User's Manual

Tsunami MP.11 2454-R, 5054-R, and 5054-R-LR Installation and Management
Chapter 3. Management Overview 26
Dynamic Frequency Selection (DFS)
The Tsunami MP.11 5054-R supports Dynamic Frequency Selection (DFS) for European Telecommunications
Standard Institute (ETSI) domains per EN 301-893 regulations. The ETSI requires that 802.11a devices use DFS
to prevent interference with radar systems and other devices that already occupy the 5 GHz band.
During boot-up, the unit scans the available frequency and selects a channel that is quiet and free of radar
interference. If the unit subsequently detects radar interference on its channel, it rescans to find a better channel.
Upon finding a new channel, the unit waits 60 seconds to detect radar interference; if it finds no interference, it
switches to the new channel.
If you are using a 5054-R unit in Europe or other applicable countries, keep in mind the following:
• DFS is not a configurable parameter; it is always enabled and cannot be disabled.
• You cannot manually select the device’s operating channel; you must let the unit select the channel.
However, you can specify a particular “preferred” channel that you want to scan first whenever the DFS
process starts. You may also make channels unavailable by manually “blacklist” them and prevent those
channels to be scanned, as well as display the Channel Blacklist Table.
• You cannot configure the Auto Channel Select option. Within the HTTP or CLI interface, this option always
appears enabled.
With Tsunami MP.11 5054-R units, Dynamic Frequency Selection (DFS) is enabled automatically based upon the
country you select. You can tell DFS is in use because the frequency selection field displays only the DFS-
selected frequency. DFS scans all available frequencies, starting with the DFS preferred channel and skipping
blacklisted channels, to select the operating frequency automatically.
A country selection with DFS enabled causes the Base Station to come up in scan mode. It scans the available
frequencies and channels to avoid radar and selects a channel with the least interference.
Note: Scanning is performed only on the frequencies allowed in the regulatory domain of the country selected
when it is required for radar detection and avoidance.
To comply with your country’s regulations, change the DFS selection to specify your country. You can do this by
logging into the unit, clicking the Configure button and selecting the System tab. There is a drop-down box
labeled Country with all available countries from which to select. Choose your country, configure the unit as
required, and reboot
for the settings to take effect.
The SU also comes up in scan mode to scan all available frequencies to find a BSU with which it can register.
Scanning may take several minutes. After establishing a wireless link, the wireless LED stops flashing and
continues to shine green.
Note: Because DFS may need to scan for radar on multiple channels, you must allow a sufficient amount of
time for the units to start up. This is considerably longer than when the unit is not using DFS. This is
expected behavior. Startup time is within four minutes if no radar is detected, but up to one minute is
added for every selected channel that results in radar detection.
DFS is required for two purposes:
1. Radar avoidance both at startup and while operational. To meet these requirements, the BSU scans
available frequencies at startup for the presence of a radar signal on all available frequencies. If a radar signal
is detected on any DFS enabled channel, the system will blacklist the channel for a period of 30 minutes in
accordance to EN301-893. Once fully operational on a frequency, the BSU actively monitors the occupied
frequency for radar interference. If radar interference is detected, the BSU blacklists the channel, logs a
message and rescans to find a new frequency free of radar interference.