Huawei dongle's connection keeps dropping off with a usb cable

I am trying to use a Huawei E3256 dongle in my laptop for my broadband. The mobile broadband signal is rubbish in my room, so I put the dongle in another room where the signal is better, and connect it with a USB cable.

However, when I do that, the connection keeps dropping off, which do NOT happen when I directly plug the dongle into my laptop. I have tried different usb cables and extention cables, and the result is still the same. Would anyone know how to fix this? Many thanks.

My laptop's OS is Vista and 3 is the mobile network I am trying to connect to, if this is any help.

 

How long is the USB cable? Are you aware of the limits of USB cables?

 

Thanks for your reply. I have tried both the 2-meter and the 5-meter types; neither works. :confused