Many references talk about WiFi spatial streams though not in terms of MIMO but like you could use all 8 or 16 streams to communicate with a single client, with a corresponding throughput increase. They invoke multipath and do a hand waving argument that somehow those little 1.5 dBi patch antennas inside the router have 16 different paths bouncing off the walls and furniture and they can all be separated at the receiver. Just like you separate H and V polarization.
From: AF <[email protected]> On Behalf Of castarritt Sent: Wednesday, October 8, 2025 5:04 PM To: AnimalFarm Microwave Users Group <[email protected]> Subject: Re: [AFMUG] 16 spatial streams how is that possible Here you go, ripped straight from the first few paragraphs of the wikipedia MIMO page. MIMO uses the spatial dimension to increase link capacity. The technology requires multiple antennas at both the transmitter and receiver, along with associated signal processing, to deliver data rate speedups roughly proportional to the number of antennas at each end. MIMO starts with a high-rate data stream, which is de-multiplexed into multiple, lower-rate streams. Each of these streams is then modulated and transmitted in parallel with different coding from the transmit antennas, with all streams in the same frequency channel. These co-channel, mutually interfering streams arrive at the receiver's antenna array, each having a different spatial signature—gain phase pattern at the receiver’s antennas. These distinct array signatures allow the receiver to separate these co-channel streams, demodulate them, and re-multiplex them to reconstruct the original high-rate data stream. This process is sometimes referred to as spatial multiplexing. The key to MIMO is the sufficient differences in the spatial signatures of the different streams to enable their separation. This is achieved through a combination of angle spread of the multipaths[1][2] and sufficient spacing between antenna elements. In environments with a rich multipath and high angle spread, common in cellular and Wi-Fi deployments, an antenna element spacing at each end of just a few wavelengths can suffice. However, in the absence of significant multipath spread, larger element spacing (wider angle separation) is required at either the transmit array, the receive array, or at both. On Wed, Oct 8, 2025 at 4:40 PM Adam Moffett <[email protected] <mailto:[email protected]> > wrote: Either way, I think the question is how does it differentiate the chains from each other? Whether it's 4, 8, or 16, it's still multiple signals on the same channel at the same time. What's the idiot's version of how that works? _____ From: AF <[email protected] <mailto:[email protected]> > on behalf of castarritt <[email protected] <mailto:[email protected]> > Sent: Wednesday, October 8, 2025 4:50 PM To: AnimalFarm Microwave Users Group <[email protected] <mailto:[email protected]> > Subject: Re: [AFMUG] 16 spatial streams how is that possible In my testing, 2x2 vs 4x4 with mu-mimo on the AP was almost unnoticeable for home wifi (with the exception of a few clients that had 4x4 radios), and some papers/blogs I've seen showed mu-mimo does very little in enterprise wifi as well. Massive MIMO in mobile and fixed wireless is a different story, big gains there. We routinely got 2-3x mu-mimo gain with 450M. 16x16 mu-mimo in wifi might be useful for something like a stadium or other wide open space with dense clients, but not much else IMO. On Wed, Oct 8, 2025 at 3:18 PM Rory Conaway <[email protected] <mailto:[email protected]> > wrote: It means the AP is handling 16 streams at once, not the clients. I've seen designs up to 64 with 32 2x2 streams. Massive MIMO is a good strategy. Rory On Wed, Oct 8, 2025 at 12:38 PM castarritt <[email protected] <mailto:[email protected]> > wrote: I thought they dropped 16x and left it at 8x like wifi6. Pretty much every client device is still going to be 2x2, or maybe you could call it 4x4 if running MLO in two bands. On Wed, Oct 8, 2025 at 2:08 PM Ken Hohhof <[email protected] <mailto:[email protected]> > wrote: In the list of supposed advantages of WiFi7 over WiFi6, I see 16 spatial streams vs 8. Can someone explain to me the mechanism for using 16 spatial streams in a typical WiFi environment? I have a hard time wrapping my head around anything more than 2 using V/H or dual slant polarization. I was willing to believe that maybe you could get more (like maybe 4 spatial streams) due to reflections off furniture and stuff, and that somehow signal processing could magically separate out the streams (even though I don’t understand how it does that). But 8 or 16 just sounds like crazy talk. Maybe it’s like the rich people houses with 16 car garages, if I were rich people I would understand? -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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