Wireshark · Wireshark-users: [Wireshark-users] R: Re: radiotap RSSI v.s. IEEE802.11 RSSI

["iodavide@xxxxxxxxx" <iodavide@xxxxxxxxx>]

>	for pcap captures with Radiotap headers, it's radiotap.dbm.antsignal,  

>shown as dBm.

After few captures It seems to be: (IEEE802.11 RSSI) = 
(radiotap.dbm.antnoise) - (radiotap.dbm.antsignal)

I'm using Wireshark 1.0.0 
(1.2.0 is not in my repository) and modified MadWiFi drivers for 802.11p.
Do 
you know any difference about how 1.0.0version and 1.2.0version capture data?

I'm going to do some test in 802.11p communication capturing data in several 
hosts using 1.0.0 and analyzing data using 1.2.0. I hope there is no 
difference! If there are some let me know and I'll spend few hours changing 
all... 

thanks

Davide

>> and a custom colums radiotap.dbm.antsignal
>> I'm 
very surprise
>> to see different values for those columns
>
>Given that the 
Radiotap code, at least in the top-of-tree version of  
>Wireshark just puts up 
the radiotap.dbm.antsignal value, I'd be  
>*extremely* susprised to see 
different values.
>
>The 1.2.0 code should behave the same as the top-of-SVN-
tree version;  
>what version of Wireshark are you using?
>>
>








>----
Messaggio originale----
>Da: guy@xxxxxxxxxxxx
>Data: 26/06/2009 22.25
>A: 
"iodavide@xxxxxxxxx"<iodavide@xxxxxxxxx>, "Community support list for Wireshark"
<wireshark-users@xxxxxxxxxxxxx>
>Ogg: Re: [Wireshark-users] radiotap RSSI v.s. 
IEEE802.11 RSSI
>
>
>On Jun 26, 2009, at 7:42 AM, iodavide@xxxxxxxxx wrote:
>

>> I'm using Atheros device and I'm capturing data from monitor interface
>> 
using Radiotap
>> To better understand link quality I've selected two columns:

>> IEEE 802.11 RSSI
>
>At least as I read IEEE 802.11-2007, RSSI is just some 
positive number  
>such that
>
>	1) it's between 0 and some maximum;
>
>	2) the 
greater the value, the more power is being received at the  
>antenna;
>
>with 
no indication of what it means other than that.
>
>What Wireshark displays in 
the "RSSI" column depends on the type of  
>capture; at least in the top-of-SVN-
tree version:
>
>	for captures from AiroPeek, it's a percentage - 
RSSI/max_RSSI*100 (as  
>that's what AiroPeek saves to the file, at least as I 
read one of  
>WildPackets' documents);
>
>	for captures from CommView, it's a 
percentage - probably the same as  
>AiroPeek, but I didn't find anything 
obvious in their document to  
>indicate what it is;
>
>	for captures from 
Windows Sniffer, I *suspect* it's a percentage,  
>probably the same as 
AiroPeek;
>
>	for captures from Shomiti's wireless version of Surveyor (Finisar 
no  
>longer seem to offer it), I don't know what it is;
>
>	for pcap captures 
with Prism headers, it's whatever the heck the  
>particular driver puts there 
- a quick look at the drivers didn't  
>indicate that they put anything there;

>
>	for pcap captures with AVS headers, it's signal strength as either:
>
>		
"Normalized RSSI" - integers in the range [0-1000] where higher  
>numbers 
indicate stronger signal, with no particular mapping to an  
>actual signal 
strength;
>
>		dBm - an actual received signal strength, in dBm;
>
>		a raw 
RSSI value, which is probably the raw IEEE RSSI value;
>
>	with the column 
indicating which it is;
>
>	for pcap captures with Radiotap headers, it's 
radiotap.dbm.antsignal,  
>shown as dBm.
>
>
>> and a custom colums radiotap.
dbm.antsignal
>> I'm very surprise
>> to see different values for those columns

>
>Given that the Radiotap code, at least in the top-of-tree version of  

>Wireshark just puts up the radiotap.dbm.antsignal value, I'd be  
>*extremely* 
susprised to see different values.
>
>The 1.2.0 code should behave the same as 
the top-of-SVN-tree version;  
>what version of Wireshark are you using?
>>
>