A wireless booster can be used to extend the range of an existing wireless network. This can be done in a number of different ways and can at first seem confusing! The Belkin F5D7132 and Linksys WRE54G both claim to work as universal boosters, but we have found products that wont work with these. Other manufacturers use a technology called WDS (Wireless Distribution System) to extend the range, both the access point (booster) and router must support this (This was used in version 1 of the Linksys WRE54G).
Another wireless boosting method is the send the signal via your power supply to another wireless access point. Devolo have a wireless extender starter kit (1215) that can do this.