参考：

Thinkpad L540, Ubuntu 13.10, ThinkPad Wireless 2 x 2 BGN+BT 4.0: No Wi-Fi.

http://ubuntuforums.org/showthread.php?t=2190347

正文：

Thinkpad Edge E440 安装 Ubuntu12.04 后 无法使用无线网卡， 需要手动安装驱动。

下载驱动原码编译安装：

sudo apt-get install build-essential linux-headers-generic

下载：http://netbook-remix.archive.canonical.com/updates/pool/public/o/oem-wireless-rtl-92ce-92se-92de-8723ae-88ee-8723be-92ee-dkms/oem-wireless-rtl-92ce-92se-92de-8723ae-88ee-8723be-92ee-dkms_0017.1016.2013~sutton1.tar.gz

解压到：~/Desktop/

cd ~/Desktop/oem-wireless-rtl-92ce-92se-92de-8723ae-88ee-8723be-92ee-dkms-0017.1016.2013~sutton1/oem-wireless-rtl-92ce-92se-92de-8723ae-88ee-8723be-92ee-0017.1016.2013~sutton1/driver

make
sudo make install
sudo modprobe rtl8723be