| 摘要 |
A communication unit (1b): begins transmitting meter reading information when a carrier detection unit (1c) detects, by carrier sensing, that a utilization channel is available; changes the utilization channel when the channel utilization rate of the utilization channel is greater than or equal to a utilization rate limit; and continues using the utilization channel, without change, when the channel utilization rate of the utilization channel is less than the utilization rate limit. When carrier sensing has been continuously performed over a fixed time, a derivation unit (1d) derives the channel utilization rate by replacing a signal generation time with a minimum time, which is obtained by multiplying the utilization rate limit by a prescribed period, if the signal generation time is less than the minimum time. |
