As the signal gets further away it weakens, and slows the connection speed. What I would do is get a second wireless router and set it up as a second hotspot I have done this in the upstairs and downstairs of my house. This is very simple to do, and takes one Cat-5 and the new router.

If you would like more information on how I set this up get at me, It might also be a problem with the wireless card on the computer you are using if it is only happening on one computer.