IEEE standards refer to the set of layer 1 and layer 2 specifications for a WLAN.

The first version was released in 1997, and 6 different versions have been brought since then. — 1) 802.11a, 2) 802.11b, 3) 802.11g, 4) 802.11n, 5) 802.11ac, and 6) 802.11ad

Collectively these standards are known as wireless fidelity (WI-FI).

All these standards are similar in 3 aspects:

  • They use half-duplex signaling. That means a device can either transmit or receive, but not perform both simultaneously.
  • They all use 2.4 GHz and 5 GHz frequency bands.
  • Layer 2 medium access control method is called CSMA/CA (carrier sense multiple access with collision avoidance).

MIMO — Multiple Input Multiple Output