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firewalker

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From: Hellas (Greece).

Registered: 2006-06-05

Posts: 557

[SOLVED] iwconfig always report -50 dBm power strength.

I noticed today that iwconfig always reports -50 dBm for the signal strength. Not for a specific card. For every wireless card I connect. I don't believe it is an iwconfig issue.

cat /proc/net/wireless

also reports -50 dBm.

iwlist scan

seems to report the correct power.

Can someone verify it?

Last edited by firewalker (2015-06-10 06:54:45)

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esa

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Registered: 2011-12-29

Posts: 143

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Re: [SOLVED] iwconfig always report -50 dBm power strength.

Hi firewalker

Which one is the dBm?

0 sea # cat /proc/net/wireless
Inter-| sta-|   Quality        |   Discarded packets               | Missed | WE
 face | tus | link level noise |  nwid  crypt   frag  retry   misc | beacon | 22
wlp3s0: 0000   70.  -28.  -256       ? 0      0      0      0     25        0

0 sea # iw dev wlp3s0 scan | grep -B3 344 |grep dBm
	signal: -87.00 dBm

Looks fine to me.

How's your router settings?
I've set mine to only use a signal strength of 75%.

hth

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firewalker

Member

From: Hellas (Greece).

Registered: 2006-06-05

Posts: 557

Re: [SOLVED] iwconfig always report -50 dBm power strength.

Your dBm is -28.  Can you move arount and verify that -28 changes?

For me it doesn't the router I connect to. It's always -50 dBm.

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ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,193

Re: [SOLVED] iwconfig always report -50 dBm power strength.

What is your wireless chipset?  Check with lspci -nn
Edit:  I did note you said "Every" card you connect.  But, they all might have the same chipset / driver 

Last edited by ewaller (2015-06-08 15:26:21)

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firewalker

Member

From: Hellas (Greece).

Registered: 2006-06-05

Posts: 557

Re: [SOLVED] iwconfig always report -50 dBm power strength.

Tested with:

1. Network controller [0280]: Intel Corporation Centrino Wireless-N 1030 [Rainbow Peak] [8086:008a] (rev 34)
2. 148f:3070 Ralink Technology, Corp. RT2870/RT3070 Wireless Adapter
3. 0cf3:9271 Atheros Communications, Inc. AR9271 802.11n

Last edited by firewalker (2015-06-08 15:39:11)

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ewaller

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From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,193

Re: [SOLVED] iwconfig always report -50 dBm power strength.

Weird.  They most definitely do not use the same drivers.   From my systems:

ewaller@odin ~ 1002 %iwconfig
enp3s0    no wireless extensions.

wlan0     IEEE 802.11bg  ESSID:"Woodlyn"  
          Mode:Managed  Frequency:2.412 GHz  Access Point: C4:3D:C7:5D:EB:8F   
          Bit Rate=36 Mb/s   Tx-Power=30 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=70/70  Signal level=-22 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:26127  Invalid misc:2752615   Missed beacon:0

lo        no wireless extensions.

ewaller@odin ~ 1003 %ssh turing
ewaller@turing's password: 
Last login: Mon Jun  8 08:05:35 2015 from 192.168.1.104
ewaller@turing ~ 1001 %iwconfig
wlo1      IEEE 802.11abgn  ESSID:"Woodlyn-hi"  
          Mode:Managed  Frequency:5.745 GHz  Access Point: C4:3D:C7:5D:EB:8C   
          Bit Rate=40.5 Mb/s   Tx-Power=22 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:on
          Link Quality=42/70  Signal level=-68 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:604   Missed beacon:0

eno1      no wireless extensions.

lo        no wireless extensions.

ewaller@turing ~ 1002 %uname -a
Linux turing 4.0.4-2-ARCH #1 SMP PREEMPT Fri May 22 03:05:23 UTC 2015 x86_64 GNU/Linux
ewaller@turing ~ 1003 %
Connection to turing closed.
ewaller@odin ~ 1004 %uname -a
Linux odin 3.19.3-3-ARCH #1 SMP PREEMPT Wed Apr 8 14:10:00 CEST 2015 x86_64 GNU/Linux
ewaller@odin ~ 1005 %

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firewalker

Member

From: Hellas (Greece).

