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The Coverage Hole Detection and Correction Algorithm of the WLC


(Lets abbreviate the Coverage Hole Detection and Correction Algorithm as CHDCA in the subsequent text in our discussion)

Since , in the event of a coverage hole, the power of an AP needs to be increased , hence , the first point to understand is that the CHDCA algorithm is used

to increase the transmit power of the antenna of the AP.


- the CHDCA works according to the quality of the signal of a wireless client , that is to say the wireless client's RSSI (signal strength),




- the performance of a wireless client can be different (while being in the coverage area of APs joined to different controllers)


(-a separate instance of CHDCA runs on each controller. In other words, CHDCA runs independently on each controller.)

So, each controller, runs the CHDCA algorithm, for each AP, for three minutes (by default).


Regarding the CHDCA algorithm, we should know the following:


1. What is considered as the poor signal by the CHDCA algorithm ?

2. Which condition, when results to be true, triggers the CHDCA algorithm, to run ?

3. When is a wireless client said to have been detected with poor signal ?

4. Once ran, what does this CHDCA algorithm, do ?


1 = > By a controller, when a wireless client's RSSI value will be detected to be , below a given threshold value of RSSI, for at least 60 continuous seconds, the CHDCA algorithm will initiate it execution. This cutoff-threshold value of RSSI, is by default -80 dbm (and we know that -80dbm is not a good signal)

2 => if, for an AP, "poor" signal gets detected by


EITHER (at least N number of w/l clients)

OR         (at least 25% of the total clients associated to an AP )



{the CHDCA algorithm starts working on to increase the power level of the concerned AP}

3 => if within a time period of *180* seconds (3 minutes), a wireless is detected to be below the RSSI threshold , continuously for 60 seconds (a minute), that wireless client is said to be getting poor signal.

4 => Increases power level of the AP , in question, to which are associated the w/l clients, who were getting poor signal, which resulted the CHDCA algorithm to start.

*N* number of clients can be configured in the WLC.

The time period of  *180* seconds can be configured in the WLC

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‎06-10-2014 10:21 PM
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