No, it's not the number of antennas (although there is always more than one), the method relies on the phase (or "time delay") of the signal at each antenna.
I say no because the system relies on multiple antennas, but beyond a few, the advantage evaporates while the workload increases. I wouldn't be surprised if the system limits itself to three well-placed antennas surrounding the target device, just to simplify the calculations.
> The more antennas you have, the cleaner you can keep the beam and minimize constructive interference happening in the wrong places.
Beyond three antennas surrounding a given device, this just isn't true -- more antennas don't produce a proportional increase in performance to compensate for the increased computation workload.
Not for one client device, but it definitely helps when handling lots of clients. The more antennas the fewer spots
with unwanted constructive interference.
> The more antennas the fewer spots with unwanted constructive interference.
Yes, true, but the entire system becomes more complex for a small improvement in performance. Also, most of the theoretical work in a scheme like this would focus on the least common denominator, which is three antennas.
Interestingly, for a roughly circular array of antennas, you end up with concentric rings of high signal strength as you approach the midpoint of the array. So even the thesis that you've eliminated unused hot spots breaks down in some cases.
Here's my diagram for three phase-controlled antennas (the blue dots):
The wavelengths in this diagram are longer than for a cell system, it's just to show how this idea works. Buy adjusting the phase at each antenna, you can move the high-strength lobes around to match up with the location of a given device.
