User Guide

OmniAccess RN: User Guide
54 Part 031650-00 May 2005
the RF environment as they hear it, independent of the switch. This results in a
highly scalable and reliable RF environment while also significantly reducing
the time the AP takes to adapt to the changing RF environment.
The APs scan all valid channels (channels in the regulatory domain) at regular
intervals and compute the following metrics per channel:
z Coverage index: Signal to noise ratio for all valid APs
z Interference index: Signal to noise ratio for all APs
These metric are used by the APs to decide the best channel and transmit
power settings for optimal coverage.
Deciding the Channel Setting
In addition to the interference index, the APs use the free-channel index for
deciding the optimal channel setting. The free-channel-index is configurable
parameter on the switch used by an AP to qualify a channel before moving to
it. An AP will choose to move to a new channel only if its current channel
interference index is greater than the interference index on the new channel by
a value greater than or equal to the free-channel index. If the criteria are not
met, the AP will remain on the current channel.
Deciding Power Settings
The power assignment decisions are based on the APs coverage index. The
benchmark used here is the ideal coverage index. The ideal-coverage index is
the ideal power setting that an AP should have for good coverage. It is a
configurable parameter on the switch. The AP will increase or decrease its
power settings based on the difference between the value of its current
channel coverage index and the ideal-coverage-index value. The power
settings increment/decrement by a single unit at any given time.
Advantages of Using ARM
Using ARM provides the following benefits:
z With ARM, the switch does not have a downtime for initial calibration.
Though this process is still optional, it is no more a necessity.
z The AP response time to noise is quick and reliable, even to the non-802.11
noise, especially when the client traffic starts generating errors due to the
noise.
NOTE—Non-801.11 noise detection is disabled by default and needs to be explicitly
enabled.