| 摘要 |
<p>A mobile communication system for preventing marked reduction of the coverage even in a disaster and realizing a large throughput even though the coverage decreases. The mobile communication system comprises radio base stations each forming a cell area. One of the radio base stations has a communication unit for distributing the frequency bands and output power according to the distribution areas of radio terminals by using a predetermined frequency band and predetermined output power so as to communicate with radio terminals. In a normal operation, the communication unit uses high multilevel modulation scheme for communication with the radio terminal in an area having a small distribution area near the center of the cell area. The communication unit communicates with the radio terminal having a distribution area increasing as it goes toward the periphery of the cell area by a sequentially smaller multilevel modulation scheme. In a disaster for all the areas of the distribution area, the communication unit communicates by the smallest multilevel modulation scheme, sets the output power to a minimum value for communication with the radio terminal having an area where the distribution area near the center of the cell area is small, and sets the output power for communication with the radio terminal having a distribution area increasing toward the periphery of the cell area in such a way that the output power increases gradually.</p> |
