802.11n performance for AR9280

[Gleb Romanov]

Hello,

I have a question about 802.11n performance for AR9280 ( my card is Ubiquiti SR71E ) in hostap mode. To measure performance, I'm looking at the download speeds from my file server (Samba) through a FreeBSD AP to a laptop with Centrino 6300 (agn 3x3:3).
I see 3-4 MBytes/s on the 2.4 GHz band (using ht/20 or ht/40 - doesn't matter) and around 5-6 MB/s on the 5 GHz band (ht/40). 
The laptop is running Win 7 and can do 8-9 MB/s with a commercial AP (2.4 GHz  ht/20  2x2:2)

I run 9.1-RELEASE GENERIC and the question is this is the expected performance (from 9.1 RELEASE ) or I'm just doing something wrong? May be bad antennas or wires?
If it is expected and I need to switch to HEAD to do better, can I only update the "ATH_module_releated_stuff" and leave the rest of the base untouched?
Any comments would be helpful!

Gleb


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Here is some info about the system:
Right now it is configured for 2.4 GHz simply because of the range. With 5 GHz I need to in the same room with the AP to get the speeds I mentioned.

uname -a
FreeBSD fwall 9.1-RELEASE FreeBSD 9.1-RELEASE #0 r243825: Tue Dec  4 09:23:10 UTC 2012     root at farrell.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64

pciconf -lv
ath0 at pci0:3:0:0:        class=0x028000 card=0x4e050777 chip=0x002a168c rev=0x01 hdr=0x00
    vendor     = 'Atheros Communications Inc.'
    device     = 'AR928X Wireless Network Adapter (PCI-Express)'
    class      = network

/etc/rc.conf
wlans_ath0="wlan0"
create_args_wlan0="wlanmode hostap"
ifconfig_wlan0="apbridge mode 11ng ht channel 3:ht/40"
hostapd_enable="YES"    #for wlan0
hostapd_program="/usr/local/sbin/hostapd"   #run from port instead of base

ifconfig
wlan0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
        ether 00:15:6d:85:25:13
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
        media: IEEE 802.11 Wireless Ethernet autoselect mode 11ng <hostap>
        status: running
        ssid badaboom-n channel 3 (2422 MHz 11g ht/40+) bssid 00:15:6d:85:25:13
        country US ecm authmode WPA2/802.11i privacy MIXED deftxkey 2
        AES-CCM 2:128-bit AES-CCM 3:128-bit txpower 27 scanvalid 60
        protmode CTS -htcompat -ampdu ampdulimit 64k ampdudensity 8 -amsdu
        smps wme burst dtimperiod 1 -dfs

/etc/hostapd.conf: 
ht_capab=[HT40+][SHORT-GI-20][SHORT-GI-40][TX-STBC][RX-STBC12][DELAYED-BA][MAX-AMSDU-7935][DSSS_CCK-40][LDPC][GF][SMPS-DYNAMIC][PSMP][LSIG-TXOP-PROT]
(Here I used all available options. I don't see any difference between using the line and commenting it out. Huh?)