Get Qualcomm Atheros AR93xx Wireless Network Adapter to work under Ubuntu 14.04

I'm trying to install TP-Link TL-WDN4800 Adapter with Ath9k under trusty. It should work just out of the box for windows and linux. On windows it works, but on ubuntu 14.04 (same computer) it doesn't. Sometimes I am able to connect, but then the internet is still veeeery slow.

I also changed the bandwidth of the router from "20/40 MHz (auto)" to "20 MHz". After that, I wasn't able to connect to the wlan at all. So I changed it back.

From all solutions I have read in the internet so far, nothing works.

Network manager can see the ssids of different networks, but fails to connect.

$ uname -r
3.13.0-43-generic


$ sudo lshw -C network
  *-network               
       description: Ethernet interface
       product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
       vendor: Realtek Semiconductor Co., Ltd.
       physical id: 0
       bus info: pci@0000:01:00.0
       logical name: eth0
       version: 0c
       serial: 44:8a:5b:a0:12:03
       size: 1Gbit/s
       capacity: 1Gbit/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl8168g-2_0.0.1 02/06/13 ip=192.168.0.110 latency=0 link=yes multicast=yes port=MII speed=1Gbit/s
       resources: irq:91 ioport:e000(size=256) memory:fea00000-fea00fff memory:d0800000-d0803fff
  *-network
       description: Wireless interface
       product: AR93xx Wireless Network Adapter
       vendor: Qualcomm Atheros
       physical id: 0
       bus info: pci@0000:02:00.0
       logical name: wlan0
       version: 01
       serial: c4:6e:1f:1f:b0:78
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list rom ethernet physical wireless
       configuration: broadcast=yes driver=ath9k driverversion=3.13.0-43-generic firmware=N/A latency=0 link=no multicast=yes wireless=IEEE 802.11abgn
       resources: irq:36 memory:fe900000-fe91ffff memory:fe920000-fe92ffff


$ lspci -nn | grep -i net 
    01:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 0c)
    02:00.0 Network controller [0280]: Qualcomm Atheros AR93xx Wireless Network Adapter [168c:0030] (rev 01)

Just in case someone wants to point me to firmware-atheros:

E: Unable to locate package firmware-atheros

any help would be appreciated

EDIT:

I tried what was suggested:

$ cat /etc/modprobe.d/ath9k.conf 
  options ath9k nohwcrypt=1

But that did not help. So I tried to understand the output of dmesg

[ 1835.890681] wlan0: authenticate with f0:7d:68:83:97:82
[ 1835.903235] wlan0: send auth to f0:7d:68:83:97:82 (try 1/3)
[ 1836.449019] wlan0: send auth to f0:7d:68:83:97:82 (try 2/3)
[ 1836.905084] wlan0: authenticated
[ 1840.903373] wlan0: deauthenticating from f0:7d:68:83:97:82 by local choice (reason=3)
[ 1860.900842] wlan0: authenticate with 64:70:02:5c:0c:56
[ 1860.908795] wlan0: send auth to 64:70:02:5c:0c:56 (try 1/3)
[ 1862.399231] wlan0: send auth to 64:70:02:5c:0c:56 (try 2/3)
[ 1862.911212] wlan0: authenticated
[ 1865.907029] wlan0: deauthenticating from 64:70:02:5c:0c:56 by local choice (reason=3)
[ 1885.899599] wlan0: authenticate with 64:70:02:5c:0c:56
[ 1885.907701] wlan0: send auth to 64:70:02:5c:0c:56 (try 1/3)
[ 1887.398561] wlan0: send auth to 64:70:02:5c:0c:56 (try 2/3)
[ 1887.906374] wlan0: authenticated
[ 1890.907982] wlan0: deauthenticating from 64:70:02:5c:0c:56 by local choice (reason=3)

Right after authentication, wlan is deauthenticated (what is reason=3?). I dn't know why.

EDIT2: I also tried this answer: sudo killall wpa_supplicant Oddly, that helped me to connect, but it didn't really work (veeery slow connection).

This time dmesg says:

[ 3166.968051] cfg80211: Calling CRDA to update world regulatory domain
[ 3166.976276] cfg80211: World regulatory domain updated:
[ 3166.976281] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
[ 3166.976284] cfg80211:   (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[ 3166.976286] cfg80211:   (2457000 KHz - 2482000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[ 3166.976289] cfg80211:   (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
[ 3166.976291] cfg80211:   (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[ 3166.976293] cfg80211:   (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[ 3168.753735] wlan0: authenticate with 64:70:02:5c:0c:56
[ 3168.764904] wlan0: send auth to 64:70:02:5c:0c:56 (try 1/3)
[ 3169.764107] wlan0: authenticated
[ 3169.771922] ath9k 0000:02:00.0 wlan0: disabling HT/VHT due to WEP/TKIP use
[ 3169.779500] wlan0: associate with 64:70:02:5c:0c:56 (try 1/3)
[ 3171.081643] wlan0: associate with 64:70:02:5c:0c:56 (try 2/3)
[ 3171.777353] wlan0: RX AssocResp from 64:70:02:5c:0c:56 (capab=0x431 status=0 aid=1)
[ 3171.777634] wlan0: associated

UPDATE: With EDIMAX WLan Stick (8€) everything works out of the box. But with TP-Link TL-WDN4800 (35€) I have these problems...

As stated in the answer and comments the solution could be to remove TKIP. But I have a secondary router in repeater mode and that doesn't work with AES (don't know why). However, I don't see why removing TKIP would help, when connection is possible with different wlan adapters.

But still I'd love to get the TP-Link Wlan adapter to work under Ubuntu.