I've recently bought Lenovo z5070, I've installed on it both windows 8.1 and Ubuntu 14.04.2 trusty. I have some serous problem with Wi-Fi in Ubuntu.
First, when I turn on laptop at that moment the Wi-Fi connect correctly but after sometimes if I want to change my access point or if the Wi-Fi be disconnected, the Wi-Fi won't connect again or sometime ask for password and even I enter the password correctly the Wi-Fi won't connect to access point again and I have to restart.
Second problem is that I'm using the access points of university so I need to connect to the VPN server of university to accessing the global internet, VPN connection be disconnected after sometimes and won't connect again.
Third problem and the strangest problem is that when I connected to the access point and I have connection with VPN server, the speed of connection is so low and it's look like that I've not connected to the net.
Model of my wireless card is Realtek RTL8723BE.
The output of wireless diagnostics right after starting my labtop is here
The wireless was connected to the net but it can't receive any data. I disconnect it and connect it again(that was fortunate that it connects again). I ran the wireless diagnostics and the output of it is here