I looked into several repositories and none of them provide this driver.
Then,when I searched the whole web,I found instructions to install it.
I didn't test if this works so no guarantee for anything...

1. Thanks to others that also had the problem and shared their sources, here is a list of all available Download links for you to use while Mediatek decides to help Linux and open up:
http://www.mediafire.com/download/l3zoch2y1hbcali/RT3290.tar.gz
Rename the file to 2012_0508_RT3290_Linux_STA_v2.6.0.0.tar.bz2 because Mediatek did a great job on making sure the file works correctly.
Extract the file and it should create a folder named DPO_RT3290_LinuxSTA_V2600_20120508
Go to DPO_RT3290_LinuxSTA_V2600_20120508/os/linux/ and edit the file config.mk
On line 31 you should find the variable HAS_NATIVE_WPA_SUPPLICANT_SUPPORT=n. Change it to

HAS_NATIVE_WPA_SUPPLICANT_SUPPORT=y
  and save the file.
Go to your main extracted folder (It should be the DPO_RT3290_LinuxSTA_V2600_20120508 folder) and type:
make
sudo make install
If everything compiled correctly do the following:
modprobe rt3290sta
If step 7 runs without any problems, we add the module to the list of modules to loaded on every boot:

sudo -H gedit /etc/modules
and add a line at the end of the file that says rt3290sta. Save and exit.

https://bbs.deepin.org/user/99187 Please try this and tell us if it works.