Frequency Domains and Channels
Tsunami MP-8100 Installation and Management Guide 190
Dynamic Frequency Selection (DFS)
The Tsunami MP-8100 supports Dynamic Frequency Selection (DFS) for FCC, IC, and ETSI regulatory domains per FCC Part 15
Rules for U-NII devices, IC RSS-210, and ETSI EN 301-893 and 302-502 regulations, respectively. These rules and regulations
require that the devices operating in the 5 GHz band must use DFS to prevent interference with radar systems.
DFS is required for three purposes:
1. Radar avoidance both at startup and while operational. To meet these requirements, the BSU scans available
frequencies at startup. If a DFS-enabled channel is busy or occupied with radar, the system will blacklist the channel
for a period of 30 minutes in accordance with FCC, IC, and ETSI regulations. Once fully operational on a frequency,
the BSU actively monitors the occupied frequency. If interference is detected, the BSU blacklists the channel, logs a
message and rescans to find a new frequency that is not busy and is free of radar interference.
Radar detection is performed only by the BSU and not by the SU. When an SU is set to a country/band in which DFS is
used, it passively scans all available channels upon startup looking for a BSU that best matches its connection criteria
(such as BSU Node System Name, Network Name, and Shared Secret). The SU connects to the BSU automatically on
whatever frequency the BSU has selected. Because of this procedure, it is best to set up the BSU and have it fully
operational before installing the SU, although this is not required. If a BSU rescans because of radar interference, the
SU loses its wireless link. The SU waits for 30 seconds and if it finds that it could not receive the BSU in this amount of
time, it rescans the available frequencies for an available BSU.
2. Guarantee the efficient use of available frequencies by all devices in a certain area. To meet this requirement,
the BSU scans each available frequency upon startup and selects a frequency based upon the least amount of noise
and interference detected. This lets multiple devices operate in the same area with limited interference.
3. Uniform Channel Spreading. To meet this requirement, the BSU randomly selects operating channel from the
available channels with least interference. If the channel is occupied by radar, the device blacklists that channel and
scans other available channels for the one with least interference. This implements the Uniform Channel Spreading
requirement by automatically selecting the channel with least interference.
NOTE: If the DFS Preferred Channel is configured, the device begins by scanning that channel. This allows the installer
to manually select a channel with least interference from a channel plan.
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