Asus RT-AC56U FW 3.0.0.4.374.38_2 - 'TX Power' setting seems to be broken

[EU1]

The router is RT-AC56U (HW rev. 2.20) with Merlin FW 3.0.0.4.374.38_2.

RSSI measured on Intel N2230 card (2.4 GHz) does not depend on TX power at all.

I have measured RSSI of about -30dB 3-4 meters away in the same room and about -75...-70dB behind two concrete walls.
Measured values with the router TX power of 1mW and 100mW were the same, so it seems that 'TX Power' setting does not actually change output power.

I would appreciate if somebody confirm my concern or explain why my assumption may be wrong.

 

[ikoul]

I think that setting is more of a maximum, and no matter what you set there you're still going to be subject to regional laws on maximum transmit power and the firmware's decision about what power it needs to be using at any given time. Also, going from 80 to something like 160mw sounds like a lot, but from the client side that might get you a change of 2-3 dB (although in my experience, going too high just makes your signal worse from noise). I think the signal level is on a logarithmic scale or something.

 

[EU1]

I think that setting is more of a maximum, and no matter what you set there you're still going to be subject to regional laws on maximum transmit power and the firmware's decision about what power it needs to be using at any given time.

It would be a maximum, but 1 mW vs. two concrete walls (each wall is about 20 cm width) sounds like a fantastic... Therefore I believe that the real transmission power is much more than 1 mW.

I think the signal level is on a logarithmic scale or something.

ikoul, on AC56U Tx power is configured in mW, so I expect that the scale is linear. Therefore when I change power from 100 mW to 1 mW I expect that RSSI would decrease on 20dB. But it is not changing at all.
That's why I suspect that there is something wrong with this setting.

 

[DrTeeth]

(although in my experience, going too high just makes your signal worse from noise).

It isn't 'noise'.

I think the signal level is on a logarithmic scale or something.

It is.

 

[RMerlin]

It's been over a year since I paid any attention to that part of the code, but previously, the output power was set in steps rather than directly applied based on the value entered. For instance, all values between 61 and 79 mW would apply the same setting to the wireless driver. There was also a floor value of 20mW, which was the lowest step applied to the driver.

 

[L&LD]

We don't have direct control over the Tx power setting. What we can do is 'suggest' to do more or less.

What the driver does is adjust the power as it sees fit for the best connection (probably at the least power and the least noise). Depending on the wireless environment, the distance to the device, etc., etc...

I see a 2 to 3 dBm change when I change Tx power from the default 80mW to 100mW in my setups.

Your environment may be more noisy/busy and the radio amps cannot increase as much as they need to for you to measure a difference.

I would recommend instead doing a throughput test at different power levels. Then you should see a difference as I have seen. Although my testing has shown that setting the Tx level to 100mW is the optimum for at least the RT-N66U, the RT-AC56U, the RT-AC66U and RMerlin's latest firmware. I believe this should be the new 80mW 'default' for these routers.

And no offense to the Intel N2230 card: but it is not one of Intel's best efforts (I have had several laptops with those cards inside).

Can you try an Intel AC7260 card for ~$30 in that laptop?

In my experience; it will be money well spent (Windows 8.1 recommended; because of more stable drivers for the AC7260 device).

 

[EU1]

RMerlin, thanks for useful information.
Do you know whether it is possible to get WI-FI radio stats (especially router side RSSI and TX power) through SSH?

I see a 2 to 3 dBm change when I change Tx power from the default 80mW to 100mW in my setups.

Interesting... Do you use RT-AC56U?
In my setup RRSSI is the same with 20 mW and 100 mW (while 5x difference in TX power should give us about 7 dB of RSSI difference).

I would recommend instead doing a throughput test at different power levels. Then you should see a difference as I have seen.

No notable difference between 20, 80 and 100 mW. In all these configurations throughput with was almost the same (+/-5% without dependency on TX power).

And no offense to the Intel N2230 card: but it is not one of Intel's best efforts (I have had several laptops with those cards inside).

Can you try an Intel AC7260 card for ~$30 in that laptop?

In my experience; it will be money well spent (Windows 8.1 recommended; because of more stable drivers for the AC7260 device).

Yep, N2230 is not the best card I ever use
I've ordered AC7260 and I hope I will get it in few days.
Hope built-in 2.4GHz antennas will work normally on 5GHz band.

 

[RMerlin]

RMerlin, thanks for useful information.
Do you know whether it is possible to get WI-FI radio stats (especially router side RSSI and TX power) through SSH?

The wireless radios can be manipulated using the "wl" command. Run it to get a list of available options, there are quite a few.

I don't remember if RSSI is available through this command or only through an iocontrol call (which means it has to be done with C code).

 

[DrTeeth]

The wireless radios can be manipulated using the "wl" command. Run it to get a list of available options, there are quite a few.

