On Wed, 2008-03-19 at 16:25 +0100, Holger Schurig wrote: > > > I also found that the average noise floor is -86 dBm, not > > > -96 dBm. So I changed this constant. Maybe this is wrong, > > > what values do your cards report? > > > > When possible, we should use a window-ed average of the cards > > reported noise from beacons or received frames instead of a > > constant, that's a further improvement though. > > The changed value of MRVDRV_NF_DEFAULT_SCAN_VALUE is only used to > magically conjure the missing noise value for scan results, see > my other mail about this. > > Okay, it's also used in the case of a failed GET_RSSI command :-) > > > Well, when we had the (badly) averaged array values in there, > > the noise floor was available to the scan reporting. > > Something might have been available for scan reporting, but if > this "something" made sense is a different question. See my > other mail :-) > > > There are tables to map RSSI -> dBm for each part which should > > be in the firmware spec or seen in the driver code. > > I didn't see such a table so far, where is it? See section 7.3 of the 5.1 spec: 7.3 RSSI and Noise Floor Support The firmware supports the reporting of RSSI and Noise Floor values: • RSSI can be derived by adding Noise Floor to SNR value • Noise Floor is returned in each received packet through the NF field in the Rx Descriptor (dBm). • Signal Quality is determined by RSSI and SNR. Section 3.1 as well (Receive Packet Descriptor): "RSSI should be calculated in the driver as a summation of the SNR and NF" So Marvell doesn't really provide a table, but we'll have to do some investigation here. The RSSI is almost always a random value defined by the manufacturer [1] or in dBm. We're not 100% sure what Marvell is using here, but some investigation will show whether the value is actually in dBm or in some other units. A quick check of the RSSI reported by the current BSS in scan results versus the output of GET_RSSI might show something interesting. Dan -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
