User's Guide Part 1

Chapter 3: System planning Radio spectrum planning
Regions with mandatory radar detection
In regions that mandate DFS, the unit first ensures that there is no radar activity on a given
channel for a period of 60 seconds before radiating on that channel. Once a channel has been
selected for operation, the unit will continually monitor for radar activity on the operating
channel. If detected, it will immediately cease radiating and attempt to find a new channel. In
DFS regions, choose
DFS
or
DFS with DSO
:
•
Dynamic Frequency Selection (DFS)
: Once a channel is selected, the unit will only attempt
to find an alternative channel if radar activity has been detected on the operating channel.
•
DFS with DSO
: In addition to switching channels on detection of radar, the unit will also
switch to a channel which has a significantly lower level of interference than the current
channel of operation. Before radiating on the newly selected channel, the unit must again
ensure that there is no radar activity on the new channel for a period of 60 seconds. This
mode therefore provides the benefit of switching to a channel with lower interference but
at the expense of an outage of approximately 60 to 120 seconds. For this reason,
the threshold for switching channels is greater than when DSO is operating in a non-radar
region.
Radar avoidance requirements in the 5.4 GHz band are defined as follows:
• For the EU: in specification EN 301-893.
• For the US: in the specification FCC part 15.407 plus the later requirements covered in
Important Regulatory Information in this User Guide.
• For Canada: in the specification RSS210 Annex 9.
Radar avoidance at 5.8 GHz is applicable to EU operation (not FCC/IC) and the requirements are
defined in EN 302 502 v1.2.1.
Avoidance of weather radars (USA only)
To comply with FCC rules (KDB 443999: Interim Plans to Approve UNII Devices Operating in the
5470 - 5725 MHz Band with Radar Detection and DFS Capabilities), units which are installed
within 35 km (22 miles) of a Terminal Doppler Weather Radar (TDWR) system (or have a line of
sight propagation path to such a system) must be configured to avoid any frequency within
+30 MHz or –30 MHz of the frequency of the TDWR device.
This requirement applies even if the
master is outside the 35 km (22 miles) radius but communicates with outdoor clients which
may be within the 35 km (22 miles) radius of the TDWRs. If interference is not eliminated, a
distance limitation based on line-of-sight from TDWR will need to be used. Devices with
bandwidths greater than 20 MHz may require greater frequency separation.
When planning a link in the USA, visit http://spectrumbridge.com/udia/home.aspx
, enter the
location of the planned link and search for TDWR radars. If a TDWR system is located within 35
km (22 miles) or has line of sight propagation to the PTP device, perform the following tasks:
• Register the installation on http://spectrumbridge.com/udia/home.aspx.
• Make a list of channel center frequencies that must be barred, that is, those falling within
+30 MHz or –30 MHz of the frequency of the TDWR radars.
The affected channels must be barred as described in Barring channels on page 7-39.
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