On 11/23/2011 1:06 AM, Mohammed Shafi wrote: > > Hi Daniel, > > sorry was busy with some other urgent work. a value upto 127 seems to > be valid for Atheros chipsets, bad -128 > http://en.wikipedia.org/wiki/Received_signal_strength_indication :) > further the negative value should be caught by the check in > ath9k_process_rssi unless my_beacon is 'false' hope i had not missed > something. > > if (rx_stats->rs_rssi< 0) > rx_stats->rs_rssi = 0; > > i will test this behavior and do further investigation. > >
Hey Shafi, No worries, I completely understand. So while 127 is a valid value for the chip, the reality is that it would not be (legally) possible. if the noise floor is -90dBm and the RSSI was 127 then the signal power at the antenna would have been 37dBm. Even if the TX antenna was right next to the RX antenna that would still be more powerful than what is legally allowed by the FCC. In this case the devices creating the offending traffic are Android smartphones (a HTC and a Motorola; based off of MAC), which typically have a max tx power around 15dBm, which again with a -90dBm noise floor would have a RSSI of 105 in a zero-loss free space. All those numbers are theoretical so for a baseline I set a Nokia N900 right next to the antenna (antenna is ~5' away and has a 6' coax whip) the largest signal strength (rssi + noise) I saw was -29dBm. For testing, take a look at the analysis that Adrian and I have been pursuing. It seems that the invalid RSSI occur for aggregate frames when there are still additional frames left in the aggregate, i.e. rs_isaggr and rs_moreaggr are both set. Thanks for taking some time to help look at this! Daniel _______________________________________________ ath9k-devel mailing list [email protected] https://lists.ath9k.org/mailman/listinfo/ath9k-devel