Registered: 2006-06-05

Posts: 557

Re: [SOLVED] iwconfig always report -50 dBm power strength.

Does the power level change (in relation to distance for example) or is it constant?

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mauritiusdadd

Member

From: Benevento, Italy

Registered: 2013-10-27

Posts: 776

Re: [SOLVED] iwconfig always report -50 dBm power strength.

I can confirm this. Moreover I did some tests and this are the results:

• iwlist scan reports the correct signal strength which changes if I move my laptop farther from the router:

  # iwlist wlp1s0 scan | grep level    # ~ 0.3m from the router
                      Quality=70/70  Signal level=-28 dBm  
  # iwlist wlp1s0 scan | grep level    # ~ 1m from the router
                      Quality=70/70  Signal level=-39 dBm  
  # iwlist wlp1s0 scan | grep level    # ~ 2m from the router
                      Quality=61/70  Signal level=-49 dBm  
  # iwlist wlp1s0 scan | grep level    # ~ 4m from the router
                      Quality=48/70  Signal level=-62 dBm 

• The signal level shown by iwconfig changes only if I reboot the machine (turning off the adapter is not enough).

• The signal level shown by iwconfig does not change if I move my laptop farther from the router and its value is determinate at boot-time:

  # iwconfig  wlp1s0 | grep level    # ~ 0.3m from the router
            Link Quality=70/70  Signal level=-30 dBm
  # iwconfig  wlp1s0 | grep level    # ~ 1m from the router
            Link Quality=70/70  Signal level=-30 dBm
  # iwconfig  wlp1s0 | grep level    # ~ 2m from the router
            Link Quality=70/70  Signal level=-30 dBm
  # iwconfig  wlp1s0 | grep level    # ~ 4m from the router
            Link Quality=70/70  Signal level=-30 dBm

I have a  Intel(R) Centrino(R) Advanced-N 6235 AGN, REV=0xB0

$ uname -a
Linux 530U3C 4.0.5-1-ck #1 SMP PREEMPT Sat Jun 6 13:50:09 EDT 2015 x86_64 GNU/Linux

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firewalker

Member

From: Hellas (Greece).

Registered: 2006-06-05

Posts: 557

Re: [SOLVED] iwconfig always report -50 dBm power strength.

Ok, where should we report it? Kernel wireless?

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ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,193

Re: [SOLVED] iwconfig always report -50 dBm power strength.

A problem is that iwconfig is deprecated. Unless your hardware requires wext, you should consider using iw
https://wiki.archlinux.org/index.php/Wi … nual_setup

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mauritiusdadd

Member

From: Benevento, Italy

Registered: 2013-10-27

Posts: 776

Re: [SOLVED] iwconfig always report -50 dBm power strength.

Ok, where should we report it? Kernel wireless?

I don't know if it has something to do with the kernel but since the problem exists even using different drivers I think it is a problem with iwconfig itself.

A problem is that iwconfig is deprecated. Unless your hardware requires wext, you should consider using iw

Indeed, iw correctly reports the actual signal strength:

# iw dev wlp1s0 link | grep signal    # ~ 0.3m from the router
	signal: -38 dBm
# iw dev wlp1s0 link | grep signal    # ~ 1m from the router
	signal: -44 dBm
# iw dev wlp1s0 link | grep signal    # ~ 2m from the router
	signal: -53 dBm
# iw dev wlp1s0 link | grep signal    # ~ 4m from the router
	signal: -73 dBm

--edit: typo

Last edited by mauritiusdadd (2015-06-08 18:03:36)

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firewalker

Member

From: Hellas (Greece).

