[LEDE-DEV] Bug in ath9k coverage distance

Koen Vandeputte koen.vandeputte at ncentric.com
Tue Jun 7 04:02:45 PDT 2016


Hi all,

Chaoscalmer has a lot less wifi bandwidth when coverage class is increased.
Even when 2 devices are only a few meters apart.

In Barrierbreaker release, the rates were a lot higher in this usecase.

When doing Iperf benchmarks (~ 30 sec);

  * The barrierbreaker 14.07 release is able to hit ~53Mbit from start
    to finish
  * Chaoscalmer starts at ~6Mbit/s, than slowly goes up to ~20Mbit/s.
    But starts at 6 again when the test is repeated


Hardware used for testing:

2x Gateworks Laguna CNS3xxx    + AR9280 (Ubnt sr71-15)
2x Gateworks Ventana IMX-6        + AR9300 (WLE350NX)


Branch tested:

5770678122e76079debd6eeeb118f32e3fc78b84 (Master @ June 1st 2016)


Following setup:

  * 2 identical devices
  * IBSS mode using wpa_supplicant WPA2
  * 2 meter apart
  * Free 5GHz channel (confirmed using spectrum analyzer)
  * HT20 (HT40 has same behaviour)


  * Coverage class 32 (up to 14400m)

Iperf using BarrierBreaker build: ~52Mbit/s
Iperf using ChaosCalmer build: ~6Mbit/s


  * Coverage class 16 (up to 7200m)

Iperf using BarrierBreaker build: ~53Mbit/s
Iperf using ChaosCalmer build: ~12Mbit/s


  * Dynack

Iperf using BarrierBreaker build: ~55Mbit/s
Iperf using ChaosCalmer build: ~53Mbit/s


Steps taken without success:

  * Upgraded wpa_supplicant to latest trunk
  * Checked ath9k code hw.c & recv.c (Acktime, slottime, etc. But code 
doesn't differ between BB release and Master branch)
  * Disabled any possible background scanning
  * Patches deleted - In delta to BB release: (in kernel/mac80211/patches)

--> 326-ath9k-make-NF-load-complete-quickly-and-reliably.patch
--> 330-mac80211-minstrel-Change-expected-throughput-unit-ba.patch
--> 334-mac80211-fix-wiphy-supported_band-access.patch
--> 335-mac80211-minstrel_ht-set-A-MSDU-tx-limits-based-on-s.patch
--> 336-mac80211-minstrel_ht-set-default-tx-aggregation-time.patch
--> 337-mac80211-minstrel_ht-fix-a-logic-error-in-RTS-CTS-ha.patch
--> 343-mac80211-minstrel_ht-improve-sample-rate-skip-logic.patch


Not yet checked:

  * Minstrel_ht


If more information is required, please let me know.

Thanks,

Koen Vandeputte
nCentric Europe



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