Dynamic Frequency Selection
Dynamic Frequency Selection ( DFS ; German " Dynamic Frequency Selection " ) is a mechanism by the European regulatory authority ETSI for the operation of wireless equipments in the 5 GHz frequency range is required. This function was implemented in the 802.11h standard introduced in 2003 , so that 5 GHz WLAN devices can now also be operated in Germany on channels> 48.
With DFS, a WLAN can automatically change channels if another device is detected on the channel used. This is intended in particular to prevent the weather radar systems operating in this frequency range from being disturbed by WLANs. In order to recognize other systems, the channel must be monitored periodically. As soon as a foreign transmitter has been recognized, a change of channel must be initiated immediately. The new channel is selected randomly and is usually carried out by the access point and then communicated to the other network participants. In an ad hoc network , one of the participating stations has to listen to the channel and organize the channel change.
When operating in Germany, DFS must be used on channels 52 - 64 (5.25 - 5.35 GHz) and 100 - 140 (5.47 - 5.725 GHz).
Situation in USA
In the USA, DFS is also compulsory in the UNII band, but slightly different from the European variant in technical terms.
DFS must be used on channels 52-64 (5.25-5.35 GHz) and 100-140 (5.47-5.725 GHz).
Web links
- The European Commission is regulating the 5 GHz range across Europe
- Federal Network Agency: general allocation of frequencies in the ranges 5150 MHz - 5350 MHz and 5470 MHz - 5725 MHz for radio applications for broadband data transmission, WAS / WLAN ("Wireless Access Systems including Wireless Local Area Networks") (PDF) (28 kB)
- WLAN / RLAN requirements for 5 GHz systems in Switzerland (indoor and outdoor) on the OFCOM website
Individual evidence
- ↑ Adelstein, McDowell: MEMORANDUM OPINION AND ORDER. (No longer available online.) In: Federal Communications Commission . June 30, 2006, formerly in the original ; Retrieved November 23, 2012 . ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ↑ COMPLIANCE MEASUREMENT PROCEDURES FOR UNLICENSED-NATIONAL INFORMATION INFRASTRUCTURE DEVICES OPERATING IN THE 5.25-5.35 GHz AND 5.47-5.725 GHz BANDS INCORPORATING DYNAMIC FREQUENCY SELECTION. In: Federal Communications Commission . November 20, 2012. Retrieved November 23, 2012 .
- ^ Charles T. Glass: Electronic cde of federeal regulation Part 15E U-NII. (No longer available online.) In: Federal Communications Commission . June 27, 2006, archived from the original on April 8, 2013 ; Retrieved November 23, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
