To provide a transmission power controlling method for achieving desired reception quality, while preventing increase in average transmission power, even when gain variations in propagation path in relatively short period occur.

The transmission power is controlled so as to increase the capacity of a communication path, in response to gain variations of a propagation path, and data rate is controlled, in response to variations in increased capacity of the transmission path. The transmission power is determined so that the sum of noise power (= received noise power/gain of the propagation path) converted into a transmission end becomes constant for increasing the capacity of the propagation path. As a result, the transmission power is controlled so as to decrease when the gain of the propagation path is lowered, and to be increased when the gain of the propagation path increases, unlike the conventional one.

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