How to Increase a Wi-Fi Signal
Most larger buildings are likely to have at least one dead spot where you can't receive a wi-fi signal at all. Many buildings, no matter the size, present problems just based on their construction materials. Microwave ovens and cordless phones are also signal killers. No matter how many obstacles stand between you and a signal, there are cost effective ways to push a signal through.
Mount the router on the wall. This is the easiest and fastest way to reduce interference with a wi-fi signal. Raising the router often puts the signal above any electromagnetic fields or other interference located in the area such as computers, microwave ovens and cell and cordless phones, all of which are generally kept at desk level in a room.
Install a wireless repeater, which picks up the wi-fi signal and rebroadcasts it with the strength of the original broadcast. Netgear and Belkin both have repeaters in their product lines. The AirPlus DWL-800AP+ by D-Link is both affordable and recommended.
Use a power line extender to boost the wi-fi signal to a computer or laptop that's plugged into a wall socket. A power line extender plugs into the router and into a wall socket and sends the wi-fi signal over the electrical line rather than via Ethernet. Just be sure that the computer or laptop is plugged into the same electrical circuit as the power line extender.