Wireless connection keeps dropping with an Intel 3945ABG card

Question

After updating to 11.10 from 11.04, my wireless connection keeps dropping off from time to time.

Now, I already experience this problem when I was using 10.04 (the workaround back then was to replace NetworkManager with wicd. But the thing is I'm not really a fan of wicd and seeing that the problem seems to have been fixed in previous releases, I think there's a similar solution that I can try.

Here's the some more detail of my system

$ sudo lshw -C network

*-network
       description: Wireless interface
       product: PRO/Wireless 3945ABG [Golan] Network Connection
       vendor: Intel Corporation
       physical id: 0
       bus info: pci@0000:03:00.0
       logical name: wlan0
       version: 02
       serial: 00:19:d2:ad:20:4d
       width: 32 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=iwl3945 driverversion=3.0.0-12-generic firmware=15.32.2.9 ip=192.168.1.3 latency=0 link=yes multicast=yes wireless=IEEE 802.11abg
       resources: irq:44 memory:84100000-84100fff

$ sudo lsmod | grep iwl

iwl3945                73329  0 
iwl_legacy             71499  1 iwl3945
mac80211              272785  2 iwl3945,iwl_legacy
cfg80211              172392  3 iwl3945,iwl_legacy,mac80211

$ dmesg

[43972.920056] wlan0: no IPv6 routers present
[44533.245630] wlan0: deauthenticating from 94:0c:6d:c0:51:ca by local choice (reason=3)
[44533.260462] cfg80211: All devices are disconnected, going to restore regulatory settings
[44533.260472] cfg80211: Restoring regulatory settings
[44533.260488] cfg80211: Calling CRDA to update world regulatory domain
[44533.273177] cfg80211: Ignoring regulatory request Set by core since the driver uses its own custom regulatory domain 
[44533.273181] cfg80211: World regulatory domain updated:
[44533.273184] cfg80211:     (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
[44533.273188] cfg80211:     (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[44533.273191] cfg80211:     (2457000 KHz - 2482000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
[44533.273195] cfg80211:     (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
[44533.273198] cfg80211:     (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[44533.273202] cfg80211:     (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[44534.078574] ADDRCONF(NETDEV_UP): wlan0: link is not ready
[44539.626843] wlan0: authenticate with 94:0c:6d:c0:51:ca (try 1)
[44539.628827] wlan0: authenticated
[44539.629214] wlan0: associate with 94:0c:6d:c0:51:ca (try 1)
[44539.631514] wlan0: RX AssocResp from 94:0c:6d:c0:51:ca (capab=0x411 status=0 aid=1)
[44539.631522] wlan0: associated
[44539.633667] ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[44551.104169] wlan0: no IPv6 routers present
[44987.241475] wlan0: deauthenticating from 94:0c:6d:c0:51:ca by local choice (reason=3)
[44987.288269] cfg80211: All devices are disconnected, going to restore regulatory settings
[44987.288279] cfg80211: Restoring regulatory settings
[44987.288294] cfg80211: Calling CRDA to update world regulatory domain
[44987.309376] cfg80211: Ignoring regulatory request Set by core since the driver uses its own custom regulatory domain 
[44987.309383] cfg80211: World regulatory domain updated:
[44987.309385] cfg80211:     (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
[44987.309389] cfg80211:     (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[44987.309393] cfg80211:     (2457000 KHz - 2482000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
[44987.309396] cfg80211:     (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
[44987.309400] cfg80211:     (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[44987.309403] cfg80211:     (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[44988.074180] ADDRCONF(NETDEV_UP): wlan0: link is not ready
[44993.648439] wlan0: authenticate with 94:0c:6d:c0:51:ca (try 1)
[44993.651354] wlan0: authenticated
[44993.651651] wlan0: associate with 94:0c:6d:c0:51:ca (try 1)
[44993.653990] wlan0: RX AssocResp from 94:0c:6d:c0:51:ca (capab=0x411 status=0 aid=1)
[44993.653995] wlan0: associated
[44993.655984] ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[45005.400035] wlan0: no IPv6 routers present

Thanks,

Solution

Got to say i'm sorry; at that time the code posted here http://ubuntuforums.org/showpost.php?p=11356188&postcount=35 seemd to have worked but haven't.

I found a solution on launchpad which seem to work - /etc/modprobe.d/iwl3945.conf options iwl3945 disable_hw_scan=0. It works even after a system reboot. Cheers!

Comments

[user3129805]

Hi, thanks I tried that but got the following: Error for wireless request "Set Power Management" (8B2C) : SET failed on device wlan0 ; Operation not supported..

[Jras]

Apparently power management for this driver was disabled in newer kernels due to frequent connection drops. Kinda ironic. If you have administration access to the router on your network, you can try different settings - e.g. use 802.11g mode only and strictly WPA, or WPA2 for encryption (if you are on secured network).

[Jras]

Another recommendation is from Ubuntu Forums although it's a speed related problem - ubuntuforums.org/showpost.php?p=11356188&postcount=35 - anyway, if everything fails, WICD still seems to be solution.

[user3129805]

I did seem to make the problem go away (or at least recurring less often) by adding wireless-power off at the end of /etc/network/interfaces and reboot. Now I'm putting the wireless interface under constant load for sometime to see if the problem is indeed fixed.

[user3129805]

Nope. Still getting random disconnect every now and then. :( But the intervals do feels much further apart.

[Jras]

Also, see this question - askubuntu.com/questions/69141/… - again, the solution is to use wicd which isn't as pretty as NM but apparently it just works...