Campus lan and Wireless lan solution Design Guide

Overriding the TPC algorithm with minimum and maximum transmit power settings 
The TPC algorithm balances RF power in many diverse RF environments. However, it is possible that automatic 
power control will not be able to resolve some scenarios in which an adequate RF design was not possible to 

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implement due to architectural restrictions or site restrictions—for example, when all APs must be mounted in a 
central hallway, placing the APs close together but requiring coverage out to the edge of the building. 
In these scenarios, you can configure maximum and minimum transmit power limits to override TPC 
recommendations. The maximum and minimum TPC power settings apply to groups of APs through the use of 
RF profiles within RF tags. When used as a global configuration option, the settings apply to all APs attached to 
the specific controller. 
If you configure a minimum transmit power, RRM does not allow any AP attached to the controller to go below 
this transmit power level, regardless of which function is directing the power change (RRM TPC or coverage 
hole detection). For example, if you configure a minimum transmit power of 11 dBm, then no AP will transmit 
below 11 dBm, unless the AP is configured manually and no longer under control of RRM. 
Dynamic Channel Assignment 
The 802.11 specification defines multiple channels for operation. The channels are essentially different 
frequency ranges that are non-overlapping and can be assigned using a channel designator. The behavior is 
analogous to lanes on a highway—you only get the full benefit of the lane if it is completely separate from 
another lane on the same highway. If the lanes overlap each other (or worse, merge into a single lane), then the 
highway slows to a crawl. 
Channels in an RF network work similarly. However, there is an additional consideration of power, equivalent to 
making lane wider or narrower (the coverage of the AP). The job of Dynamic Channel Assignment is to track the 
available lanes (channels), which differ by regulations depending on the country of installation. Secondly, DCA 
assigns channels to APs that do not conflict with channels already assigned. For a given AP, potential 
throughput is dependent upon interference free operation. DCA is aware of what channels on which you are 
allowed to operate and assigns these channels to be as interference-free as possible, based on over-the-air 
observations. 
After all APs have been installed, it is a best practice to then calibrate DCA by invoking the RRM start-up mode.
The RRM startup mode is invoked in the following conditions: 
● 
In a single-controller environment, the RRM startup mode is invoked after a successful upgrade of the 
controller software; otherwise, it is manually initiated (see below). 
● 
In a multiple-controller environment, the RRM startup mode is invoked after an RF Group leader has 
successfully upgraded the software; otherwise, it is manually invoked from the CLI. 
You can trigger RRM startup mode from CLI, using the following command: 
ap dot11 {24ghz | 5ghz} rrm dca restart 
RRM startup mode runs for 100 minutes (10 iterations at 10-minute intervals). The startup mode consists of 10 
DCA runs with high sensitivity and no dampening (making channel changes easy and sensitive to the 
environment) to converge to a steady state channel plan. After the startup mode is finished, DCA continues to 
run at the interval and sensitivity as specified by the organization.