However, dual-band 802.11a/b/g adapters are selling well, creating an environment where client devices can communicate with either 802.11a or 802.11g APs. If dual-band adapters become the norm, then 802.11a APs will become more broadly interoperable. Dual-band 802.11a/b/g APs are also on the rise, particularly in enterprise-class APs where client diversity is common and must be dealt with now.
802.11a has two main advantages over 802.11g: channels and interference. As you note, A uses a different frequency band that's less congested and therefore less vulnerable to interference from Bluetooth, cordless phones, microwaves and other devices that operate in the 2.4 GHz band. The 5 GHz band used by A is also wider, supporting up to 12 channels in the U.S. as compared to 3 for B/G. More channels not only reduces interference, but also allows higher-density WLANs (i.e., more capacity in one spot). For this reason, 802.11a is popular for backhaul wireless links that carry aggregate traffic from one network to another.
This was first published in July 2004