The antennas of base stations are connected with optical fibers. If roads are swept away or utility poles are tumbled down by tsunamis in a disaster, underground optical fibers or communications networks will be disrupted. One of our strategies against these situations is implementation of wireless transmission by microwave, which can transmit broadband signals and is therefore used in the relay transmission of television broadcasting and multiplex telephone signals. We will amplify and relay these wireless microwave signals at base stations installed about every 50 km of sight distance. Both transmission routes have already been in operation; so, preparation for an emergency has been in place.
Our second strategy is our stock of alcohol fuel cells; that is, fuel cells in which alcohol is used as the fuel. To transmit radio waves, electric power is required. Because electric power cannot be transmitted, fuel cells that can run with alcohol for three days are stocked. This means that the communications service will not be interrupted if the base stations can be refueled within three days of the occurrence of a disaster.
Our third strategy is communication area control. If there is an intact communications network to which base stations are connected, then the stations may be remotely controlled. If radio waves are directed more upward to the sky by remote control, the range of the radio waves may be increased, thereby expanding the coverage. The radio waves are usually directed downward because they otherwise interfere with the antennas in adjacent areas, but in the event of disasters, we remotely control the angle of radio waves in particular areas, making sure people in the affected areas can use our service.
With these strategies, we are aiming to ensure communications of 96% of our users in the event of the Nankai megathrust earthquake, during which we predict that smartphones will not function as usual, but emergency services such as the disaster message board and the disaster voice messaging service will work properly.
In Kansai, there is also a possibility of river flood damage in mountain forest areas of Wakayama or Nara Prefecture. For such situations, we are prepared to implement measures similar to those described above to secure intact communications. “If something happens, use DOCOMO,” this is what we aspire to hear from mobile phone users. To accomplish this goal, we are working to ensure safety and security with the number one effort in the industry.