Ubuntu/Mint (trusty) : Wifi keeps shutting down

I Run Mint on my desktop and I'm facing a very annoying problem : wifi keeps shutting down after a few minutes or a few hours and it never comes back automatically.

To restore network, I have to manually run :

sudo service network-manager restart

I have several other devices connected and no problem with them.

My network controller :

lspci | grep Network
02:00.0 Network controller: Qualcomm Atheros AR93xx Wireless Network Adapter (rev 01)

Linux :

uname -a
Linux nunux 3.13.0-24-generic #47-Ubuntu SMP Fri May 2 23:30:00 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

Log :

tail -f /var/log/syslog

<incoming wifi permanent shutdown, starting from these lines>

Jan 17 14:27:25 nunux wpa_supplicant[976]: message repeated 5 times: [ wlan0: CTRL-EVENT-SCAN-STARTED ]
Jan 17 14:27:50 nunux wpa_supplicant[976]: wlan0: CTRL-EVENT-DISCONNECTED bssid=16:ae:67:0d:aa:dc reason=4 locally_generated=1
Jan 17 14:27:31 nunux NetworkManager[27991]: message repeated 5 times: [ <warn> nl_recvmsgs() error: (-33) Dump inconsistency detected, interrupted]
Jan 17 14:27:50 nunux NetworkManager[27991]: <warn> Connection disconnected (reason -4)
Jan 17 14:27:50 nunux kernel: [702301.796637] cfg80211: Calling CRDA to update world regulatory domain
Jan 17 14:27:50 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: completed -> disconnected
Jan 17 14:27:50 nunux kernel: [702301.802743] cfg80211: World regulatory domain updated:
Jan 17 14:27:50 nunux kernel: [702301.802745] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
Jan 17 14:27:50 nunux kernel: [702301.802747] cfg80211:   (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Jan 17 14:27:50 nunux kernel: [702301.802749] cfg80211:   (2457000 KHz - 2482000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Jan 17 14:27:50 nunux kernel: [702301.802750] cfg80211:   (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
Jan 17 14:27:50 nunux kernel: [702301.802751] cfg80211:   (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Jan 17 14:27:50 nunux kernel: [702301.802752] cfg80211:   (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
Jan 17 14:27:50 nunux wpa_supplicant[976]: wlan0: CTRL-EVENT-SCAN-STARTED 
Jan 17 14:27:50 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: disconnected -> scanning
Jan 17 14:27:52 nunux wpa_supplicant[976]: wlan0: SME: Trying to authenticate with 16:ae:67:0d:aa:dc (SSID='freebox_cyrille' freq=2462 MHz)
Jan 17 14:27:52 nunux kernel: [702303.549641] wlan0: authenticate with 16:ae:67:0d:aa:dc
Jan 17 14:27:52 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: scanning -> authenticating
Jan 17 14:27:52 nunux kernel: [702303.564745] wlan0: send auth to 16:ae:67:0d:aa:dc (try 1/3)
Jan 17 14:27:52 nunux kernel: [702303.690627] wlan0: send auth to 16:ae:67:0d:aa:dc (try 2/3)
Jan 17 14:27:52 nunux kernel: [702303.773740] wlan0: send auth to 16:ae:67:0d:aa:dc (try 3/3)
Jan 17 14:27:52 nunux kernel: [702303.892245] wlan0: authentication with 16:ae:67:0d:aa:dc timed out
Jan 17 14:27:52 nunux NetworkManager[27991]: <info> (wlan0): roamed from BSSID 16:AE:67:0D:AA:DC (freebox_cyrille) to (none) ((none))
Jan 17 14:27:52 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: authenticating -> disconnected
Jan 17 14:27:53 nunux wpa_supplicant[976]: wlan0: CTRL-EVENT-SCAN-STARTED 
Jan 17 14:27:53 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: disconnected -> scanning
Jan 17 14:27:54 nunux wpa_supplicant[976]: wlan0: SME: Trying to authenticate with 16:ae:67:0d:aa:dc (SSID='freebox_cyrille' freq=2462 MHz)
Jan 17 14:27:54 nunux kernel: [702306.080545] wlan0: authenticate with 16:ae:67:0d:aa:dc
Jan 17 14:27:54 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: scanning -> authenticating
Jan 17 14:27:54 nunux kernel: [702306.095800] wlan0: direct probe to 16:ae:67:0d:aa:dc (try 1/3)
Jan 17 14:27:55 nunux kernel: [702306.299217] wlan0: direct probe to 16:ae:67:0d:aa:dc (try 2/3)
