Connection breaks frequently with Connection Sharing (3G to WLAN)

[Juhani Jaakola <juhani jaakola kolumbus fi>]

I have a PC with A-Link WL54H WLAN card (driver rt2500pci) and a USB 3G modem. I connect to the Internet via the 3G modem and I want to share that connection with other PCs via WLAN. I'm running Fedora 10.

I connected to Internet with "Auto GSM network connection". Then I chose "Create New Wireless Network..." to share the 3G connection to other PCs with WLAN. I created a network with security NONE. Then I connect to the new ad hoc WLAN network from ThinkPad with Windows XP SP3.

My problem is that the WLAN connection to the ThinkPad breaks very frequently. Last hour the connection broke 13 times! This is what I get in /var/log/messages:

--- begin of /var/log/messages ---
Jan 20 16:45:29 tik NetworkManager: <info>  (wlan0): supplicant connection state:  completed -> associated
Jan 20 16:45:29 tik NetworkManager: <info>  (wlan0): supplicant connection state:  associated -> completed
Jan 20 16:45:32 tik dnsmasq[3661]: DHCPDISCOVER(wlan0) 00:16:6f:05:8e:88 
Jan 20 16:45:32 tik dnsmasq[3661]: DHCPOFFER(wlan0) 10.42.43.10 00:16:6f:05:8e:88 
Jan 20 16:45:32 tik dnsmasq[3661]: Ignoring domain foo-domain.net for DHCP host name otherpc
Jan 20 16:45:32 tik dnsmasq[3661]: DHCPREQUEST(wlan0) 10.42.43.10 00:16:6f:05:8e:88 
Jan 20 16:45:32 tik dnsmasq[3661]: DHCPACK(wlan0) 10.42.43.10 00:16:6f:05:8e:88 otherpc
Jan 20 16:46:53 tik NetworkManager: <info>  (wlan0): supplicant connection state:  completed -> associated
Jan 20 16:46:53 tik NetworkManager: <info>  (wlan0): supplicant connection state:  associated -> completed
Jan 20 16:48:18 tik dnsmasq[3661]: DHCPRELEASE(wlan0) 10.42.43.10 00:16:6f:05:8e:88 
Jan 20 16:48:40 tik dnsmasq[3661]: DHCPDISCOVER(wlan0) 00:16:6f:05:8e:88 
Jan 20 16:48:40 tik dnsmasq[3661]: DHCPOFFER(wlan0) 10.42.43.10 00:16:6f:05:8e:88 
Jan 20 16:48:40 tik dnsmasq[3661]: Ignoring domain foo-domain.net for DHCP host name otherpc
Jan 20 16:48:40 tik dnsmasq[3661]: DHCPREQUEST(wlan0) 10.42.43.10 00:16:6f:05:8e:88 
Jan 20 16:48:40 tik dnsmasq[3661]: DHCPACK(wlan0) 10.42.43.10 00:16:6f:05:8e:88 otherpc
--- end of /var/log/messages ---

And /var/log/wpa_supplicant.log contains the following lines repeated many times:

--- begin of quote ---
Associated with 02:16:6f:10:ef:33
CTRL-EVENT-CONNECTED - Connection to 02:16:6f:10:ef:33 completed (reauth) [id=0 id_str=]
--- end of quote ---

ps -ef shows the following arguments for the key processes:

NetworkManager --pid-file=/var/run/NetworkManager/NetworkManager.pid

/usr/sbin/pppd nodetach lock nodefaultroute ttyUSB0 noipdefault usepeerdns lcp-echo-failure 0 lcp-echo-interval 0 ipparam /org/freedesktop/NetworkManager/PPP/0 plugin /usr/lib/pppd/2.4.4/nm-pppd-plugin.so

/usr/sbin/dnsmasq --no-hosts --keep-in-foreground --bind-interfaces --no-poll --except-interface=lo --listen-address=10.42.43.1 --dhcp-range=10.42.43.10,10.42.43.100,60m --dhcp-option=option:router,10.42.43.1 --dhcp-lease-max=50 --pid-file=/var/run/nm-dnsmasq-wlan0.pid

/usr/sbin/wpa_supplicant -c /etc/wpa_supplicant/wpa_supplicant.conf -u -f /var/log/wpa_supplicant.log

My versions are:

kernel-2.6.27.9-159.fc10.i686
NetworkManager-0.7.0-1.git20090102.fc10.i386
dnsmasq-2.45-1.fc10.i386
wpa_supplicant-0.6.4-2.fc10.i386