On 24 Aug, 2014, at 2:40 am, Steinar H. Gunderson wrote: > On Sun, Aug 24, 2014 at 02:29:50AM +0300, Jonathan Morton wrote: >> Multi-target MIMO allows an AP to transmit to several clients >> simultaneously, without requiring the client to support MIMO themselves. >> This requires the AP's antennas and radios to be dynamically reconfigured >> for beamforming - giving each client a clear version of its own signal and >> a null for the other signals - which is a tricky procedure. APs that do >> implement this well are highly valuable in congested situations. > > FWIW; I don't think you're right about the nulls. Beamforming has some gain, > and there are some “darker spots”, but they're not what the algorithm is > aiming for (it aims to maximize the signal at the client, not to minimize it > at all other clients), and it's not -inf dB, more like -10 dB.
That's true of plain beamforming, whose goal is to increase SNR to a particular client. That's been around since 802.11g days. But that's not what I'm talking about here. I'm talking specifically about 802.11ac multi-target MIMO, which *does* attempt to null out the other clients to which it is simultaneously transmitting, purely so that it *can* transmit to them simultaneously. But that's only two or three other clients to form nulls for, not the hundred others who are not involved in that particular timeslot. - Jonathan Morton _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
