What is a Mobile Signal Booster? Mobile Signal Boosters (also known as cell phone repeaters) were developed to address the two factors that cause poor cell phone reception. They're designed to amplify a weak outside signal and bypass any obstructions to provide a strong inside signal to an area that was originally lacking. The system works by mounting an outside antenna in a location that currently has signal, which is typically on the roof. The signal is passed from the outside antenna, by a cable to a signal amplifier inside the building. Once the signal is amplified, it is then sent to an inside antenna, where it is broadcast out to the area which needs better reception. The system also works in reverse, with the signal from your phone being amplified and broadcast back to the tower, ensuring strong, two-way communication. Mobile Signal Boosters only amplify specific frequencies of radio waves, which pertain to specific carriers (Airtel, Vodafone, IDEA, Reliance, BSNL, etc.) and networks on those carriers (2G, 3G, or 4G LTE). The first thing you need to know is which carrier(s) you need to support, as well as which networks on those carriers, as that determines which signal amplifiers you'll be able to use and which type of outside antenna you'll need.