AC68U: what are my options to "lower" the tx power ?

[develox]

Hi to all,

I've been reading quite a lot today among several threads here, and was left with a feeling that I hope is "not" confirmed.

I just got my AC68U, and one of the winning points over the Nighthawk R7000 was the ability to lower the tx power. I discovered early that with either the latest stock or Merlin or Merlin fork firmware, whatever the value I put in the web UI, it seems to have no effect.

I've read a lot of threads of people here striving to raise the tx power. As I use the router "mainly" in a living room fairly open with a little daughter around all the time, I not only don't need the full power, but actually want to decrease it to the minimum stable signal. Now, from what I've read, it looks like that tx power parameter in the UI is actually broken since the latest wireless drivers included in recent builds of the firmware. Is that right ? Is it just in the UI or even via CLI (I saw threads going this route to overcome the max power limits up to a few weeks ago) ?

What are my options (whatever, I once was fairly sysadmin oriented if need be) to accomplish this ?

Thanks anyone
Peppe

 

[L&LD]

I can appreciate that you want to keep your little one safe, but unless you are letting her play right on top of the antennae, you are worrying for nothing.

From the lowest power setting to the highest power setting that will allow you to connect reliably with your devices, even in the same room, will still subject her and anyone else in that room with effectively the same energy.

Best thing to do (even after the issue gets fixed)? Put it as high up as you can so that no matter where she moves, she is still at least 8 to 10 feet away from the antennae.

 

[develox]

I can appreciate that you want to keep your little one safe, but unless you are letting her play right on top of the antennae, you are worrying for nothing.

From the lowest power setting to the highest power setting that will allow you to connect reliably with your devices, even in the same room, will still subject her and anyone else in that room with effectively the same energy.

Best thing to do (even after the issue gets fixed)? Put it as high up as you can so that no matter where she moves, she is still at least 8 to 10 feet away from the antennae.

Yes, that's the point. I just want to keep it as safe as possible without sacrificing opportunities. The router is indeed standing high, rarely at less than 3mt from anyone, on average 5mt.

Yet, I want to try as much as I can to find a way, either via UI or CLI, to play the tx power down. Interestingly enough, I took the AC68U to swap out a NightHawk R7000 because this last could not do it (or it could, but in a rather tricky way that in the end didn't survive reboots and left the telnet to the router open without asking username/passwords), and of course because the UI and freedom offered by the Asuswrt (especially Merlin's) are just another planet ...

 

[L&LD]

At those distances, I don't think the effective energy will be significantly different even with the power level slider working.

At least, not for the small lifespan we humans have.

 

[develox]

At those distances, I don't think the effective energy will be significantly different even with the power level slider working.

At least, not for the small lifespan we humans have.

I just tend to be optimistic as you, and indeed there's still no reason enough to stop enjoying the technology.

Yet I like to be "informed", and as I grow my knowledge of the subject, I would like to get more knowledgeable about my toy and how to bend it to my will (and cautious approach).

 

[john9527]

As far as I know, the power setting does work on both the 374 and earlier code (input a value) and 376 (the slider) to reduce the power settings from the default values...increasing will not always work because of regulatory restrictions.

I know of at least 2 cases where people have solved intermittent dropouts by reducing the power levels when the client was close to the router.

My personal opinion is that people have the expectation that the relatively small changes in power levels (mW) we are talking about should be easily seen at the client level when talking normal distances router to client....I don't think that's true. If you had special signal measurement equipment, you might be able to see something. If you are talking going out to the long distance limits, you may see some signal strength change at the client and a somewhat more stable connection with increased power.

For your concerns, I would lower the power to where I maintained stable connections, with a lower limit of about 20 mW or 25% on the slider (there is some code that customizes the wireless parameters in ranges based on the desired power setting).

 

[watusi]

I don't see any point whatsoever in having the power slider. It is a marketing gimmick.

No commercial router is going to let you INCREASE the power beyond regulatory limits. The only meaningful use would be to remove the limitation in order to permit higher power (within bounds of cooling capacity!).

OK, the other reason would be if you are in a region where regulations are in place that require lower power, and you bought a router designed for another region. If you want to be a really nice guy, you could lower the slider.

Transmit power is regulated automatically already to use the lowest power needed to maintain a good signal margin. Always using the lowest power needed improves reception margins on the same router, and reduces cross-band interference.

If you want to limit power density, limit connection speeds, and only enable one radio. Use quiet hours to shut off the WiFi completely during sleep hours.

Look at s/n. Below 25db you are getting dicey. You can maintain a connection below that, but speed can be extremely limited.

 

[watusi]

My personal opinion is that people have the expectation that the relatively small changes in power levels (mW) we are talking about should be easily seen at the client level when talking normal distances router to client....I don't think that's true.

That's certainly an incorrect expectation.

It's an exponential function. 3db increase takes twice the power, and is about the minimum noticeable difference.

10db takes 10 times the power, and will give a result that is "twice as good".

(Being very simplistic here, I could dig-out my Radio Handbook...)

Received signal strength will be reduced by distance according to inverse-square law, as well.

 

[develox]

Apologies for my absence.

Indeed I expect to see some changes in the received power on my clients. Days before I opened this thread, I thoroughly tested this kind of response with a TP-Link W8960N (that I use as modem) and a Netgear R7000. The former has a specific setting on the UI, the latter needed some tweak to access the wl command via telnet. In both cases, as I progressively diminished the tx power, I could see an almost proportional RSSI decrease on the clients, very clearly, from -40dbm down to -60dbm roughly (with TX power set from 100% down to between 5% and 10%).

