Replying to Networking Help

First of all I have the standard linksys w-whatever-g wireless router. With a wireless adapter in my xbox 360,(ive tried a couple), I always lag. Ive tried a few different types of routers also, and the one i have now works the best. My xbox is too far away to connect via ethernet cord, yet when i do(ive done it its just through windows and shit in my house) i have no lag, but i CANT use the ethernet cord so my question is what should i do? Would a wireless bridge work.. some advice please.