Question about wireless hookup!

[Groo The Perverted]

Okay I needed to know the answer to this but wasn't sure exactly how to ask it via google for search results, so I thought I would try to explain myself here.

I have my internet through Comcast set up via Wireless, so while my laptop is plugged in via ethernet, my PS3 is hooked up via the wireless connection.

My buddy just moved into a new room upstairs and to the left of me. Now he's in a back room (the front room closer to me is the kitchen area) and he can't get my signal anymore.

Is there a way for me to go into my wireless settings (router) to expand my wireless signal to a wider area?

For some reason I was thinking that I could expand or shrink the area that my wireless would reach.

Much thanks for the help!