This question already has an answer here:
I have installed 12.04 on a dell vostro 2520 (previously 11.10) and wifi is gone now but wired network remains. I've reviewed the other questions and tried this one:
and some stuff but no luck yet. The following is the process so far so hopefully someone can help.
I have the Broadcom bcm43142 chip.
I have made sure in the bios that the wlan is turned on, and it appears the laptop does not have a wireless hardware switch, only the keyboard function shortcut which turns bluetooth on and off on the taskbar but there is no lightup of the wireless function on the laptop itself.
Dell does not appear to have any drivers for ubuntu and google does not appear to be much help :( Perhaps someone can please provide the recovery disk ISO that originally came on the hard drive?
Thanks in advance! .