Jan 17 14:27:55 nunux kernel: [702306.503176] wlan0: direct probe to 16:ae:67:0d:aa:dc (try 3/3)
Jan 17 14:27:55 nunux kernel: [702306.707096] wlan0: authentication with 16:ae:67:0d:aa:dc timed out
Jan 17 14:27:55 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: authenticating -> disconnected
Jan 17 14:27:56 nunux wpa_supplicant[976]: wlan0: CTRL-EVENT-SCAN-STARTED 
Jan 17 14:27:56 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: disconnected -> scanning
Jan 17 14:27:58 nunux wpa_supplicant[976]: wlan0: SME: Trying to authenticate with 16:ae:67:0d:aa:dc (SSID='freebox_cyrille' freq=2462 MHz)
Jan 17 14:27:58 nunux kernel: [702309.395341] wlan0: authenticate with 16:ae:67:0d:aa:dc
Jan 17 14:27:58 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: scanning -> authenticating
Jan 17 14:27:58 nunux kernel: [702309.410560] wlan0: direct probe to 16:ae:67:0d:aa:dc (try 1/3)
Jan 17 14:27:58 nunux kernel: [702309.614027] wlan0: direct probe to 16:ae:67:0d:aa:dc (try 2/3)
Jan 17 14:27:58 nunux kernel: [702309.817970] wlan0: direct probe to 16:ae:67:0d:aa:dc (try 3/3)
Jan 17 14:27:58 nunux kernel: [702310.021894] wlan0: authentication with 16:ae:67:0d:aa:dc timed out
Jan 17 14:27:58 nunux wpa_supplicant[976]: wlan0: CTRL-EVENT-SSID-TEMP-DISABLED id=0 ssid="freebox_cyrille" auth_failures=1 duration=10
Jan 17 14:27:58 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: authenticating -> disconnected
Jan 17 14:28:03 nunux wpa_supplicant[976]: wlan0: CTRL-EVENT-SCAN-STARTED 
Jan 17 14:28:03 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: disconnected -> scanning
Jan 17 14:28:05 nunux NetworkManager[27991]: <warn> (wlan0): link timed out.
Jan 17 14:28:05 nunux NetworkManager[27991]: <info> (wlan0): device state change: activated -> failed (reason 'SSID not found') [100 120 53]
Jan 17 14:28:05 nunux NetworkManager[27991]: <info> NetworkManager state is now DISCONNECTED
Jan 17 14:28:05 nunux NetworkManager[27991]: <warn> Activation (wlan0) failed for connection 'Auto freebox_cyrille'
Jan 17 14:28:05 nunux dbus[586]: [system] Activating service name='org.freedesktop.nm_dispatcher' (using servicehelper)
Jan 17 14:28:05 nunux NetworkManager[27991]: <info> (wlan0): device state change: failed -> disconnected (reason 'none') [120 30 0]
Jan 17 14:28:05 nunux NetworkManager[27991]: <info> (wlan0): deactivating device (reason 'none') [0]
Jan 17 14:28:05 nunux dbus[586]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Jan 17 14:28:05 nunux NetworkManager[27991]: <info> (wlan0): canceled DHCP transaction, DHCP client pid 28011
Jan 17 14:28:05 nunux avahi-daemon[694]: Withdrawing address record for fe80::eade:27ff:fe08:a434 on wlan0.
Jan 17 14:28:05 nunux avahi-daemon[694]: Leaving mDNS multicast group on interface wlan0.IPv6 with address fe80::eade:27ff:fe08:a434.
Jan 17 14:28:05 nunux avahi-daemon[694]: Interface wlan0.IPv6 no longer relevant for mDNS.
Jan 17 14:28:05 nunux kernel: [702317.110822] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
Jan 17 14:28:05 nunux avahi-daemon[694]: Withdrawing address record for 192.168.0.11 on wlan0.
Jan 17 14:28:05 nunux avahi-daemon[694]: Leaving mDNS multicast group on interface wlan0.IPv4 with address 192.168.0.11.
Jan 17 14:28:05 nunux avahi-daemon[694]: Interface wlan0.IPv4 no longer relevant for mDNS.
Jan 17 14:28:05 nunux NetworkManager[27991]: <warn> DNS: plugin dnsmasq update failed
Jan 17 14:28:05 nunux NetworkManager[27991]: <info> Removing DNS information from /sbin/resolvconf
Jan 17 14:28:05 nunux dnsmasq[28030]: setting upstream servers from DBus
Jan 17 14:28:05 nunux NetworkManager[27991]: <warn> Couldn't disconnect supplicant interface: This interface is not connected.
Jan 17 14:28:07 nunux NetworkManager[27991]: <info> (wlan0): supplicant interface state: scanning -> inactive

Please, tell me you know what's going. It has driven me crazy for too many months.