802.11g

The 802.11g standard uses orthogonal frequency division multiplexing
(OFDM) manipulation; however, for backward compatibility, it can also
work with the more commonly used 802.11b devices by supporting complementary
code keying (CCK) and packet binary convolutional coding
(PBCC) modulation.

802.11g offers speeds in the same range as 802.11a as well as backward
compatibility; however the modulation issues include unresolved
problems between key vendors whose support is divided between ODFM
and PBCC modulation schemes.
The ultimate compromise is the adoption of support for 802.11b’s
CCK modules so that it will ultimately support all three types of modulation.
The advantage is that vendors can have dual mode devices that
function in both 2.4 GHz and 5 GHz and use OFDM for both modes to
cut costs.

This means that 802.11g could theoretically excel in the European
areas should 802.11h not succeed as the high-speed standard in that
part of the world.