RT-AC66U - DFS supported? (UNII-2/UNII-2e)

[andertrack]

RT-AC66U - DFS (dynamic frequency selection) supported? (UNII-2/UNII-2e)

I just got a AC66U (updated to latest firmware) and set it to these options:

This is working fine and I am getting pretty good results. The only thing is that I am in a dense 5Ghz environment and my network is overlapping with about 2 others. This screen is from Wifi Explorer:

According to this article (http://www.networkcomputing.com/wir...on-part-3-the-channel-dilemma/a/d-id/1234489?) using 802.11 AC without DFS there are really only two channels.

My question is this: does this router (or any other router) support DFS so that the channel can be set to 52-64 or 100-140 (UNII-2 and UNII-2 extended)?

It might just be that there is radar/etc in my area. Has anyone seen their router go to these DFS channels?

 

[jegesq]

You don' t want to be using channels where DFS is implemented. DFS (and TPC) will only make the channels inoperable for a minimum of 10 minutes, and typically 30 minutes once radar bursts are detected, and up to one entire day where multiple radar is detected. This is why even on routers where DFS and TPC are implemented and the channels that require both DFS and TPC are exposed so they can be used without end-user modification, no professional installers will ever use these channels in an environment where reliability and constant uptime is required. DFS is NOT a panacea....it's actually a recipe for your channels to NOT work whenever radar is detected, and thus they introduce a whole new level of unreliability and non-functionality to your wireless experience. So you should avoid using channels 52-64 and 100-140 (assuming you can use them without modifying your router), even if it looks like no one else is using them. Radar bursts can be detected up to 30+ miles away and DFS will just kill those channels. And then you'll be posting here complaining that your router's wireless 5ghz isn't working and you'll want to know why....And the answer will be "DFS and TPC"...because this is what they are designed to do, i.e., allow military, weather and aviation weather to take complete precedence on channels 52-64 and 100-140 and to kill any further use of those channels for unlicensed wifi.

I do not know for a fact whether DFS or TPC are implemented in the AC66U, believe they are. Nevertheless, those channels that require DFS and TPC cannot be accessed on the AC66U without modifying the region code in the firmware, to expose those channels. The fact that the channels where DFS and TPC are required to be implemented, i.e., 52-64 and 100-140, are not exposed and cannot be used without altering the region code of the AC66U s a pretty good indication Asus doesn't want end-users using those channels. And neither does the FCC, even though the channels are technically "available" for unlicensed use (but only with DFS and TPC implemented).

There is an entire thread here at SNB started by Kenhlan, in which there's a lot of discussion about DFS and TPC. Ken's experience was with highly aperiodic non-functionalit on the upper band channels using both AC66U's and an AC68U (which I do know does implement DFS and TPC). It was his believe that his experience was caused by channel "bleeding" at the out ediges of frequencies into areas where DFS and TPC become operative due to the presence of radar bursts. You can read the thread here: http://forums.smallnetbuilder.com/showthread.php?t=7742

 

[andertrack]

Thanks for the good info. I don't want to modify anything and get the FCC knocking on my door. I guess we will just have to wait for them to clear out more spectrum.

It sounds from that Cisco blog that once enterprise starts using those DFS channels and works out the kinks it will trickle down to consumer gear.

 

[andertrack]

Got this reply from Asus:

We regret the inconvenience. I am really sorry, there is no DFS so far. We havent got any information regarding the next update.

I will take this as a feedback and I will forward this to our concerned department.

We recommend you to use channel 40 or 44 or 48.

Edit:

My original question:

[Problem Description]
I just set up my router and it is working well. The 5ghz band where I am is a little
crowded and I think I would get better results on another channel. Does this model
support DFS or will it support DFS at a later time?

 

[jegesq]

Got this reply from Asus:

The reply seems to suggest that DFS (and by implication TPC) are not implemented on the AC66u, but I wish I could have seen the question you asked in your e-mail to be certain that this is what the reply from Asus means.

If that's what the reply means, this is important information, and it would completely explain why Asus doesn't expose certain channels in the U.S and EU, i.e., because the router doesn't implement DFS and TPC that are required if those channels are to be used. And it also substantiates why end-users shouldn't be changing their regions to expose those channels, because the use of them would be in violation of either ETSI (in the EU), FCC (in the U.S.), or other applicable regional regulations, not to mention the potential impact on weather radar, military and civilian aviation radar and air safety.