how to install firmware for wifi when lan is not working

[Abhishek Dixit]

I recently installed Ubuntu 11.04 on my laptop.
Wireless is not working.
I do not have a lan card working  so as to  connect to it and use.Any
how I want to use the wifi so what do I need to install on it.
I will need to download any thing in the windows OS only (my laptop is
dual boot) and then install in Ubuntu.
So how should I go on.
lspci out put of my device is

0c:00.0 Network controller [0280]: Broadcom Corporation BCM4312
802.11b/g LP-PHY [14e4:4315] (rev 01)
	Subsystem: Dell Wireless 1397 WLAN Mini-Card [1028:000c]
	Flags: bus master, fast devsel, latency 0, IRQ 17
	Memory at f69fc000 (64-bit, non-prefetchable) [size=16K]
	Capabilities: <access denied>
	Kernel driver in use: b43-pci-bridge
	Kernel modules: ssb



-- 
Regards
Abhi