In my Ubuntu 12.04 sony vaio when trying to download packages from Ubuntu repositories wifi speed is very slow. Internet works fine for other downloads/browsing. I tried with changing the download server but no change. Getting a download speed <1kbps.
1 Answer
What worked for me is running the commands below in sequence:
sudo iwconfig wlan0 power off
sudo iwconfig
Basically, it turns of the power management system to mess with the wifi adapter. You may try other Ubuntu wireless problem fixes listed in this page. For me they did not work.