Wireless connection with an Atheros AR9285 keeps dropping every 20 minutes

Question

There are other questions on this but none have been taken very far in their analysis.

I get disconnects very often - sometimes every 20 mins or so, but sometimes even every few minutes.

The way I have been getting around it is to disconnect from the Wifi connection and reconnect - and then it works fine again until the next disconnect.

I am running Ubuntu 11.04 on an ASUS A52F. Can anyone help me please?

EDIT: My investigations have led me to believe this might be the router, as the same problem is duplicated on my gf's HTC smartphone. Any ideas of how to solve?

Output of lspci | grep -i net

02:00.0 Network controller: Atheros Communications Inc. AR9285 Wireless Network Adapter (PCI-Express) (rev 01) 04:00.5 
Ethernet controller: JMicron Technology Corp. 
JMC250 PCI Express Gigabit Ethernet Controller (rev 03)

Answer 1

Try this command,

sudo dhclient -v

There shouldn't be any errors. My successful output looks like this,

Listening on LPF/eth3/00:e0:52:ce:a0:f6
Sending on   LPF/eth3/00:e0:52:ce:a0:f6
Listening on LPF/eth2/00:50:43:00:f5:c7
Sending on   LPF/eth2/00:50:43:00:f5:c7
Listening on LPF/eth0/20:cf:30:4f:60:43
Sending on   LPF/eth0/20:cf:30:4f:60:43
Sending on   Socket/fallback
DHCPDISCOVER on eth3 to 255.255.255.255 port 67 interval 3
DHCPREQUEST of 192.168.11.100 on eth2 to 255.255.255.255 port 67
DHCPREQUEST of 192.168.1.107 on eth0 to 255.255.255.255 port 67
DHCPACK of 192.168.1.107 from 192.168.1.1
RTNETLINK answers: File exists
bound to 192.168.1.107 -- renewal in 40407 seconds.

Answer 2

Try this:

echo "options ath9k nohwcrypt=1" | sudo tee /etc/modprobe.d/ath9k.conf

sudo modprobe -rfv ath9k
sudo modprobe -v ath9k`

And make sure that your router is set on WPA2 encryption.

Answer 3

This is due to a DHCP lease time with a router/DHCP router. Check this file and see what the renewal times are.

 vi /var/lib/dhcp/dhclient.leases

A lease looks like this.

lease {
  interface "eth0";
  fixed-address 192.168.1.107;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 86400;
  option routers 192.168.1.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.1.1;
  option domain-name-servers 208.67.222.222,208.67.220.220,8.8.8.8,4.2.2.2,68.94.156.1;
  option dhcp-renewal-time 43200;
  option dhcp-rebinding-time 75600;
  option host-name "bust0ut5";
  renew 0 2012/03/04 00:29:06;
  rebind 0 2012/03/04 10:44:45;
  expire 0 2012/03/04 13:44:45;
}