On Mon, Mar 21, 2011 at 1:45 PM, Steve Brown <sbr...@cortland.com> wrote: > I'm trying to replace an existing 900MHz 11000 meter link w/ two Alix > boxes with Ubiquiti XR9's. These are "Atheros Communications Inc. AR5413 > 802.11abg NIC (rev 01)" radios that down convert to the 900MHz ISM > band. > > I'm using a 5MHz channel. The units run flawlessly at short distances, > but repeatedly connect and drop out at 11000 meters. As the current > link's signal is 6dB over noise, I've discounted signal strength as the > problem. My spec analyzer says the part of the band I'm using is fairly > quiet and that the bandwidth of the radios is 5MHz. So, that leaves > coverage class. > > Without the knowledge to verify the coverage class logic, I compared the > values of the IFS_SIFS, IFS_SLOT, IFS_EIFS, IFS_MISC and TIME_OUT > registers for various values of coverage class with the closed hal > madwifi r3314. I used a 20MHz channel. The comparisons are attached. > Given the same coverage class, the values are quite different between > the two drivers. > > I also collected the register values for various coverage classes for > ath5k using a 5MHz channel. The madwifi driver doesn't do 5MHz channels. > The value computed for SIFS_DUR_USEC is 0x40 which is larger than the > mask for that field (0x3f) in IFS_MISC. So that computation is suspect. > Also, the ack/cts timeout values don't get changed from the default > values to the 5MHz values unless a set coverage class command is issued. > I've attached that collection as well. > > I'm not sure where to go from here. > > Steve
That sounds to me like signal strength could indeed be your problem. At 5MHz channel width, you should be restricted to OFDM, and the drivers typically want to give up on OFDM once signal strength dips below 7dB. -Brian _______________________________________________ ath5k-devel mailing list ath5k-devel@lists.ath5k.org https://lists.ath5k.org/mailman/listinfo/ath5k-devel
