Is there any advantage in having 802.11h enabled on the 5GHz Professional tab, or should I just leave it disabled? Thanks in advance for the help.
If you're using channels in the 5ghz frequency band that are subject to radar interference, 802.11h is designed to implement DFS (Dynamic Frequency Selection), and TPC (sometimes also referred to as TPME, or "transmit power management extensions"). If radar bursts on these channels are detected this will cause DFS and TPC to search for other channels to use instead of the one(s) you've assigned.
If you're in the U.S. and using only channels 36-48 or 149-161, you probably don't need to worry about this setting (since these are channels that are generally free from radar interference). On the other hand, several users (e.g., Kenhlan for one) has reported issues with adjacent radar signals that have caused him to have intermittent issues with what he described as "aperiodic loss of connectivity" which is just another way of saying that he lost connectivity when using 80mhz channel width in the upper band (149-161) due to what he believes was interference from radar at the outer edge of the band, and this would cause him to not be able to use anything wider than 40mhz channels (i.e., only two 5ghz channels bonded together), and thus he couldn't get true .11ac speeds from the upper frequencies (channels 149-161).
But you see, this is the rub with DFS and TPC: The whole purpose of DFS/TPC in the first place is to prevent you from using the channels you've selected when radar bursts (from military, civilian aviation, or weather radar) are detected on those channels. The least amount of time you'll be unable to use the designated channel is 10 minutes, sometimes as long as 30 minutes, and in some regions, DFS and TPC will disable a channel for up to 24 hours. Obviously, if you only have a limited number of combinations to make 80 MHz wide channels (by bonding four adjacent 5ghz channels together) and you can't use even one of them, this will prevent you from using the full .11ac channel width. And if you're in the EU, where only 4 channels are actually exposed on most commercial routers at this time (without modifying the region codes or in some other way monkeying with your CFE), you really won't be able to get .11ac speed at all if radar "bleeds" over into the four channels that are available.
But you also don't want to be using channels that also are subject to radar bursts either because that presents a safety issue for radar itself, i.e., a signal as low as 100mw can throw off Doppler radar completely, or potentially interfere with civil aviation safety...and who knows what it does with military). And with DFS and TPC, even assuming you do have access to those channels, connectivity is going to always be an issue anyway. And this, in a nutshell, is the conundrum that is the 5ghz band, and in particular the channels that are smack in the middle, i.e., 52-64 and 100-140).
So implementing 802.11h will in fact trigger DFS and TPC to be triggered if there are radar bursts detected on one of your assigned channels, and depending on your perspective, that's both a good thing (from a public safety point of view) and a bad thing (if all you're concerned about is your own selfish interests and your own connectivity.
My suggestion would be that if you're not having any issues with using the full 80 MHz width channel and you're in the U.S. and thus using channels that are technically outside the radar frequencies anyway, (and keep in mind that if you're in the EU, both the types of radar and channels that are subject to radar frequencies are different than they are in the US), just leave the "Regulation Mode" selection (found in "Professional" set to "off".
If on the other hand, think you're having issues with connectivity on the 5ghz band, give it a try to see if it has any positive effect if set to "802.11d". I doubt it will show any positive improvement, but then you never know until you try it. If it doesn't, just leave it set to "off".
