Let's say we have a wifi router which supports IEEE 802.11n, 802.11ac with 2x2 or 3x3 MIMO, and is also backward compatible with 802.11a, 802.11b, 802.11g.
Given that 802.11a/b/g are non-MIMO standards, does that mean that it will only transmit on 1 antenna if operating in those modes?
What is the best that it can do for those older IEEE wireless standards?
答案1
When only dealing with a single spatial stream, a good MIMO radio should use the spare radio chains to do beamforming.
答案2
They would either use 1 antenna, or multiple radios on multiple frequencies.
The question "What is the best you can do for these older IEEE wireless standards" can not be answered without first describing the goal. You can, for example, use highly directional antennas, different alignments (horizontal, verical, circular polarisation), amplifiers, higher sensitivity receivers etc.