RRM Question - should I turn it on?

Unanswered Question
Nov 1st, 2009
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Hi community,

I used to work a lot with Cisco WLAN controllers. The last software I really tested was the last 4.2 release. But I still have a question regarding RRM, nobody was able to answer. Maybe some of you guys know it:


I'm never completely sure if I should take the risk of enabling RRM. I always set the channel and transmit power at fixed values. Here is why:


DCA (Dynamic Channel Assignment):

In theory, when an AP performs the RRM algorithm (default: every 10 minutes), and decides to switch the channel, how should an associated client know, that the AP plans to switch the channel. For the client point of view, it's like shutting down its AP, when the AP switches the channel.

With the latest Intel drivers, I recognized a connectivity loss of 5 - 15 seconds, until the client associates to another AP, or the AP which switched the channel.

The client cannot prepare for the roaming (channel changing) process. In the regulatory domain of ETSI (Europe), we have to use an altered standard for 802.11a (802.11h), which introduced DFS (Dynamic Frequency Selection). Within this process, the AP has to change its channel, if it recognized radar in the 5 GHz band.

802.11h has some flags to inform the 802.11h capable clients, that the AP plans to switch the channel - so the clients have the chance to prepare for this event (roam).

Due to the connectivity loss for clients within DCA, I switched off that feature.

Did someone experience the same? Or is my theory totally bugged?


TPC (Transmit Power Control):

The only thing that concerns me, is when I attach something different than the standard 2,2dBi dipole antenna. When doing so, I am not allowed to transmit at 17dBm.

How does the AP know, that it isn't allowed to use the power value of 1 if a 6dBi antenna is attached? Does the antenna gain (0,5 x dBi) field in the AP settings work?

I never found something on CCO, stating this.

Again: Did someone experience the same? Or is my theory totally bugged?


Thank you for your help. I'm looking forward to this discussion :-)


Johannes


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