Wi-Fi is technically referred to as the 802.11 protocol. Over time, Wi-Fi has improved, giving rise to different variations of the protocol:
This version operates at 54 Mbps. It is considered as the favorite wireless LAN protocol for IP telephony. The problem with it is distance; beyond 100 feet, you are out of the network.
This version operates at 11 Mbps, but the distance of transmission is 300 feet, which is a considerable improvement over its predecessor. This version is used for public hotspots and small campus environments.
This version is relatively new and is considered as a high-speed replacement for 802.11b. It works at 54 Mbps.