Hi all, I have some behaviour I'm observing with some Atheros cards we use that doesn't seem to match what the initvals of ath5k are set up to. These are the cards I used: http://www.mini-box.com/s.nl/it.A/id.387/.f
I have run a saturated iPerf flow on a conducted testbed with both stations being inside RF-shielding boxes. They are set to 802.11a mode, on channel 1. I then parse the trace, looking for ACK-DATA pairs, and calculating the time difference between them. From this, I remove the TX_TIME of the DATA frame, as well as a DIFS: ACK_TIMESTAMP + DIFS + CONTENTION_TIME + DATA_TX_TIME = DATA_TIMESTAMP which will leave me with the CONTENTION_TIME. Dividing this time by a SLOT_TIME will give me the slot which was chosen by the hardware. According to the driver, in ath5k.h: #define AR5K_TUNE_CWMIN 15 CWMIN is initialised to 15. The actual distribution of contention slots I'm observing resembles this: Slot Number,Count 0,1315 1,1302 2,1249 3,1291 4,1347 5,1219 6,1249 7,0 8,0 9,0 <truncated> as well as 1360 frames which came in with a negative CONTENTION_TIME. Ignoring the fact that some frames are coming up with a negative CONTENTION_TIME (which potentially points to another problem), what is being observed here is that CW_MIN appears to start at 7, rather than the 15 which it should be. I'm just wondering if anyone would have any idea why this is occurring? Thanks, -- Jonathan Guerin
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