Configuring Auto-RF 393
Nortel WLAN—Security Switch 2300 Series Configuration Guide

Channel and power tuning

Auto-RF can change the channel or power of a radio, to compensate for RF changes such as interference, or to
maintain at least the minimum data transmit rate for associated clients. A radio continues to scan on its active
data channel and on other channels and reports the results to its WSS.
Periodically, the switch examines these results to determine whether the channel or the power needs to be
changed.

Power tuning

By default, the switch evaluates the scan results for possible power changes every 300 seconds (5 minutes),
and raises or lowers the power level if needed.
If Auto-RF determines that a power change is needed on a radio, WSS Software ramps the power up or down
until the new power level is reached. Ramp-up or ramp-down of the power occurs in 1 dBm increments, at
regular time intervals. The default interval is 60 seconds and is configurable. The power ramp amount (1 dBm
per interval) is not configurable.

Channel tuning

By default, the switch evaluates the scan results for possible channel changes every 3600 seconds (1 hour).
WSS Software uses the following parameters to determine whether to change the channel on a radio:
• Presence of active sessions.
By default, if the radio has active sessions, WSS Software does not change the channel. If the
radio does not have any active sessions, WSS Software uses the remaining parameters to
determine whether to change the channel.
• Received signal strength indication (RSSI)
• Amount of noise on the channel
• Packet retransmission count, which is the rate at which the radio receives retransmitted packets.
• Utilization, calculated based on the number of multicast packets per second that a radio can send on a
channel while continuously sending fixed-size frames over a period of time.
• Phy error count, which is the number of frames received by the AP radio that have physical layer errors.
A high number of Phy errors can indicate the presence of a non-802.11 device using the same RF
spectrum.
• Received CRC error count. A high number of CRC errors can indicate a hidden node or co-channel
interference.
The thresholds for these parameters are not configurable. Auto-RF also can change a radio’s channel when the
channel tuning interval expires, if a channel that has less disturbance is detected. Disturbance is based on the
number of neighbors the radio has and each neighbor’s RSSI.
A radio also can change its channel before the channel tuning interval expires to respond to RF anomalies. An
RF anomaly is a sudden major change in the RF environment, such as sudden major interference on the
channel.