The range of your WiFi depends in part on who else nearby is on the same or adjacent channels. Use a "sniffer" to find out what else is around, and change your channel to suit. If possible, you want to be at least three channels away from any other WiFi.
I live in a long, thin house with a workshop off one end where I want WiFi. I have two wireless access points, one at each end of the house. The laptop and my iPhone connect to whichever one has the better signal. It works well.