Netstumbler vs. Netsh

CubicVirtuoso · 03-03-2009

Hey folks,

Long time admirer of netstumbler; however as most of you are familiar, netstumbler is not availble for Vista... which is perfectly fine and understandable I am not here to complain.

However, I was wondering if anyone knew the conversion between netstumblers SNR ratio and Vista's netstat signal percentage...

I.E. <blank>% roughly equates to 20SNR.

I've thought about taking my vista laptop, and my XP laptop and basically doing a quick site survey - comparing 20SNR to whatever the percentage was in Vista, but that would depend on the network card and other factors.

It's probably a lot to ask, but wondering if anyone has done any research into it. And no... Installing XP is unfortunately not an option.

CubicVirtuoso · 03-03-2009

Solved my own issue this morning... for anyone who is interested.

Netstumbler uses a base noise floor of -100 for the APs I was testing on... the way netstumbler calculates the SNR is it takes the signal (in DB) and adds the absolute value of the noise floor.

Eg: -52 signal -100 noise floor = 48SNR

Unfortunately netsh doesn't output RSSI values so I found a much better program called inSSIDer developed by the good people at metageek that prints out RSSI values based on the module. Adding the netstumbler noise floor of 100 to the RSSI value will result in the SNR value.

For those who cannot run inSSIDer for any reason I also found some sample C# code written by Peter Bromberg:

Code:

public static int GetSignalStrengthAsInt()
{
Int32 returnStrength = 0;
ManagementObjectSearcher searcher = null;
try
{
// Query the management object with the valid scope and the
correct query statment
searcher = new ManagementObjectSearcher( @"root\WMI",
"select Ndis80211ReceivedSignalStrength from
MSNdis_80211_ReceivedSignalStrength where active=true" );

// Call the get in order to populate the collection
ManagementObjectCollection adapterObjects = searcher.Get();
// Loop though the management object and pull out the signal
strength
foreach ( ManagementObject mo in adapterObjects )
{
returnStrength = Convert.ToInt32( mo[
"Ndis80211ReceivedSignalStrength" ].ToString() );
break;
}

}
catch ( Exception e )
{

}
finally
{
if ( searcher != null )
{
searcher.Dispose();
}
}

return returnStrength;
}

This should return the RSSI value. Hope that helps someone else like me :P

Feel free to correct any of my ramblings if they are incorrect.

BennyTB9 · 03-28-2009

SNR is not the value you want. SNR = Signal to Noise Ratio. This is only an accurate reading if your program and your wireless adapter show Noise. Noise is unwanted signal from Microwaves/Cordless Phones/Electrical interferrence etc.. Most wireless cards do not show noise. The important number is the Signal Strength. I know a negative number can be confusing but it is a ratio of dB/mV Decibles per millivolt. The closer to a positive number the better. Some wireless AP's will transmit a positive signal ratio directly out of the antenna. I hope this helps.

03-03-2009	#1 (permalink)
CubicVirtuoso Registered Member Join Date: Feb 2007 Posts: 5	Netstumbler vs. Netsh Hey folks, Long time admirer of netstumbler; however as most of you are familiar, netstumbler is not availble for Vista... which is perfectly fine and understandable I am not here to complain. However, I was wondering if anyone knew the conversion between netstumblers SNR ratio and Vista's netstat signal percentage... I.E. <blank>% roughly equates to 20SNR. I've thought about taking my vista laptop, and my XP laptop and basically doing a quick site survey - comparing 20SNR to whatever the percentage was in Vista, but that would depend on the network card and other factors. It's probably a lot to ask, but wondering if anyone has done any research into it. And no... Installing XP is unfortunately not an option.

03-03-2009	#2 (permalink)
CubicVirtuoso Registered Member Join Date: Feb 2007 Posts: 5	Solved my own issue this morning... for anyone who is interested. Netstumbler uses a base noise floor of -100 for the APs I was testing on... the way netstumbler calculates the SNR is it takes the signal (in DB) and adds the absolute value of the noise floor. Eg: -52 signal -100 noise floor = 48SNR Unfortunately netsh doesn't output RSSI values so I found a much better program called inSSIDer developed by the good people at metageek that prints out RSSI values based on the module. Adding the netstumbler noise floor of 100 to the RSSI value will result in the SNR value. For those who cannot run inSSIDer for any reason I also found some sample C# code written by Peter Bromberg: Code: public static int GetSignalStrengthAsInt() { Int32 returnStrength = 0; ManagementObjectSearcher searcher = null; try { // Query the management object with the valid scope and the correct query statment searcher = new ManagementObjectSearcher( @"root\WMI", "select Ndis80211ReceivedSignalStrength from MSNdis_80211_ReceivedSignalStrength where active=true" ); // Call the get in order to populate the collection ManagementObjectCollection adapterObjects = searcher.Get(); // Loop though the management object and pull out the signal strength foreach ( ManagementObject mo in adapterObjects ) { returnStrength = Convert.ToInt32( mo[ "Ndis80211ReceivedSignalStrength" ].ToString() ); break; } } catch ( Exception e ) { } finally { if ( searcher != null ) { searcher.Dispose(); } } return returnStrength; } This should return the RSSI value. Hope that helps someone else like me :P Feel free to correct any of my ramblings if they are incorrect.

03-28-2009	#3 (permalink)
BennyTB9 Registered Member Join Date: Aug 2006 Posts: 1	SNR is not what you want SNR is not the value you want. SNR = Signal to Noise Ratio. This is only an accurate reading if your program and your wireless adapter show Noise. Noise is unwanted signal from Microwaves/Cordless Phones/Electrical interferrence etc.. Most wireless cards do not show noise. The important number is the Signal Strength. I know a negative number can be confusing but it is a ratio of dB/mV Decibles per millivolt. The closer to a positive number the better. Some wireless AP's will transmit a positive signal ratio directly out of the antenna. I hope this helps.

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