Why wait SIFS time before sending ACK?

Question

Question about the MAC-protocol of 802.11 Wifi.

We have learned that when a station has received the data it waits for SIFS time. Then it sends the packet. When searchin

Answer 1

SIFS = RTT (based on PHY Transmission rate) + FRAME PROCESSING DELAY AT RECEIVER (PHY PROCESSING DELAY + MAC PROCESSING DELAY) + FRAME PROCESSING DELAY (FOR COMPOSING RESPONSE CTS/ACK)+ RF TUNER DELAY (CHANGE FROM RX to TX)

A the Transmitter side, after last PHY Symbol (of RTS, e.g), the time required to change to RX mode (at RF). So, I would see SIFS as a RX side calculation than a TX side.