Thanks to Mrn CCIEW https://wordpress.com/read/feeds/6837197
for putting a new 802.11ax packet capture for research to the public. Many features few in the legacy wireless protocols (802.11n, 802.11ac) worth understanding.
Beamforming and MIMO? I still am a bit confused with the extreme focus on MIMO and beamforming. Yes that’s great technology, but there are other functions that are still important, like antenna selection. Perhaps antenna selection is there somewhere, but I only see antenna selection (ASEL) in 802.11n. Seems to me that in many cases, you will have simple wireless systems that need to only select between 2 or more antenna. Antenna selection can quickly improve radio signal. Remember an antenna can transmit a signal in three dimensions, and polarity varies also. That is millions of combinations!! Out of those millions of possibilities, some provide better signal than others. Simple switching of antenna (diversity) selection is often really the only important feature for simple radio connections. Antenna diversity and the variety of implementations is explained pretty well, here:
If you combine diversity with feedback between radios, you have powerful system for keeping good radion links. They have some of diversity and feedback in these protocols, but I’d like to learn more how they can be used in simple radios.
In 802.11n wireless frames, a HT Capabilities tag (802.11n D1.10)
26 bytes in length, showing transmit beam forming. Also has an
“Antenna Selection (ASEL) Capabilities. This appears to have antenna feedback possibility. There is Tx sounding PPDU here, also “rx ASEL”
There is also the VHT capabilities (802.11ac, 5ghz only), which has more beamforming but less about antenna selection.
Then there is the HE capabilities (802.11ax/D3.0)
Question. In a indoor environment, testing shows that 5ghz signal always has less range than 2.4 ghz. You notice that 2.4 ghz signal power is actually less dbm than the 5 gigahertz channels. It appears the 802.11a signal, the 5 gigahertz wireless channel sends a more powerful radio signal!! With a stronger signal, yet the range is still considerably less than the 2.4ghz channel. Why is that?