title: Why wait SIFS time before sending ACK?
body: <p>Question about the MAC-protocol of 802.11 Wifi.</p>
  
  <p>We have learned that when a station has received the data it waits for SIFS time. Then it sends the packet. When searching online the reason that is always mentioned is to give ACK packets a higher priority. This is understandable since a station first has to wait DIFS time when it wants to send normal data (and DIFS is larger than SIFS).</p>
  
  <p>But why wait at all? Why not immediately send the ACK? The station knows the data has arrived and the CRC is correct, so why wait?</p>