I´m little bit busy this days
Well, I used to think that on "old fashion" spatial diversity I'll have 2 antennas, same polarization, vertically spaced, each one connected to a spatial diversity enabled ODU, e.g. a dual receiver, dual down converter, dual IF ... and some RF switch that will be driven by received signal level.
Then the RX IF signal will be routed to IDU, always the strongest one. Better the one that has better S/N.
May be for a single PSK modulated carrier it was ok. Some drops when switching and data errors recovered by some retries here and there.
I guess today it's possible to track bit error rate and chooses the smallest value and use this receiver. Add some buffers and no packet loss.
May be a step forward use both chains and "combine" correct data from each one to have the final packet.
I'm watching this "feature" simply as an aditional resource for - under certain circumstances - extend receiver operation withouth errors. Signals are already OFDM so destructive multipath affects some carriers but not all of them (as a single carrier PSK, BPSQ, QAM etc modulated).
I guess multiplexing on such chips extends rx threshold, on M mode increasing the troughput.
But on G only seems there's not multiplexing, may be sort of switch (mux) uses data from a single receiver, I don't know if RSL based, SNR based, BER based or what.
The "beauty" I intuitively observed is that the eventual switching from one antenna to the other is somewhat sinchronyzed so there's no detectable disruption on raw data stream when switching.
And at this test I'm doing - instead of use 2 cards, 2 antennas, 2 AP names, telling each CPE to lock to mac XX.XX or mac YY.YY, mainly those where the signal difference from AP1 to AP2 is small - this unofficial spatial (or mux) resource is helping a lot.
I'm ready to test a PTP with two R52nM configured the same way. May be 2 antennas vertically spaced, may be one V another H ...
This link is over the water (2Km) and both sides have dense vegetal covereage so lots of reflections, delays & etc. Early in the mornings there's lake evaporation that causes some deep fades (10 ... 30min around 6AM). Besides that, some airplanes cross by, 1 ... 1.5Km above, creating some scattering. Depending on the time of the day, one airplane each 4 minutes.
Another nice setup I finished this weekend: I have 2 distant APs, one of them using a 15dBi omni and a grid to a remote area, both APs at the same pole. One CPE 1.2Km away without rain/fog always connect (-70dBm) to the omni. But under rain/fog this signal starts to drop while it grows at the grid. Untill then it has two or three outages a day and netwatch let me know abt. Manually I switched the AP at this CPE. Now ... it's connected since last saturday evening, zero drops.
Regards;