I recently bought this wireless-n USB adaptor for use with Ubuntu as I had read it was "Linux compatible", or at least as compatible as a wireless card can be with Linux. It proved tricky to get working, so this post may help others who are thinking of attempting the same thing.

There are basically 2 ways to make this usb dongle work, once you have overcome the first hurdle and discovered that this uses the Realtek 8192 chipset inside.

The easy way
Easiest method is to use the Windows Realtek driver and a nifty program called ndiswrapper (or ndisgtk if you prefer to use a graphical interface). The drawback is this will only give you wireless-g capability, not wireless-n. Here's how (you can get the driver from here if you don't have a driver disk):

unzip UGL2430-U2H2_XP_Vista.zip
sudo ndiswrapper -i XP_Vista/88_91_92_SU_Driver/WinXP2K/net8192su.inf
sudo ndiswrapper -l
sudo ndiswrapper -m
sudo modprobe ndiswrapper
iwconfig

Then you can manage your newly created "wlan0" or "wlan1" device using Network manager, or you can configure it manually if you like.

The hard way (recommended)
To get the full wireless-n potential from this usb dongle you have to compile the Realtek driver from source. The drawback to this process is it is complicated, several prerequisite steps are required.

Download the driver files from here: RealTek_Network_RTL8191SU-driver-download and save it to ~/realtek

Assuming that your kernel version is 2.6.32 (check using uname -r) get the kernel source:

sudo apt-get install build-essential linux-source-2.6.32 linux-headers-generic
cd /usr/src
sudo tar -xvjf linux-source-2.6.32.tar.bz2
sudo ln -s /usr/src/linux-source-2.6.32 /usr/src/linux

If this was all fine, go back and unzip the driver file:

cd ~/realtek
unzip rtl8191SU_usb_linux_v2.6.0006.20100226.zip
cd rtl8191SU_usb_linux_v2.6.0006.20100226/driver
tar fzxv rtl8712_8188_8191_8192SU_usb_linux_v2.6.0006.20100226.tar.gz
cd rtl8712_8188_8191_8192SU_usb_linux_v2.6.0006.20100226/

Now for the crazy part. You now have to hack the source code of the driver to stop it from throwing build errors. Follow the instructions in this blog post first, and then it will build successfully. Do the 'make' and 'make install' as root (sudo su -)

make
make install
depmod -a
modprobe 8712u
iwconfig

Now you should have full wireless-n networking on this device, iwconfig will show "IEEE 802.11bgn" if it was installed correctly.

Edit: Looks like there is now an easier way to do this, explained here on the Ubuntu Forums.