Measure RSSI in adhoc networks

Measure RSSI in adhoc networks

[Kai Timmer]

Hello,
I need to get the rssi values in an adhoc network from every available
node separately.
I noticed that on some of my devices, in a adhoc network, there are
all values set to 0. Some other devices are showing values. I am not
sure how to interpret this values. If there are more than 2 nodes in
the adhoc network, it has to be some kind of average value. Am I right
with this? And if yes, is there any way to get the rssi value for
every available node?

I am not sure if this is the right place to ask these questions, if it
is not, please redirect me to a more fitting place.

Greets,
-- 
Kai Timmer
Email : email@kait.de
Jabber: kai@kait.de

Re: Measure RSSI in adhoc networks

[Dan Williams]

On Wed, 2009-04-22 at 15:08 +0200, Kai Timmer wrote:
> Hello,
> I need to get the rssi values in an adhoc network from every available
> node separately.
> I noticed that on some of my devices, in a adhoc network, there are
> all values set to 0. Some other devices are showing values. I am not
> sure how to interpret this values. If there are more than 2 nodes in
> the adhoc network, it has to be some kind of average value. Am I right
> with this? And if yes, is there any way to get the rssi value for
> every available node?

You can only get an RSSI if there are other nodes in the network, and
then you get the RSSI of *that* node, as received by your node.  You
can't measure your own RSSI, because RSSI = *Received* Signal Strength
Indicator, and you can't really receive your own traffic since you're
radiating tons of power on TX and that completely deafens the RX chain.

Not all drivers report RSSI in adhoc mode at this time.  But even if
they did, they could only report RSSI when they receive a beacon or
traffic from some other node in the adhoc network, and that's pretty
useless because it doesn't give you a general quality of the "network",
it gives you a specific quality of the radio path between two points in
the network.

Dan

> I am not sure if this is the right place to ask these questions, if it
> is not, please redirect me to a more fitting place.
> 
> Greets,

Re: Measure RSSI in adhoc networks

[Kai Timmer]

2009/4/23 Dan Williams <dcbw@redhat.com>:
> You can only get an RSSI if there are other nodes in the network, and
> then you get the RSSI of *that* node, as received by your node. =C2=A0=
You
> can't measure your own RSSI, because RSSI =3D *Received* Signal Stren=
gth
> Indicator, and you can't really receive your own traffic since you're
> radiating tons of power on TX and that completely deafens the RX chai=
n.

Ok, that was clear to me. I don't know where you read that i want my
own RSSI? That would just make no sense.

> Not all drivers report RSSI in adhoc mode at this time. =C2=A0But eve=
n if
> they did, they could only report RSSI when they receive a beacon or
> traffic from some other node in the adhoc network, and that's pretty
> useless because it doesn't give you a general quality of the "network=
",
> it gives you a specific quality of the radio path between two points =
in
> the network.

Maybe i should point out, what i am trying to do :)
I need the RSSI values for distance measurements between the nodes. So
what i need is not a "quality value" for the whole network, but the
recieved mW from every reachable point in the network. So i think the
RSSI value for every network node (if i can print them out seperatly)
should do the job.

Greets,
--=20
Kai Timmer
Email : email@kait.de
Jabber: kai@kait.de
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Re: Measure RSSI in adhoc networks

[Johannes Berg]

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On Thu, 2009-04-23 at 12:36 +0200, Kai Timmer wrote:

> I need the RSSI values for distance measurements between the nodes. 

Note that is very unreliable...

> So
> what i need is not a "quality value" for the whole network, but the
> recieved mW from every reachable point in the network. So i think the
> RSSI value for every network node (if i can print them out seperatly)
> should do the job.

iw dev wlan0 station dump

johannes

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Re: Measure RSSI in adhoc networks

[Kai Timmer]

2009/4/23 Johannes Berg <johannes@sipsolutions.net>:
> On Thu, 2009-04-23 at 12:36 +0200, Kai Timmer wrote:
>
>> I need the RSSI values for distance measurements between the nodes.
>
> Note that is very unreliable...

I know, it is a work for my diploma thesis. I'm trying to combine it
with some kind of round trip time measurements. It is in the very
early stages,...

>> So
>> what i need is not a "quality value" for the whole network, but the
>> recieved mW from every reachable point in the network. So i think the
>> RSSI value for every network node (if i can print them out seperatly)
>> should do the job.
>
> iw dev wlan0 station dump

That works on my laptop, but on not on my Openmoko Freerunner devices.
There I get the following:

runner1:~# iw dev eth1 station dump
nl80211 not found.

I assume that something with the freerunner wireless driver is not
compatible with the linux wireless stack. The driver is called
"ar6000".

Greets,
-- 
Kai Timmer
Email : email@kait.de
Jabber: kai@kait.de
Blog: http://blog.kaitimmer.de

Re: Measure RSSI in adhoc networks

[Luis R. Rodriguez]

On Thu, Apr 23, 2009 at 4:39 AM, Kai Timmer <email@kait.de> wrote:
> 2009/4/23 Johannes Berg <johannes@sipsolutions.net>:
>> On Thu, 2009-04-23 at 12:36 +0200, Kai Timmer wrote:
>>
>>> I need the RSSI values for distance measurements between the nodes.
>>
>> Note that is very unreliable...
>
> I know, it is a work for my diploma thesis. I'm trying to combine it
> with some kind of round trip time measurements. It is in the very
> early stages,...
>
>>> So
>>> what i need is not a "quality value" for the whole network, but the
>>> recieved mW from every reachable point in the network. So i think the
>>> RSSI value for every network node (if i can print them out seperatly)
>>> should do the job.
>>
>> iw dev wlan0 station dump
>
> That works on my laptop, but on not on my Openmoko Freerunner devices.
> There I get the following:
>
> runner1:~# iw dev eth1 station dump
> nl80211 not found.
>
> I assume that something with the freerunner wireless driver is not
> compatible with the linux wireless stack. The driver is called
> "ar6000".

The ar6000 driver uses wext and not cfg80211 which all new shiny
mac80211 drivers use. The command Johannes gave you was for cfg80211
devices.

  Luis

Re: Measure RSSI in adhoc networks

[Kai Timmer]

2009/4/28 Luis R. Rodriguez <mcgrof@gmail.com>:
> The ar6000 driver uses wext and not cfg80211 which all new shiny
> mac80211 drivers use. The command Johannes gave you was for cfg80211
> devices.

Thats what i thought. But is there a wext equivalent to these commands?

Greets,
-- 
Kai Timmer
Email : email@kait.de
Jabber: kai@kait.de

Re: Measure RSSI in adhoc networks

[Johannes Berg]

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On Tue, 2009-04-28 at 09:59 +0200, Kai Timmer wrote:
> 2009/4/28 Luis R. Rodriguez <mcgrof@gmail.com>:
> > The ar6000 driver uses wext and not cfg80211 which all new shiny
> > mac80211 drivers use. The command Johannes gave you was for cfg80211
> > devices.
> 
> Thats what i thought. But is there a wext equivalent to these commands?

No.

johannes

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