User manual

Configuring Auto-RF 323
Nortel WLAN—Security Switch 2300 Series Configuration Guide
• 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.
By default, a radio cannot change its channel more often than every 900 seconds, regardless of the RF environ-
ment. This channel holddown avoids unnecessary changes due to very transient RF changes, such as activation
of a microwave oven.
Tuning the transmit data rate
A radio sends beacons, probe requests, and probe responses at the minimum transmit data rate allowed for
clients. This gives them the maximum distance. All other packets are transmitted at a rate determined by their
destination. All packets are transmitted at the same power level.
By default, the following minimum data rates are allowed:
• 5.5 Mbps for 802.11b/g clients
• 24 Mbps for 802.11a clients
You can statically change the transmit data rates for radios, on a radio profile basis. (For information, see
“Changing transmit rates” (page 246).) However, Auto-RF does not change transmit rates automatically.
Auto-RF parameters
Table 1 lists the Auto-RF parameters and their default settings.