I don't remember if RSSI is available through this command or only through an iocontrol call (which means it has to be done with C code).

If there a way to pipe that info to a text file for saving for future reference? This technique would be very handy for other commands too.

TIA

DrT

 

[RMerlin]

If there a way to pipe that info to a text file for saving for future reference? This technique would be very handy for other commands too.

TIA

DrT

In Linux, you can easily redirect the output of a command to a text file:

wl > /mnt/sda1/usage.txt"
wl cmds > /tmp/sda1/cmdlist.txt"

Adjust the path based on your own USB disk mount point.

 

[DrTeeth]

In Linux, you can easily redirect the output of a command to a text file: <snip>

Thank you SO much.

DrT

 

[EU1]

AC-7260 minicard is out of stock in Ukrainian stores, so I've bought desktop AC-7160 kit for $55 (which contains AC-7260 minicard, PCI-E to PCI-E minicard adapter, and dual band antennas assembly).

I've compared kit antenna with my laptop built-in antennas and found that RSSI is almost the same, so I guess that my laptop antennas are OK for 5.2 GHz band.

Then I've used the following commands to measure router side RSSI:
wl -i eth2 rssi [MAC_ADDR]
wl -i eth2 phy_rssi_ant

RSSI on router is 10-15 dB lower than RSSI on client. It is strange, because basing on FCC info, AC-7260 output power is 50 mW, so server-side RSSI should be only 6 dB less than client -side RSSI, maybe this is due to different RX sensitivity...


Yesterday I've made some measurements. I've created poor man's RF detector which is not a precise measurement equipment, but allows to estimate output power. I found the following:

- RSSI on the router is changed when TX power is changed in AC-7260 settings. Also I've noted TX power change on the oscilloscope connected to the RF detector. So this works as expected.

- RSSI on AC-7260 is NOT changed when the router TX power setting is changed. Power measured with RF detector is not changed as well and it is much higher than 7260 TX power. It seems that the router works on max power (200 mW) even if it is configured for 20 mW.

Therefore I think that TX power doesn't work. The same is with original ASUS firmware.
My goal is to decrease TX power, because I don't need this 200 mW, I guess that 50 mW would be more than enough for my setup. So I will appreciate any ideas how to do this.

PS: "wl -i eth2 txpwrlimit" command always return 200 mW and "wl -i eth2 pwr_percent" - 100%.
I've tried to change "pwr_percent", but didn't noticed any TX power changes.

 

[RMerlin]

Try doing a router reboot after changing the output power. Last time I did any testing around output power (about a year ago), I noticed that sometimes the changes weren't applied until a router reboot, and sometimes they were immediately applied. I suspect Broadcom never really intended for the power to be adjustable on-the-fly.

 

[EU1]

Just tried to reboot the router after changing TX power several times. Nothing changed .

 

[danyxp]

Hi
I noticed that the max power for 2.4 GHz is 100 and for 5 GHz is 200, is this normal ? I'm using the latest official firmware.
I keep the values at maximum because I need some signal outside the house...

 

[Stimpy]

It's been over a year since I paid any attention to that part of the code, but previously, the output power was set in steps rather than directly applied based on the value entered. For instance, all values between 61 and 79 mW would apply the same setting to the wireless driver. There was also a floor value of 20mW, which was the lowest step applied to the driver.

I personally think that it was a mistake on Asus's part to make it a free numerical input. It really should have been some kind of drop-down list of available power levels, ones that actually work!

I have almost given up on being able to adjust the power output, as it really does not ever seem to change, rebooting or not, no matter if I input 20 or 200, at least according to SSiD on my laptop.

 

[EU1]

Hi
I noticed that the max power for 2.4 GHz is 100 and for 5 GHz is 200, is this normal?

It is OK.

I keep the values at maximum because I need some signal outside the house...

You would set any value, it seems that this setting doesn't work at all.

 

[thaui]

It's been over a year since I paid any attention to that part of the code, but previously, the output power was set in steps rather than directly applied based on the value entered. For instance, all values between 61 and 79 mW would apply the same setting to the wireless driver. There was also a floor value of 20mW, which was the lowest step applied to the driver.

I am living in the EU. Is it right if I change the CFE file to US that I will get 125mW as a maximum Tx Power? The standard signal with 100mW is very weak in my enviroment. The old RT-N56U was much better on 2,4 Ghz.

 

[yelo3]

I think I might know why the WiFi range is so low.
In EU regulatory domain, the maximum transmit power for this router is 15dbm, which is something around 30mw.
At least it's what I've understood after having executed the command

wl txpwr_target_max

 

[john9527]

If there a way to pipe that info to a text file for saving for future reference? This technique would be very handy for other commands too.

TIA

DrT

Here's a reference on 'wl'....a little old but I've found it useful....

http://www.dd-wrt.com/wiki/index.php/Wl_command#Setup