User guide

AirMagnet Spectrum XT User Guide
Chapter 9: Radar Detection Tool 113
Radar Detection Tool
Chapter 9:
Chapter Summary
This chapter discusses the Radar Detection Tool that can be used to detect radar in the
wireless LAN environment. It covers the following topics:
•Introduction
• Radar Tool UI Components
• Using the Radar Detection Tool
Introduction
The 5-GHz band is an Unlicensed National Information Infrastructure (UNII) band, which is
divided into several segments, each being designated for a specific use. The UNII-2 (5.25
GHz~5.35 GHz) and UNII-2 extended (5.47 GHz~5.725 GHz) bands used to be set aside
exclusively for military and weather radar systems. When the FCC decided to open these
bands up for WiFi networks, its ruling came with an important caveat: Dynamic Frequency
Selection version 2, or DFS2, compliance.
DFS is a mechanism that tells the transmitter to dynamically listen for radar signals in the
airwave and automatically switch to another channel if a radar signal is detected. The
mechanism is designed to protect the incumbent military and weather radar systems from the
RF interference from 802.11a/n devices in their vicinity. With DFS2, the transmitter on a WiFi
device will continuously listen for radar signals, both before and during transmission. IF a
radar signal is detected on a channel, it will either vacate that channel or flag it as unavailable.
DFS2 is a must-have on 802.11a/n APs in order for 802.11a/n network systems to co-exist
with military and weather radar systems. According to the latest FCC ruling, all WiFi devices
operating in the UNII-2 and UNII-2 extended bands are required to support DFS, to detect
and automatically switch channels to prevent WLAN operations from interfering with
military or weather radar systems. The mandate became effective on July 20, 2007 in the US
and Canada. A similar mandate became effective on April 1, 2008 in the EU.
Since then, in April 2009 new EN 301 893 v1.5.1 requirements also called DFS-3 Compliance
have also been enforced for 802.11 APs operating in Europe.
AirMagnet Spectrum XT Radar Detection Tool
The only radar signals that AirMagnet Spectrum XT can detect are those described by the
regulatory bodies as part of the DFS requirements.
AirMagnet Spectrum XT supports all six of the FCC radar types, all six of the ETSI EN 301
893 V1.5.1 radar types, and all eight of the ETSI EN 302 502 V1.2.1 radar types.
Of the ten radar types defined by the Japanese DFS requirements, AirMagnet Spectrum XT
supports Type 1, and Types 5-10, which have exact equivalents in the FCC types.
Japanese radar Types 2-4 are currently not supported.