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To address the primary aims the Spectrum Management algorithm implements a radar
detection function which looks for impulsive interference on the Operating channel only. If
impulsive interference is detected Spectrum Management will mark the current Operating
channel as having detected radar (Unavailable channel) and initiate a channel hop to an
available channel. The previous Operating channel will remain in the Unavailable for thirty
minutes after the last impulsive interference pulse was detected. After the thirty minutes have
expired the channel will be returned to the Usable channel pool.
The equipment can only transmit on Available channels of which there are none at initial
power up. The radar detection algorithm will always scan a Usable channel for 60 seconds
for radar interference before making the channel an Available channel. This compulsory
channel scan will mean that there is a 60 seconds service outage every time radar is detected
and that the installation time is extended by 60 seconds even if there is found to be no radar
on the channel.
NOTE: On system installation or start-up this extends the initial scan time of the Master unit
by 60 seconds. To address the "provide aggregate uniform loading of the spectrum across all
devices" requirement, the channel selection algorithm will choose a channel at random from a
list of available channels. The channel selection algorithm is initiated at link initialization and
when radar interference is detected.
5.3.2
5.8GHz Restrictions
5.3.2.1
RTTT Avoidance and Other Channel Use Restrictions
Where regulatory restrictions apply to certain channels these channels are barred. The user
should note that the number of channels barred is dependant on the channel raster selected.
For example see the effect of the UK RTTT channel restrictions in Figure 11, where blocks in
red indicate channels that are barred. Barred channels are indicated by a "No Entry" symbol
displayed on the "Spectrum Management" web page, see Section 8.3.9 "Spectrum
Management Control - With Operational Restrictions".
5 General Considerations
43
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