Motorola 2.1 - Manual (Page 135)

Appendix A:
• When the scan concludes, the decision on how a channel is chosen is based on the strength and
number of beacons on each channel. Also, non-overlapping channels are weighted as highly
preferred channels.
• This scan can occur through three different methods:
o
Upon the Boot-up
o
Through a manual channel rescan command via Wireless Manager
o
Through a scheduled channel rescan command via Wireless Manager
High Interference and channel scan on the 2.4GHz radio
• High interference can be defined as the Duo node being incapable of receiving or transmitting
due to an extremely high noise floor.
• In this case, the Duo node will initiate a reboot if it is in this state for an extended amount of time.
• The reboot will force the node to execute an Auto Channel Rescan where it is expected to select
a channel that is cleaner.
• If this still exists, the Duo node will keep rebooting until it finds a cleaner channel.
• An operator of the network has the ability to monitor this behavior through Wireless Manager. If a
Duo node is rebooting due to extreme interference, a threshold alarm can be set that will indicate
a frequent node that is rebooting. Through this threshold alarm, a network operator will be notified
that a node has had a high number of reboots which would highlight further investigation of that
node.
High Interference and channel scan on the 5.4GHz radio
• High interference can be defined as the Duo node being incapable of receiving or transmitting
due to an extremely high noise floor.
• The behavior for the 5.4GHz radio is similar to the behavior of the 2.4GHz radio during high
interference. However, the channel scan on a 5.4GHz radio is different. It is also different
between IAP’s an MWRs.
• When an MWR initiates a channel rescan, it will look for an IAP.
• If there are multiple IAP’s that are within range, it will choose the IAP based on the best link
metric.
• When an IAP disappears, the MWR will prefer to stay on the current channel rather than rescan
on other channels.
• It will scan the current channel for other IAP’s and once again choose the IAP that has the best
link metric.
• If it does not find an IAP on that channel, it will trigger a channel rescan.
• After this channel rescan concludes, it will have chosen a new channel and a new IAP on that
channel.
Impact of Interference Avoidance on the Network :
The impact of interference avoidance in the network is similar to the impact of radar avoidance. The
exception is that the channel in which the interference is detected is not blacklisted for 30 minutes when a
scan is initiated.
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