The signal can be strengthened by a larger antenna. There are internal and external antennas specially developed for this purpose. These can be connected to the routers easily. Should this be not enough (because of extra thick walls) the signal can be forwarded, by so called repeaters. If the repeater can receive the internet via a wire from a central router, then a simply “Access Point” is enough. There is wireless signal forwarding (WDS), which can be done by a router.
