Wi-Fi networks communicate via radio frequencies, so they are prone to interference from walls and other radio signals. A Wi-Fi signal booster increases the power of a network without cables or extra wiring.
Wi-Fi signal boosters are also called repeaters. This product receives the signal from your wireless router, amplifies it and sends it back out, according to High Speed Internet Access Guide.
For a regular router, you can just purchase longer wire. Wireless networks are prone to interference from walls and furniture as the Wi-Fi "bubble" expands. A repeater can boost your signal strength up to three times and even pick up signals outside of your wireless network.
Linksys and D-Link are the major producers of repeaters in the U.S., and you can get one for $50 to $100, according to High Speed Internet Access Guide. Computer expert Bob Rankin suggests an Airport Express for Apple users.