What is needed for a rescue professional to call the cell phone of a person trapped under the rubble?
The cellular radio network is designed to overcome the signal loss between the cell phone user and the distant base station even if it has to pass through a few walls of a building along the way. However, many of us have had the experience of losing our cell phone connection in the subway, because the signal from the distant base station could not overcome the additional signal loss after passing through the dirt and rock above the subway. Many subway stations in the world overcome this problem by putting a repeater in the subway station that is much closer to the user. In an earthquake, a similar situation exists when we try to call a person trapped beneath the rubble. Since the base station is far away from those trapped, the radio signal is already quite weak when it enters the rubble. Yet if the mobile base station can be brought 100 times closer, the signal strength entering the rubble will be at least a 10,000 times more powerful. When a rescue mobile base station is brought very
