User's Manual Part 1
Release8PlanningGuide
Issue2,November2007 Draft5forRegulatoryReview 133
12.2.4 RadarSignatureDetectionandShutdown
With Release 8.1, Cyclone meets ETSI EN 301 893 v1.2.3 for Dynamic Frequency
Selection (DFS). DFS is a requirement in certain countries of the EU for systems like
Cyclone to detect interference from other systems, notably radar systems, and to avoid
co-channel operation with these systems. All 5.4 GHz modules and all 5.7 GHz
Connectorized modules running Release 8.1 have DFS. Other modules running Release
8.1 do not. With Release 8.1, Canopy SMs and BHSs as well as Cyclone APs and BHMs
will detect radar systems.
When an AP or BHM enabled for DFS boots, it receives for 1 minute, watching for the
radar signature, without transmitting. If no radar pulse is detected during this minute, the
module then proceeds to normal beacon transmit mode. If it does detect radar, it waits for
30 minutes without transmitting, then watches the 1 minute, and will wait again if it
detects radar. If while in operation, the AP or BHM detects the radar signature, it will
cease transmitting for 30 minutes and then begin the 1 minute watch routine. Since an
SM or BHS only transmits if it is receiving beacon from an AP or BHM, the SMs in the
sector or BHS are also not transmitting when the AP or BHM is not transmitting.
When an SM or BHS with DFS boots, it scans to see if an AP or BHM is present (if it can
detect a Cyclone beacon). If an AP or BHM is found, the SM or BHS receives on that
frequency for 1 minute to see if the radar signature is present. For an SM, if no radar
pulse is detected during this 1 minute, the SM proceeds through normal steps to register
to an AP. For a BHS, if no radar pulse is detected during this 1 minute, it registers, and
as part of registering and ranging watches for the radar signature for another 1 minute. If
the SM or BH does detect radar, it locks out that frequency for 30 minutes and continues
scanning other frequencies in its scan list.
Note, after an SM or BHS has seen a radar signature on a frequency and locked out that
frequency, it may connect to a different AP or BHM, if color codes, transmitting
frequencies, and scanned frequencies support that connection.
For all modules, the module displays its DFS state on its General Status page. You can
read the DFS status of the radio in the General Status tab of the Home page as one of
the following:
◦ Normal Transmit
◦ Radar Detected Stop Transmitting for n minutes, where n counts
down from 30 to 1.
◦ Checking Channel Availability Remaining time n seconds, where
n counts down from 60 to 1. This indicates that a 30-minute shutdown has
expired and the one-minute re-scan that follows is in progress.
DFS can be enabled or disabled on a module’s Radio page: Configuration > Radio >
DFS.
Operators in countries with regulatory requirements for DFS must not disable the feature
and must ensure it is enabled after a module is reset to factory defaults.
Operators in countries without regulatory requirements for DFS will most likely not want
to use the feature, as it adds no value if not required, and adds an additional 1 minute to
the connection process for APs, BHMs, and SMs, and 2 minutess for BHSs.
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