My problem here is that I see no change at all with the AC68U. Since my experience with TX power set to less than 10% was absolutely satisfying, I'm hardly looking for a similar result on my Asus. So, any hint on how I could achieve this would be very much appreciated.

Peppe

 

[john9527]

Apologies for my absence.

Indeed I expect to see some changes in the received power on my clients. Days before I opened this thread, I thoroughly tested this kind of response with a TP-Link W8960N (that I use as modem) and a Netgear R7000. The former has a specific setting on the UI, the latter needed some tweak to access the wl command via telnet. In both cases, as I progressively diminished the tx power, I could see an almost proportional RSSI decrease on the clients, very clearly, from -40dbm down to -60dbm roughly (with TX power set from 100% down to between 5% and 10%).

My problem here is that I don't see no change at all with the AC68U. Since my experience with TX power set to less than 10% was absolutely satisfying, I'm hardly looking for a similar result on my Asus. So, any hint on how I could achieve this would be very much appreciated.

Peppe

Between measurements to look for differences, in addition to the 'Apply' button also perform a reboot. There are some cases where just restarting the wireless subsystem (the default action for apply) doesn't quite work. Just verified it on my AC68R running my fork. Changed the power from the default 80mW to 20mW and had a 10dbm change measured at the client (but only after the reboot).

 

[develox]

Between measurements to look for differences, in addition to the 'Apply' button also perform a reboot. There are some cases where just restarting the wireless subsystem (the default action for apply) doesn't quite work. Just verified it on my AC68R running my fork. Changed the power from the default 80mW to 20mW and had a 10dbm change measured at the client (but only after the reboot).

Thanks a lot John for your attention. I've indeed rebooted the unit, with no luck.

I'm running Merlin 3.0.0.4.376.48_1 at the moment. Do you think there could be any relevant differences in the wireless drivers or anything else between the two fw and that can explain the difference in behaviour ?

Peppe

 

[john9527]

Thanks a lot John for your attention. I've indeed rebooted the unit, with no luck.

I'm running Merlin 3.0.0.4.376.48_1 at the moment. Do you think there could be any relevant differences in the wireless drivers or anything else between the two fw and that can explain the difference in behaviour ?

Peppe

I wouldn't think so....they of course changed from the 'value' to 'percentage' for the power, but that's relatively straight forward. The drivers are a different build, but again, wouldn't think this would break. I'll load up Merlin's code and rerun the same test later today to check it out.

 

[develox]

I wouldn't think so....they of course changed from the 'value' to 'percentage' for the power, but that's relatively straight forward. The drivers are a different build, but again, wouldn't think this would break. I'll load up Merlin's code and rerun the same test later today to check it out.

Very much appreciated John, I swapped out the Nighthawk R7000 not just for the product itself (AC68U), but because I saw how valuable your contribution and Eric's are here to the benefit of the community.

Thanks again
Peppe

 

[john9527]

Here are some measurements I took on reducing power on the 376 vs 374 codes. The numbers aren't any type of statistical measures, just me looking at the display and recording my best estimate of a mean value. Remember this is a specific environment and 'your mileage may vary'

It looks like the slider does work in 376, although it seems to have less effect for what should be the same measurements as 374. Could possibly be some 'banding' going on in the power calculations or maybe the wireless driver....hard to tell. It's especially noticeable on the 2.4GHz band where there was definitely some change, but minimal.

Two other observations.... it seems the 374 driver has a slightly higher power output, at least in this test. Also, I confirmed on both code loads the you must reboot after hitting the 'Apply' button for the change in power level to take effect.

 

[develox]

You're seeing greater variations than I did John. I might repeat my tests with both fw as well. Is there any issue exporting/importing settings when switching back and forth between Merlin and fork?

 

[john9527]

You're seeing greater variations than I did John. I might repeat my tests with both fw as well. Is there any issue exporting/importing settings when switching back and forth between Merlin and fork?

Yes, the wireless drivers are different between the levels, so you need to do a factory reset or clear the nvram when switching between the levels. I did put up a utility to ease the pain that you can use to save and restore just your 'user' settings that you may want to take a look at.

http://forums.smallnetbuilder.com/showthread.php?t=19521

 

[develox]

Yes, the wireless drivers are different between the levels, so you need to do a factory reset or clear the nvram when switching between the levels. I did put up a utility to ease the pain that you can use to save and restore just your 'user' settings that you may want to take a look at.

http://forums.smallnetbuilder.com/showthread.php?t=19521

Hi John,

I apologize for being so late in following up this thread, but in the past months I've had to redirect my attention.

Right after your suggestion I mad some tests using Xirrus on a client laptop. I tried with both Merlin and fork (thanks for the script, I've hence used it and it's worked flawlessly). I even took screenshots of the results but can't find the files now at this distant time.
However, I remember well that indeed using the fork (and by the way after a reboot every time), by changing the slider I saw a noticeable difference (though not as much as I see with the TpLink toy or saw with the R7000), while the same couldn't be said running Merlin (as Eric himself clearly explains in some threads here). Unfortunately I've had no chance lately to repeat the test (swapping fw) and produce the screenshots (as in these days I got again some spare time and hitting the walls trying to run snort on the AC68U), but I thought your attention to this thread at that time deserved an ack.

Thanks !