Signal Strength Discrepancies

[Panzer240]

I have started evaluating Wirelessmon. Right of th bat I see a huge difference in RSSI levels indicated by the software and the driver control panel site survey screen. I am using a Linksys WPC54G V2.0 pcmcia adapter using the most current drivers for my Win2k Pro IBM A22m laptop. The Linksys driver shows RSSI of 93% whilst the Wirelessmon software indicates 64%. Since I am only about 25 feet from the AP, I tend to believe the Linksys site survet reading. Is there anyway to adjust the software to correct the discrepancy ??



Panzer

[Tim (PassMark)]

Manufactures drivers have much greater access to information from the network card, and RSSI values can be quite different between different manufactures.

When WirelessMon queries the network card it can return a signal strength in dBm or an RSSI value, if a dBm value is returned we convert it to a percentage based signal strength, which may not match the signal percentage value set by the manufacturer for that signal strength.

[Panzer240]

Manufactures drivers have much greater access to information from the network card, and RSSI values can be quite different between different manufactures.

When WirelessMon queries the network card it can return a signal strength in dBm or an RSSI value, if a dBm value is returned we convert it to a percentage based signal strength, which may not match the signal percentage value set by the manufacturer for that signal strength.

Would it be possible to inckude perhaps a "fudge factor" so that one might offset the readings to bring them into alignment? As it stands, there is close to a 50% difference in the reading.


Panzer

[David (PassMark)]

The problem is that is the RSSI to percent conversion can be different for every card on the market. As far as we know there is not a standard forumla for the conversion. We could be wrong however?

I guess we could look at adding a fudge factor that the user can tweak.

[quickstrike]

When WirelessMon queries the network card it can return a signal strength in dBm or an RSSI value...

Let me get this straight, if I see a positive number (1-100), this is RSSI. If I see a negative number (0 - -100), this is dBm? If not, how do I know if I am looking at RSSI or dBm?

Also, there is something a little weird here. When connected to an access point, WirelessMon shows a TxPower of 100mW (or 20 dBm). However, when I am in the access point's settings, it says the Antenna Transmit Power is 17 dBm. Why is there a 3dB discrepancy? How does WirelessMon get it's TxPower reading?
One solution I thought was that the antenna (omnidirectional, which is roughly 2-3 dBi) is being accounted for in the TxPower, so 17dBm + 2-3dB = 19-20dBm, but how would WirelssMon know what antenna is being used to transmit?

Thanks for your help.

[Tim (PassMark)]

That's right, positive will mean an RSSI is being retrieved.

The TxPower is the transmit power level of the NIC, not the access point.