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Wireless LAN Design Guide for High Density
Client Environments in Higher Education
37 © 2011 Cisco and/or its affiliates. All rights reserved.
Dynamic Channel Assignment (DCA) Algorithm
• Defaults should suffice with the following exceptions:
o Avoid foreign AP interference. This tells the DCA to accommodate channels in use by a foreign AP and to attempt to
work around that assignment. If on the border with another coverage zone under a separate RF group, enable this
(default). Disable this if there are other networks operating that are outside of your control.
o DCA channel sensitivity (medium is the default) should work fine in most applications. Set to low to make a channel
change highly unlikely. Set to high to encourage channel changes in response to environmental changes.
o In 802.11a only environments with a channel width of 20 MHz/40 MHz, most high density environments will benefit
more from more available channels. But certain applications, such as video, will utilize 40 MHz effectively.
o DCA channels 100-140 and 165 disabled by default enable extended UNII-2 channels to select 100-140
automatically.
Coverage Hole Detection Algorithm
• Coverage threshold: Data RSSI should be set for the minimum acceptable RSSI level to support the minimum data rate
required in the high-density coverage area. This will allow Coverage Hole to report instances where a client exceeded that
threshold.
Note: Default values should be sufficient for client exception levels. Enabling a realistic threshold will allow the system to track
and report clients by MAC address that fall below the threshold. If location services are available, this can be plotted on the map
display. This can be very useful in troubleshooting the final deployment or to identify a new client type that has different
RF capabilities.
General – Profile Threshold for Traps
• Adjust these for expected levels in the high-density coverage zone. It will make the traps and alerts meaningful.
Wireless=>802.11a/802.11b=>High Throughput (802.11n)
• Should be enabled for both bands, with all MCS rates supported
Wireless=>Media Stream
• Enable if supporting video streaming applications.
• For more information: Cisco Unified Wireless Network Solution: VideoStream Deployment Guide
For all of the above commands, it is strongly suggested that WCS and the AP and Controller Templates be used to make
changes and assignments. Using the AP groups feature is also highly recommended for organizing APs by coverage zone and
WLAN SSID configuration.
Conclusion
The performance of a high-density WLAN within a higher education environment is highly dependent on how well the network
requirements are understood before the network is deployed. A good understanding of these concepts will enable the designer
to modify the design to accommodate the unforeseen.