Asus RT-AC66U issues connecting to 5 ghz band

[jegesq]

Ken,

You will be interested in this link, which is the IEEE's 2007 paper on "Best Practices" for using 5ghz. It contains some really interesting info on DFS and Radar (including military, weather, etc). You'll find it very interesting.

[PDF]Spectrum Sharing in the 5 GHz Band DFS Best Practices

 

[kenhlan]

Yeah, and that was 7 years ago....

FCC implemented some definitive rules in 2010, if I recall.

Some interesting excerpts from that paper that caught my eye.

A lot of folks seem to miss this point, or believe you need to be selected on a DFS channel in the router GUI in order to apply/comply: "The DFS requirements can be split in two parts: the detection criteria and the “response criteria”. The former specify the RF power and signal timings of radar signal that the wireless LANs must be able to recognize. The latter describe what the wireless LAN is required to do in response to a detection event."

I think you know and have read, like I do now that you only have to interfere or be within 30Mhz of an active/characterized one for it to apply.

"Because of the very high gain of the typical radar antenna, only very little Wireless LAN energy is needed to cause interference to radar systems. Therefore wireless LANs (without DFS) will cause interference not only when they are operating on the same frequency as the victim radar and the radar antenna points at the wireless LAN, but also when the wireless LAN is nearby and seen by the sidelobes of the radar antenna."

"Weather radars are used for measuring weather conditions at large distances. Typically, these radars implement a complex scan patterns that include helical scanning and probing storm spots. The result is that such a radar may be pointing away from a given (RLAN) location for up to 10 minutes. However, if the radar is close by – at less than a few miles – its
antenna sidelobes may be visible to the RLAN. This may cause the same pulse train to be seen multiple times – or even continuously."

"Pulse patterns
The typical “search” radar rotates regularly and as its beam sweeps over an object, that object is illuminated by a train of radar pulses. The pulse interval varies with the operating range of the radar: for 200 pps for long range radars to 4000 pps for short range radars.

It is quite possible that more than one radar may be visible to an RLAN on the same RLAN channel. If this happens the RLAN may see a variable pattern of pulses – some stronger than others - but as both radars will not be synchronised, there will be no time correlation between the pulse trains."

"Other transmitters may not be as clean as the example above and produce relatively high side lobes. Due to the high power levels and the high antenna gain of radar systems these sidebands may well exceed the DFS detection threshold, notably if the RLAN is relatively close to the radar – e.g. a few miles away. The implication is that an RLAN may see the same radar at different frequency channels. In the example below a single radar at a
short distance away from the RLAN will trigger DFS on about half of the channels in the 5470 to 5725 MHz band."

Of course I have now way of knowing if any or all of these might be impacting my environment, but looking at the whole 5G band play in wireless as a whole, there are certainly thinks folks should know, in order to manage and gauge (even expectations) accordingly.

Fortunately some of the latest FCC changes recently (April 2014) approved will open some things up a bit (as well as allow full power up to 1W on the lower channels).

"We extend the upper edge of the 5.725-5.825 GHz band to 5.85 GHz and consolidate the Part 15 rules applicable to all digitally modulated devices operating across this 125 megahertz of spectrum to ensure that all such devices comply with U-NII requirements intended to protect authorized users from harmful interference."

https://apps.fcc.gov/edocs_public/attachmatch/FCC-14-30A1.pdf

An IEEE powerpoint summary: https://mentor.ieee.org/802.11/dcn/14/11-14-0524-00-0reg-fcc-14-30-u-nii-devices.pptx

http://blogs.cisco.com/wireless/win...channels-adds-capacity-to-5ghz-wi-fi-spectrum

In the last week or two I've learned more about DFS than I cared to know.

 

[john9527]

You may want to try loading Merlin's latest....376.49_2. It looks like ASUS either deliberately or accidentally started logging some radar detection events.
Users have reported syslog entries like this on the latest code.

Dec 25 16:29:17 kernel: SKIPPED false Type 1 Radar Detection. min_pw=12 pw_delta=0 pri=52679 fm_min=0 fm_max=0 nconsecq_pulses=3. Time from last detection = 1383, = 23min 3sec. Detected pulse index: 5
Dec 25 16:51:18 kernel: SKIPPED false Type 1 Radar Detection. min_pw=13 pw_delta=0 pri=52696 fm_min=0 fm_max=0 nconsecq_pulses=3. Time from last detection = 1320, = 22min 0sec. Detected pulse index: 5
Dec 25 17:07:18 kernel: SKIPPED false Type 1 Radar Detection. min_pw=14 pw_delta=0 pri=52638 fm_min=0 fm_max=0 nconsecq_pulses=3. Time from last detection = 960, = 16min 0sec. Detected pulse index: 5
Dec 25 17:11:18 kernel: SKIPPED false Type 1 Radar Detection. min_pw=14 pw_delta=0 pri=52724 fm_min=0 fm_max=0 nconsecq_pulses=3. Time from last detection = 240, = 4min 0sec. Detected pulse index: 5

 

[kenhlan]

Loaded it just for giggles, but did not see any log entries, despite some signal loss/shutoff events occurring.

That said, I was only looking at the log (General and Wireless) screens in the GUI.

I have not set up, nor know how to any other logging capability. I think I ran across some discussion of using jffs or something, but never really got smart on it...

Reverting back to your Fork -06

BTW - Only loaded it on my AC68U to try.

 

[rt392]

Ways to test upper channels. Reduce received signal levels.
Take router, smart phone into:
Best is RF shielded chamber, possibly refrigerated (metal) room. Or.
Into basement. Or.
Remove antennas. Or. put in small straight pin antennas. Or.
Put bucket, grounded, over antennas.
If the router works on upper channels with restricted received signals then you have a chance to use the upper channels. If not probably the firmware is excluding those channels, bandwidths just in case.

Need to be careful that what your using to test functionality of router doesn't have its own channel exclusion firmware/driver. Spectrum Analyzer

Ray