An Overview of Worldwide Regulatory Requirements
The advent of the 802.11a wireless market and the constant push to open up spectrum for unlicensed use required that a mechanism be implemented for spectrum sharing. Dynamic Frequency Selection (DFS) is the mechanism that was adopted to allow unlicensed devices to use the 5 GHz frequency bands already allocated to radar systems without causing interference to those radars. The concept of DFS is to have the unlicensed device detect the presence of a radar system on the channel they are using and, if the level of the radar is above a certain threshold, vacate that channel and select an alternate channel.
The regulatory requirements for DFS, along with requirements along with Transmit Power Control (TPC), have been adopted in Europe, the United States of America, and many other geographical areas. The following is an overview of the current DFS requirements for Europe, the USA, Canada, Taiwan, Australia, and Japan.