Hi,
Please ensure you have your router communicating on a non congested wireless channel. You can go to the Google Play store and search for the Amped Wireless Wifi Analytics tool>download it>it will tell you the least congested channels to use as well as other tools.
You may also download the program called InSSIDer if you have a windows based laptop and it will also scan networks and provide the congestion data as well.
From there you would go to the following Router Control Panel area (general example-yours may vary):
More Settings>2.4Ghz Settings>Basic Settings>Select the channel that is the least congested>Apply
Do the same for the 5Ghz band as well.