Definition - What does IEEE 802.11a mean?
802.11a uses radio frequencies in the 5 GHz band and supports theoretical throughput of up to 54 Mbps. The standard uses the same base protocol as the original 802.11 standard, but uses orthogonal frequency-division multiplexing (OFDM).
Also known as IEEE 802.11a-1999.
Techopedia explains IEEE 802.11a
Despite being superior in many ways, 802.11a never achieved the level of commercial success as 802.11b due to price. 802.11.b was cheaper, and got adopted as the de facto standard. It's more common in recent days to see tri-mode wireless routers with 802.11n and 802.11b/g. 802.11a isn't obsolete per se, it's just another example of how the business side of technology trumps performance.