Registered: 2006-06-05

Posts: 557

Re: [SOLVED] iwconfig always report -50 dBm power strength.

It is not only iwconfig. A number of programs display the wrong power. I think those programs look inside /proc/net/wireless (WEXT). 

How iw reads the infos?

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ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,193

Re: [SOLVED] iwconfig always report -50 dBm power strength.

How iw reads the infos?

https://en.wikipedia.org/wiki/Netlink

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esa

Member

Registered: 2011-12-29

Posts: 143

Website

Re: [SOLVED] iwconfig always report -50 dBm power strength.

cat'ing /proc/net/wireless didnt change.
But using iw i got -46 and -48 at two different locations in my flat. (where it was 87 initialy)

hth

EDIT:
Thinking about that, thats quite bad

Last edited by esa (2015-06-08 18:48:39)

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ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,193

Re: [SOLVED] iwconfig always report -50 dBm power strength.

You do realize that -46dBm is 7 dB better than -53dBm ?

Edit:  simple math is not going well today for me

Last edited by ewaller (2015-06-08 18:49:59)

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Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
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esa

Member

Registered: 2011-12-29

Posts: 143

Website

Re: [SOLVED] iwconfig always report -50 dBm power strength.

So you are saying, that as the clouds came up, and rain falls down, and the signal is down to -36, its better?
Speaking of the actual weather outside here.
I'm just irrated, as i'm used to get lower numbers with 'bad weather' and higher ones while the sun shines.

AwesomeWM doesnt show me the AP and strength on the interface yet, as i still connect via my 'default' script and not via NM.

But since i set the strength of my router to 75%, and the usual strength shown in the status bar is about 70% when the sun shines, i figured that might be related.. somehow.

EDIT:
Just irritated now.

Last edited by esa (2015-06-08 18:55:03)

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ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,193

Re: [SOLVED] iwconfig always report -50 dBm power strength.

0 dBm is 1 mW. 
-3 dBm = 0.5mW
-10dBm = 0.1mW
-20dBm = 0.01mW
-30dBm = 1uW
-40dBm = 0.1uW
-50dBm = 0.01uW

3dBm = 2mW
10dBm = 10mW
20dBm = 100mW
30dBm = 1W

(I think I did all that correctly, If not, I'll find out soon enough )

Last edited by ewaller (2015-06-08 18:58:06)

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Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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firewalker

Member

From: Hellas (Greece).

Registered: 2006-06-05

Posts: 557

Re: [SOLVED] iwconfig always report -50 dBm power strength.

What is the correct place for a WEXT bug? Linux -> Networking -> Wireless ?

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ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,193

Re: [SOLVED] iwconfig always report -50 dBm power strength.

So you are saying, that as the clouds came up, and rain falls down, and the signal is down to -36, its better?

Yes.   Rain attenuation only happens when the RF has to pass through the rain

Edit: Sorry, we are kind of hijacking the thread.  Back on topic now

Last edited by ewaller (2015-06-08 19:06:24)

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Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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mauritiusdadd

Member

From: Benevento, Italy

Registered: 2013-10-27

Posts: 776

Re: [SOLVED] iwconfig always report -50 dBm power strength.

What is the correct place for a WEXT bug? Linux -> Networking -> Wireless ?

There, or maybe you can ask on the Linux wireless mailing list: https://wireless.wiki.kernel.org/en/use … eport_bugs

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firewalker

Member

From: Hellas (Greece).

Registered: 2006-06-05

Posts: 557

Re: [SOLVED] iwconfig always report -50 dBm power strength.

Fixed.

https://bugzilla.kernel.org/show_bug.cgi?id=99691

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mauritiusdadd

Member

From: Benevento, Italy

Registered: 2013-10-27

Posts: 776

Re: [SOLVED] iwconfig always report -50 dBm power strength.

Thank you for reporting this, the speed with it has been fixed is impressive!
Remember to mark the thread as [SOLVED]

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