3-21
RF-7800W
SYSTEM ADMINISTRATION AND CONFIGURATION
DFS is currently supported for the 5.725 - 5.875 GHz band per
ETSI EN 302 502.
3.8.9.1 DFS Action
DFS can be configured to either turn off the radio transmitter for 30 minutes or change the radio's operating
frequency. If either event occurs, a DFS event trap is sent via SNMP to any configured receivers. The channel change
feature respects the configured frequency list. When the radio changes channels, it also turns the transmitter off for
one minute and monitors the channel. If radar is detected again, the radio will continue to change channels until a
vacant channel is found.
3.8.9.2 Antenna Gain
DFS requires knowledge of the antenna in use in order to properly set the trigger sensitivity. The default gain is set
to the highest gain antenna that is offered for use with the radio, but should be changed to the gain of the actual
antenna in use. When this setting is higher than the actual antenna gain, the radio is not sensitive enough to radar
signals. Conversely, the radio will be too sensitive and may inadvertently trigger a DFS event if this is set lower than
the actual antenna gain.
3.8.9.3 EIM Detection
Since interference may not affect both radios in a link, EIM is configured to detect interference separately on the SC
and SS radios. EIM looks for unusually low SINADR for a given RSSI, unusually high bit-error rates and an
unusually high noise floor. Link Min Burst Rates are used as the threshold for interference detection. The Min Burst
Rate should be set to the lowest value that achieves the necessary throughput for a particular Link. SNMP traps are
sent to network managers when EIM events occur and when interference has cleared.
3.8.9.4 EIM Auto Channel Change
When interference is detected, the radio has the option of initiating all radios to jump to a new, potentially cleaner
operating frequency. There is minimal downtime when this occurs. The radios will iterate through a number of
frequencies. If interference is found on many different frequencies, one likely conclusion is that the radio is being
deliberately interfered with over its entire operating band. This situation is known as “barrage interference” and
results in the radios settling on the last operating frequency. Auto-Scan should be enabled on SS when using EIM
Auto Channel Change to account for situations in which radios are unable to link after a channel change due to high
interference levels. When the radios change channels and if barrage interference is detected, different SNMP traps
are sent to network managers.
EIM Auto Channel Change reduces the maximum possible
user data throughput by around 10 percent.
3.8.9.5 EIM Relative Noise Floor
While EIM is turned on, the radios monitor the noise floor of the channel during the quiet periods between
transmissions. The difference between the expected noise and the measured noise is displayed as the relative noise
floor. This value will vary with different installation environments. A sharp increase in this value relative to the
average value could indicate the presence of interference.
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