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Senior Editor

Wireless standards

Jul 19, 20042 mins
Cellular NetworksNetwork Security

* The latest wireless standard to emerge, 802.11h

In the alphabet soup world that is wireless standards, there’s another one emerging you might be interested in: 802.11h.

802.11h defines the mechanisms 802.11a-based wireless systems should use to avoid interfering with radar and other bandwidth technologies in that ilk.

Key to 802.11h are two technologies dynamic frequency selection (DFS) and transmit power control (TPC). According to our Technology Update author this week (, DFS defines a mechanism to detect the presence of other devices using the same radio channel and switch to another channel if necessary. DFS is responsible for avoiding co-channel interference with other devices, such as radar systems or other WLAN segments, and for uniform utilization of channels.

TPC is intended to reduce interference from WLANs to satellite services by reducing the radio transmit power WLAN devices use. TPC can also be used to manage the power consumption of wireless devices and the range between the access point and wireless device, our author states. Products deploying 802.11h should begin to appear later this year.

In case you need an update on the 802.11 alphabet, it foes something like this:

* 802.11a: Describes WLANs for the 5-GHz band, with a data rate of 54M bit/sec.

* 802.11b: WLANs in the 2.4-GHz band, 11M bit/sec data rate.

* 802.11d: Enables 802.11 hardware to work in various countries where it can’t today.

* 802.11e: Enhances the 802.11 Media Access Control layer for quality-of-service features, such as prioritizing voice or video traffic.

* 802.11f:: Recommends practices for WLAN equipment makers so that all their 802.11 access points can interoperate.

* 802.11g: Also in the 2.4-GHz band, but uses 802.11a modulation to reach 54M bit/sec.

* 802.11h: Supports measuring and managing the 5-GHz radio signals in 802.11a WLANs.

* 802.11i: Repairs weaknesses in the Wired Equivalent Privacy encryption scheme.

* 802.11k: Creates a way for access points to pass specific radio frequency health and management data to higher-level management applications.

* 802.11n: Designed to boost throughput, not raw data rate, to 100M bit/sec. The idea is to make WLANs feel like 100M bit/sec switched Ethernet LANs.

For more on his article see: