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Chapter 4 - Operation and Administration
Sector Menu
In certain regions there are radar systems operating in the 5 GHz band.
Applicable regulations dictates that wireless access systems operating in these
bands shall not interfere with the operation of the radar systems. This means that
the wireless access system must be able to automatically detect the presence of
radar signals and avoid transmissions on frequencies used by radar systems in its
vicinity.
The Dynamic Frequency Selection (DFS) mechanism is based on monitoring of the
frequency being used and automatic switching to a radar-free frequency upon
detection of radar activity on the current frequency. The test for radar activity is
performed according to the applicable standards (ETSI or FCC), according to the
selected DFS Type.
Before initiating transmission on a new frequency that is not defined as Available
(at start-up after power up or reset none of the frequencies are defined as
Available) the unit performs a Channel Availability Check to ensure that there is
no radar operating on this frequency. During normal operation, the unit
continues monitoring the operating frequency (In-Service Monitoring) to ensure
that there is no radar operating on the frequency. After deciding that a frequency
is Available, it is considered as an Available frequency for a period defined by the
Startup Test Valid Period parameter.
Upon detection of radar activity on the operating frequency, the unit will
automatically stop transmissions on this frequency that will be marked as
Unavailable (Radar Detected) channel. The unit may continue transmissions on
this frequency for a very limited period, allowing it to complete some
transmissions of data and send control and management signals to support the
transition of the served devices to a new channel. The frequency on which radar
was detected will be considered as Unavailable for a period defined by the
configurable Channel Non Occupancy Period parameter. If the Random Channel
Selection parameter (see
"Random Channel Selection" on page
102) is set to
Disable, the unit will switch randomly to another frequency in the Usable
Frequencies List that is not considered as Unavailable. If the Random Channel
Selection parameter is set to Enable, the unit will switch randomly to another
frequency in the relevant frequency band that is not considered as Unavailable. If
the selected frequency is not marked as Available, the unit will check for radar
activity before initiating transmissions on the new frequency.
If DCS is enabled, it will be activated upon startup or detection of radar activity.
The new channel selected by the DCS mechanism will be tested for presence of
radar activity before initiating transmissions on the new frequency.
In configurations with two sectors, when the DFS Frequencies Management Level
(see
"DFS Frequencies Management Level" on page
103) is set to BTS Level, the
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