At least 10,000 cellular phone base stations ceased operation immediately after the Great East Japan Earthquake owing to the damage and power failure caused by the earthquake. Because of the rapid increase in communication traffic, up to 90% of telephone calls were suppressed by the telephone companies to maintain stable operations. Many wired communication networks and the emergency municipal radio communication systems were destroyed, and the vulnerability of the systems to disasters was completely exposed. As a result of this, the safety of residents was compromised as well as their ability to grasp the magnitude of the disaster. It also proved to be fatal during disaster relief operations such as the mobilization of medical services and rescue supplies by government and public organizations. This resulted in extensive social and economic losses.
To realize strong wireless networks in a disaster, we studied both satellite communications and wireless mesh networking technology. We focused especially on fully automatic earth stations for the WINDS satellite and wireless mesh network system realized by bridging satellites, unmanned aerial vehicle (UAV), and ground wireless nodes.