device need to "see and process all antennas directly" but it goes even further that the antennas need to have the correct spacing and orientation or it won't function properly. – YLearn Mar 23 '18 at 6:43
  • @YLearn: In principle, you can do MIMO with all kinds of spacings and orientations, but some will work better than others, and some will work really badly (e.g. when the spacing is a multiple of the wavelength in direction to the other station, for several stations). So while there's no need to stick religiously to the given antenna layout (unless the hardware designers implemented an unnecessary dependency on the layout), yes, you shouldn't change it until you have some idea what you are doing. – dirkt Mar 23 '18 at 9:19
  • For MIMO, you are correct. For beamforming and MU-MIMO (which makes use of beamforming), you would be incorrect. – YLearn Mar 23 '18 at 9:22
  • @YLearn: I don't see why beamforming should be restricted to a particular antenna layout. You get phase differences even if you move antennas, and yes, that's for MU (multiple users). Would you care to explain? – dirkt Mar 23 '18 at 9:23
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Yes one can....create a meshed/trucked network ending up with 8×8 up to 32×32 BUT.... It will ACTUALLY be up to 4 networks if you got (eight times 8x8 MU-MIMO capable cards forming) 4 networks. With software and bridge(bridging)/tunneling one can use 4 networks 8 nics as one network.... Thus in the end get up to 40-85% the speed of 32×32 MU-MIMO IF you got enough bandwidth on the rest of the hardware since peaks could go as high and fast as 10-120 Gbits/s with the latest non-released technologies and hardware. But ONLY in ideal conditions, meaning antenna setup of 20-120 meters spread apart, no interference, software scripting managing the tiering of NIC's as well as drivers and firmware....on and on and on....many things but potentially fabulous results. If one could run a cable, go with fiber optics NIC's and setup several NIC's as one network over bridging/tunneling. One could use 1 NIC with 2 up to 6 connectors or several of those NIC's and on firm/hard-ware level set them up as one device and/or network. And thus allowing 40 up to 480Gb/s from/to one system. (If hardware like MOBO BUS and PCI, CPU's can handle the bandwidth troughput)

Keep in mind, a 32×32 MU-MIMO is pointless if cables could be pulled or space is limited... In the end....a deasond 32×32 setup has 64 coaxial cables and at least 16 antennas...preferably 16 antennas ON EACH END of the setup requiring massive amounts of space.

I would advice a 32×32 (= 4x 8×8 MU-MIMO) setup in a building with 5/7 up to 10 floors. A highly powerful setup with 4 antennas on each floor could provide a building with up to 8Gb/s internet flawlessly if the rest of the building and externally every connection is wired optics and hardware is capable of 10Gb/s(or more) capable on each single connetion.

Besides that obviously us a high end capable quad CPU 1-6TB RAM capable router with LOTS(8+) of PCI slots for wireless and 40-160Gb/s NIC's on both ends.

In the end, fiber is likely A LOT cheaper second hand, but yeah, a range of cards could be fun as heck with the right hardware and setup.

Maximum I seen was 4+4 x 6x4 MU-MIMO setup on firmware level.

8 of the same cards, software replacing firmware and drivers.... And after an afternoon of setups and another day of tweaking and tuning......... They had 10-75Gbit/s Wi-Fi on various distances, so....yeah it can be done, but is not adviced or advisable unless you got line-if sight when ranged and have no other options for cabled networking. Fiber after all can be used and placed along with the existing power sockets and wiring.

Thus, fiber could be implemented nearly anywhere and thus any room could have 40 up to 240Gb/s through merely the power sockets. (4x 60Gb/s fiber optics)

Then again, I nearly only work with Windows. (And am happy my phone does up to 2.8Gbit/s on networking)

Keep in mind, with several wireless NIC's on each end one needs to at the very least setup band usage to prevent interference.

Good Luck.

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