Just remember that when you add a booster (as suggested by Ranman256), you seriously increase the radius of your signal. If you are NOT using encryption with a password, you are enabling your neighbors (for a fairly wide radius) to use your WiFi for free. If you have a lot of greedy neighbors and a router that uses DHCP*, you might have some routing collisions if too many devices are in the area. Even if you DO use a password, because the DHCP has to be assigned BEFORE you could log in.
* DHCP = Dynamic Host Control Protocol, a method of assigning temporary local IP addresses for all connections within the same router, and an essential part of the method generically referred to as Network Address Translation.
