Thursday 30 January 2014

5GHz (802.11h)

The FCC added 11 new channels in February 2004, and in 2008, we finally get to begin using these channels based on manufacturers’ releases of more 802.11a 5GHz products. This means that soon, we’ll gain access to up to 23 non-overlapping channels! And there are two new features of the 5GHz radio that are part of the 802.11h specification: Transmit Power Control (TPC) and Dynamic Frequency Selection (DFS).

DFSThis cool feature continuously monitors a device’s operating range for any radar signals that are allowed to operate in portions of the 5GHz band as well as 802.11a before transmitting. If DFS discovers any radar signals, it’ll either abandon the occupied channel or mark it as unavailable to prevent interference from occurring on the WLAN.  

TPCEven though it’s been used by the mobile phone industry for a long time, this technology has some handy new uses. You can set the client machine’s adapter and the access point’s transmit power to cover various size ranges—a feature that’s useful for many reasons. For one, setting the access point’s transmit power to 5mW reduces cell range, which works great if you’ve got a compact area with high-density usage. Further advantages include the fact that TPC enables the client and the access point to communicate.

This means the client machine can fine-tune its transmit power dynamically so it uses just enough energy to preserve its connection to the access point, conserve its battery power, plus reduce interference on the neighboring WLAN cells—sweet!

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