Dtyjlui

I'm using Ubuntu 12.04. I have a problem with my wifi, but not always. My system detects wifi networks some times and display it in the available wifi networks list and is able to connect properly. But, some times it doesn't detect available wifi networks at all.

Can any tell me a way to make Ubuntu look for available wifi networks?

Here is the iwconfig info

ppp0      no wireless extensions.



lo        no wireless extensions.



wwan0     no wireless extensions.



eth1      IEEE 802.11abg  ESSID:off/any  

          Mode:Managed  Access Point: Not-Associated   

          Retry  long limit:7   RTS thr:off   Fragment thr:off

          Power Management:off



eth0      no wireless extensions.

Result of lspci is

Network controller: Broadcom Corporation BCM4313 802.11b/g/n Wireless LAN Controller (rev 01)

Open a terminal. Type the following:

sudo crontab -e  

Now type the following:

* * * * * iwlist eth1 scan  

Save it and exit.

Use this in terminal

   sudo lsmod | grep ipw2200

If it returns some lines then it will ensure that the driver is loaded perfectly or else you have to contact Ubuntu Forms
Or else try this:

open the ‘Synaptic Package Manager‘ (if you are using Ubuntu 11.10 then install it first from the software cemter) and search for ‘bcm’
uninstall the ‘bcm-kernel-source‘ package
make sure that the ‘firmware-b43-installer‘ and the ‘b43-fwcutter‘ packages are installed
type into terminal:

cat /etc/modprobe.d/* | egrep '8180|acx|at76|ath|b43|bcm|CX|eth|ipw|irmware|isl|lbtf|orinoco|ndiswrapper|NPE|p54|prism|rtl|rt2|rt3|rt6|rt7|witch|wl' 

(you may want to copy this till the end if it is not visible properly) and see if the term ‘blacklist bcm43xx‘ is there

if it is, then type cd /etc/modprobe.d/ and then sudo gedit blacklist.conf put a # in front of the line: blacklist bcm43xx then save the file (I was getting error messages in the terminal about not being able to save, but it actually did save properly).
reboot

Use iwlist. The man page (actually http://manpages.ubuntu.com/manpages/wily/en/man8/iwlist.8.html) says:

wlist.8.gz

Provided by: wireless-tools_30~pre9-8ubuntu1_i386



NAME



       iwlist  -  Get  more  detailed  wireless  information  from  a wireless

       interface



SYNOPSIS



       iwlist [interface] scanning

snip...

PARAMETERS



       scan[ning]

              Give the list of Access Points and Ad-Hoc cells  in  range,  and

              optionally  a  whole  bunch  of  information  about them (ESSID,

              Quality, Frequency, Mode...). The type of  information  returned

              depends on what the card supports.

              Triggering  scanning  is  a privileged operation (root only) and

              normal users can only read left-over scan results.  By  default,

              the way scanning is done (the scope of the scan) is dependant on

              the card and card settings.

              This command takes optional arguments, however most drivers will

              ignore  those.  The  option essid is used to specify a scan on a

              specific ESSID. With  some  card/driver,  this  enables  to  see

              hidden  networks.  The  option  last does not trigger a scan and

              read left-over scan results.