Skype requires only 1.5Mbps/1.5Mbps for both download and upload speeds in order to achieve satisfactory performance. To have an uninterrupted video call with clear sound and image, one may need higher download/upload speeds. Sometimes, a Skype connection is simply unstable due to other factors, i.e. the weather, the server and so on. One cannot say absolutely the ideal Internet speed in some of these cases. I suggest that students conduct a Skype video call with family or friends to ensure the connection is good enough. Through this website called SpeedTest, you can test your current Internet speed. The bandwidth I am currently using here in Taipei is: Download Speed 60Mbps/Upload Speed 20Mbps.
You do not need to have a speed as fast as mine in order to have Chinese tutorial lessons. A long-term student of mine located in Canada uses 25Mbps/10Mbps and another long-term student in Italy uses 30Mbps/3Mbps. Our lessons rarely have any connection issues. It can be helpful to use wired Internet rather than wireless Internet during Skype video calls. Wired Internet simply allows the connection on your computer to be more stable, for you are not replying on the WI-FI signal.