144.4Mbps-20MHz/2S/SGI
Take https://mcsindex.com/ as reference document: HT = 802.11n , VHT= 802.11ac, (HE =802.11 ax)
The above interface rate is:
- HT MCS15 (or 2x VHT MCS07) encoding, rate is 144.4Mbps
- bandwidth is 20 MHz (not 40MHz)
- 2S= dual stream (two independent data streams, uses 2 antenna)
- SGI = short guard interval 0.4µs
.
300Mbps-40MHz/2S/SGI
- HT MCS15 encoding, rate is 300Mbps
- bandwidth is 40 MHz
- 2S dual stream
- SGI short guard
.
243Mbps-40MHz/2S
is HT MCS14 (or 2x VHT MCS06) , interface rate 243Mbps, bandwidth 40MHz, dual stream, long guard
Some rules:
- bandwidth 20/40/80 is negotiated, but mostly set by AP (client must be able to execute, and normally keeps all options open, but may not have 80MHz)
- MCS index is dynamically changed, independent for both directions. Bad transmissions (>HW retry) makes the interface step down in MCS , good transmissions trigger step ups
-dual stream: if both devices support it, and if the radio can maintain it. Sometimes 2S is dropped as not maintainable. Client and AP # of antenna defines max # streams.
So: hAP AC is 3S, but except for iMAC not many clients have 3S. e.g.: Tablet will connect as 2S
So: laptop is mostly 2S, tablet 2S, smartphone 1S. Smartphone will always connect as 1S to hAP ac and hAP ac2, (even to the 4x4 Audience). - short guard: as set in AP. short/long/auto. With auto it depends on signal quality
In 802.11ac in 40MHZ/2S/SGI highest MCS09, interface rate is 400Mbps
In 802.11ac in 80MHz/2S/SGI highest MCS09 , interface rate is 866,7Mbps
In 802.11ac in 80MHz/3S/SGI highest MCS09 , interface rate is 1300Mbps
Effective user datarate is much lower. The overhead becomes more important with higher interface rates. A lot depends on the driver and the aggregation used. http://forum.mikrotik.com/t/ac2-vs-ac3-wifi-not-over-200mb/148289/1
On MT 400Mbps interface rate yields 260Mbps, 866Mbps drops to 360Mbps. (other brands and wifiwave2 drivers will go to 500Mbps+)