<Li> IEEE 802.11 y - 2008 extended operation of 802.11 a to the licensed 3.7 GHz band . Increased power limits allow a range up to 5,000 m . As of 2009, it is only being licensed in the United States by the FCC . </Li> <Li> Based on short guard interval; standard guard interval is ~ 10% slower . Rates vary widely based on distance, obstructions, and interference . </Li> <Li> IEEE 802.11 af about using white space spectrum for WiFi based on the PHY layer of 802.11 ac </Li> <P> The original version of the standard IEEE 802.11 was released in 1997 and clarified in 1999, but is now obsolete . It specified two net bit rates of 1 or 2 megabits per second (Mbit / s), plus forward error correction code . It specified three alternative physical layer technologies: diffuse infrared operating at 1 Mbit / s; frequency - hopping spread spectrum operating at 1 Mbit / s or 2 Mbit / s; and direct - sequence spread spectrum operating at 1 Mbit / s or 2 Mbit / s . The latter two radio technologies used microwave transmission over the Industrial Scientific Medical frequency band at 2.4 GHz . Some earlier WLAN technologies used lower frequencies, such as the U.S. 900 MHz ISM band . </P>

Comparison of ieee 802.11 a b g and n standards pdf