Broadcom Wireless driver can be installed using Additional Drivers application in Ubuntu 12.04, 11.10, 11.04, 10.10, 10.04.
To Open Additional Driver Application
If your using Unity then goto dashhome and search for Additional Drivers, then open it. Check the screen shot below.
Others, goto System->Administration->Additional Drivers. Check the screen shot below.
Once you open the application it will search for the available drivers, for your machine. Check the screen shot below.
After searching it will show you a list of drivers available for your machine, check the screen shot below.
From the list select Broadcom Wireless Driver and click on the Activate button. Provide password for the user when prompted
Once it finish installing the driver, Restart your system.
After restarting your system the driver is activated and you can use the wireless network.
Broadcom STA Wireless driver
This package contains Broadcom 802.11 Linux STA wireless driverfor use with Broadcom’s BCM4311-, BCM4312-, BCM4313-, BCM4321-,BCM4322-, BCM43224-, and BCM43225-, BCM43227- and BCM43228-basedhardware.
Broadcom B43 Wireless driver
This package installs the firmware needed for usage of the b43 kerneldriver. Supported chipsets:- BCM4312 (with Low-Power aka LP-PHY)
Hope this will be helpful for you!!!