wifi not working on dell laptop in ubuntu

Question

I recently installed ubuntu 12.04 on my machine, but I am not able to use wi-fi in ubuntu. Actually there is a toggle button to turn on the wifi and when the wifi is ON an LED will glow. But all the time I presses that button it don't glow.

So I tried installing the driver form the solution suggested in question: How do I install BCM43142 wireless drivers for Dell Vostro 3460/3560

since the wifi device on my machine is also Broadcom Corporation Device [14e4:4365]. I got the driver successfully installed but still I am not able to turn on the wifi means the LED not glows.

Also here are the output of some commands which might be helpful

lshw -C network

*-network UNCLAIMED
   description: Network controller
   product: Broadcom Corporation
   vendor: Broadcom Corporation
   physical id: 0
   bus info: pci@0000:02:00.0
   version: 01
   width: 64 bits
   clock: 33MHz
   capabilities: bus_master cap_list
   configuration: latency=0
   resources: memory:f1900000-f1907fff

and iwconfig

lo        no wireless extensions.

usb0      no wireless extensions.

here usb0 is what I am using with my mobile connected with data cable to access internet.

And rfkill list

0: dell-wifi: Wireless LAN
        Soft blocked: no
        Hard blocked: no
1: dell-bluetooth: Bluetooth
        Soft blocked: no
        Hard blocked: no

Also one more thing when I toggle the wifi button off the rfkill list gives both in blocked mode.

Please help... Thanks.