GPS Synch and ACS (Automatic Channel Selection) setup


Can you use GPS Synch and ACS (Automatic Channel Selection) at the same time for a four (4) sector ePMP system? 

Or, if the settings are allowed, what will be the disadvantages of using setup that has these options enabled?


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That's an interesting question!

First off, yes, you can use GPS sync and ACS at the same time for the four sectors.

So assuming they all are powered on at the same time, there's a chance that all 4 sectors could possibly choose the same channel (or even close to the same channel), which, even though you have GPS sync turned on, would not be good because the SM's would receive the beacons from the adjacent sectors on/near the same channels and get 'confused'. In back to back frequency reuse, you don't want your adjacent sectors to be on the same channel as the sector your facing.

Assuming that all four are turned on and there's an event that causes one more to reboot, thus forcing another ACS scan, those radios would most likely never choose the channel that any of the other radios that weren't rebooted chose due to the detected high energy signature. This would negate any prior frequency reuse benefits that you possibly had before.

If the goal is to use GPS sync/back to back frequency reuse, I think you're probably better off running ACS on each radio, one at a time, and making a note of the recommended channel(s), then turning off ACS and specifying the aforementioned good channel and making a decision as to whether or not to use back to back frequency reuse on your two sets of back to back radios.

I hope that all makes sense... to sum it up, you can do it, but it's probably not going to be an optimal arrangement and there are more disadvantages then advantages that I can see.



Just to add to what Eric said above, in a 4 sector ABAB frequency reuse scenario, you do not want to have ACS enabled. Use ACS to do exactly what Eric suggests above. Once you have the two channels you want to reuse between the four sectors, you set them and turn OFF ACS. This is because ACS, when enabled, will always run on bootup. So if any of your APs reboot for whatever reason it will most likely choose a channel that's not A or B.

Hope that make sense. 



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