Hi,

What you need is a Wireless Range Expander. I have used and installed the linksys Wireless-G Range Expander (WRE54G) before and i know it works perfectly fine. Its cable free and meets your requirements. You can check out its details:

http://homesupport.cisco.com/en-us/wireless/lbc/WRE54G?referrer=www.link...

I hope that answers your question.