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Because 802.11a wireless networks operate in the 5-GHz radio frequency band and support as many as 24 non-overlapping channels, they are less susceptible to interference than their 802.11b/g counterparts. However, regulatory requirements governing the use of the 5-GHz band vary from country to country, hampering 802.11a deployment.
In response, the International Telecommunication Union recommended a harmonized set of rules for WLANs to share the 5-GHz spectrum with primary-use devices such as military radar systems. Approved in September, the IEEE 802.11h standard defines mechanisms that 802.11a WLAN devices can use to comply with the ITU recommendations.These mechanisms are dynamic frequency selection (DFS) and transmit power control (TPC). WLAN products supporting 802.11h will be available in the second half of this year.
DFS detects other devices using the same radio channel, and it switches WLAN operation to another channel if necessary DFS is responsible for avoiding interference with other devices, such as radar systems and other WLAN segments, and for uniform...