I agree with the above. Make sure your router is not a "B" band (slow) router and you are using at least a "G" band router set in g & b mode or g mode only.
Here are two programs that are free that scan for routers and give graphs to show channel usage for your computer.
Do a Google search for "Vistumbler" and "Inssider" and run ether one of them. Then look at the usage graph and then you can chose a channel for your router that is best for you.
Router collisions will gum up/interfere with data transfer if your router and your neighbors are on the same channel and the signal strength of the other router (s) is strong compared to yours.
There are several good android apps that also do the same thing that you can run on your fire.
Look and try WiFi analyzer for example.
Tho a dual band router is a nice choice.