Cel-Fi is a device, similar to a cellular repeater, designed to eliminate in-building dead zones and improve indoor mobile phone reception. Created by , the Cel-Fi systems are designed with smart antenna technology to seek out the best available signal to maximize signal gain to phone users. The Cel-Fi consists of two wireless devices, a window unit and coverage unit, that work jointly to increase 3G and 4G mobile broadband connectivity throughout the building. The window unit receives the signal and relays it to the receiver, which converts it and amplifies it.