User guide

March 2005 Designing Your Canopy Network
Through Software Release 6.1
Page 100 of 425 Issue 1
Canopy System User Guide
12.2.4 Radar Signature Detection and Shutdown
In Release 4.2.3 and later releases, the Dynamic Frequency Selection (DFS) for United
Kingdom feature in the 5.7-GHz AP and BHM senses military radar and shuts down the
radio. The 5.4-GHz AP and BHM likewise sense military radar and shut down. The
shutdown of an AP/BHM effectively shuts down the SMs/BHS, which transmit only while
receiving the beacon of the AP/BHM.
When an AP or BHM in this frequency band range is enabled for DFS, the radio scans for
a radar signature throughout the first minute after a boot. During this or any later scan, if
the radio detects radar, then the radio
1. shuts down for the next 30 minutes.
2. re-scans for one minute.
However, the scan delay is unfavorable where regulations do not require radar signature
detection and shutdown. For this reason
◦ the default state of the DFS parameter in the Configuration page of the AP/BHM
is Disabled.
◦ the network operator where radar signature detection and shutdown is required
must toggle the DFS parameter to Enabled
− when the module is first deployed.
− if ever the parameters have been reset to factory defaults.
RECOMMENDATION:
Where regulations require that radar sensing and radio shutdown is
enabled, you can most effectively share the spectrum with satellite
services if you perform spectrum analysis and select channels that are
distributed evenly across the frequency band range.
12.3 CONSIDERING FREQUENCY BAND ALTERNATIVES
For 5.2-, 5.4-, and 5.7-GHz modules, 20-MHz wide channels are centered every 5 MHz.
For 2.4-GHz modules, 20-MHz wide channels are centered every 2.5 MHz. This allows
the operator to customize the channel layout for interoperability where other Canopy
equipment is collocated.
Cross-band deployment of APs and BH is the recommended alternative (for example, a
5.2-GHz AP collocated with 5.7-GHz BH).
IMPORTANT!
Regardless of whether 2.4-, 5.2-, 5.4-, or 5.7-GHz modules are
deployed, channel separation between modules should be at least 20
MHz.