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I'm testing my new home 802.11n network.

router - slax 7, kernel 3.8.2, AR9382 mini pci-e (sparklan WPEA-121N)

wlan0     IEEE 802.11abgn  ESSID:"xyz"
          Mode:Ad-Hoc  Frequency:2.412 GHz  Cell: 96:77:38:F7:80:C8
          Tx-Power=16 dBm
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:on

desktop - slackware 14.1, kernel 3.10.17, AR9287 pci-e x1 (tp-link TL-WN881ND)

wlan0     IEEE 802.11bgn  ESSID:"xyz"
          Mode:Ad-Hoc  Frequency:2.412 GHz  Cell: 96:77:38:F7:80:C8
          Tx-Power=20 dBm
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off

laptop - windows 7, intel centrino advanced-n 6205

All computers are in the same place, standing next to each other, InSSIDer shows no interference with other networks, very good signal quality. All wireless adapters can theoretically work in 802.11n 300Mbps speed.

I set up ad-hoc network with iw wlan0 ibss join xyz 2412 HT40+

I'm testing speed with iperf. I can't get more than 3-4Mbps between any of my devices. When using 802.11g (NOHT option) I get 17-19Mbps between my desktop and server. Laptop still at 4Mbps.

Whats going on? Why I can't reach even 50% of 802.11g?

When doing iwlist wlan0 scan I never see available bitrates > 54Mb/s for my network.

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The speeds promised for 802.11g are theoretical maximum speeds, and any of a lot of factors -- such as other networks using the same frequency ranges in your neighborhood -- will slow it down. –  samiam Feb 2 at 0:21

1 Answer 1

A good starting point for debugging is:

/sys/kernel/debug/ieee80211/phy0/netdev:wlan0/stations/98:d6:f7:xx:xx:xx/rc_stats

    HT    MCS   Rate    Success    Retries   XRetries        PER
                1.0:          0          0          0          0
                2.0:          0          0          0          0
                5.5:          0          0          0          0
               11.0:          0          0          0          0
  HT20      1  13.0:          0          0          0          0
  HT20      2  19.5:          0          0          0          0
  HT20      3  26.0:          6          3          0          0
  HT20      4  39.0:         50         41         14         14
  HT20      5  52.0:         36         96         36         12
  HT20      6  58.5:          7         84         42         48
  HT20      7  65.0:          0          2          4         40

It shows what rates you use. Any other information in /sys/kernel/debug/ieee80211/ is very useful.

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