Cisco Cisco 4404 Wireless LAN Controller Folheto



Set the Coverage measurement (defaults to 12dB) to 3dB for most deployments. 

With Version 4.1.185.0, enhancements such as the Tx Power Up Control and User-configurable 

number of SNR profile threshold-violating clients, the defaults of 12dB for 802.11b/g and 16dB for 
802.11a should work fine in most environments. 

  

The Coverage measurement, 12 dB by default, is used to arrive at the maximum tolerable SNR per client. If 
the client SNR exceeds this value, and if even one client exceeds this value, the CHA is triggered by the WLC 
whose access point (AP) detects the client with poor SNR. In cases where legacy clients are present (who 
often have poor roaming logic), tuning the tolerable noise floor down to 3dB results provides a short-term fix 
(this fix is not required in 4.1.185.0 or later). 

This is further described under Sticky Client Power-up Consideration in the 

Coverage Hole Detection and 

Correction Algorithm

 section. 

  



The longer the configured interval between transmitting neighbor messages, the slower 
convergence/stabilization time will be throughout the system. 



If an existing neighbor is not heard for 20 minutes, the AP is pruned out of the neighbor list. 

With Version 4.1.185.0, the neighbor list pruning interval is now extended to keep the neighbor 

from whom a neighbor packet has not been heard for up to 60 minutes. 

  

Neighbor messages, by default, are sent every 60 seconds. This frequency is controlled by the Signal 
Measurement (termed Neighbor Packet Frequency in 4.1.185.0 and later) under the Monitor Intervals section 
on the Auto RF page (see 

Figure 15

 for reference). It is important to understand that neighbor messages 

communicate the list of neighbors that an AP hears, which is then communicated to their respective WLCs, 
who in turn form the RF Group (this assumes that the RF Group name is configured the same). The RF 
convergence time entirely depends on the frequency of neighbor messages and this parameter must be 
appropriately set. 

  



Use the On-Demand button for finer control, and deterministic RRM behavior. 

With Version 4.1.185.0, predictability can be achieved via the usage of DCA’s anchor-time, 

interval and sensitivity configuration. 

  

For users that desire predictability on algorithmic changes throughout the system, RRM can be run in on-
demand mode. When used, RRM algorithms compute optimum channel and power settings to be applied at 
the next 600-second interval. The algorithms are then dormant until the next time on-demand option is used; 
the system is in a freeze state. See 

Figure 11

 and 

Figure 12

, and the respective descriptions for more 

information. 

  



The default setting for load-balancing is ON, with the load-balancing window set to 0. This window 
should be changed to a higher number, such as 10 or 12. 

In release 4.1.185.0 and later, the default setting for load-balancing is OFF and if enabled, the 

window size defaults to 5. 

  

Although not related to RRM, aggressive load-balancing can result in sub-optimal client roaming results for 
legacy clients with poor roaming logic, which makes them sticky clients. This can have adverse effects on the 
CHA. The default load-balancing window setting on the WLC is set to 0, which is not a good thing. This is 
interpreted as the minimum number of clients that should be on the AP before the load-balancing mechanism 
kicks in. Internal research and observation has shown that this default should be changed to a more practical 
value, such as 10 or 12. Naturally, every deployment presents a different need and the window should 
therefore be set appropriately. This is the command-line syntax: