If you are experiencing poor throughput, start by simply restarting your AirPort Extreme. To do so, disconnect power from the Router - then wait 30 seconds before reconnecting power.
After the Router fully reboots (which may take 2-3 minutes), the light on the front of the Router should transition to steady green.
After restarting the AirPort Extreme, you may need to restart your iPad and/or other WiFi devices. Restarting the Router itself resets the volatile DHCP, ARP and routing tables - all of which can have significant influence upon the performance of your WiFi network and internet connection.