It addresses problems like interference with satellites and radar using the same 5 GHz frequency band.
The standard provides Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) to the 802.11a PHY.
Wireless technology has been more and more popular and a lot of standards have been finalized over the past decade.
This holds especially for ISM bands (Industrial, Scientific and Medical) which are unlicensed and free to use.
It addresses problems like interference with satellites and radar using the same 5 GHz frequency band.